Car stumbles on startup...Please help?

[Solar_Eclipse2]

I just took my car out of the garage for the first time this year over Easter weekend. It usually stays in the garage from October/November until April or so. Over the course of the winter I start and run the car for about 15 minutes or so to circulate fluids and get it up to operating temps.

After bringing the car out last weekend I had a problem where the car would start up and then die in about 15 seconds or so. The only way to keep it running was to rev the RPM up about 4k for a few minutes and then I could drive it. As long as I was driving, no problem but if I shut the car off I'd have to do the whole thing over again.

After I got home I hooked up my Predator tuner and increased the idle RPM up to about 900 RPM and reloaded my tune. This seemed to help the car quite a lot. Now the car will start up and the idle will go up to about where I set it (RPM wise), then dip down again to around 650 or so, then come back up to 900 or 950 and the car will idle fine. Every once in a while while stopped at a stop sign or just as I'm stopping at a light the idle will drop down and the car will stumble some and come back up also.

I've checked under the hood for any loose connections.
Checked for cracked hoses.
Checked for vacuum leaks, using carb cleaner.
Gotten a new tank of fresh gas, twice.
**Edit** Also cleaned air filter and MAF sensor.

All seems ok there.

The car has FRPP hotrod cams, FRPP shorty headers, FRPP CAI (the one that uses the stock intake tube) and a custom tune.

Is there anything I could log in the tuner to help diagnose the issue?
The car isn't throwing any other codes and otherwise behaves fine.

 

[BruceH]

The motor hunting for idle can be solved with a few simple adjustments in the tune that compensate for the airflow change caused by the cams. It can be a delicate balance between hanging rpms or hunting rpms.

The motor ran fine prior to being put away?

 

[Solar_Eclipse2]

Yeah the car ran fine before putting it away.

I just took it out for a drive with the wife and noticed that it acts this way until the car is up to operating temp or close to it. After I've been driving the car for a while.

The motor hunting for idle can be solved with a few simple adjustments in the tune that compensate for the airflow change caused by the cams. It can be a delicate balance between hanging rpms or hunting rpms.

No doubt in my mind this can be fixed in the tune. I'm not sure what needs to be done or if I can do it in the hand held programmer. I'm no tuner, just a shade tree mechanic.

I really don't want to have to deal with the guy that tuned the car originally because he seemed kind of crazy and he's like a 3 hour drive from me. Nor do I have the scratch right now to pay for a new tune by a new tuner. Sucks to be me.

 

[BruceH]

Yeah the car ran fine before putting it away.

I just took it out for a drive with the wife and noticed that it acts this way until the car is up to operating temp or close to it. After I've been driving the car for a while.



No doubt in my mind this can be fixed in the tune. I'm not sure what needs to be done or if I can do it in the hand held programmer. I'm no tuner, just a shade tree mechanic.

I really don't want to have to deal with the guy that tuned the car originally because he seemed kind of crazy and he's like a 3 hour drive from me. Nor do I have the scratch right now to pay for a new tune by a new tuner. Sucks to be me.

You can't do it with the hand held. A competent tuner should be able to take care of it though. You could tell your tuner about the idle and ask for an email revision. American Muscle has a driveable tune for Hot Rods. It doesn't make much power (at least the one I saw on a dyno didn't) but it's very safe and inexpensive at $75. IIRC Justin at VMP also does na email tunes for $75. If I wasn't doing my own tuning I'd be a lito customer. Don't know what he charges for an na tune though.

 

[Solar_Eclipse2]

You can't do it with the hand held. A competent tuner should be able to take care of it though. You could tell your tuner about the idle and ask for an email revision. American Muscle has a driveable tune for Hot Rods. It doesn't make much power (at least the one I saw on a dyno didn't) but it's very safe and inexpensive at $75. IIRC Justin at VMP also does na email tunes for $75. If I wasn't doing my own tuning I'd be a lito customer. Don't know what he charges for an na tune though.

I sent my tuner an e-mail this morning asking if he can send me an e-mail revision. I hope he's reasonable.

If I have to go with another person to tune the car I want to get away from the Predator and get an SCT tuner because it seems like that's the more accepted programmer for the Mustang.

Just curious, do you know what numbers the AM tune for the hot rods made?

 

[Solar_Eclipse2]

Took the car out again today and turned the A/C on and the idle was bouncing around. Going low and then back up to normal and back down...Would that mean there is a vacuum leak and I just didn't find it yet? The car definitely did not do this before.

 

[BruceH]

I sent my tuner an e-mail this morning asking if he can send me an e-mail revision. I hope he's reasonable.

If I have to go with another person to tune the car I want to get away from the Predator and get an SCT tuner because it seems like that's the more accepted programmer for the Mustang.

Just curious, do you know what numbers the AM tune for the hot rods made?

It was right at 300rwhp. The car belonged to hemilol.

Took the car out again today and turned the A/C on and the idle was bouncing around. Going low and then back up to normal and back down...Would that mean there is a vacuum leak and I just didn't find it yet? The car definitely did not do this before.

There is a seperate idle in the tune just for a/c. It's time to get an sct tuner. Buy one from Justin at vmp and it comes with a custom tune. Or, buy a used and unlocked one for $200-$250 and buy a tune from someone. I'd be contacting lito, Eric Brooks, or VMP. lito is very easy to work with and goes to great lengths to get the tune correct.

 

[Solar_Eclipse2]

I'm going to have to do something. Getting pissed because I contacted the guy who tuned my car minutes after I posted on the 9th and haven't heard back from the guy.