04 For Ranger 4.0 SOHC

I had recently just replaced timing components along with all new gaskets. Valves and seals were done along with surfacing while I had the heads off. New plugs, wires, coil, injectors, crank sensor, harmonic balancer, PCM, thermostat and housing.

All seemed well on first startup besides a code for one of the sensors on my thermostat housing. I got around to changing the sensor and the code went away but shortly after I’m getting a code P2198 that is persistent. I drove it around for a little while around town like that not too bothered as pickup was running just fine.

Now I’m getting codes P0316, P0306, P0304 and P0300. Of course these misfire codes are on the same bank as my biased stuck rich 02 sensor. These codes are not constant, they come and go randomly. Occasionally I will get the dreaded flashing CEL.

When I first got the flashing CEL for cylinder 4 and 6 misfiring I limped it home and let it sit for a couple weeks before trying to figure out why. I pulled plugs 4 and 6 and both were carbon fouled. Plug 5 was the normal brownish color. I put a couple new plugs in and they quickly became carbon fouled as well. Used another set of spark plug wires and the issue remained the same. Next I made sure injectors were properly plugged in and gave them a nice wiggle back and forth, and this seemed to have made the random misfire disappear for a short while until today when I took it out on the highway. I drive about 5 miles before turning around and as soon as I turned around the CEL started flashing with P0306 and P0304. You could feel when the misfire was about to throw a code and also when it was firing on those cylinders again and the CEL would go out. Sometimes it would take 2 minutes for misfire and CEL to return and sometimes it would happen almost immediately after the last tantrum.

While I’m here I might as well add in that the pickup wants to overheat, however it is also inconsistent. I can let the pickup idle for 1.5hours and will never go over 188 degrees. The problem seems to come when I drive it around town. I took it out on the highway earlier today, started on highway at around 206 degrees and drove for about 10miles, and watched the temp slowly going down to around 190 degrees. Sometimes it overheats quicker than other times. If I leave the radiator cap off I can’t seem to get it to overheat.

I never lose any coolant. When the temp reached a certain point I start getting a few small bubbles into the overflow. Once again these are never consistent, I may get 2 or 3 and then 10 minutes later get a group of 5 or 6 and so on. I do not have any milky coloration on dipstick or filler cap. Also I have tried the glove test and it doesn’t indicate combustion gases as the glove lays flat the whole time. I put the glove on it at start up and literally left it on there for 45mins to an hour. At this time the engine did not go above 188 degrees and I was not getting any small bubbles into overflow.

I noticed my temp gauge would reach about the halfway point at normal operating temp and wouldn’t go up until around 222 degrees and then gauge would start to slowly tick towards hot.

Im unsure if these issues are related but figured I would include all the information I could. Thanks for the read and looking forward to hear from you gurus.

 

Blackish spark plug tips on #4 and #6 may be from leaking injectors, also the Rich O2 code on that bank

All Fuel Injection computers have a "Clear Flooded Engine" mode a driver can use
After engine is warmed up shut it off
Turn key on
Press gas pedal down to the floor all the way and hold it down
When computer see 0 RPMs and Wide Open Throttle(WOT) it will enter "Clear Flooded Engine" mode
This means it will shut off Fuel Injector pulses, but leave spark on, while driver cranks engine over to "dry out" a flooded engine

Try this test, if engine fires or starts then possible leaking injectors

Other test using the above, but cold engine
Disable coil pack, unplug 4 wire connector
Use "Clear Flooded Engine" mode
Crank engine over a few times, no spark
Pull out spark plugs 4, 5, and 6
All should be DRY, if 4 and 6 are WET and 5 is DRY then the 4 and 6 injectors are leaking



Change the thermostat even if new
Check heater's warm air temp as coolant temp on engine goes up, should correspond, if heater air gets colder then you are low on coolant(have an air pocket), if warmer then coolant is actually getting hotter so not a "sensor" reporting error


Just a heads up in general
"New" used to mean "tested and working"
New now means "Never EVER tested, you test it, and we will replace it if its bad", i.e. warranty

 

Thanks RonD for the reply.

I tried the cold start method first. When I pulled the plugs all 3 appeared to be dry. They certainly weren’t “wet” with fuel. And of course 4 and 6 had a layer of carbon buildup. I did not clean plugs before test, so I believe they got carbon fouled from yesterday not the test.

After the pickup has warmed up and I try the WOT test it will not start.

I think I’ll try and get ahold of a pressure gauge and hook to fuel rail to confirm I’m not getting a leaky injector.

As far as the thermostat goes I completely agree and will change it out with another to eliminate the possibility of that.

I pulled the 02 sensor for bank 2 sensor 1 and it looked just about the same as plugs 4 and 6 with all the carbon buildup on it. Bank 2 sensor 2 looked the normal color and very little carbon on it.

I didn’t try and I’m unsure if you can even clean these 02 sensors without damaging them. Is it possible the 02 sensor could be the problem for running rich on that bank or is it throwing that code as a result from something else?

Also I will make my way to parts store to get some MAF cleaner just so I can eliminate that as well.

 

O2 sensors are the only sensors that wear out, 12 years or 100k miles which ever comes first, they use a chemical reaction to detect Oxygen in the exhaust, and chemicals simply get used up by exhaust or time
Bocsh brand was what Ford used, about $32 each, so cost you about $2.50 a year to use for 12 years

No, cleaning doesn't really work with O2s, if the chemicals get covered with a soot, like the spark plugs then it can interact with the Oxygen in the exhaust, so cleaning off the soot might help but probably not

If the Clear Flooded engine test didn't show leaking injectors, which it didn't, then dirty spark plug tips can only be from oil leaking in from valve guide seals
Burning oil in a cylinder will cause the dirty tips and also the residue on the O2 sensor

So what your oil level status between changes?

 

Dang not exactly what I was hoping to hear lol.

When I overhauled the motor I had taken the heads in for surfacing and they changed valves and guides. It wasn’t exactly cheap and at this point I don’t want to remove motor again to take heads back in. I will if that’s what it takes though.

I’ve driven this pickup a whopping 150 miles total if that since I bought it. I thought I was getting a decent deal when advertised as needing a head gasket. I knew nothing about these 4.0s and would have never bought this thing if I did. Needless to say it needed timing components as well as head gasket. So to answer your question about oil consumption I can’t have an opinion. It’s still on the full mark but that isn’t saying much with how much I’ve driven it.

Also while I was out I picked up a new 02 sensor and I still get the bank 2 biased rich code.

As far as valve seals leaking, what’s the best way to pinpoint that as the issue?

Thanks again

 

Pretty easy actually to test for that

Oil gets sucked into the intake from valve cover area via intake valve guide seals
Because with engine running intake area has negative air pressure, 18-21" of vacuum
And when you coast downhill using engine as a brake, then you get 30+" of vacuum in the intake

So go down a hill in gear at at least 40mph and allow engine to slow you down
When you get near the bottom press gas pedal down slightly and WATCH the exhaust/tailpipe
If you see a puff of smoke then leaking valve guide seals


You don't need to pull the heads to fix these, just the valve springs, but you do need to hold the valve up inside the cylinder when you release the spring and replace the valve guide seal
DIY is to use a smaller diameter rope that fits down spark plug hole, feed in enough so it coils up on the top of the piston then turn the crank so coil of rope presses on the valves to hole them inplace
Shops used compressed air in spark plug hole
And there is a bladder type device that will fit down spark plug hole and then you inflate it

And it may be that the valve guide seals were just not seated well when installed, remove valve cover and have a look, you can usually push them down thru the gaps in the springs with two small screwdrivers

 

I’ll give that a try and see if I can’t produce any smoke from tailpipe. I’m a little worried about driving it around if my CEL decides to start flashing. What do you think?

When I changed 02 sensor and sprayed the MAF sensor today I started it and got the same ordeal, flashing CEL and ran like crap. I was watching my fuel trims and the flashing CEL would start when my STFT bank 2 would get near 0, from there it would hop up to around -23 and it took a few seconds to adjust then CEL would go out. I could get the light to go out quickly if I raised the RPMs from idle to 1500 or so. Then it would take a few minutes for STFT to come down to 0 and rinse and repeat. At that point I disconnected battery cables and stuck them together for 15 minutes. Started it back up and didn’t get the flashing CEL and let it run for a good 30 minutes or so until it was starting to get too warm for comfort and shut it down. Also during that time fuel trims were pretty in sink with bank 1 at 0 +- 5. The LTFT was sitting about -25 the whole time with little fluctuation.

 

Those are odd readings if engine was warmed up

Flashing CEL just means Back Off the gas pedal usually, because there is a misfire, so not an issue if you "back off the gas pedal"

LTFT at -25% is also bad, it means STFTs have been at least -25% average previously

Computer calculates STFT of 0, it THEN adds LTFT to it, so STFT 0 is now actually -25%
If STFT then shows -5% it means its actually -30%

STFT is OPEN TIME for fuel injectors
Computer calculates air flow based on RPM(engine size), then gets air Weight from MAF, and air temp from IAT sensor
It now has a total "weight" of the incoming air at that moment
Gasoline uses an air:fuel ratio of 14.7:1 this is a weight ratio not volume
14.7 pounds of air to 1 pound of gasoline
14.7 grams of air to 1 gram of gasoline

Computer is programmed with size of stock fuel injectors, and the expected fuel pressure, and the Weight of gasoline
So computer knows how long to open a fuel injector to match the weight of the air and the weight of the gasoline, its just math

And thats 0 STFT
-5% STFT means computer closed injector 5% sooner to keep upstream O2 sensor in the 0.4v range
+5% means computer left injector open 5% longer to keep O2 in 0.4v range

-25% LTFT means way too much fuel was flowing into engine when injectors were opened
Could be fuel pressure regulator has failed
If injectors were changed then wrong ones were used, way too big

 

I've been dealing with a biased stuck-rich 02 sensor on bank 2, and it turned out to be a corroded wire on the female terminal. Spliced in a new connector pigtail, and it started running normally. I suspect it's been doing that for the whole 2 years I've had the truck. Live and learn. I dumped 15k into mine.