Odd P0172-P0174 issues in a 3.0L
#1
12-12-2022
Odd P0172-P0174 issues in a 3.0L
Its a bit of a long winded problem, but... here we go.
I bought a 2004 ranger a while ago that has developed a problem... the dreaded P0171 & P0174 codes.... with a few oddball twists. Its a 3.0L 4wd. 190k. Runs fine. Gets about 13mpg which I think its pretty bad, but might not be for a 3.0L. This ain't my first ranger, but its my first 3.0L Ranger. All my others and the other 2 I have are 4.0L SOHC. I had a couple older OHV pushrod 4.0Ls and wore them out. I never had any problem with those old engines.
Anyway...On with the 3.0L problems....
I have an Ultra gauge hooked to it on the dash, to watch the various data in real time as I drive it, initially because it has a slightly rough idle that seems to be too low. So I started out trying to figure that one out. When I bought it, I took it to get inspected, I had the guy tune it up, new plugs, wires, an oil change, replace the muffler....some other minor stuff. After that, trying to get rid of that slow rough idle, I replaced the MAF sensor, air filter, fuel filter...about a gallon of sea foam and berrymans and lucas thru the tanks of gas, thinking it might be dirty injectors. No real luck. Then one day the CEL came on. I stuck the ultra gauge on it and its a P0171. Lean on bank 1. Ok I thought, no big deal, probably sucking some air somewhere. I gave it a good look, all the hoses are good and tight, PCV is clean and jiggly. Throttle body is clean, no carbon. I smoke tested the engine, left it pressurized with smoke for 30 min.... no trace of smoke anywhere. I made sure it was full and putting out smoke at several open lines before I sealed it back up. No apparent vac leaks. The fuel pressure on the rail is 65psi key on, engine off, and while running.
So I started driving it again, and set the gauge to show the 02 voltage on both upstream sensors, and the downstream sensor, also the STFT and the LTFT for both bank 1&2, engine temp, intake air temp, battery voltage. I started watching this data as I drove around.
Keep in mind, the truck runs great. Starts easy, no smoke, no choke, no hesitation, good power (for a 3.0L). Nothing at all to make you think there is anything wrong anywhere.
Exept that slow rough idle... Which is not really that bad, just... not right.
So here is how this went for a long time... Normal on bank 2, only slightly high + LTFT, between say +3-8. The LTFT on bank 2 ran a bit higher, 10-12 while driving around. In general the higher the RPM and load, the closer they ran to 0.00.
Then I noticed, if you left it sit and idle, the LTFT on bank 2 would go UP. Way up. 15...17...24.. while bank 1 kept it its normal +3-5. Start driving and bank 2 would go down.
Looks like a vacuum leak to me. I searched everywhere for a vac leak, smoked it again, rechecked all the lines. Nothing. So I figured, its not too bad, just dont let it sit and idle too long and it wont set the p0171. And for a while it didn't.
And keep in mind, this truck runs like a new one. No smoke, no hesitation, no nothing. Youd never think anything was wrong. Except the low idle, and really bad MPGs. I mean, 13mpg? I could have a bigger truck for that kinda pain. But its paid for and it does run really, really good.
A few days ago, things got worse. Now both banks are going UP into the 20's and 30's, when you leave off the pedal not only to sit and idle, but while driving. Bank 2 is still a bit higher all the time, but not by much. Its become a problem on both banks.
Still.... runs just fine.
So, I disconnected the battery and left it clear the PCM and whatever else needed it. I hooked it up, and it idled perfect, for the first time. No slow rough idle, it was smooth and a little higher than before. The STFTs were doing their normal thing, the LTFTs were staying withing 3% of 0.00 all day. I was happy, life was good.
Until it relearned its idle thing the way they do when you clear the computer. Now its back to rough slow idle, high LTFTs on both, pretty much no matter what you do. Put a load on it, lke going uphill or out on the freeway, both LTFTs come down to 7..8..10.. pretty much the same on both banks. Slow down and let off the pedal and boom, up they go past 24 and the CEL will eventually pop on, now with both the P0171 &P0174 codes.
Lean on both banks.
If I had hair, I'd start pulling it out.
I got in there and cleaned the IAC out, and re-cleaned the PVC because, why not. It didn't help.
So I'm stuck. The O2 sensor data shows them switching up and down, pretty normally. The IAC might be screwed, but it looks clean and when you unplug it, the idle does get worse, and better when you plug it back in. Same for the MAF (which is new, but new can be bad out of the box sometimes).
Any ideas where to look? Did I miss checking anything?
I was going to run a compression test but, it has no symptoms of a dead cyl, or low compression. I Put a vac gauge on it, and it shows everything is good.... Needle is steady and moves smoothly right where its suppose to, so I'm assuming the valve train is good, and compression is even enough.
Before I start throwing parts at this thing hoping to hit the problem, I'd appreciate some feedback. I did order a new PCV valve, on the off chance the old one is actually bad.
So to recap.... what has been done to it so far with no improvment is;
New plugs and wires, new MAF sensor, engine was smoke tested, a couple times. Lots of injector cleaner run thru several tanks of gas. Vacuum gauge tested, fuel pressure tested. New fuel filter. All the vac lines removed checked and sealed up tight. Cleaned the IAC out. Unplugged and cleaned a lot of connections. Reset the computer a couple times leaving the - terminal off overnight. Oil changed, air filter changed. Maybe a few things I forgot about along the way.
Symptoms are...Other than a low slightly rough idle and pegged out LTFTs, none. Runs like a new one. Starts easy. No smoke no choke no hesitation.
Help me out dudes....
Thanks!
I bought a 2004 ranger a while ago that has developed a problem... the dreaded P0171 & P0174 codes.... with a few oddball twists. Its a 3.0L 4wd. 190k. Runs fine. Gets about 13mpg which I think its pretty bad, but might not be for a 3.0L. This ain't my first ranger, but its my first 3.0L Ranger. All my others and the other 2 I have are 4.0L SOHC. I had a couple older OHV pushrod 4.0Ls and wore them out. I never had any problem with those old engines.
Anyway...On with the 3.0L problems....
I have an Ultra gauge hooked to it on the dash, to watch the various data in real time as I drive it, initially because it has a slightly rough idle that seems to be too low. So I started out trying to figure that one out. When I bought it, I took it to get inspected, I had the guy tune it up, new plugs, wires, an oil change, replace the muffler....some other minor stuff. After that, trying to get rid of that slow rough idle, I replaced the MAF sensor, air filter, fuel filter...about a gallon of sea foam and berrymans and lucas thru the tanks of gas, thinking it might be dirty injectors. No real luck. Then one day the CEL came on. I stuck the ultra gauge on it and its a P0171. Lean on bank 1. Ok I thought, no big deal, probably sucking some air somewhere. I gave it a good look, all the hoses are good and tight, PCV is clean and jiggly. Throttle body is clean, no carbon. I smoke tested the engine, left it pressurized with smoke for 30 min.... no trace of smoke anywhere. I made sure it was full and putting out smoke at several open lines before I sealed it back up. No apparent vac leaks. The fuel pressure on the rail is 65psi key on, engine off, and while running.
So I started driving it again, and set the gauge to show the 02 voltage on both upstream sensors, and the downstream sensor, also the STFT and the LTFT for both bank 1&2, engine temp, intake air temp, battery voltage. I started watching this data as I drove around.
Keep in mind, the truck runs great. Starts easy, no smoke, no choke, no hesitation, good power (for a 3.0L). Nothing at all to make you think there is anything wrong anywhere.
Exept that slow rough idle... Which is not really that bad, just... not right.
So here is how this went for a long time... Normal on bank 2, only slightly high + LTFT, between say +3-8. The LTFT on bank 2 ran a bit higher, 10-12 while driving around. In general the higher the RPM and load, the closer they ran to 0.00.
Then I noticed, if you left it sit and idle, the LTFT on bank 2 would go UP. Way up. 15...17...24.. while bank 1 kept it its normal +3-5. Start driving and bank 2 would go down.
Looks like a vacuum leak to me. I searched everywhere for a vac leak, smoked it again, rechecked all the lines. Nothing. So I figured, its not too bad, just dont let it sit and idle too long and it wont set the p0171. And for a while it didn't.
And keep in mind, this truck runs like a new one. No smoke, no hesitation, no nothing. Youd never think anything was wrong. Except the low idle, and really bad MPGs. I mean, 13mpg? I could have a bigger truck for that kinda pain. But its paid for and it does run really, really good.
A few days ago, things got worse. Now both banks are going UP into the 20's and 30's, when you leave off the pedal not only to sit and idle, but while driving. Bank 2 is still a bit higher all the time, but not by much. Its become a problem on both banks.
Still.... runs just fine.
So, I disconnected the battery and left it clear the PCM and whatever else needed it. I hooked it up, and it idled perfect, for the first time. No slow rough idle, it was smooth and a little higher than before. The STFTs were doing their normal thing, the LTFTs were staying withing 3% of 0.00 all day. I was happy, life was good.
Until it relearned its idle thing the way they do when you clear the computer. Now its back to rough slow idle, high LTFTs on both, pretty much no matter what you do. Put a load on it, lke going uphill or out on the freeway, both LTFTs come down to 7..8..10.. pretty much the same on both banks. Slow down and let off the pedal and boom, up they go past 24 and the CEL will eventually pop on, now with both the P0171 &P0174 codes.
Lean on both banks.
If I had hair, I'd start pulling it out.
I got in there and cleaned the IAC out, and re-cleaned the PVC because, why not. It didn't help.
So I'm stuck. The O2 sensor data shows them switching up and down, pretty normally. The IAC might be screwed, but it looks clean and when you unplug it, the idle does get worse, and better when you plug it back in. Same for the MAF (which is new, but new can be bad out of the box sometimes).
Any ideas where to look? Did I miss checking anything?
I was going to run a compression test but, it has no symptoms of a dead cyl, or low compression. I Put a vac gauge on it, and it shows everything is good.... Needle is steady and moves smoothly right where its suppose to, so I'm assuming the valve train is good, and compression is even enough.
Before I start throwing parts at this thing hoping to hit the problem, I'd appreciate some feedback. I did order a new PCV valve, on the off chance the old one is actually bad.
So to recap.... what has been done to it so far with no improvment is;
New plugs and wires, new MAF sensor, engine was smoke tested, a couple times. Lots of injector cleaner run thru several tanks of gas. Vacuum gauge tested, fuel pressure tested. New fuel filter. All the vac lines removed checked and sealed up tight. Cleaned the IAC out. Unplugged and cleaned a lot of connections. Reset the computer a couple times leaving the - terminal off overnight. Oil changed, air filter changed. Maybe a few things I forgot about along the way.
Symptoms are...Other than a low slightly rough idle and pegged out LTFTs, none. Runs like a new one. Starts easy. No smoke no choke no hesitation.
Help me out dudes....
Thanks!
#2
12-12-2022
"Gets about 13mpg which I think its pretty bad", You are RIGHT, that is very bad
Lets start with O2s, everything computer does with fuel mix is based on the O2s, "word of God" to the computer
O2s WEAR OUT
Only sensor that does, 12 years or 100k miles and they are done, start to go lean and MPG goes with them
No codes yet because computer has nothing to compare them to just lower and lower MPG
Eventually Lean codes, but by that time you could have bought 5 O2 sensors, for each side, in wasted fuel money, lol
So if you don't know the age of the O2s, change them, 2004 is 18 years old, so should be mid-way thru 2nd set
Once you have new O2s the fuel trims and lean code can be addressed, but not until then, or you will be basing repairs on incorrect data, like changing a light bulb while the switch is off...............by the 3 light bulb you need to check the switch, lol
Also Clogged Exhaust system, poor MPG and Lean codes
Use a Vacuum gauge on the engine
At idle should see 18-21"
Raise RPMs to 2,500(approx.) and hold there, should see steady vacuum at at lease 16" and NOT dropping slowly
Also Blip throttle, i.e. open wide then let it snap closed, vacuum should drop to 0-2" and then INSTANTLY come back up to 18-21", slow return is clogged exhaust
Lets start with O2s, everything computer does with fuel mix is based on the O2s, "word of God" to the computer
O2s WEAR OUT
Only sensor that does, 12 years or 100k miles and they are done, start to go lean and MPG goes with them
No codes yet because computer has nothing to compare them to just lower and lower MPG
Eventually Lean codes, but by that time you could have bought 5 O2 sensors, for each side, in wasted fuel money, lol
So if you don't know the age of the O2s, change them, 2004 is 18 years old, so should be mid-way thru 2nd set
Once you have new O2s the fuel trims and lean code can be addressed, but not until then, or you will be basing repairs on incorrect data, like changing a light bulb while the switch is off...............by the 3 light bulb you need to check the switch, lol
Also Clogged Exhaust system, poor MPG and Lean codes
Use a Vacuum gauge on the engine
At idle should see 18-21"
Raise RPMs to 2,500(approx.) and hold there, should see steady vacuum at at lease 16" and NOT dropping slowly
Also Blip throttle, i.e. open wide then let it snap closed, vacuum should drop to 0-2" and then INSTANTLY come back up to 18-21", slow return is clogged exhaust
The following users liked this post:
HT08 (12-14-2022)
#4
12-13-2022
Ron, I did a vac gauge test, and its right where it should be, good response and no needle drifting.
I agree the 02s are probably toast. I have a couple new ones here I had for another ranger, they are the same NKG part # so.. they'll be next.
Early this morning I ran a test that I didn't think of when I smoke it... I plugged off all the vac ports except the PCV valve I left in place. The PCV intake, the evap purge valve, the brake booster and the heater control vac port all plugged off at the manifold. I hooked up the battery and left it idle. The STFT took no time at all to exceed +25%. I took the plug off the IAC and the engine idled down to almost a stall, plugged it back in, and the idle resumed to perfect....quiet and smooth.
So there is a whole list of things it isnt....
I have a new PVC valve here somewhere, the old one is really dirty, but still jiggly. it looks like its never been changed. So I'll stick that in there later today, with all those ports plugged off still and see what it does.
BUT.. I agree with you the 02s must be changed, and are probably the problem. I thought for a long time since it was on bank1 only, it was a vac leak. But over time bank 2 started the same thing so... they didnt fail at the same time, which makes sense.
I'll put the new 02s in. Thanks for the advice.
I agree the 02s are probably toast. I have a couple new ones here I had for another ranger, they are the same NKG part # so.. they'll be next.
Early this morning I ran a test that I didn't think of when I smoke it... I plugged off all the vac ports except the PCV valve I left in place. The PCV intake, the evap purge valve, the brake booster and the heater control vac port all plugged off at the manifold. I hooked up the battery and left it idle. The STFT took no time at all to exceed +25%. I took the plug off the IAC and the engine idled down to almost a stall, plugged it back in, and the idle resumed to perfect....quiet and smooth.
So there is a whole list of things it isnt....
I have a new PVC valve here somewhere, the old one is really dirty, but still jiggly. it looks like its never been changed. So I'll stick that in there later today, with all those ports plugged off still and see what it does.
BUT.. I agree with you the 02s must be changed, and are probably the problem. I thought for a long time since it was on bank1 only, it was a vac leak. But over time bank 2 started the same thing so... they didnt fail at the same time, which makes sense.
I'll put the new 02s in. Thanks for the advice.
#5
12-13-2022
#6
12-13-2022
I changed my original 02 sensors after 180,000 miles and the difference in fuel mileage was noticeable.
Also, read the thread below. I too dealt with the P0171 and P0174. Truck drove fine, everything seemed fine, but my CEL came on and my fuel trims were through the roof. Problem was resolved as detailed in the thread.
P0171 and P0174 - Ranger-Forums - The Ultimate Ford Ranger Resource
Also, read the thread below. I too dealt with the P0171 and P0174. Truck drove fine, everything seemed fine, but my CEL came on and my fuel trims were through the roof. Problem was resolved as detailed in the thread.
P0171 and P0174 - Ranger-Forums - The Ultimate Ford Ranger Resource
#7
12-13-2022
Here is a stupid question I just came up with thinking about that O2 sensor I ordered... I ordered the same one, and I am sure I bought it for the 2000 ranger I had with the 4.0L engine, in the upstream position.
I put that one on the passengers side today, and the plug fits. However I looked on rock auto's site and a few others they list the NTK 22500 as the downstream sensor...fits the 3.0L 2004 ranger.
Other vendors and NGK simply list fitment for the ranger 3.0l but do not specify up or down. Does it make a difference as long as the plug fits? or is it all just down to wire length?
I hope it doesn't matter, I already put the dang thing on the drivers side... didnt start it yet.
My head tells me, if the connector plug is the same then its the same sensor no matter what they say.
I never gave it much thought... and I know that new sensor I have was one left of a pair I got for the 2000 ranger we had, because I put the passengers side on and the drivers side was seized so bad I just left it there... it was just a tune up new part and it worked still so... why fight with the rusty thing. I got a set of ntk 22500 sensors, off Amazon, I looked up my old order. Amazon didn't specify bank 1 or 2 OR up or down... just that it fit the year and engine.
I put that one on the passengers side today, and the plug fits. However I looked on rock auto's site and a few others they list the NTK 22500 as the downstream sensor...fits the 3.0L 2004 ranger.
Other vendors and NGK simply list fitment for the ranger 3.0l but do not specify up or down. Does it make a difference as long as the plug fits? or is it all just down to wire length?
I hope it doesn't matter, I already put the dang thing on the drivers side... didnt start it yet.
My head tells me, if the connector plug is the same then its the same sensor no matter what they say.
I never gave it much thought... and I know that new sensor I have was one left of a pair I got for the 2000 ranger we had, because I put the passengers side on and the drivers side was seized so bad I just left it there... it was just a tune up new part and it worked still so... why fight with the rusty thing. I got a set of ntk 22500 sensors, off Amazon, I looked up my old order. Amazon didn't specify bank 1 or 2 OR up or down... just that it fit the year and engine.
#8
12-13-2022
I changed my original 02 sensors after 180,000 miles and the difference in fuel mileage was noticeable.
Also, read the thread below. I too dealt with the P0171 and P0174. Truck drove fine, everything seemed fine, but my CEL came on and my fuel trims were through the roof. Problem was resolved as detailed in the thread.
P0171 and P0174 - Ranger-Forums - The Ultimate Ford Ranger Resource
Also, read the thread below. I too dealt with the P0171 and P0174. Truck drove fine, everything seemed fine, but my CEL came on and my fuel trims were through the roof. Problem was resolved as detailed in the thread.
P0171 and P0174 - Ranger-Forums - The Ultimate Ford Ranger Resource
When I ran the fuel pressure test, it held at 65psi key on engine off, at idle and at 2500 rpm, and the STFTs were still hovering around 25%. aT 65PSI I would think if that was the main problem, the STFTs would have dropped to normal at that pressure.
Also this started on bank 1 only for a long time... bank2 was always pretty normal. Bank 2 just started doing it too recently and driving or under load now doesn't push the trims to near normal on either bank...
Before if I just didnt sit and idle, it didn't trim high on bank1, it was only a problem when you left it idle for over say... 30 seconds.
As I understand fuel pressure wouldn't effect one bank only... But I will certainly keep your solution in mind.
Thanks!
#9
12-14-2022
Hello Fred, Here is my post about Oxygen Sensors for my 2003 with 3.0, I hope this helps you out.
I thought I would post this here as I had to replace my downstream sensor (the one after the catalytic converter) because I had a DTC code for it. I used a Bosch Exact Fit (per the Bosch website) for my 2003 Ranger 3.0 Automatic for the one after the CAT (Downstream). While I had the inner fender wells out I realized I can access the sensors very easily and after 244K miles on the original ones I decided to change those also. These are the 2 before the CAT (Upstream).
Here are the part numbers:
O2 Sensor Downstream - Bosch part number 15716, you only need one.
O2 Sensors Upstream - Bosch part number 15664, you will need 2.
One for each side of the engine, they are located right after the exhaust manifold (there is one on the driver's side and one on the passenger side (bank 1 and bank 2).
I hope this helps.
I thought I would post this here as I had to replace my downstream sensor (the one after the catalytic converter) because I had a DTC code for it. I used a Bosch Exact Fit (per the Bosch website) for my 2003 Ranger 3.0 Automatic for the one after the CAT (Downstream). While I had the inner fender wells out I realized I can access the sensors very easily and after 244K miles on the original ones I decided to change those also. These are the 2 before the CAT (Upstream).
Here are the part numbers:
O2 Sensor Downstream - Bosch part number 15716, you only need one.
O2 Sensors Upstream - Bosch part number 15664, you will need 2.
One for each side of the engine, they are located right after the exhaust manifold (there is one on the driver's side and one on the passenger side (bank 1 and bank 2).
I hope this helps.
#10
12-14-2022
Well I just spent the morning putting in the other o2 sensor, a new pcv and putting it all back together. Warmed it up and took it for a ride.
Runs better, actually. Idles better. Has more power. The problem didnt go away. It got marginally better, its back to running STFTs on both banks around =/- 4. The LTFTs on both banks are pretty even, a bit higher on bank1 like before. Driving around at 2k rpm the LTFTs are under 10%, sometimes as low as 3%. Let off the gas and up they go. Coast down a hill... up they go. Sit and idle, up they go. After an hour driving around, the LTFTs don't seem to go higher than 18% now. If you let it sit and idle for a couple min bank1 goes up to 20% bank 2 goes up to 18, but that is as high as they are going now. A marginal improvement. But the problem remains.
And my power steering pump is going bad... ugh. I'm starting to hate this truck.
So anyway.... As I see it, it still acts like a vac leak. But that is pretty much been eliminated I think. Clogged up or bad injectors? shot injector O rings? Maybe lower intake gaskets... I dunno. The injectors on bank 1 where I can reach them seem to wiggle a bit more than they probably should. Cyl 1 injector is looser than the other 2. Maybe I'll shoot some carb cleaner around it and see how it acts.
As long as it doesn't trim past 20-24% and set a code, do you think it will do any damage? It is trimming now within its limits. I don't have the time weather or money right now to put a set of injectors and an upper gasket while its apart.
It'll have to sit here as a spare truck when we need it for the winter. maybe by spring/summer I'll have figured it out.
Fuel pressure, I cant see, because when you put a load on it, the trims drop to 3% to 8% depending on your rpms. If I recall, if it was fuel starvation it would get worse the more fuel it needed under load. Is it possible the injectors are only working right when you put it under load/high fuel demand/ longer on time, and fail to spray the shorted the on time is?
On the upside, the new O2 sensors did do it some good. Still has a slight roughness to the low idle but not as bad.
Anyone wanna buy a nice looking truck?
Runs better, actually. Idles better. Has more power. The problem didnt go away. It got marginally better, its back to running STFTs on both banks around =/- 4. The LTFTs on both banks are pretty even, a bit higher on bank1 like before. Driving around at 2k rpm the LTFTs are under 10%, sometimes as low as 3%. Let off the gas and up they go. Coast down a hill... up they go. Sit and idle, up they go. After an hour driving around, the LTFTs don't seem to go higher than 18% now. If you let it sit and idle for a couple min bank1 goes up to 20% bank 2 goes up to 18, but that is as high as they are going now. A marginal improvement. But the problem remains.
And my power steering pump is going bad... ugh. I'm starting to hate this truck.
So anyway.... As I see it, it still acts like a vac leak. But that is pretty much been eliminated I think. Clogged up or bad injectors? shot injector O rings? Maybe lower intake gaskets... I dunno. The injectors on bank 1 where I can reach them seem to wiggle a bit more than they probably should. Cyl 1 injector is looser than the other 2. Maybe I'll shoot some carb cleaner around it and see how it acts.
As long as it doesn't trim past 20-24% and set a code, do you think it will do any damage? It is trimming now within its limits. I don't have the time weather or money right now to put a set of injectors and an upper gasket while its apart.
It'll have to sit here as a spare truck when we need it for the winter. maybe by spring/summer I'll have figured it out.
Fuel pressure, I cant see, because when you put a load on it, the trims drop to 3% to 8% depending on your rpms. If I recall, if it was fuel starvation it would get worse the more fuel it needed under load. Is it possible the injectors are only working right when you put it under load/high fuel demand/ longer on time, and fail to spray the shorted the on time is?
On the upside, the new O2 sensors did do it some good. Still has a slight roughness to the low idle but not as bad.
Anyone wanna buy a nice looking truck?
#11
12-14-2022
I had a misfire that turned out to be a clogged injector. I had the injectors serviced and the result was night and day before and after + the misfire is gone. Something to think about as I also tried the injector cleaners but that didn't help despite the fact that the truck is used daily and gets a tank of gas every 2 to 3 days so it does not get a chance to sit. HTH
#12
12-14-2022
#14
12-14-2022
No,won't hurt the engine to run it that way
+ fuel trims means the computer is opening injectors longer, +10 is 10% long than computer calculated
If its a False +18% then spark plug tips will show blackened tips from Rich Running
If spark plug tips look OK then the +18% means computer is compensating for another issue
The new O2s are needed to see which it is, as there is NO OTHER feedback for fuel trims except O2s, everything is based on that feedback
+ or -10% is normal, usually + as engine ages
Drive it for a week or two and check spark plug tips, at least 1 on each bank of engine
A False Lean(blackened tips) with new O2s could mean computer is the issue
If spark plugs tips have a nice light brown color then you are still fighting a sensor issue, or reduced air flow or clogged exhaust
+ fuel trims means the computer is opening injectors longer, +10 is 10% long than computer calculated
If its a False +18% then spark plug tips will show blackened tips from Rich Running
If spark plug tips look OK then the +18% means computer is compensating for another issue
The new O2s are needed to see which it is, as there is NO OTHER feedback for fuel trims except O2s, everything is based on that feedback
+ or -10% is normal, usually + as engine ages
Drive it for a week or two and check spark plug tips, at least 1 on each bank of engine
A False Lean(blackened tips) with new O2s could mean computer is the issue
If spark plugs tips have a nice light brown color then you are still fighting a sensor issue, or reduced air flow or clogged exhaust
#15
12-16-2022
I will check those plugs in a week or so. I did run a few more tests, the lower intake gaskets are intact, and there is no change in idle with the water test for vac leaks. The Evap system was disconnected off the intake, and there was no change in trims or anything else.
I'm down to just change the upper gaskets and put in new injectors at some point in the spring and see what that does. No real downside to that, I'm sure it needs both done by now anyway.
I did get the air purged from the power steering this morning and put new ATF in it. That seems to new be working smooth and quiet again.
I'm down to just change the upper gaskets and put in new injectors at some point in the spring and see what that does. No real downside to that, I'm sure it needs both done by now anyway.
I did get the air purged from the power steering this morning and put new ATF in it. That seems to new be working smooth and quiet again.
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RonD (12-16-2022)
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