1990 K2500 350 5.7 TBI Stalls in reverse or drive

[Joe B]

So I have been creeping around the forum for a while looking to see what I can do to fix my stall problem. I can keep the truck going it I hold the brake down and give it gas, but I need to get this fixed.

So here is what I did based on what I have read here on the forums.

Set the timing with the advance wire disconnected
Replaced gas filter
Tested gas pressure, its 12 PSI
Replaced the IAC and set it to the correct depth, 1 1/8"
Replaced EGR
Tested TPS - good
Test MAP - good
Replaced vacuum hoses, connectors and added a clamp to the brake booster end
Replaced the TDI, gas was coming out of the injectors, one has a small leak

One thing to note about the timing, when I set it, watching it with the timing light, I get it set, and then i bounces, then goes back to being set.

When it stalls, it winds down. Here's a video of it, so you can hear it if you want:

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Thanks in advance for your help.

Joe

 

[lessersivad]

So I guess I didn't see anything about a 'check engine light'. Is it lit??

How long have you had that exhaust leak? THAT could be throwing the O2 sensor off.

How long has this been going on? A week? A day? A month?

Have you tried hooking a scan tool up to look at the fuel trims? (Yea I know it's a '90 but you should still be able to read the trim specs IF you have a scan tool worth a crap).

 

[Joe B]

No check engine light. The exhaust leak has been going for awhile, I can't say if the problem started when that happened.

As for how long, its been at least 8 months. When it started, it wasn't that bad, but it has got progressively worse. Maybe it has to do with the exhaust leak, like you were saying. As the hole gets bigger, my problem got bigger.

As for a scan tool, I don' have an OBDI reader, so I have never checked. I will work on the exhaust leak and see if that helps.

Thanks for your help!

 

[evilunclegrimace]

You made no mention of checking/setting the base idle speed. It needs to be done any time you replace the TBI unit and/or the IAC.

The ECM controls the IAC. There is no way to measure this once it is installed. The correct setting procedure for setting the BASE IDLE is to ground the ALDL terminals A&B which are the top two terminals on the right side, turn the key to the run position and wait about 30 seconds. Then verify that the IAC pintel is seated by looking the idle passage of the TBI body. once you have verified that the pintel is seated unplug the IAC and set the base idle to the proper speed.(650 RPM'S in drive? I have to look up the spec). once that is done remove the grounding clip and reconnect the IAC. Cycle the key on for 10 seconds and of for 10 seconds and then start the truck.


I can dig up my 1990 light duty truck Fuel and Emissions manual if you need more specifics

 

[DerekTheGreat]

Beyond "Block Learn" data I don't think these will let you look at fuel trims, unless you have that software people use for their lap tops. I have a Snap-On MT2500 scanner and while I can see what other sensors and things are doing, I can't see anything but o2 sensor voltage. So I can see that it's working correctly but I can't graph it. I think short term fuel trims on these are "Integrator" values and long term fuel trim data is "Block Learn". The way GM's book describes those values is a bit ambiguous though. Like the various blocks correspond to different load conditions and speed but they don't define which speeds or load it looks for. 131 is the target value IIRC. Anything above that means the computer is adding fuel, anything under that means it's trying to subtract it.

 

[magimerlin]

That exhaust leak is definitally not helping the issue at all.

When was the last time you did a complete tune up?

Get the icm(ignition control module), under the distributed cap, tested. Most Auto parts stores can test them. You have to take it(just the module)out to get it tested. Don't forget to put new "thermal grease" on it before mounting it back up if it's good. A new module usually comes with new grease. I use the "arctic" computer processor heatsink thermal paste. Can be found at most stores that sell computer stuff..

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[magimerlin]

On another note.... almost sounds like your torque converter is stuck engaged.

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[lessersivad]

Beyond "Block Learn" data I don't think these will let you look at fuel trims, unless you have that software people use for their lap tops. I have a Snap-On MT2500 scanner and while I can see what other sensors and things are doing, I can't see anything but o2 sensor voltage. So I can see that it's working correctly but I can't graph it. I think short term fuel trims on these are "Integrator" values and long term fuel trim data is "Block Learn". The way GM's book describes those values is a bit ambiguous though. Like the various blocks correspond to different load conditions and speed but they don't define which speeds or load it looks for. 131 is the target value IIRC. Anything above that means the computer is adding fuel, anything under that means it's trying to subtract it.

Yup, 'block learn' which IMHO would give a good indication (target I thought was 128) fuel trim wise as to what is going on.

Also the O² voltage could be used.

If I were Joe B I would get the exhaust leak fixed first then see what it does.

 

[Joe B]

I can't for the life of me find where it is leaking from the exhaust?!

I hope this is really the problem. Thinking about it, I was slowly having problems and as it got worse, the exhaust leak was getting louder. I am hoping this is the problem.

So now, I have a new dilemma. I can get a new manifold for ~$69 (per side) and I only need one. I get can get a pair of headers for $153. Is it worth the hassle for replacing them both and paying the extra $15? And then, do I have to redo the rest of the exhaust system?

As for the fuel trim, I am going to have to do some research about that to figure out what you guys are talking about.

Two other things, since I'm here, can anyone tell me what this sensor is? I started to pull it out and antifreeze started to pour out. I can only guess it is temp sensor? Does this have two of them? I already replace a different one. There is one more closer to the bottom of engine that looks like there should be a tube attached.

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[lessersivad]

The sensor in the first pic is the knock sensor.

I'm saying the 2nd one is PROBABLY the coolant temperature SENDER for the gauge. If it only has 1 terminal then that is for the gauge. IF it has 2 terminals then it's the coolant temperature SENSOR.