Weird idle miss !! Please help

[dubbsix]

Hey all.

My bone stock and in need of TLC 89 LX 5.0 is having a weird problem. When it starts and idles.. every now and then it will sound like his has a major miss, but when i get in the car and look at the tach.. the rpm's dont drop and it doesnt seem to miss while driving it.

I am sure the car is in need of something. Im in the process of rebuilding her. I have checked the wires for proper resistance levels, i have replaced the cap and rotor BUT i have not changed the plugs because they looked good.

Can anyone help with a low rpm /idle miss or vibration?

 

[dubbsix]

anyone ??

Can anyone help with this ?

 

[whtpny]

First thing check for codes. Just because the CEL is not on does not mean a code is not there. Clean the idle air control valve. Clean the MAF sensor. I am sure others have ideas as well.

 

[dubbsix]

I've pulled codes but...

Thanks for the reply. I have an auto X ray and it says everything checks out good. I did take the MAF apart and clean it, but i havent done that to the IAC.

 

[Daggar]

Try reseating your TFI module. Use a liberal amount of di-electric grease when you reinstall it.

Check your cap, rotor, and wires for cracks and/or ware.

Reseat your coil input wires (also with di-electric grease).

Reseat your timing lock-out plug as well.

 

[Flavadave4]

Sounds like a faulty IAC.....

 

[dubbsix]

If the IAC was bad would the rpm flux when it seems to miss? The thing with my car at idle is that the rpms dont jump around on the tack, but you just feel this hard stumble every now and a gain.

Can the IAC be cleaned? or is it better to just buy a new one ?

 

[jrichker]

See "Help me create the Surging Idle Checklist" at http://forums.stangnet.com/showthread.php?t=698148
for help with your idle problems. The first two posts contain all the updates to the fixes. I continue to update it as more people post fixes or ask questions.

 

[dubbsix]

See "Help me create the Surging Idle Checklist" at http://forums.stangnet.com/showthread.php?t=698148
for help with your idle problems. The first two posts contain all the updates to the fixes. I continue to update it as more people post fixes or ask questions.

Thanks!

 

[dubbsix]

Is this really a miss?

If i have a miss at the engine wouldnt i see it on the tach? Here is where i am with this issue:

Car doesnt throw any codes
The tach doesnt fluctuate when i feel the "miss" and/or vibration from the motor
The exhaust note is smooth and uninterrupted. No Puffs sounds
The "miss" only happens while idling. No miss is felt while driving

Can anyone help with this? I know someone posted the surging idle check list, but i am not so sure that will help in this case. If the IAC were bad the idle would stick high until i shut it down correct?

Is there a way to test the following:

Motor mounts
harmonic balancer?

 

[jrichker]

Print the "Surging Idle Checklist out and go through it. There are a number of different idle problems that have fixes found in the checklist.

The IAC will flutter or stick and cause an odd surge. A bad TPS will hang the idle high until you shut off the engine. A bad IAC will not do that.

 

[dubbsix]

Looks like there wasnt a problem with my engine and/or electronics at all. I took at look at my mounts today and they looked like this on both sides:

http://forums.stangnet.com/attachment.php?attachmentid=50270&d=1178482780

 

[HISSIN50]

If the miss is consistantly occurring, run a cylinder balance test. The test can pick up anomalies that we cannot.

Good luck.

 

[dubbsix]

I have run all tests on the car and everything passes. I guess im gonna write it off to the busted motor mounts and see if thats really the issue.