Starts Right Up, Then Calmly Dies

[broncogirl]

Any ideas on first things to check (and how to check - I'm a novice).

'88 BII, 2.9, EFI, AT w/ 88K miles. Tune up and new computer chip installed in the fall, new drive shaft and brakes a few months back, and it's been running fantastic - driving almost daily on long and short trips. Started right up every single time at high altitude and low, cold weather and warm. Just last week it started and ran smooth in snow storm. Ran great last time I drove - Thursday night; suddenly, this Monday morning, I can't keep it running for more than few seconds unless I hold the gas pedal down (the check engine light will come on while I do this).

Tried about five times. It started right up every time then, after a few seconds, check engine light came on and it just died. Not running rough or sputtering, just stops running. Generally, I don't have to keep my foot on the gas, even in cold weather, but I tried doing that after first few times it died. <EDIT - just went home for a few minutes at lunch and found I could keep it running a bit longer (didn't try for too long, because it I'm worried I'm damaging something) by constantly giving it quite a lot of gas, but the check engine light comes on and stays on after a few seconds and it will die within about two seconds of taking my foot off the gas. Took two tries to move it about 15 feet back up the driveway.>

Fuel tank is almost full and gauge is working.

Since it starts right up, repeatedly, I take it it isn't the battery, but could it be some other electrical issue? Not sure what or how to test, since it won't stay running.

The automatic transmission shifter has been slightly out of adjustment for awhile and it will occasionally not seat in park properly. However, it was firmly in park this morning and it started every time (before quickly dying), so I assume that means it isn't related to the transmission or the neutral safety switch. Neutral safety switch prevents it from starting at all by blocking the electrical needed to start the car - right?

Hubs unlocked, transfer case in 2wd when last driven and this morning, so my issues with the transfer case shifter slipping from 4 high into neutral should have nothing to do with this.

 

[detty_motorsports]

have you checked the fuel pumps.... there is 2 of them... one is in the tank and the other is located on the frame..... to do this u can check the fuel pressure...... im not shure what it is suppose to be ill have to get back with the details....

 

[broncogirl]

Thanks. I don't know how to check the two fuel pumps. If you have more instructions, I'd appreciate it.

Do they fail suddenly (when parked) without previously running rough or poorly? If one or more is not working properly, wouldn't it have trouble starting? It starts right up with no gas pedal needed every time - just dies after a few seconds. Also, does a fuel pump failure make the check engine light come on? The light's coming on before it dies.

I just edited my post above, as I ran home at lunch and found I could keep it running longer by keeping constant pressure on the gas pedal. The check engine light comes on after a few seconds and stayed on for the approximately 25 seconds I kept it running with gas pedal before taking my foot off and letting it die.

Limped it up the short driveway and had a very quick look under the hood, too. Saw nothing wrong right off - no mouse nest in the air intake, though I plan to check the air filter assembly tonight. It's damp, as usual, under the hood - my early bronco body and hood allow more rain in than a regular BII, I think. Can't see fluid leaks in the muddy driveway, but did not smell fuel.

 

[detty_motorsports]

u need a fuel pressure gauge... and then connect to the bleed valve on the fuel rail. it looks knida like a valve stem..... I'm not shure if this would make the check engine light come on but it will cause the truck run and then die like you said....

 

[holeshot]

I had a similar problem on my 86. Found out that water had leaked onto the main computer (up under the dash on the passenger side) and caused some corrosion. had to buy a replacement from a junk yard. I think BII's are notorious for rusting out in the corners of the windsheilds and allowing water to leak in. (right onto the computer box).

 

[broncogirl]

Thanks. Will get a fuel pressure gauge and check. This valve is like a schrader valve on a tire? Think I've seen one or two under the hood in the past, but thought they were for AC. I take it the pumps start pumping when you turn the key - don't have to start it and keep it running to test? Or, should I get it running and get somebody to hold the gas down and try to keep it running while I test?

I had a similar problem on my 86. Found out that water had leaked onto the main computer (up under the dash on the passenger side)

Sounds quite possible for my leaky truck. Got the hard top back on late this year and haven't had the time on a dry day to really seal it up properly, so lots of moisture in the cabin right now. My dash is very modified, as it has very little depth in the early bronco body. No room for stereo, no ducts for the side heater/ac vents, etc. Can you tell me more about what I'm looking for? Size, shape, color, metal or plastic housing? is this main computer also called the engine control unit or something like that? My mechanic put a new "computer chip" in a few months ago, does it plug into the main computer?

Thanks a million!

 

[detty_motorsports]

Thanks. Will get a fuel pressure gauge and check. This valve is like a schrader valve on a tire? Think I've seen one or two under the hood in the past, but thought they were for AC. I take it the pumps start pumping when you turn the key - don't have to start it and keep it running to test? Or, should I get it running and get somebody to hold the gas down and try to keep it running while I test?

yes its like a schrader valve... the fuel rail runs along the intake where the upper and lower bolt together on the drivers side of the intake is where u will find the bleed valve. and yes the pumps should both run for a few seconds when you first turn on the key.....

 

[adsm08]

Fuel pressure should be about 35 PSI. When my rail pump went it ran poorly with low power for a week or two before hand.

This kinda sounds like an IAC issue to me. Unless you need to have it floored to keep it running I'd check the IAC before looking at fuel pumps.

 

[retep88]

+1 for the IAC. Pull it off and clean it out with some carb cleaner, put it back on and see if that will fix the problem.

 

[detty_motorsports]

+1 for the IAC. Pull it off and clean it out with some carb cleaner, put it back on and see if that will fix the problem.

this is also a good possiblity...

 

[adsm08]

This is on a 4.0 Explorer. Yours is identical, located on the pass side right near the Throttle body. Take it off, spray it out with carb cleaner until it runs clear, see if it helps.

 

[broncogirl]

Will try cleaning the IAC. Thanks.

Also, think I found the computer. Metal box, about the size of a car stereo? Goes by "Engine Control Module" on parts sites - is that right? It's sadly mounted on the passenger side kick panel right in front of the door with the wiring harnes at the bottom. Carpet covers it and retains the moisture. It was very damp and the way it is mounted, the water runs down to the wiring harness where the black plastic cap catches it and keeps those connections soaked. Also saw there are two ground wires with this harness. They are attached to a ground screw right next to the ECM (but it looks like they veer off from the wire cluster to the screw instead of the ECM). One of these is a bare wire with no sheath and it looks pretty corroded. The other has a black coating and also seems corroded at first glance. I'll try to clean these up and any other crusty wires, pull the ECM, dry it out inside the house, clean the connections, etc.

Had to change an alternator belt in the pouring rain on my other car last night, so did not get to spend much time messing with this (and it was getting wetter with the door open for me to access it). I pried off the black plastic cap but saw a bolt that seems to hold the wiring harness (plug?) on and didn't get a chance to try and remove it. Tried to dry it a bit with paper towels and then tried starting again. It still starts right up, lights check engine up, and then dies in about 5 seconds.

Since it was getting wetter with the door open, I just proped the ECM up away from the wet carpet so it might possibly dry a bit. I'll try to pull it out and take it inside the house to dry tonight.

Is it likely that might fix the problem, or do these need some kind of reprograming or replacement once they lose their minds? Was the "computer chip" my mechanic replaced inside this thing? It seems factory sealed, so I don't see how. Any harm in breaking the seal and opening it up to see if anything is obviously corroded? Any recomendations for good online sources for remanufactured or new ECMs? I see some on ebay, but not my particular year/model.

Thanks again.

 

[BlackBII]

My bet is on the IAC. It's probably not opening and therefore your motor isn't getting an air, and is dying. That's why it'll stay running with your foot on the gas.

Although I doubt there is anything wrong with the computer, drying it and cleaning the connections isn't a bad idea.
(given that it still runs and you got a CEL)

Im curious as to what this "chip" was your mechanic replaced...any more details on that?

Also, pull the codes:
http://www.therangerstation.com/tech_library/OBD_I.html
http://www.therangerstation.com/tech_library/2digitcodes.html

 

[CopyKat]

Prolly the TFI module on the distributer.

 

[adsm08]

Yes, you found your Engine Computer. I would try to dry it and the area around it out.

The "chip" that your mechanic replaced probably was CopyKat's TFI module. These are a very common failure item on the 2.9s. I've been through three of them in the last 7 years. One was used and died about 2 years later at the same age as the original. One was aftermarket and was crap, one was not actually the problem.

I doubt you need to replace your ECM since you have a CEL and it does actually run, and the best way to go about it is to buy a reman, they aren't reprogrammable, until about 1996. A remaned one is about $300.

I think I saw somewhere on here a while ago that the CEL on these old RBVs isn't a malfuntion indicator so much as a maintenance reminder. If you open up your glove box and drop it down the whole way there should be some sort of button that you push to reset it. I have not seen this myself but I can go look at mine later and see if I can find it.

If you can get it down to a local autozone or advance auto and get some codes that would be a great help. They pull them for free and can usually even offer a suggestion as to what might fix it.