Surging Horribley

[CrawlinTBSS]

anyone have any ideas on stuff to check?

cars starts up idles at 1200 for like 30secs and once it goes down to idle around 900 like usually it drops and starts surging up and down from 500-1k.

No codes/CEL
IAC is okay - been checked and replaced
ECT is okay - checked and replaced

I see/hear no vac leaks or see any cracks or problems. engines sounds mechanically fine and normal aside from it surging up and down.

but a few times when i let the car go long enough or gave it gas to warm it up it seemed to straighten out and idle fine once it was warmed up. first time i replaced IAC and still chugged and got it warmed up and was okay, went and drove it and it drove perfectly fine. but once it cooled down and started up again it did the same thing again.

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[KaMaSuTrA]

Check the ECU, you might have some shitty caps. Also check the coolant system, you might have air pockets and that can cause a loopy idle.

 

[Bru]

My cousin (blakbearddelite) has had a similar problem with his GT that we haven't been able to track down. It's intermittent and a real pain in the ass to replicate. I'm sure he can chime in and you guys can compare issues.

 

[Angus]

even though i don't have much experience with this car yet, but I know my bmw had a similar problem and needed a new ecu...

 

[CrawlinTBSS]

gonna get a scanner on it tomarrow to see if its anything i can see while logging it.

gonna clean maf and intake and tb and maybe replace plugs tomarrow. its really pissn me off. been sittin in garage since last wednesday now.

 

[blakbearddelite]

Is this on the Mustang? I thought you sold that last year?

 

[CrawlinTBSS]

yes its the stang. nope still have it. didnt decide what i wanted to do with it but now im just sick of it.

 

[blakbearddelite]

I'm having intermittent surging issues as well. This coming spring we're going to check the wires, change all coil-packs/plugs, and clean the MAF. I also have my days where I want to drive that car off a cliff. It could go months without any issues, and then it'll be crazy for a week. But this last time seems to be permanent. It hasn't run right since late Sept, but it's now in storage. I never have my scanner/laptop with me when it's acting up. And then when I do have it with me, the car is acting fine. If we can't resolve the issue by April, I'm going to take it to this mustang tuner down south in Mattison(sp?), IL. I don't mind paying someone to troubleshoot, I just want the damn car running normal again.

 

[KaMaSuTrA]

It might not throw a code to scan although thats not a bad idea. You're probably going to have to pull the ecu and check for burn marks, leaks, and such if the maf, ignition system, and tb is ok.

 

[CrawlinTBSS]

ive never really heard of these cars having problems with burning out computers like the imports seem to do.

im getting a scanner so i can look the parameters while the car is surging. i know theres no codes already for the car.

 

[Ron Vogel]

My cousin (blakbearddelite) has had a similar problem with his GT that we haven't been able to track down. It's intermittent and a real pain in the ass to replicate. I'm sure he can chime in and you guys can compare issues.

EGR

 

[CrawlinTBSS]

i dont have a functioning EGR, at least for me. maybe he does.

my EGR is pinched and shut off in my tune. hasnt been hooked up since car has had LT headers. so i know that is not my problem.

gonna check out and try and new PCV valve tomarrow.

 

[Dasfinc]

Here's a bit of a stupid question... You ever sea-foam the thing? Helps clear out IACV passages in the intake manifold and just about everything else (I don't know exactly how everything is plumbed for the stang manifold, but it couldn't hurt, and I saw you replaced the IAC valve)

Sorry if this sounds stupid:

Do the mustangs have those little charcoal canisters on them off a vac line somewhere ? I know the SHO had a funky little charcoal canister with a plug going to it that caused a funny idle back and when (my first one) because it was toasted/clogged/melted.

 

[CrawlinTBSS]

yes most cars have the evap canister, id really not like to have to replace that shit.

im very close to scrapping this POS. and parting out the whole damn thing. i cant bare to spend anymore money on this thing. its pissing me off to the max.

 

[Angus]

wow.. hope you can figure it out...

 

[CrawlinTBSS]

me too. this car has been a nightmare ever since my old headers broke and had to put new ones in. its just one thing after another.

 

[bluzohh6]

what about plugs? Loose wire? Something with the ignition.

 

[bikrboy128]

maybe a bad boot? or coil? these coil over ignition systems are hard to diagnose. it's really hard to test for spark strength....

good luck.

 

[CrawlinTBSS]

finally the got battery unhooked, damn nuts for the clamps are frozen, reset the computer and ive ran it 4 times now and its running fine. so all i can do is hope and see after a few my cycles.

 

[slowchevy]

do you drive it in the winter at all? maybe you could take it for a long drive and then shut it off.. then start it later to see if the problem replicates itself for ya.

 

[DanJ]

Maybe one of the battery connections was bad/corroded? Have you checked the ground wires for the battery, etc.?