88 GMC Sierra 1500 runs great but will die after 15 minutes like clockwork

[will2679]

I have been looking all over to find an answer to my problem and have yet to find anything that helps so I decided to start this new thread.

I have an 88 GMC Sierra 1500 4.3 v6 TBI that runs like a champ for 15 minutes then like clockwork will die. I wait about 15 minutes and then start it up and it will run great again, for another 15 minutes and die. I just bought the truck and now the guy is being all kinds of shady, found he rolled back the odometer etc.....but that is another story.

What I have done.
Hooked up jumper and got ODB1 code 42 no others.
-replaced ignition coil
-replaced ignition control module
-replaced Coolant Temp Sensor
-flushed radiator
-changed fuel filter
-cleaned TBI
-Ran injector cleaner and gas system treatment through the tank.

It still does the same thing. One thing I did notice that right when it starts acting up I noticed the oil pressure gage goes from 45 where it is at start to about 30 then it dies. Not sure if that is just because the engine is dying or what but thought that may be important.

This weekend I am going to replace the oil pressure sensor (just in case) and get the oil changed again. It has not even been 1000 miles on it since It was changed, and only about a month, but whatever.

Anyone have any idea what else I can look at?

Thank you all in advance.

 

[happy 2011]

well you need to do some trouble shooting to find out whats up.

Frist you need to remove air cleaner and run till it dies out. Have someone crank it over for you and see it the injectors are spaying fuel. If not give the computer a wack.(behing glove box)

If you have fuel then check spark. Frist remove coil wire and have someone crank it over spark should jump to coil bracket. (should jump at least 1/2 inch)
If the coil sparks then reinstall coil wire and remove 1 plug wire. get a spark tester or a jumper wire to test spark.

Lets us know the results and will give more info

Once you know what your missing will be a eazy fix.

 

[will2679]

It appears to be spark. I had someone turn it over when it was acting up and there is fuel coming from the injectors. I will try testing the coil for spark tonight when it is acting up and let you know, and thank you for the help.

 

[Z15]

Years ago I had a Chevy van that would often just stop for no reason and it was intermittent but after it would sit for a while would start again and run for days without stalling. I took it to a local Chevy dealer and they could not find a thing wrong. So I keep driving it and then one day it up and died a block from a another Chevy dealer in another town. I was dead on the road and a guy w/pickup pushed me about a block and I coasted into the Chevy dealers lot. I explained what was happening to the SA and what the other dealer did. So he said I can take a quick look and see if I spot anything but if not then you will have to leave it. 10 min later he comes and shows me the ignition switch half melted away. That was the first thing he looked at and he found the problem. Weather the switch was melted or not before that day? He replaced the switch and I never had any sudden stalling ever again and it had been ongoing for at least 2 months.

So its possible you have something along these lines, it gets hot and breaks an connection?

There is a pickup in the distributor that has been a common failure on 4.3L engines but that usually ends up in a no-start again. The magnetic pick up coil is located inside the distributor underneath the rotor and weight and spring assembly. There will be no spark from the dist if this is dead.

 

[will2679]

not even sure

Well I tested for spark, spark was good, fuel was coming out of the injectors.....I came across some extra money so I finally took it to a mechanics shop so they can run some diagnostics. Three days later I call them and they tell me that it has been running great and they are not able to find anything at all wrong with it. I came to pick it up and it has not done it since. They told me they could not charge me for it since they didnt do anything, so that is a plus. Drove it for about 20 minutes this afternoon and really did not have a problem. Not sure what to think about that. I am gonna get a new distributor, plugs and wires, just in case but not really sure what to think about this.....It really does not make sense. Thank you for the reply about the ignition I will check the ignition switch as well. Hopefully it is fixed and dont have to worry about it again. It was really a baffling problem. Thank you all for your help and I will let everyone know if it happens again.

Hopefully my experience will help someone else with the same issue.

 

[dirtclod]

A consideration

A friend had a similar problem, although it didn't show itself like clock work, as yours does. He found a rag in his gas tank. Apparently, a previous owner had lost the gas cap. I think the chances of this being your problem are slim, but it is a possibility.

 

[Z15]

For it to be intermittent it almost has to be electrical.

I know you said you put in new parts but are those new parts any good. Lots of cheap imported junk electronic parts. First thing I would do is make sure all your ignition parts are genuine AC Delco or GM and not part made in China. Note-Many well know name brands have cheaper imported parts available and unless you demand USA made parts (if available), you won't get them automatically. The GM parts might cost more but they are worth every penny. I have several customers who own/operate their own repair shop and they can all tell you horror stories of failed brand new imported ignition parts. Make sure the ignition parts made in USA or Canada.

 

[john1989]

We have a 89 SLE that was doing the same thing...took my 30 mintues of driving.

First we put on a new dist cap and rotor and replaced some gagiet down under the dist on the intake manifold, electron item that was OEM to 1989 (no help)

Then we replaced the plugs and wires (no help)

Then the gargae finally listen to me and kept the truck running unitl, you guessed it.

They replaced the engine module, i think that is what they acalled it, computer part...under the glove box. What was happenning if you look down the throate of the carb you will see the injectors will start to "pulse" not good.

Runs fine now...no worries

 

[will2679]

Eureka!!!

Ok I finally figured out what it was. The problem appears to be the guy that owned the truck before me was a moron.

He replaced the passenger side speaker but instead of installing it correctly it was resting on the ECM. It ran great for the mechanic, he turned the radio off. I ran it with the radio off and it ran great forever. Turned the radio on and bam 15 minutes like clockwork. It took me a minute to figure out why the radio would cause that.

It appears that the magnetic field from the improperly installed speaker was messing with the ECM after about 15 minutes. I know others probably will not have this problem but hopefully this helps. Thank you all for your help!!!!