Cold Start-Up Idle Surging… & Shut Off.

[motorhead]

This has developed since the cold weather kicked in. Yeah, this car is temperamental… heavy on the mental.

Basically, the car is searching up and down over and over again. 700-1400-650-1300-710-1410-… and so on. And occasionally the thing will shut off when the RPMs drop low enough.

The IAC has been reset, is kinda low @ 13-14. But it is better than the 45-56 I had before. TPS is at .43v

Is there anyway to tune this out? Or am I looking at a new IAC motor?

PS. The car idles great when cool and idling in gear, kinda like the load. Hmmm….

 

[FJM568]

Sounds like a vacuum leak after the MAF somewhere...Check your MAF pipe and all the hose connections, and check your TB to doghouse gasket as well as the vacuum block gasket...And obviously all the vacuum hoses...

Are the rpm oscillations kind of slow or are they fast, i.e., idle up and down slow or fast???

Also, whose chip are you running???

 

[motorhead]

Originally posted by FJM568
Sounds like a vacuum leak after the MAF somewhere...Check your MAF pipe and all the hose connections, and check your TB to doghouse gasket as well as the vacuum block gasket...And obviously all the vacuum hoses...

Are the rpm oscillations kind of slow or are they fast, i.e., idle up and down slow or fast???

Also, whose chip are you running???

Hmm... the maf pipe looks good... just reinstalled it the other day. Triple checked it.

I'll break out the propane torch later and send some gas around the dog house. Check for an idle speed increase.

The idle is quick up and down. Over and over.

I am running a Jay Carter chip.

Thanks,

 

[T-Type Mike]

I was having the same persisting problem until last week when finally I was able to diagnose it... My chip is Fubar'd. I swapped in my 110 race chip and all my problems went away, You can always give that a try!

 

[b231v6]

Mine always hunts up and down when its in open loop. When it changes to closed loop it's fine.Thats in about 2 minnutes or so. If it dies I just re start it. The faster it goes into closed loop the better it is.

 

[motorhead]

Originally posted by b231v6
Mine always hunts up and down when its in open loop. When it changes to closed loop it's fine.Thats in about 2 minnutes or so. If it dies I just re start it. The faster it goes into closed loop the better it is.

Sounds like my situation.

T-type Mike: The car has always done this, stock chip, RA93, and now my JC94 for blue-tops. But, I can try it.

 

[Sinful6]

My car was doing that for a while, I would check your O2sensor(as your problem only seems to manifest during closed loop), also you could change your PCV valve for the heck of it(maybe a leak).

 

[motorhead]

Originally posted by Sinful6
My car was doing that for a while, I would check your O2sensor(as your problem only seems to manifest during closed loop), also you could change your PCV valve for the heck of it(maybe a leak).

Thanks, Sinful6... however, both the PCV and O2 are brand new... this is rather queer.

I am sure that it is something simple.

 

[TurboJim]

This was one of the reasons I started doing my own chips.

Anyway, one of the problems is the car isnt warm enough to run at 14:1 when the car goes to closed loop.

The remedy in most cases I've seen is raising the closed loop enable temp, and increasing the timer once the temp is achieved for closed loop. This will not fix a problem with a car that is not calibration related, but should fix most cars where everything else is dead balls on.

Set $3403-$3404 to 00 9A and $3405 to 68

If memory serves me it says wait till the car is 111 degrees and then count 150 seconds. I'd haveta look at my notes for the exact conversions, but its something to that effect. Stock is like wait till 60* and count to 40 or something like that. So the car is at maybe 80* when it goes to 14:1 AF, which is too lean to hold a nice idle. In my cal its around 120+ degees and it will run at that AF no prob.

Just a FWIW..may not be your problem at all....

 

[motorhead]

Originally posted by TurboJim
This was one of the reasons I started doing my own chips.

Anyway, one of the problems is the car isnt warm enough to run at 14:1 when the car goes to closed loop.

The remedy in most cases I've seen is raising the closed loop enable temp, and increasing the timer once the temp is achieved for closed loop. This will not fix a problem with a car that is not calibration related, but should fix most cars where everything else is dead balls on.

Set $3403-$3404 to 00 9A and $3405 to 68

If memory serves me it says wait till the car is 111 degrees and then count 150 seconds. I'd haveta look at my notes for the exact conversions, but its something to that effect. Stock is like wait till 60* and count to 40 or something like that. So the car is at maybe 80* when it goes to 14:1 AF, which is too lean to hold a nice idle. In my cal its around 120+ degees and it will run at that AF no prob.

Just a FWIW..may not be your problem at all....

WOW. That is a lot to swallow.

Hmm... it is something to pursue... and it does sound very probable since this is cold weather related (no sign until the amb temps started dropping).

I have a bud with a burner and some knowledge of chips I see if I can get him to work with me in the spring on a fix. Hmm... custom spring/fall chip It's what is in fashion!