Idle Problems

BLK3DGT

Member
Feb 22, 2006
47
0
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I have a 91 Mustang Gt 5.0 that I just rebuilt. The block is bore out to 4.030 over (306). New probe 10:1 pistons , crank balanced and polished. Top end is Trick Flow street with aluminum heads and the stage 1 camshaft. Accufab 70 mm t/b with C&L 73 mm MAF. Holley afpr set to 40lbs with vacumn line off and timing set at 14 degress.155lb fuel pump in tank. Car runs really strong and only has 900 miles on the motor as of now. Still breaking it in and trying to get some of the bugs out. Car is N/A also, no juice!!

With the engine idling, it stays around 1200-1400 rpms for a few seconds then drops to 950 and will idle ok. I have replaced the IAC, TPS and set the voltage to .95 at idle and wot at 4.86. Tried everything to get engine to idle correctly.:bang:

The car was originally an AOD and I did the t-5 conversion. I was told that i did not have to change the computer that this vehicle year has a A9L in it and is the better one. The engine had 19lb injections before and now with all the modifications I installed 24lbs and changed the maf sensor tube (blue one ) in the C&L maf.

Can this computer be upgraded with a dyno tune or chip? Maybe it is not reading the new injectors correctly and keeps change the A/F ratio. I have not put it on a scanner yet or taken it someone, Car really runs strong otherwise. I have spoken to other stang owners who have modified their cars and this idle problem seems to be something I may have to put up with. Everything is still hooked up, pollution control a/c and smog. I have had a check engine light come on twice, but as soon as i shut the car off and restart it the light goes out?

Any suggestions will be greatly appreciated.

Thanks,

BLK3DGT:SNSign:
 
BLK3DGT said:
With the engine idling, it stays around 1200-1400 rpms for a few seconds then drops to 950 and will idle ok. I have replaced the IAC, TPS and set the voltage to .95 at idle and wot at 4.86. Tried everything to get engine to idle correctly.:bang:


BLK3DGT:SNSign:

it stays around 1200-1400 after you step on the gas then drops to 950? Is this while you are at a dead stop or coming to a stop?
 
See the sticky "Help me create the Surging Idle Checklist" at the top of the forum for help with your idle problems. The first post has all the updated answers. I add to the first post as new fixes and suggestions are posted.