[BayAreaCobra77]

Alrite guys help me out, i just rebuilt my 99' cobra engine with a new forged rotating assembly, L/T's, and a new clutch, i honed out the cylinders and made sure i had a good cross-hatch, and the crank turned almost by hand, it was a thing of beauty

so i started it and ive put about 300 miles on it, its smoothing out alot, but when i shift, or bring the rpms up, they dont drop immediately when i let off the throttle like normal, or even close to normal, makes for an annoying shift.

i compression tested each cylinder, everything was good around 200 psi, and i did a leak down test, checked for vacuum leaks. all sensors are working properly and no check engine light or anything is on

any ideas guys?

the heads are also the only thing i didnt touch, just took them off, then oiled them up and put them back on once the new rotating assembly was in

[Safi]

Mine does that every once in a while also

[BayAreaCobra77]

haha isn't it wonderful

it wasnt doing it too bad before the rebuild, im not sure.

i flashed the computer and it got a little better, but i can definately tell its still doing it

[97Dustang]

can you take a video of it? are the rpms staying up when you let off or are they just dropping slower than usual?

[BayAreaCobra77]

they hesitate for a second when i let off the throttle and then really slowly come back down.

i don't even have a video camera haha x)

[tbird88tbo]

i would check the iac, they go bad often and when they do they stick. It wont always set a code either if its just starting. Take off the iac and check for carbon build up. Also, if the batt was dissconnected for an extended amount of time it may have reset the computer. I have seen it several times where after just the time it take to chance a battery it will reset and cause this type of issue. However, i wouldnt suspect that since you have driven it over300 miles already...that should have been enough time for it to relearn, usually it only take a few miles, 10 or 20 tops. If you dont have any vac leaks i would most likely suspect the iac.

[97Dustang]

did you put an aluminum flywheel on it?

[BayAreaCobra77]

nah no flywheel, just a resurface.

im pretty sure its my MAF sensor, i checked the codes and it says that Bank 1 is running too rich, and a few people have told me that people often oil up their air filter and it destroys the MAF sensor :/

[97Dustang]

yea if you over oil your filter it gets on the wire and ruins it, you can try to spray it off with brake cleaner to clean it. also im not sure if mustangs do this or not but some cars run a cleaning cycle with the key on engine off, it super heats the maf to burn anything that may be on the signal wire.

[BayAreaCobra77]

hmm interesting. im gonna try a few things. i have a JLT CAI, if i end up having to replace the MAF should i go with a 90 mm? there isnt a specific one for my intake and the filter i have doesnt look like it will fit any of the aftermarket sensors

[Trick Tuners]

If you have a hanging or high idle - Trick Tuners Forums

[BayAreaCobra77]

thats a good forum

i tried everything there and it helped alittle, but its still noticabally hanging and coming down slow, i keep hearing its the MAF

[wraitherx]

Originally Posted by Trick Tuners If you have a hanging or high idle - Trick Tuners Forums

+1, tried these and it corrected it but every sooo often it still did it. Joe (Tricktuners) tuned it to damn near almost gone but it would creep back once and awhile, used to be 10x worse before the tune. Ive read from different forums that it was attributed to either the maf, the intake, or the screen from the original intake.

The theory is that with certain CAI when you are coming to a stop being that the MAF is down there so low that it still senses air coming in thus increasing the idle. Some have also thought that the screen not being there was the culprit. I tested it out and my problem was attributed to the CAI and the maf being soooo low. I put my stocker on for about a month and no issues what so ever and this was after checking my TPS reading, MAF, IAC, vacuum leaks, etc.

Not saying that it is your problem but hope it helps.

[BayAreaCobra77]

thanks wraither thats exactly what im thinking is the issue, on account of the massiveness of the JLT intake haha. im gonna try the stocker and see what happens

[wraitherx]

no problem brotha

[BayAreaCobra77]

well got a new MAF on the way, hopefully that does the trick