nate_clouse

Ok, so I have a 1990 5.0 LX. Trick Flow Upper and Lower intake, 75mm throttle body, performance valve job, roller rockers, ported heads and Trick flow drag cam, bbk shorty headers and 2 3/4 exhaust with flowmaster mufflers, straight pipes. I've been having issues with it idling at a consistant RPM. It will idle fine for a little while then on its own jump up to 2,000 RPM for maybe a minute than drop back down to around 700 RPM then sometimes die or maybe jump back up to 1,500 its really irratic. Drove it this morning idling acted the same way, had consistant power for about 10 min then it seemed like I lost most of my power all together. It has the stock injectors and the guys down at the ol AutoZone told me to start with upgrading injectors to 28-32lbs. Just wondering if anyone knows if that is an accurate route to go in this situation and if so would 24lbs be too little for my setup? My neighbor has a set of 24lb injectors with the programmable MAF sensor he said he would sell to me for cheap. Just wanna try and make the right decision here. Any advice or info would be great!! Thanks

dawson1112

Clean the maf, and iac. check for vacuum leaks, and do a base idle relearn.

Does the car give any codes, check engine light on?

nate_clouse

no check engine light. every once and a while i see it come on pretty random though never stays on.

dawson1112

That random check engine light is setting a dtc in the computer youll have to pull the codes to see what it is setting.

http://www.dfwmustangs.net/forums/showthread.php?t=7908

nate_clouse

ok, i'll see what the code is about. Any thoughts about the injectors? Wanna upgrade them anyway.

nate_clouse

Thanks for the link too, thats great!

dawson1112

If your just running the stock heads ported your 19lb injectors are fine. If you can get the 24lb with maf cheap it wont hurt. Don't listen to those guys at autobone , your no where close to needing a 32lb injector. If it was a problem with injectors being to small you would have problems at high rpm or wot.

nate_clouse

Ok thanks for the info. Called trick flow this morning they suggested 24lb injectors. New maf and adjustable fuel regulator.

Ran codes last night:

21-ECT out of self test range 0.3-3.7 volts
23- closed throttle TPS voltage higher or lower than expected
24- ACT sensor out of self test range 0.3-3.7 volts
34-PFE or EVP circuit has intermittently failed above the closed limit if 0.67 volts

Without research not really sure what all that means right now.

dawson1112

sounds like a ground problem or a short,

nate_clouse

Guess that would make sense. Although I may clear the codes and retry cause it had been sitting for a while with a dying battery then no battery. Just recently dug back into the thing last weekend.