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87 350 TBI, I'm lost need help.

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KC88

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Howdy folks, I'm resorting here in hopes somebody could help me figure this out. I'll try to keep this as brief and descriptive as possible.

87 Silverado, 350 TBI, 700R4, 4X4.

Truck will just randomly die, only once that I recall has it done it under a load/my foot in it. Otherwise always at idle or coasting. This problem started some time back, spark tester showed wasn't getting spark. It needed a tune up anyway so I went ahead and did that along with the ignition coil.

Problem still persisted and went with the usual suspects, pickup coil and module. Seemed to work for a while but still random issues. Reached a point where it wouldn't start at all and I got a bad replacement pick up coil. Swapped that out and still have random issues. I didn't mess with it for some time but eventually started driving it some and the problem got worse.

I'm getting fuel, can't find any bad grounds ect. So a couple weeks ago I took it to a friends dads shop for a diagnostic. Said there wasn't enough output from the distributor and recommended that I replace it as he suspected that was the culprit. So I did, made it a couple blocks after the swap before it died, did t do it again after that for about a hundred miles. Two tone wire was in hooked when we re timed it and set at zero..... Money. Thing is it runs like a boss until it dies, but it always starts back up! There's been some times where it will idle/bog down while sitting and once it started thumping like it had a cam chucked in it.

I took it back to his shop and told him what's up, he couldn't find anything but said it did idle/bog down once while it was sitting. Of course it wouldn't die when he's drove it.

So now I've got all new ignition, can't find any bad grounds nor could he. I've never ever had a fuel pump on anything that would just randomly cut out and stop working. Anything is possible I guess right? Could this be a computer issue?

I'm tired of throwing parts at this thing and so is my wallet, any input is much appreciated.

Thanks!!
 
I will be the first to say it. Ac delco ignition control module only. All of the others are crap and can cause these issues.
 
Can you still get these from GM dealerships or do you have to go treasure hunting on the Internet?
 
Just due to age, not because your symptoms definitely point to it, if you have autozones out there, go borrow their fuel pressure tester, and make sure yours is in spec, and stays there.

Hook it up at the fuel filter, or where the lines go up to the block, not at the TBI unit. IMO they are way easier to access under the truck, and less likely to strip them out.

If the pump is unknown vintage, the rubber in tank fuel hose is suspect. I could see a minor tear in that hose causing some odd symptoms.
 
dyeager535 said:
Just due to age, not because your symptoms definitely point to it, if you have autozones out there, go borrow their fuel pressure tester, and make sure yours is in spec, and stays there.

Hook it up at the fuel filter, or where the lines go up to the block, not at the TBI unit. IMO they are way easier to access under the truck, and less likely to strip them out.

If the pump is unknown vintage, the rubber in tank fuel hose is suspect.
Click to expand...


Fair enough! Also for what it's worth I've not swapped the fuel filter on this rig, but I highly doubt that's the issue here.
 
Others have reported that ethanol (apparently) has left water in the fuel filter and caused issues, but I haven't seen that on my truck.

My filter is ~10yrs old, and I'm dropping at most 1.5PSI across it (for TPI that's about 2%)...it's not something I just replace because. :)
 
I would be looking at the fuel pump,similar issue with mine until I replaced the pump,also you mentioned all new ignition parts,be sure to replace the icm as well
 
If it only dies at idle or coast,it might be a vacuum leak--maybe the PCV valve is sticking open,or the EGR valve isn't closing,it could be the power brake booster if it dies when you apply the brakes only too--..
 
^^^^^^
What he said. Check for codes, sounds like an EGR problem. A dirty/bad one one will cause those symptoms.
 
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