Low Idling and Occasional Stall

SeanC

Registered User
Just picked up a 93 SC Auto with a new long block (8000 miles on it) After driving it for a few days I noticed that the cars idle while in Drive or Reverse sits at about 400 RPM. Sits at 600 RPM while in Park/nuetral. It stalled out a couple time while turning into a parking space. Guessing the PS load brought the RPMS below 400. Anyway, my question is: Could this be an IAC issue, MAF sensor or do I just need to turn the idle up? If just the Idle can you tell me were the adjustment location is?

Anyones help is much appreciated.
Thanks
Sean
 
underneath the white, rubber nipple there is a set screw. Screw it in or out to adjust idle speed.
 
Forgot to also mention that it has a rough time starting when warm. Usually cranks 5-8 sec before it turns over.
 
Funny you mention battery. It did feel like it did not have much juice to restart. Battery is 3 years old but it was abused since it sat for long periods of time and had to be jumped each time it started. Might be a good investment even if it's not the problem!
 
sounds like you need a new battery, and a new ps pump mines doing the same thing i go to turn and it almost dies. but yea turn that set screw on the bottom of the tb stop and that should raise your idle.
 
Will due. New Battery this weekend for starters. Iwill fill you in after I'm done. Also the MAf is before the bend that shoots down into the wheel well.

Thanks all for the direction. Out of curiosity, does anyone know how the batterty affects the idle? Just curious.....

Thanks
Sean
 
Out of curiosity, does anyone know how the batterty affects the idle? Just curious.....

well, your alternator works much harder to charge the batt and it will takes up a few hp to do so.... therefore lower idle speed.
 
Ok, Got a new battery in it. Other than it cranking faster, it still has same problem. It cut off on me yesterday while parking and gave me a pretty rough time starting back up. So I guess two things. I would like to pull the codes. Used to be able to do it with a jumper on my old trans am. (not sure on this one) And I cannot find the idle adjustment (would like to up that until I figure out the problem). Anyone have a pic or diagram sitting around.

Thanks everyone.
Sean
 
Adjusting idle speed

Sean-

To up the idle, look on the in board side of the TB, next to the SC. Now look for a rubber cap, about mid drift of the body. You will find an allen head adjustment screw there. Counter clock wise to raise idle and vise versa to lower.

Hope this helps.............

Butch
 
MAC intake...

another thing to try is to turn your MAF off center a bit.. about 1/4"-3/8" counter clockwise..

i used to have a MAC CAI in mine before, and i had to move it around a bit to optimize the throttle response & idle also.
 
Ok,

Found the idle adjustment. No rubber cap no allen head screw. Seems the the previous owner somehow sheered the head of the screw of. Was able to grab it with a pair of grips and make the proper adjustment. So looks like my stalling issue has been resolved for now. Still wanna look deeper into it though. (Thanks for the detailed location instructions Butch) Also thanks for the link to the Rangerstation website GSXR.

Appreciate the help everyone.
Sean
 
I do agree that your problems sounds like a power related electrical problem. If it comes back the stalling could be coming from a short and the hard starting can be caused by an old weakened engine block ground. There is a chance that the electrical condition may be combined with a fuel related problem like FPR or fuel pump.

The best thing to do is to duplicate the error and locate the short. Do you have a scan tool? If so run the fan PID loop. Does the engine shake and rattle at low idle when the fan is on? Does the fan actually work?

Another fan that can be problematic is the defroster fan. Is the fan running at a fast speed? Do you smell burning when going on a highway?

Lets talk about the ground wires a little. I have also seen cases where starters were not re-built correctly. I would get the starter checked (for free like in the AutoZone commercial) then I would inspect the ground wires.

Ford is notorious for under-sizing ground wires in T-Birds. They are minimally sized at best. When I put in my big engine I installed a high performance starter to turn the engine. The starter struggled and drew more amps than usual. The ground wire was not able to support this current draw. Many a time I would turn her off in a parking lot and have to wait 10 minutes to start her again. I replaced the ground wire with a zero gauge wire and that problem went away.

Now I am not saying that the ground wire is your only problem because I ma sure it is not. Because I am sure it would not cause the stalling. That is an electrical or fuel problem. But the ground wire should be looked at if the starting problem continues after the stalling problem is fixed.

Good luck...

J.Miller
Please stop by http://www.eastcoastrollingthunder.com/ and say hi. You are welcome to come to our car show next month!
 
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