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1993 TBI 5.7 dies while driving

35491 Views 48 Replies 19 Participants Last post by  Giio-03
hey guys I have a 1993 Silverado 5.7 350 throttle body injected automatic truck. the problem is that it dies while your driving it down the road completely random it seems. when it dies there is no rough running process before or after and it starts right back up after turning the key off then back on. I have replaced : coil, plugs and wires, complete distributor, timing chain, intake manifold gaskets, EGR ,vacuum hoses everywhere , fuel pump ,fuel tank ,fuel filter. I have also installed a rebuild kit on the throttle body and rebuilt the injectors as well. I have had this truck for some time and am a heavy equipment mechanic by trade. I was told by a friend that it may be clogged exhaust because it smells like its running rich and has no check engine light its pretty random when it does die. any help would greatly be appreciated and I will answer any other questions you have as fast as I can thanks!
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no codes and no check engine light. it seems as if when i unplugged my water temp sensor it would idle longer but its acting so random i don't know if it is related at all. i installed a new coil and drove it for about 25 minutes so far it hasnt died yet , but i'm not holding my breath because it died once or twice just after i installed it in the shop at work. however i noticed that the intake manifold has been leaking oil since i installed new gaskets a few months ago and the oil was somewhat low, i don't know if it is related or not. i refilled the oil.
Did you ever check the coil wiring all the way back? And engine ground? Just really sounds like a broken wire or bad connection to me. The map could be acting up but idk if it would die that fast.
I'd have to second apcnc, it sounds like a bad ground somewhere, or maybe a wire shorting. I say let it idle and dont the touch it, just turn it over and wait to see how long it takes to die. I'd polish off as many ground points as you can find for good measure just to eliminate that, and disconnect any systems that aren't essential to the truck running, and see if that helps any. Sometimes it's the weird stuff that gets ya. Does the check gages light or any other light come on at all?
If you have a little electronic knowledge, you can download winaldl and make the OBDI to serial/USB cable. There are schematics for it online. That's what I use for my TBI car and it helps a lot to watch "realtime" data from the sensors. I can't say it's realtime completely because the communication is so slow it only gets information once a second vs the new stuff which is fast.
Without having a code to go off of it could be tricky as you've found out.
Is the 12v to the ECM strong and consistent? I would follow an electrical issue as the cause. If its a rich condition causing the stall, you should be getting a manifold pressure high code (can't remember the number).
I had that a lot when I was tuning my engine and trying to run an aggressive cam with the stock converter and maintain a 700 rpm idle. The ECM will try to prevent stalling but since it's old technology it swings from rich to lean, rich, etc until it eventually dies from either overly rich or lean condition.
Does it die while driving or just at a stop? In park, or in gear? When it dies, does the fuel pump continue to run for 2-3 seconds?

Edit: read the original post and answered most of my questions, sorry.
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I've found and repaired several bad wires / grounds on mine and think "This is it!" only to have symptoms appear again. But repairing the bad wires was a necessity anyway...

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it dies at random no matter what you do. Over the weekend I let it idle, took it 45ish minutes to die. I went back to the truck and fired right back up an died before I could walk around to the engine bay. Then I drove it home from work about 4 miles to my wife's work then home another mile or so and it never died. We went out to eat and it died 4 times before I made it back home 3 or 4 miles usually when i'm in the throttle in gear with the truck pulling its weight ,however it has died with my foot off the throttle and it has died at a stop in gear and in park. The issue is completely random with no codes or no check engine lights ever. The check gauges light comes on when it dies as it should ,and goes off when it starts back up. The truck is very very hard to start if you try to start it without cycling the key off first. if the key Is cycled then it starts as it should with ease just one or two cranks and vroom runs perfect with full power and does not miss or sputter.
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Cycling the key will make it re-prime the fuel pump, vs just cranking it makes it not prime again. So, fuel pressure loss?

Hm, maybe not the pump itself, but the wiring to the pump? I may have missed it, but check anything electrical related to the fuel pump - the fuse/connection, relay/connection, the harness all the way back to where it plugs into the pump. I had my harness in my 02 Trailblazer develop a short and it just suddenly shut down and that was it. Thankfully just had to fix the harness and not drop the tank to replace the pump.
If that is the case maybe try replacing the oil pressure switch located above the oil filter? Besides the 3 second 'key on' pulse of the fuel pump, I can't say for 100% but in the 80s the fuel pump was also triggered off the distributor reference pulse as well (I've had the fuel pump prime while rotating the distributor after installation before I set the timing). Once the engine is running, the oil pressure switch takes over to keep the pump relay held closed. If this were not the case, the fuel pump would stay running if the engine dies but the key is left in the run position. Likewise the fuel pump would not stay running because it only has the 3 second prime when turning the key.
You might also want to check the wiring to the pressure switch, maybe the wire has contacted the manifold and is causing issues.

While I know it's not the ECM you are running(7747), they are similar enough that switching around a few wires would make them the same.
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I believe I have found the culprit. The HEI module in the distributor is malfunctioning, its getting to hot that it gave me a blister just touching it. I am not sure what is causing these to go bad. I bought a pretty nice billet distributor the first time it went bad ,and the second time I got a oem brand cap button and HEI module. Just gotta figure out what is causing the problem now.
Keep us informed, it's great that you are narrowing it down.
Another thing I was thinking, maybe there's some gunk in the fuel tank? Funks gets sucked up, clogs the filter, kills the truck. Then when the pressure is lost, gunk settles, and re-priming sends fuel back up the lines, and truck runs till the gunk gets sucked up?
I'm probably thinking too much into it, but on the up side, if you drop the tank and clean it out, worst case scenario you end up with a shiny clean fuel tank know, unless you have my luck XD
You mean the ICM (Ignition Control Module) under the distributor cap... Shouldn't have HEI on a 93.

Buy a good ICM not a cheap one...heres the one that I have...

I also considered this one...

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I suppose you could verify by unplugging the tan/black bypass wire and starting it up. If it doesn't die then you found your problem. Makes sense though. Hope that's what it is, it's an easy change. Don't forget to apply heat-sink grease between it and the distributor base. If that is not there it might be part of your problem.
COMPLETELY FIXED : after installing a new Ignition control module the truck stopped dying randomly ,but then developed a rough idle. I then warrantied the entire distributor which had a lifetime and was pretty new anyhow. that completely .fixed the truck. runs like a brand new one now super smooth.
getting new parts that are bad can make for a real head scratcher
a good ending to a long ordeal. Way to stay with it.
Did you ever figure out what the issue was? I'm having the exact same issue on my 88.
If you actually read the thread... you'll see that his issue was a faulty (newish) Ignition Control Module
While recently driving on the highway my 1994 TBI 5.7 engine just died. Happened before back in 2013 so I was pretty sure it was the Ignition Control Module (ICM). Took it to my local shop and they confirmed it was the ICM. I think they said they determined it was the ICM because it did not provide voltage to the coil as expected. Anyway they replaced the ICM.

Next day while driving, the engine quit but then I was able to immediately restart it. Day after that it quit twice similarly. Returned to the shop where after some time they were able to reproduce this intermittent engine dying problem. They replaced the ICM again and this one has been working okay for a couple days now.

In summary, a new ICM may exhibit intermittent failures.
I noticed your blog from 2016. I have the same truck, 1993 5.7 also is randomly stalling, usually when I stop or just start to accelerate after a stop. Did you ever find out what it was?
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