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Would a hole in this tube effect idling?


gsumann
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When I pull up to a stop light It drops below 500 almost to the point of shutting off and bounces.

Put when I accelerate it runs perfect.

Truck has new NGK spark plugs and thermostat and the cooling system was flushed last week.

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  • 1 month later...

I'd wonder if your brake booster has developed a bad leak. Does it return to a normal idle after you take your foot off of the brake?? Anytime you press your brakes with a vacuum brake booster, it will affect your idle some, It shouldn't almost kill it.

 

Also, there is a solenoid that kicks the idle speed up a tad when your AC cycles. If that's not working, it could cause a similar issue.

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There could be an issue with your brake booster killing your idle when you step on the brake.

 

Also, If you have working AC; there is a solenoid that kicks up the idle speed when the compressor kicks on that could cause a similar issue.

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There's a switch in the throttle position sensor that tells the computer when it needs to control the idle. I'm not familiar with the setup on the TBI rigs but that's where I'd start. My '95 acted up like that occasionally, fine when my foot was down but stalling at stop signs otherwise, and screwing with the TPS wiring (among other things) seemed to clear it up. I never did quite track it down, mostly because it would vanish each time I tried!

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  • 1 month later...

There could be an issue with your brake booster killing your idle when you step on the brake.

 

Also, If you have working AC; there is a solenoid that kicks up the idle speed when the compressor kicks on that could cause a similar issue.

 

Not the brakes I can have the truck at the light with no brakes applied still the same thing.

 

So I just changed the distributor cap because the it was recommended to me because my truck would not start when it was below freezing but soon at the temp outside got to around 40 degrees it would start up with no problem.

 

But now the idle is worse it will actually drop and try to shut off at idle once the truck is warmed up but it accelerates perfectly.

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  • 3 weeks later...

This problem has happened and does happen to me currently. What I found was my problem is the MAF sensor harness (Seems the ground wire tends to break in the connector).. When the engine starts to behave in this manner 100% of the time (in my case) it has been corrected by a very very very light tapping and wiggling of the harness connector. Engine picks right back up. Now I am not suggesting this is your problem but it may be and is super easy to rule out. Next time the engine starts to lope like that. Pull over, pop the hood and give the MAF harness connector a little wiggle and give the connector a very light tap with the back of a screwdriver and see if that doesn't pick the idle back up to normal 750 rpm and corrects the engine trying to stall when stopping at lights etc..

 

I also believe that the MAF itself can cause issues if its dirty or malfunctioning in colder temperatures. So maybe there is a greater problem in the MAF? Just some thoughts.

Edited by MrEviLDeD
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