'88 Chevy 1/2 ton, 305 stalls when stopped.

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I just purchased this truck and it starts and idles just fine, no roughness. But about 30 seconds after you start it, it just dies. It also does this at nearly every traffic light, twice at longer lights. If I
punch the accelerator as it is dying, it will come back to life. It runs just fine as long as I don't stop. It stalls less often if I put it in neutral while I'm stopped, but it eventually still stalls.
The seller says that this just started happening after he let it sit for a month or more without running. This engine has trottle body injection TBI.
It seems like a fuel problem to me. I guess I need a plan of attack. Here's what I plan:
1. Add some Iso-HEET to the tank to remove any water.
2. Install new fuel filter.
3. Check for fuel pressure. I'm not quite sure how to do this - even after reading the Chilton manual.
4. Install new pump if the pressure was bad, otherwise look to the injectors.
Am I heading in the right direction? Can you help with some suggestions? Will Seattle make the playoffs?
Thanks!
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Check the alternator. It has been my experience that the symtoms you describe have been because of low charge. When you come to a stop and put on the brake lights it draws so much power that the ignition suffers and dies. Check it out and you will see. :)
-- Regards Gordie
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wrote:

Thanks Gordie but this happens even if the truck is idling. It only seems to happen after it is warmed up. I can put it in park, start it up and it will die after about 5 minutes. If the engine is warm it will die sooner. It will die more often if it is in gear, like at a stop light.
I've checked the throttle position sensor, the idle air control valve, the MAP sensor, I replaced the oxygen sensor, I disconnected the engine coolant temperature sensor and the rpms increased so I assume that it is working.
I look at the injectors when it dies and they are continuing to spurt right up to the last, which indicates that it probably isn't a fuel supply problem. Under normal conditions when you turn off the key, the injectors stop immediately.
This has the guys at the local parts store stumped, not to mention me (I only know what I read in the manual, and that ain't much).
I'm starting to think that it might be ignition system related because it acts like someone just disconnected the ignition system. But if I give it some gas, it comes back and if I keep the rpms up, it doesn't happen - which doesn't sound electrical to me, but I'm a novice. I'm starting to think maybe the ECM (brains) is bad.
Any more advice? Anyone? If I haven't fixed it by Monday I'm taking it in to the shop.
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Not sure if you did this or not, but have you checked the plugs and wires? I had an AMC Eagle a very long time ago that didn't want to stay running if I didn't have my foot on the gas (can't remember if it had anything to do with it being warm or cold). Gave it a tune up, and never had a problem again.
HTH Bill
wrote:

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Thanks Bill. I know how to pull the plugs and check them out, but I'm not sure how to check the wires. The way I used to do it many years ago is open the hood on a pitch dark night. If I saw a lightning storm on top of my engine, I knew it was time to get a new set of wires.
First I think I'll check out the knock sensor. Someone suggested that if it gives a false knock, the computer might retard the timing until the engine stops.
Thanks again.
wrote:

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Check and clean the EGR valve.
Ed

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Thanks Ed. Checking the EGR valve is involved and requires a vacuum tester that I don't have. Before I do it, could you give me a short description of how EGR valve failure would cause the engine to die only while idling? Meanwhile I'm going to check the timing.
Thanks again, Dan

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if it sticks open, exhaust gas gets into the plenum and dilutes the A/F mix to a point that is barely burnable. above idle, the ratio of exhaust gas to A/F is much smaller. A properly functioning EGR valve is more or less octane adjustment on the fly. it does this by diluting the A/F mix at cruise to slow it's rate of burn (the Octane rating is a comparison of the burn rate of gasoline and pure octane gas, less than 100 octane and the gasoline is burning faster, higher than 100 and the gas burns slower) so more timing can be run to get better gas mileage.
-Bret

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Thanks Bret. Some of that is over my head, but I get the drift.
Just to reiterate (if I didn't iterate already) the engine doesn't idle rough, it just dies all of sudden, as if someone disconnected the distributor or pulled on the choke.
I located a stripped thread on a distributor cap screw, actually on the distributor itself, (I didn't do it, honest!) so I'm going to take care of that now. I guess I'll just ream out the dist cap hole and tap the screw hole in the dist to the next size screw. Someone tell me if this is a bad idea.
Off to the hardware store. Thanks again!

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Well on Saturday I took it to a mechanic who was nice enough to take a look at it for nothing. I told him everything I did and he couldn't figure it out, but suggested replacing the timing chain if there was too much play. I checked the play and it is 10 degrees - a lot. So I'm replacing the timing chain and I've got down to the crank pully. I've got the 3 bolts off and now I'm trying to get the center bolt off (the damper bolt) but I can't keep the crank from turning.
Any ideas?

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it should zip right out with an impact wrench... I'd suggest using a chain wrench to hold the crank, but it would just ruin the damper.
HTH, Bret

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Thanks Bret! I solved that problem by taking the fan belt, wrapping it around the existing pullies and doubling it back on itself at the crank pully so that it binds on itself - sort of like a huge strap wrench. That's about the best I can describe it. It worked. Then I about screwed up my pulling tool and the center threads on the crank when I tried to pull the damper without a bolt in the center hole. I ended up forcing the center post of the puller into center hole on the crank. Luckily the threads on the puller were big and deep enough that I could recarve the threads with a Dremel tool. Crazy. You'd think they'd make a nice big cone shaped focrum for the puller.
Anyway I got the sloppy, old chain and gears off and now I have the new ones on - most of the way. The crank gear doesn't seem to want to seat all the way (and I'm not sure where "all the way" is). This doesn't surpise me since the old one was so hard to get off.
How am I supposed to get the crank gear to seat all the way? I tried putting the old gear on top of the new one and banging it with a hammer - so I wouldn't mar the new gear. It helped but it still seems like it needs to go another third of an inch or so to seat all the way.
Thanks, Dan

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It is an old problem with an old solution. Merely jam a rag into the balt and pulley and you will be able to get the bolt loose. The lump of rag cannot get around with a tight belt and it is incapable of harming anything. Try it - it works on blets and also on chains.
-- Regards Gordie
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that trick won't work with the spring tensioned serpentine belt on an '88 or newer truck... the tensioner will just allow the rag to go around the pulley relatively unimpeded.
-Bret
wrote:

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did i get into the conversation late or what lol
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On Tue, 23 Sep 2003 16:55:08 -0400, "Bret Chase"

LOL guess that's what I get for being stuck in the past. We don't have serpentine belts on our vehicles. 86 GMC 1/2 Ton 84 Dodge 1/2 Ton
-- Regards Gordie
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what you may have a valve on your fuel rail for testing your pressure if not youll have to run the gauge inline if you think your pump is not putting out enough pressure sure you can change it but you also have a fuel pressure regulator that might be the prob also check your vaccume lines i had one that did the same thing and i went crazy changing this and that but it ended up being a line disconnected is your truck equipted with a MAP sensor sometimes this can cause the problem when your truck stalls try pulling the codes from the pcm more info on this if needed.it may just be a bad sensor Id pull the codes check the fuel pressure and take a look at the vacuum lines before i went and spent money changing parts i didnt have to
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Sorry I haven't checked in sooner, it's taken me 2 days so far to get the new timing chain/gears on. I should know this AM if it solves the problem.
As far as stopping the crank in order to break loose a center bolt - the suggestion about a rag won't work if you have the water pump off, which I did. My idea about using the belt as a giant strap wrench worked well, but a mechanic gave me a better idea that also involves a rag. At the starter, remove the cover that exposes the flywheel - mine was already exposed. Clamp a pair of vice-grips onto the flywheel using a rag in the jaws to prevent maring the flywheel. Now either way you turn the crank, the vicegrips will eventually be stopped by the housing and you will be able to loosen or tighten the center bolt.
This thread is a bit jagged, but I'm trying to restart it when the situation changes - also to prevent the posts from getting too big and the responses from extending too far to the right. Probably violating some rule about that.
It turns out that the auto supply store sold me the wrong damper puller for my engine and it darn near messed up my center crank threads. I got the right one and it works like a champ. I then had a problem getting the new crank gear on. Someone suggested heating it in a 200 degree oven for 30 minutes, but that didn't work. Someone at the auto supply store suggested getting a longer bolt and using spacers/washers to pull the gear on using the center bolt. This worked, but the side effect of torking on the center bolt was that the two gears were no longer aligned. I eventually got them so that the dots lined up. Then I scraped the old gaskets off and got the new ones ready to install. I discovered that I couldn't put the timing chain cover on, due to the way the oil pan gasket was installed. Eventually a mechanic told me that I'd have to drop the old pan, which I did. Out of daylight.
So that's where I am now. I think I'll replace that oil pan gasket while I have it off. I suppose it is leaking at least a little because there's fresh oil on the outside of the pan.
Also, before I took this apart, my timing light said that... I won't get into that, just let me ask, what is the time supposed to be at idle for an 88 Chevy 305 pickup? My book says 4 degrees BTC if I read it correctly.
Thanks, Dan

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DAMN!!! THAT WASN'T IT!!!
I finally got it back together and it runs pretty much the same as it did before - only it doesn't seem to stall as often - and never in park. So it wasn't the timing chain!
In the process of closing things up, I found a sensor that was disconnected on the lower right of the block, right near the bottom - about halfway back. I connected it after I got the truck running again and of course it didn't solve the problem. Anyone's guess as to what it might be? If it's a crank sensor, I don't think I tested it. I couldn't find a crank sensor and the guys at Schuck's said that this model didn't have one, but the manual says yes. It looks more like an oil pressure sensor, but I'm pretty sure that's on the right side. Anyone know for sure what this is?
My next plan is to adjust the timing. The numbers on the scale weren't visible before, but now they are. Apparently I got 14 degrees BTC on my old timing light, but the mechanic with his timing light said that it was right on. He didn't say what the spec was, but the way I read my manual the spec is 4 degrees! Could my timing light be off? It is pretty old but it doesn't seem like it would fire late under any conditions. I'll try adjusting the timing and see what happens.
After that, I'll run it by a trany guy. Sometimes it shifts hard (whiplash kind of hard). He can at least tell me why that is and maybe come up with an idea about the stalling problem.
If that doesn't work, I'll take it to the repair shop - like a normal person would. "Normal" - what a dismal fate!
Steve, thanks for your input! I don't think this is fuel supply problem because when it fails, I can see the injectors spitting fuel right up to the time it finally stops. Also the plugs indicate that it is running rich. If you still think it could be a fuel supply problem, let me know. I've checked all the vacuum lines multiple times - I even checked the EGR system per Ed's suggestion. The MAP sensor checks out (as does every other sensor I could find). The PCM or computer does not return any codes. If I disconnect the MAP sensor while it's running, the computer will return a code, so I know that it is returning codes.
Thanks everyone for you inputs!
Dan

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