92' idle problems

[hotrod310]

My truck is a 92 model silverado with a 5.7 automatic 2wd. Lately I've noticed that it occasionally wants to "miss" at idle. Sometimes its a hard miss that will cause the engine to stall. This "miss" occurs usually when the trans is in gear and i'm sitting at a red light. When the rpms are up it doesn't happen, only at idle. The ignition module was replaced about a year ago and i recently installed new plugs and wires. Could a bad pick up coil cause this miss?

[j cAT]

Originally Posted by hotrod310

My truck is a 92 model silverado with a 5.7 automatic 2wd. Lately I've noticed that it occasionally wants to "miss" at idle. Sometimes its a hard miss that will cause the engine to stall. This "miss" occurs usually when the trans is in gear and i'm sitting at a red light. When the rpms are up it doesn't happen, only at idle. The ignition module was replaced about a year ago and i recently installed new plugs and wires. Could a bad pick up coil cause this miss?

since this is only at idle the vacuum leaks/pcv hoses etc effect idle..if you had misses at the high rpm/load then I would look at ignition.


fuel supply to engine is a possibility..

[hotrod310]

Thanks j Cat. I will check my hoses again to see if there are any problems. Wouldn't a vaccum leak cause a consistent idle problem? My truck idles fine except for the occasional hard "miss". It's like it just stumbles over itself. I'll update you next week.

[2000CAYukon]

I have been fighting the same issue on my 90 GMC K1500 5.7 4L60. With a timing light on it, I can actually see the timing jump or move when it stumbles. I tried a known working dist and that did not solve my issue.

I have been kind of busy at work the last few weeks so I have not had much time to work on this. In my case, I don't suspect ignition since it only happens at idle.

In my case, the engine has 147K on it and the TBI is original; although, I did replace the injectors at one point when they started to drip. My cat is also original and the exhaust back pressure was normal.

I hope you figure this out because it has been driving me nuts.

Good luck,

//2000CAYukon

[hotrod310]

Yes, it is very aggravating. My engine has 236,000 miles on it. I have replaced the timing chain at 220,000 and put in a new oil pump. I recently put new intake gaskets on it and a new knock sensor. I also replaced the filters on the fuel injectors but didn't mess with the fuel pressure regulator. I have noticed that the miss is worse when the truck hasn't been run in a while. When i first crank it up it's noticably much worse. I flipped the top on the breather because i felt it would allow the engine to breath easier and maybe help some on the fuel mileage which is terrible. The torque converter hasn't locked up in like 6 years because the trans is wore out. Anyway, i replaced the ignition module a year or so ago and think i put a dist. cap on it about 3 years ago. I really need to inspect it because it may be my problem. What do you think?

[jdmccright]

I'd suspect plug oil fouling. Pull them and inspect for heavy residue, soot, or oily appearance. If so, you could have worn valve guide seals.

[j cAT]

Originally Posted by hotrod310

Yes, it is very aggravating. My engine has 236,000 miles on it. I have replaced the timing chain at 220,000 and put in a new oil pump. I recently put new intake gaskets on it and a new knock sensor. I also replaced the filters on the fuel injectors but didn't mess with the fuel pressure regulator. I have noticed that the miss is worse when the truck hasn't been run in a while. When i first crank it up it's noticably much worse. I flipped the top on the breather because i felt it would allow the engine to breath easier and maybe help some on the fuel mileage which is terrible. The torque converter hasn't locked up in like 6 years because the trans is wore out. Anyway, i replaced the ignition module a year or so ago and think i put a dist. cap on it about 3 years ago. I really need to inspect it because it may be my problem. What do you think?

with as I suggested you check the vacuum...you do this with a vacuum guage...this is like checking your blood pressure...much can be revealed by the observed gauge needle movement/readings !

[hotrod310]

Originally Posted by jdmccright

I'd suspect plug oil fouling. Pull them and inspect for heavy residue, soot, or oily appearance. If so, you could have worn valve guide seals.

Plugs are new. Pulled them again to check them and not a drop of oil. I need to check for vaccum leaks though like jcat suggested. Thanks

[hotrod310]

Did you unplug the connector on the firewall? If you did then I would suspect your knock sensor is bad 2000CAYukon.

[j cAT]

Originally Posted by 2000CAYukon

I have been fighting the same issue on my 90 GMC K1500 5.7 4L60. With a timing light on it, I can actually see the timing jump or move when it stumbles. I tried a known working dist and that did not solve my issue.

I have been kind of busy at work the last few weeks so I have not had much time to work on this. In my case, I don't suspect ignition since it only happens at idle.

In my case, the engine has 147K on it and the TBI is original; although, I did replace the injectors at one point when they started to drip. My cat is also original and the exhaust back pressure was normal.

I hope you figure this out because it has been driving me nuts.

Good luck,

//2000CAYukon

this could be the ignition module...but usually it should have totally died by now..since it has been 2 months ago..

these ignition modules usually go 175-225,ooo mi...sooner if wires or cap had arcing..