newb with idle questions

Tyler16 · Oct 2, 2009

Ok so a while back I bought this 94 GT. It has a e303 cam and 24lb injectors with a c&l maf. Everything else is stock. I put in a a9l computer thinking it would help with a idle surge I have on a cold start. Once it warms up its good to go. I ran the codes and have code 11 on koeo and kero which mean all clear/no codes. Also I had a smoke machine go through it and there is only a small leak on the drivers side header at the head. My question is... Is it my cam? is it the injectors? and I need to get it tuned? even though i have the c&l meter? or should I keep looking for vac leaks? The leak on the header is so small I just don't see it causing the surge.

I have a buddy with stock injectors that wants my 24lbs. Do you think swapping back to stock would solve my problem? or is it the cam?

302GTS · Oct 2, 2009

Has the car had a tune? I know the E303 isn't supposed to need a tune, but I'm sure it couldn't hurt.

What's your idle set at? My GTS with stock h/c/i idles at around 750, but I've heard that when you add a cam you may need to bump up the base idle to give it room for that lope basically.

Vac leaks are a definite possibility, along with that leak at the header. It's before the o2 sensor, so it could be letting in/out air screwing with the sensor on that header.

Try this out though, it's an easy enough thing to try. Ford Mustang Base Idle Reset
I'd try setting it to around 900 rpms or so, and see if that helps to smooth out your idle.

LethalInjection · Oct 2, 2009

If your C&L air meter isn't calibrated for the 24lb injectors and your computer isn't tuned to take them into account, then that could cause some erratic idle situations. If your computer works like mine, on startup it's reading the base tables from open loop side of the computer (which is calibrated factory for 19lb injectors), then once the coolant temp sensor reaches a certain point, it switches to closed loop mode which is still calibrated for 19lbers, but takes more readings from the sensors, and makes adjustments to timing and fuel to try to get to it's target AF ratio which may be why it's clearing up a bit when warm. In that case you will either need to get the meter calibrated for the injectors OR get a chip burnt for them. The E cam should run just fine with that computer.

302GTS · Oct 2, 2009

LethalInjection said:
If your C&L air meter isn't calibrated for the 24lb injectors and your computer isn't tuned to take them into account, then that could cause some erratic idle situations. If your computer works like mine, on startup it's reading the base tables from open loop side of the computer (which is calibrated factory for 19lb injectors), then once the coolant temp sensor reaches a certain point, it switches to closed loop mode which is still calibrated for 19lbers, but takes more readings from the sensors, and makes adjustments to timing and fuel to try to get to it's target AF ratio which may be why it's clearing up a bit when warm. In that case you will either need to get the meter calibrated for the injectors OR get a chip burnt for them. The E cam should run just fine with that computer.

Didn't even consider the injector/MAF combo! OP, definitely look into what LethalInjection said!

Tyler16 · Oct 2, 2009

Thanks for takin the time to help out. The C&L is calibrated for the injectors. The mustang has seen some better days so I don't want to have to tune it untill im ready to build up the motor. So do you think I should just swap for my buddy's 19lb injectors?

LethalInjection · Oct 2, 2009

Tyler16 said:
Thanks for takin the time to help out. The C&L is calibrated for the injectors. The mustang has seen some better days so I don't want to have to tune it untill im ready to build up the motor. So do you think I should just swap for my buddy's 19lb injectors?

If your buddy will let you try them then I would test it out first to see if that's your problem. Don't forget, you'll have to use his MAF that is cal'd for the 19lb'ers. If you have stock heads,intake, etc then you don't really NEED the 24lb'ers at the moment, but if everything is calibrated then they should only be spraying enough of their duty cycle to support the amount of fuel you need based on the fuel tables as well as MAF readings and O2's. If you upgrade the heads and intake later, then you are goin to need the 24lb injectors and MAF. I would honestly do the idle reset procedure and then go through all of your vacuum lines just to make sure. Seems like your problem may be isolated to open loop on cold engine though. If it were vacuum, then I would think that it would continue when warm as well.

Tyler16 · Oct 2, 2009

Do you think even if I put the 19lbs back in that it would surge just due to the cam and no tune? Or should it be able to run fine with that cam and no tune? ....It does have the a9l in it at the moment.

HISSIN50 · Oct 3, 2009

Even bone stock A9L cars can have the surge. The Fox side has a tech sticky with things to try in order to fix it (the thread is about 14 pages long at this time).

Tyler16 · Oct 3, 2009

Ill try that thread out. Thanks!

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