Finally got the engine started. It was a 96 rebuild with forged internals for more boost. 9:1 compression. Its in a 2000 j-bod. Starts fine. Once warmed up the idle drops to about 500 and seems like its going to die. Its automatic. It'll start to studder pretty bad and have a rough idle. If you give it gas, it smooths out. Occasionally it will jump up to 700-800rpm on its own then drop back down. Vac is at about -15mmHg. When is starts to studder the vac needle is bouncing back and forth between about 13-16mmHG. It looks like its vibrating it goes so fast. Occasionally the vac dropped to -10mmHG and it just stalls. Also, when you put it into drive or reverse, it will stall if you don't give it more gas to keep the idle up. No vacuum leaks were found. I'm not sure if maybe the IAC is bad or if I should just try to increase the idle a touch with the throttle screw... It only threw one code as it stalled, and that was for injector 3 open circuit, I played with the plug and check it. All seemed solid. CEL hasn't come back on for that since, but it still acts the same. Any ideas on what to try?
12.6 @ 114.6 MPH
I was gonna say IAC or TPS.
~2014 New Z under the knife, same heart different body~
______________________
WHITECAVY no more
2012 numbers - 4SPD AUTOMATIC!!
328 HP
306 TQ
Auto's idle around 600 stock.
With that said on a fresh motor the rings need to seat. This could cause a compression mis, and a rough idle. Get some miles on it and get the rings seated.
Also adjusting the throttle screw will do nothing.
FU Tuning
i know every build i have ever done (mainly SBC's) we set it to idle at about 1500-2000 for 15-20 minutes to allow it to heat up and get to temp and let the rings seat.
EvoFire wrote:i know every build i have ever done (mainly SBC's) we set it to idle at about 1500-2000 for 15-20 minutes to allow it to heat up and get to temp and let the rings seat.
Thats usually for cam break in.
The break in for our motors for the rings is to get up to 45mph and let the car slow down (just let off the gas) 5-10mph, then accelerate back up to 45 mph, and do that like 10-15 times.
FU Tuning
Would the rings not being fully seated cause that kind of random rapid vacuum variation though?
12.6 @ 114.6 MPH
--Glowin Cavy-- wrote:Would the rings not being fully seated cause that kind of random rapid vacuum variation though?
I have seen fouled plugs do it.
FU Tuning
Hmm. I'll recheck the plugs. I don't get why it would keep stalling when put into gear though. The extra load would cause it to stall right away unless it was given gas too to keep the rpm's up a bit.
12.6 @ 114.6 MPH
I pulled the plugs today and they seemed okay, but they did look a touch fouled. Not much at all though. The electrode ground (part you can bend) was white/gray while the electrode itself and the threads were carbon coated. I did notice that the plugs came out extremely easy. Not necessarily loose, but deff not tight. Didn't even need a wrench to unthread them. Gaps were checked and were between .030-.034, Regapped them all to .030. Made sure they were nice and tight this time. Fired up fine and idled good even once warm. Idled at 550rpm. Idle vac at about -16 to -17mHg. All is well when revving too, still only issue noticed is when put in gear it started to studder and the vac rapidly fluctuates. Didn't stall though. Ideas on the in gear studdering and vac fluctuation?
12.6 @ 114.6 MPH
--Glowin Cavy-- wrote:I pulled the plugs today and they seemed okay, but they did look a touch fouled. Not much at all though. The electrode ground (part you can bend) was white/gray while the electrode itself and the threads were carbon coated. I did notice that the plugs came out extremely easy. Not necessarily loose, but deff not tight. Didn't even need a wrench to unthread them. Gaps were checked and were between .030-.034, Regapped them all to .030. Made sure they were nice and tight this time. Fired up fine and idled good even once warm. Idled at 550rpm. Idle vac at about -16 to -17mHg. All is well when revving too, still only issue noticed is when put in gear it started to studder and the vac rapidly fluctuates. Didn't stall though. Ideas on the in gear studdering and vac fluctuation?
I would worry less about it and get some miles on the motor. Also allowing the ECU to get use to being used again and allowing fuel trims to adjust.
I bet as the motor breaks in it will get smoother.
Auto's do idle rough when they have stiffer mounts.
FU Tuning
Will do. I'll get some miles on it and see if that helps. It still seems odd to me though that now it only acts up when in gear. The rough idle in gear isn't just feeling it from the mounts, but you see the boost/vac gauge start going crazy.
12.6 @ 114.6 MPH
Mine did this when I rebuilt it with forged internals, ever smoked too, after I let the rings seat everything was fine!! Boy was I worried though!
Sorry, mine wasnt rough at first with my built motor. Somethings f'd up.
~2014 New Z under the knife, same heart different body~
______________________
WHITECAVY no more
2012 numbers - 4SPD AUTOMATIC!!
328 HP
306 TQ
