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Electrical Issue Help!

  #1  
Old 02-24-2019
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Electrical Issue Help!

'90 Ford Ranger 2.9L V-6 couple weeks ago I started noticing an issue when I tried to hit passing gear or take off quickly from a standing stop the engine would start to spit and sputter and lose power. Soon as I let up on the gas it smooths out again. Runs fine as long as you don't stomp on the gas. will do 70-75 on the freeway, idles at 700-800 no problems. At the same time I noticed it was taking longer to spin over in the mornings before starting. Last thursday morning it refused to start altogether. Engine spins fast but wouldn't hit. Called my mechanic friend to come over and we ran some tests and he thought I needed to replace the Throttle Control Sensor. The engine eventually started on its own while we were monkeying with it about two hours after I first got in and tried to start it. Spent about 45 min waiting for him to arrive.

Here's what I've done so far, Had Catalytic converter checked and it was bad, fixed that muffler is fine, Injectors are firing and the plugs are firing and there is no flooding. Fuel pressure is fine and holds well. Replaced the TPS (Throttle Position Sensor) and still have the same issues. Distributor and ICM was replaced three years ago with genuine Motorcraft parts, plugs replaced a year ago. Coil replaced same time as Distributor, ICM and distributor cap and wires.

Engine idles fine and runs well in general and gas mileage has not changed so what would affect both the starting of the engine (it spins 4 to 8 seconds now before firing sometimes need to release the key then hit start a second time) and smooth quick acceleration? Don't want to just keep throwing parts at it . I feel like it's something related to the ignition timing. Any ideas?
 
  #2  
Old 02-24-2019
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I would check the Vacuum hose to A4LD transmission's modulator, passenger side of trans, see if there is ATF inside the hose, shouldn't be but just good to take that off the table

Yes, could be spark advance issue
The way TFI system works is that the distributor/TFI module does RPM advance on its own and the engine computer does Load advance(vacuum advance in the old days)
When you step on the gas hard, fuel mix gets Rich and engine load goes up, so spark needs LESS advance to get good power, richer mix burns faster
If you slowly accelerate then RPM advance is all you really need.

So either the TFI module(ICM) is not accepting "suggestions" from computer or SPOUT connector came unplugged
SPOUT is SPark OUT, it is the signal from computer that does the vacuum advance, and it has a removable connector so you can set Base Spark timing of 10-12deg BTDC

On the 2.9l SPOUT connector should be on passenger side of engine near distributor on top of lower intake

Image here: https://f01.justanswer.com/Eclayton4...8457_SPOUT.jpg

Yours would probably have 2 Yellow wires, the plastic plug pulls out to disconnect the two wires, which disables computer's load advance

It is possible the TFI module has failed, or the computer has

TFI testing info here: https://therangerstation.com/tech_li...agnostic.shtml


TPS(throttle position sensor) was not a bad guess, but easy to test these with volt or ohm meter
TPS serves the same purpose as the Accelerator Pump did on a carburetor, it gives the engine computer the "heads up" to add more fuel quickly from driver input(gas pedal)
And this would also initiate computer sending changed spark advance info to TFI module on SPOUT wire
 
  #3  
Old 02-24-2019
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Thanks Ron that's a big help. Unfortunately I learned how to test the TPS after I already bought a new one and it's non refundable so that's $42 down the drain but one thing I can omit anyway. I have the Chilton's book on Rangers and was reading about the SPOUT thing and there was no picture or direction on how to find it. I don't get both CHilton and Hanes, they give illustrations on all the stuff I already know then throw in something like SPOUT I never heard of before with absolutely no guidance on where it is or how to find it Grrrrrrr!.

If the weather holds I should have time tomorrow to run some of these tests and maybe determine if I have an EEC problem or need another ICM. I really don't get why the ICM's seem to go bad so often. My very first thought as an old school shade tree mechanic was that it was somewhere in the timing advance but then the issue with starting threw me for a loop on that logic but evidently with the computer control stuff the two are related after all.

Thanks again for the info I'll post again when I get to use it and make a determination.
 
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If you remember distributor points and what happened to them over time then you will understand why the first ICM designs didn't last as long as we might expect from solid state electronics.

There are major voltage issues on firing a Coil 3 times per revolution of the crank(6 cylinder engine), so even at 700RPM idle that's 2,100 times/sparks a MINUTE, at 3,000RPM that 9,000 times a MINUTE
Transistors and other parts simply failed over time

Ford tried Duraspark and then TFI but these modules still had issues
GM came up with HEI setup and that lasted, but it was also patented, lol.

Over time Ford did the EDIS setup and that worked much better and then the whole thing was moved into the new computers in 1995 and up Rangers

TFI is old technology and wasn't good technology even when new, but it is what you have
 
  #5  
Old 02-24-2019
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Originally Posted by RonD View Post
If you remember distributor points and what happened to them over time then you will understand why the first ICM designs didn't last as long as we might expect from solid state electronics.

There are major voltage issues on firing a Coil 3 times per revolution of the crank(6 cylinder engine), so even at 700RPM idle that's 2,100 times/sparks a MINUTE, at 3,000RPM that 9,000 times a MINUTE
Transistors and other parts simply failed over time

Ford tried Duraspark and then TFI but these modules still had issues
GM came up with HEI setup and that lasted, but it was also patented, lol.

Over time Ford did the EDIS setup and that worked much better and then the whole thing was moved into the new computers in 1995 and up Rangers

TFI is old technology and wasn't good technology even when new, but it is what you have
Well all that does make sense as your explained it. Thanks for the little electronic history lesson! I definitely remember the old points system. They did wear out fast but at least were cheap and easy to replace. This dang thing you have to remove the distributor to replace the ICM. So when that $90 part goes out it costs $300 to fix because they put the distributor in the worst possible place behind the engine and under the intake! Grrrr!
 
  #6  
Old 02-27-2019
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Originally Posted by RonD View Post
I would check the Vacuum hose to A4LD transmission's modulator, passenger side of trans, see if there is ATF inside the hose, shouldn't be but just good to take that off the table

Yes, could be spark advance issue
The way TFI system works is that the distributor/TFI module does RPM advance on its own and the engine computer does Load advance(vacuum advance in the old days)
When you step on the gas hard, fuel mix gets Rich and engine load goes up, so spark needs LESS advance to get good power, richer mix burns faster
If you slowly accelerate then RPM advance is all you really need.

So either the TFI module(ICM) is not accepting "suggestions" from computer or SPOUT connector came unplugged
SPOUT is SPark OUT, it is the signal from computer that does the vacuum advance, and it has a removable connector so you can set Base Spark timing of 10-12deg BTDC

On the 2.9l SPOUT connector should be on passenger side of engine near distributor on top of lower intake

Image here: https://f01.justanswer.com/Eclayton4...8457_SPOUT.jpg

Yours would probably have 2 Yellow wires, the plastic plug pulls out to disconnect the two wires, which disables computer's load advance

It is possible the TFI module has failed, or the computer has

TFI testing info here: https://therangerstation.com/tech_li...agnostic.shtml
I did find the SPOUT connector it was closer to the oil cap than the distributor or intake but it does have two yellow wires as you said, pulled out the plug and then reinserted it to make sure the connection was tight and checked for bad connection. It seems to be in order. Tried to look for the transmission switch but couldn't get to it without jacking up the car. The transmission was totally rebuilt two years ago and has been serviced since and I doubt that's an issue but will check when I get to where I can get it up in the air a bit. Wouldn't there be transmission fluid in other vacuum lines up in the engine compartment if it was in the line near the tranny? It's still shifting perfectly. I'm thinking at this point it's probably the ICM that's the problem but gonna try doing some testing first. I may put it in the shop for diagnosis as I don't feel up to snuff enough to be playing around with the ICM harness and putting pins in it and stuff. I'll keep you posted.
 
  #7  
Old 3 Weeks Ago
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Finally got this problem resolved. First decided after testing to go head and replace the TFI Module. Got one of those and took to my mechanic to have him do the job. After removing the module the new one would not reinstall correctly, the insulation rubber or plastic around the stator was very soft and would not let the module plug in. Went ahead and replaced the distributor, with module connected and it worked but engine still started missing under load. Just for giggles my mechanic installed a spare Coil he had an Viola! it worked fine. Miss gone engine runs fine. Coulda probably just bought a coil at the outset but it was only four years old so I didn't suspect it. Kinda glad I got the new distributor anyway though as that stator would have eventually ended it anyway and the cap and rotor were shot as well, now it's all new. Also found and fixed some vacuum leaks in the process so all is well that ends well.
 
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Good work

Thanks for the update and FIX
 
  #9  
Old 3 Weeks Ago
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You're welcome Ron. I forgot to mention one thing. I brought the defective coil home and just for kicks did the resistance tests on it described in my Chiltons book. Resistance between the negative and positive terminals was within spec and so was the resistance I got between the - terminal and high power pole (to distributor) . That was kind of confusing. Don't know why the readings were good but the coil is definitely bad. If I'd done the test on the vehicle and got good readings I'd still be looking for a cause to my problem. Only the fact that my mechanic had an extra "test" coil laying around his shop and swapped it out confirmed the issue was the coil. So lesson learned, the tests don't always tell the whole story.
 
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Old 3 Weeks Ago
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There is no way to test any ignition coil to see if its "good", single coil or coil packs

You can test if they are Bad, lol, but not good

This is because of the operating temps and the very low and very high OHMs that are used

A Primary coil runs at 1 OHM, +/- .5 ohm, and it is powered up and powered off 3,000 times a minute at 1,000RPMs on a V6 engine
And this makes it VERY HOT
And OHMs change as heat goes up

So a coil may test OK and even spark OK cold or warm, but HOT can cause it to fail.

Testing a coil with OHM meter should always be first thing you do if you suspect a spark issue, but unless it tests as bad the coil is not off the table, it could still be the problem
 
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