Don't know if anyone has been following the stuff i've been doing/having done to my car, but here's the jist of it.
>Had a remanned Jasper put in 8 months ago.
>Heads weren't machined right, coolant was leaking between the intake manifold and heads.
>Just got car back from having the engine warrantied out.
>Idle is now rough at stop lights. runs like a champ while driving, but acts like it wants to stall when stopped.
In park, I've sat and watched it go up and down from around 600 to 1000 RPMs. In drive it will sit at 600 for a little bit, then drop to around 400, and jump back up. happens really suddenly and car shakes. then hovers around 600 again. repeats every few seconds till I leave the light.
I've been searching for an answer to this, but I'm looking to see if anyone has something I've missed for me to try.
I've got new or almost new(replaced within last 8 months): injectors, FPR, fuel pump, fuel filter, plugs, wires, cap, rotor, O2 sensor, MAP sensor, ECM, CTS, 2.5" exhaust, PCV valve, probably other stuff I can't even think of...
I've gone over vacuum lines, and everything seems fine there. I'll be going over them again as I don't know what the shop might have done while that new engine was put in. But I am pretty pissed.
I've seriously put enough into this car that I could have a pretty decent new car. If this wasn't my dream car since I was about 5, it would have been gone a loooong time ago. Never thought it would turn into such a nightmare.

 

IAC bad/dirty. Clean/replace. Also, be sure to clean up the port where it screws into the TB. Make sure the base idle is set correctly. 450 RPM, IIRC.

 

Simple fix. Its running lean. Make sure the timing is at 6 degrees. Turn the fuel pressure up until it stops wondering.

 

I've been trying to figure out how to adjust the base idle. I know there's a screw on or near the throttle body, but I can't find it. anyone have pics of that?
I've ordered an IAC and I'm gonna try replacing it first. after that I'll take a look at the timing and all that. How do you turn up the fuel pressure? Is there a way to do it stock? I thought the only way to up fuel pressure was an aftermarket FPR or something.
Thanks for the help so far guys!

 

Don't buy an IAC. Try adjusting the TPS on the side of the TB.

 

Don't think this TPS is adjustable? And it was dead on at last check a few months ago. Worth looking into though. thanks

 

how critical is the 6 degrees? The guy that timed it said he set it at more like 10 b/c of the high altitude here. and I know I've seen people on here saying they can run it 10-12 without trouble. I'll time it back down if I really need to though lol, I'm just not sure that's gunna be the problem on this one.

 

I already paid for the IAC, but it can't hurt to replace a 22 year old part. I'm not too worried about it. might take care of problems I didn't even know I had.

 

I have a bad feeling I've got another symptom of the problem I've been chasing since I got the car.
https://www.thirdgen.org/forums/tech...r-i-think.html
I replaced the IAC, nothing. same exact problem. On a whim, I decided to unplug the MAP sensor. Problem is almost completely gone with MAP unplugged. still a slight fluctuation, but I assume with a sensor unplugged it won't run perfect anyway. But its definitely worse when the MAP is plugged in.
so FML.
Edit: nevermind. problem is just as bad with MAP unplugged. didn't let it sit long enough. No change with MAP unplugged at all.

 

Just tested TPS. working perfectly. any other suggestions guys? I may just go buy a timing light tomorrow, and try adusting that to see what happens. Any other tools I may need to adjust timing? Never done it on my own lol.

 

Pulled my codes just for fun to see if anything might be stored, and I found a code 34 hiding in there. no SES light on, but it's definitely there. I think that MAP sensor is the root of all my problems, and I'm gonna be calling a shop that specializes in wiring tomorrow to see if they can get this fixed once and for all. I've already tried for a year to chase this problem, and no luck. it's time to find a professional.

 

There is a timing adjustment tool you can buy. Go to the auto parts store to get it.

 

And on a different note, my heater core just blew this morning. yaaaay lol

 

That's an easy fix too!

 

at altitude, these cars DO run a little better with advanced timing. You could have MAP or IAC issues. I had a jasper put in about 4 years ago, and we are beginning to think they send us the wrong cam! If you get really stuck, I know a good mechanic in the springs that specializes in chevy muscle......

 

Man I'd really appreciate any help with finding a good mechanic.
Also, don't wanna get to excited just yet, but after I bypassed my heater core, the running problem seems to have smoothed out. I've got a couple theories.
1) I bumped the MAP sensor wiring in just the right way, and after another good bump, the problem will be back.
2) I've got a leaky vacuum line behind the dash, and when the heater core blew, that vacuum line started sucking in coolant. would also explain why it got worse when the car got hot. more pressure=more coolant being blown out=more coolant getting sucked into said hypothetical leaking vacuum line.
Any thoughts on either of those possibilities? any other reason why a blown heater core would cause a bad idle?