93 K1500 5.7 running rough

[cramer_77]

Got a truck at work that has got some problems. Heres the run down, we replaced the engine approx. 19k ago(customer ran it low on oil), replaced distributor and spark plugs approx. 10k ago, replaced cap and rotor 7k ago. Replaced distributor again 5k ago. This time in the shop we have replaced the pickup coil(out of specs), distributor cap, rotor, wires, plugs, both coolant sensors. Whats happening is truck will run extremely rough when cold, then about the time it gets warm truck will smooth right out and run like a champ. Truck ran fine after we replaced all the ignition stuff until it got up to temp, then it wanted to keep dieing. Now, its exactly opposite, runs bad cold, smooths out warm. Didn't know if anyone has ran into this before or might know somewhere to look. Took truck on a drive, got about 1/2 mile down the road and it starts bucking and running bad so i pulled over into a parking lot. Sitting there idling it kept acting like it wanted to die, and the scanner was reading no rpms. Drove it back to the shop, was never able to get above 3rd gear, and it died twice trying to get it back into the shop. Thanks in advance.

[MT-2500]

Originally Posted by cramer_77

Got a truck at work that has got some problems. Heres the run down, we replaced the engine approx. 19k ago(customer ran it low on oil), replaced distributor and spark plugs approx. 10k ago, replaced cap and rotor 7k ago. Replaced distributor again 5k ago. This time in the shop we have replaced the pickup coil(out of specs), distributor cap, rotor, wires, plugs, both coolant sensors. Whats happening is truck will run extremely rough when cold, then about the time it gets warm truck will smooth right out and run like a champ. Truck ran fine after we replaced all the ignition stuff until it got up to temp, then it wanted to keep dieing. Now, its exactly opposite, runs bad cold, smooths out warm. Didn't know if anyone has ran into this before or might know somewhere to look. Took truck on a drive, got about 1/2 mile down the road and it starts bucking and running bad so i pulled over into a parking lot. Sitting there idling it kept acting like it wanted to die, and the scanner was reading no rpms. Drove it back to the shop, was never able to get above 3rd gear, and it died twice trying to get it back into the shop. Thanks in advance.

Any engine codes?
Good hot blue spark to all plugs?
How is the fuel pressure doing?

[jdmccright]

I don't see you checking or replacing the ignition coil. Those usually just up and die, but some do get temperamental before they let go...rough running, missing, or giving off "cold" sparks. Might try a new one. Double check your grounds and other wires, too. When the truck engine is hot it may be expanding enough to make contact with a critical ground wire or sensor.

[cramer_77]

No codes have been set, I checked fuel pressure it was within specs, didn't check the color of the spark(have to do that tomorrow when i get back to work) i did the bench test for the coil and it checks out ok, although, it does look like its possibly the original coil, 200k on the truck all together. My boss talked to a mechanic friend of his today and he is supposed to come by and do a "ground sweep" never even heard of it.

[cramer_77]

just thought i would update some people on this, after having another mechanic friend stop by the shop for a couple of hours, found the distributor at fault. Replaced the distributor and truck runs like a champ. Sad part is that if my boss had listened to me then the truck wouldn't have been in the shop nearly as long.

[MT-2500]

Originally Posted by cramer_77

just thought i would update some people on this, after having another mechanic friend stop by the shop for a couple of hours, found the distributor at fault. Replaced the distributor and truck runs like a champ. Sad part is that if my boss had listened to me then the truck wouldn't have been in the shop nearly as long.

Thanks for posting back how it went and the fix.
But was wondering how you found the problem?

WAS THE DIST SHAFT BUSHING BAD?
What test was done or how did you find the dist problem?
Thanks

[samstone]

I was having the same problem. I noticed that the spark advance under the distributer cap was hard to move. I shot it with wd 40 and then shot some lube in, kept moving it until it was easy and my truck runs like a champ. I got lucky on this one.