Bad Idle, Help Needed

H

HAMMERHEAD

Member
I've had a bad idle issue for a long time now. Engine idles high, drops to almost stalling and then back up again. Some times it stalls when you put it in gear, sometimes it don't. I have checked all vacuum lines and cannot find a leak. I just replaced the plugs and wires last week.

Once while running, it went into a mode where it idled absolutely perfect with no miss but every time you went to touch the gas it would want to shut off and then it went back into the other mode. Once, a while ago, I changed the iac and it did not help so I put the factory one in.

I have no scan tool,datamater or any type of tuning tools. I need someone to look at my truck and help me diagnose the problem. I would rather them come to my house but I guess I could travel a short distance to their house.

I have read hundreds of post and tried lots of things on my own but it still runs like crap at ide. Wot performance is great. Just fluctiating idle and stalling. PLEASE, someone help........Fred
 
1madgumby

1madgumby

New member
Re: Bad Idle, Help Needed

Carbon build up in egr & even in the (iac) could make it way off. Check that.
 
H

HAMMERHEAD

Member
Re: Bad Idle, Help Needed

Once, I removed the egr and cleaned it even though it wasn't really dirty and the iac too. Even changed the iac and no change so I put the oem one back in. Recently I removed the cap on the throttle body so I could turn the idle up and tried raising and lowering the idle but still have problems. Today it was idling at 2k. Finally got it down but still stalls when you put it in gear.
 
syclonekid43

syclonekid43

New member
Re: Bad Idle, Help Needed

ever figure your problem out? i went to take mine out for the first time in 2 years and its doin the same exact thing yours is.
 
H

HAMMERHEAD

Member
Re: Bad Idle, Help Needed

Truck is still down. I have changed the ecm and put the stock chip,2 bar map sensor back in and truck still dies sometimes at idle. Runs ok but sometimes it will die when u let off the gas while comming up to a stop light. Sometimes it will die when you put it in reverse or drive but not everytime. I sometimes goes into a limp mode where it will idle perfect but will not take any gas. I changed the o2 sensor and that did not help. It idles perfect when u unplug the o2 sensor but is running pig rich. The truck has no check engine lights and it is now at a ac/delco service center and so far they have hooked up a scanner and there are no codes in the computer. They are going to test all the wires and grounds,plugs and try to pinpoint the problem. I have tried three different ecms and it is definitely not the computer. Same problem with all of them
 
ed hess

ed hess

race or get outta the way
Re: Bad Idle, Help Needed

back when I first came on this site I had a mile long thread going that began kinda like what you are describing. Since your sig says stock motor I have to wonder about miles and if its original.

Normally I don't throw out ideas to these type threads but, if its original like mine was... When I eventually pulled the motor apart the intake gaskets had become so rigid that the intake lifted away from the gaskets a little to easy. Since the new motor received each and every sensor, plug wire etc I finally determined the intake gaskets were leaking and were the real cause of my stalling issue. Good luck.

ED
 
Throws

Throws

Active member
Re: Bad Idle, Help Needed

ed hess said:
back when I first came on this site I had a mile long thread going that began kinda like what you are describing. Since your sig says stock motor I have to wonder about miles and if its original.

Normally I don't throw out ideas to these type threads but, if its original like mine was... When I eventually pulled the motor apart the intake gaskets had become so rigid that the intake lifted away from the gaskets a little to easy. Since the new motor received each and every sensor, plug wire etc I finally determined the intake gaskets were leaking and were the real cause of my stalling issue. Good luck.

ED
Click to expand...

Did you use any extra prep when putting it all back together? (gasgaritch? RTV?)

-P
 
ed hess

ed hess

race or get outta the way
Re: Bad Idle, Help Needed

Throws said:
Did you use any extra prep when putting it all back together? (gasgaritch? RTV?)

-P
Click to expand...

Asking me that question I think you missed my point.

Every sensor and ignition part except for plugs from the old motor with stalling issues was reused on the new motor. Pvc valves, hoses and check valves were also reused. The stalling problem did not transfer over to the new motor. If it had then an ignition part, sensor, or other item included previously would have been suspect. Each and every sensor and ignition part including distributo had been changed including all hoses valves etc and the idle stalling issue allways remained.

However to answer your question I allways use "the right stuff" made by permatex on my intake gaskets. And I use it to create a seal on the center front and center rear under the intake.
 
syclonekid43

syclonekid43

New member
Re: Bad Idle, Help Needed

If I have to do all that. My junk is goin back on the trailer. I changed my tps with no difference. I was ready to change the iac, but decided to try and borrow my buddies smoke machine before I go any farther
 
ed hess

ed hess

race or get outta the way
Re: Bad Idle, Help Needed

I have to wonder if those people in this thread that have this problem are having it on high mileage or original motors.

Mine had 105k when this was going on. At that age the intake gaskets had and will harden and become allmost or will be brittle.

After removing the lower intake bolts the intake lifted right off. I would think that if the intake gaskets still had any sealing capabilities there would be some adhesion between the gaskets and the sealing surfaces. However I found there to be none. Hence my conclusion that the gaskets were the real culprit.
 
Don W.

Don W.

Stab it and steer it
Re: Bad Idle, Help Needed

I struggled with the same issue. Photographic proof:

http://www.syty.net/forums/showthread.php?t=50844&highlight=intake+gasket

The above motor was "intake tested with the inner tube trick." I could hear the leak but couldn't find it. Only after removing the lower intake did everything make sense.

Also maybe I missed it but make sure the EGR valve is not leaking.

Fooling with the, so-called but not really, idle speed screw will only mask the real problem if it helps at all.
 
Throws

Throws

Active member
Re: Bad Idle, Help Needed

ed hess said:
Asking me that question I think you missed my point.

Every sensor and ignition part except for plugs from the old motor with stalling issues was reused on the new motor. Pvc valves, hoses and check valves were also reused. The stalling problem did not transfer over to the new motor. If it had then an ignition part, sensor, or other item included previously would have been suspect. Each and every sensor and ignition part including distributo had been changed including all hoses valves etc and the idle stalling issue allways remained.

However to answer your question I allways use "the right stuff" made by permatex on my intake gaskets. And I use it to create a seal on the center front and center rear under the intake.
Click to expand...

Sorry, I should have specifically asked about intake gasket prep. I've got an oil leak on mine after doing a head swap. I think it's coming from the head/block/intake corner on the drivers side. I swear I cleaned both (all 3 actually) surfaces thoroughly with mineral spirits, then used gray RTV (making sure to go up the gasket on the head about 1/2"). I'm pulling it apart this next week.... ugh. All that time only to have something slip by.

-P
 
ed hess

ed hess

race or get outta the way
Re: Bad Idle, Help Needed

Throws said:
Sorry, I should have specifically asked about intake gasket prep. I've got an oil leak on mine after doing a head swap. I think it's coming from the head/block/intake corner on the drivers side. I swear I cleaned both (all 3 actually) surfaces thoroughly with mineral spirits, then used gray RTV (making sure to go up the gasket on the head about 1/2"). I'm pulling it apart this next week.... ugh. All that time only to have something slip by.

-P
Click to expand...

When I had that issue I found the head and deck surfaces were not flat. have both checked and put a 50ra finish on them and your leaks would be gone. The leak on the outside was matched with a leak on the inside that using a boroscope showed oil seeping into no 6 cyl.

I think mineral spirits leaves a residue. Switch to brakekleen or acetone.
 
H

HAMMERHEAD

Member
Re: Bad Idle, Help Needed

Same problem with a/c on. My truck only has 28k and engine has never been opened up. The distributor has never been removed but I changed the module in the distributor and did not help. I also changed the iac and no change. There are no external vaccum leaks and my truck holds 20 pounds of vaccum at idle and my spark plugs are burning perfect.
 
syclonekid43

syclonekid43

New member
Re: Bad Idle, Help Needed

as far as the motor on my truck, i rebuilt it 6-7 years ago as far as piston and rings. all sensors and TB are factory. i did get my buddies smoke machine today and the TB is leaking bad from the shaft plus i hace a small amount coming out of the center of the egr valve
 
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