1988 Silverado 350 TBI Dies When Hot

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59woody

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Hi!

New to the forum...hoping for some help!

I've got a 1988 Z-71 Silverado with the 350 TBI. The truck runs like a champ when cold...then will just die after it gets hot...could be at idle or going down the road...won't start again until cool...maybe an hour..maybe a day..

Installed new cap, rotor, ICM, plugs...has fuel when cranking...appears to have spark..but wont fire....After she cools, fires right up...

Don't know where to go next....

Any ideas??

Thanks!!
 
is the vehicle equipped with a check engine light and if so is it on? How about the crank position sensor? any indication of flooding when it starts back up, lots of black smoke?
 
truck has a check engine light...its been on for about 10 years...(was originally an O2 sensor)

There is black smoke on restart if I had been trying to get it running for a while before. If I just wait it out, then no black smoke.

It doesn't appear to be a flooding issue, more of an ignition failure of some type....even though it appears to have spark, wont even pop when spraying ether down the intake throat.

Let it cool, and it starts in 1/2 a crank...
 
I would start to see how many codes you have before guessing what the problem is, post them here when you can. if you have other codes you'll never know if you ignore the light
 
Find out what those two codes are. You may need to take a close look at your EGR valve. I'd remove it and make sure the pintle isn't carboned up. If so, clean the carbon off and either suck on the vacuum hose or blow on it to see if the diaphram is holding vacuum. Make sure to take a stiff piece of wire and clean the passage on the intake where it's bolted on too. It can also become clogged with carbon build up.
 
Nothing revealing with the codes...12 is diagnostic mode, 15 is coolant temp/low temp....

Is there anything that can change the ignition timing when it gets hot...can a crank pos sensor change??? anything inside the distributor???

this is not a subtle change when it happens...it just shuts down right now and wont even pop when trying to restart...when its cold, it runs perfect...

Please help!! I don't want to send it to the crusher....
 
Let's get to that code 15. Are you running the engine without a thermostat? If so, put one in. I THINK the original temp stat is 195. If you do have one in there, it is probably stuck open and that can cause an engine not to run right as it takes longer for it to get up to operation temp. One other thing I thought of is if it's an automatic with overdrive. If so, it could possibly be the torque converter lock up switch. Unplug it and see how it does, if it's automatic. It SHOULD be located near the top of the transmission.
 
I agree with Chuzz, see whats going on with the thermostat. The crank sensor may be failing when hot.
 
The truck has a thermostat that is functioning correctly. There is no indication of any overheating prior to dying...

The truck runs perfect cold and all runs great for about 10 miles down the road...then nothing

Will an overheating crank sensor cause instant shutdown?
 
I'm not saying that your thermostat is making the engine run too hot. What I'm saying is that if it's stuck in the open position, it won't reach the proper operating temp.
 
I get that...but running "cold" will not cause it to suddenly die....but, the thermostat is functioning correctly..gets to proper operating temp in short order and stays there...
 
if the sensor fails when hot the engine will stop running, check the harness going to the sensor first
 
What is the failure mode when this happens...the truck still has spark...does it just throw the timing off??
 
I recommend you try google with this as the search "crankshaft sensor failure symptoms"
 
That search revealed that the 1988 model does not have a crank position sensor
 
Is that a carburetor or throttle body? Almost sounds like it's vapor locking. How close is your fuel line to the exhaust and exhaust manifold?
 
lots of hits with similar problems by using "stalling tbi hot" as the search
 
its a tbi...not vapor locking...fuel is spraying out of injectors....spraying ether directly into the throat yields no response...not even a hint of ignition.....when cools, if fires up immediately.

The truck has 180K miles..never an issue before...just started doing this out of the blue...
 
Just for s--ts and giggles, pull your control module and have it tested. They can break down and cause a no start situation when they get hot. This is what I'm referring to and THINK it's attached to the distributor. http://www.autozone.com/autozone/pa...terByKeyWord=control+module&fromString=search It's due to thermal expansion. Your local Autozone or Advance can test these for you. At least, we did when I used to work for both of them. Just depends on who you ask in the store nowadays. They hire young kids who don't know diddly about anything. That's one reason I left so many years ago. One other stupid question I have is whether or not this truck is automatic and if it had an overdrive transmission (R400)? I THINK that's the one I'm referring to. Anyway, it's got a torque converter lockup switch on it that can go bad too. When they get hot, it won't let the transmission shift down properly and will kill the engine. Once it cools off, you can drive again. IF you have an AOD tranny, unplug that switch and see what happens. They're not expensive, but unless you do it yourself, replacement is, because of the labor involved. Driving it with the switch unplugged will cost you a little bit in mileage, but it won't hurt anything but your wallet!
 
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