quirky idle

[Bostard]

My '99 Cobra with the Paxton Novi 1000 seems to have a little idle problem that bugs me. It's kinda "quirky". While sitting at a light my idle is just fine at about 750rpm. As soon as I touch the gas pedal it revs to about 2000rpm and then very slowly returns to normal. While daily driving....I shift, the idle doesn't drop like normal. It is very slow to drop. It stays right about 3000rpm until I hit the next gear. It kinda reminds me of the problems we had with old carbed engines that had a high idle.

I guess my question is if anyone else with a s/c cobra has that same issue. I wonder if it is inherent when you've made the brainbox and injector changes.

 

[Rob Smith]

Sounds like the MAF to me. Is it the stock one or do you have an aftermarket MAF?

 

[Bostard]

It is the Pro M 80mm that came with the Paxton kit.

 

[GR8WHITE]

Sometimes it is the computer trying to burn off excess emissions. It will idle up kind of high for a few seconds then drop back down. Although it does sound a bit different in your case. It didn't say in your sig if you had larger injectors. If they are still stock and you still have the stock MAF, you could try swapping the MAF back in to see if that helps.

Was the MAF installed with the kit? Are the injectors in the car the same that the MAF is calibrated for? Have you checked for any loose or dislodged intake plumbing, particularly vacuum lines?

 

[IUP99snake]

My idle sometimes sticks... but not that high. Sometimes itll stick around 1100 for a few seconds. It never did that in N/A form, but its not of concern.

-Homer

 

[Bostard]

I did find a pin hole in the air inlet hose from the mass air to the s/c. Now I am in the process of trying to get a replacement. Boy, those are hard to find. Any suggestions?

 

[GR8WHITE]

If it is only a small hole, I'd try RTV first to see if that helps any. Although I doubt such a small hole would cause that, stranger things have happened.

If you have any dryer duct type air inlet plumbing going into the fender, check it really good. That stuff gets old and dried out quicker than you may think. I had several rips in mine on my 97 and didn't realize this until I pulled all of that out of the fender. A couple of those rips were after the MAF which did cause it to run and idle weird.