Just rebuilt the motor, terrible idle on startup

[Leviathan]

Just rebuilt a 1993 Laser RS Turbo. All stock parts (did the balance shaft removal - but that's it). The car will fire up but will not idle well at all. If you hold the throttle it will stay around 1.5K or so, but when you try and rev it up when it's near where it should be idling it seems to be breaking up... misfiring or something. But when its revving to 4K or so it's smooth. The kicker here is that I bought the car last fall and it hadn't run since 2005. So we drained out all the bad gas and put new stuff in it. That didn't seem to have an effect. Tried adjusting the CAS (flipping it 180*) that really didn't make a difference either. We hooked the MAF directly up to the throttlebody to eliminate any possiblities of leaks in the charge pipes. It still ran the same. Then we unplugged the MAF and it ran better. It still didn't idle, but it didn't seem to break up around idle. We checked the physical timing 3 times when we put it together so it's not that.

Any ideas?

[sleepydsm]

Boost leak test, first.

[Leviathan]

We took the tube that goes from the MAF to the turbo and connected it straight to the throttlebody and it ran the same. So we eliminated boost leaks

[Shane@DBPerformance]

You can have boost leaks at and after the throttle body. Those are the ones that screw things up the most.

Do you a datalogger for it to see if some sensor is reading totally wrong?

[scheides]

Do you have the correct MAF hooked up, and what injectors are you using, is the car setup for them, etc?

[sleepydsm]

I had all 4 injector seals leaking so bad the car wouldn't idle, or even run.

Do a boost leak test.

[Leviathan]

Originally Posted by Shane@DBPerformance

You can have boost leaks at and after the throttle body. Those are the ones that screw things up the most.

Do you a datalogger for it to see if some sensor is reading totally wrong?

I don't have a data logger unfortunately. I have a friend with a Genisys scanner who may have OBD I hookups. I'll try that tomorrow. After driving it today it seemed to idle better. Meaning it will idle for a second or two before dying off. If I don't see anything crazy from the sensors I'll check into leaks around the throttlebody, injector o-rings, and any other vacuum source I can think of.

[Leviathan]

Originally Posted by scheides

Do you have the correct MAF hooked up, and what injectors are you using, is the car setup for them, etc?

Yes it's hooked up. Stock injectors. Stock ECU.

[Leviathan]

Originally Posted by sleepydsm

I had all 4 injector seals leaking so bad the car wouldn't idle, or even run.

Do a boost leak test.

I'll check into it tomorrow.

[Shane@DBPerformance]

Maybe you just have the typical DSM idle problems.

[Leviathan]

Originally Posted by Shane@DBPerformance

Maybe you just have the typical DSM idle problems.

I don't think so. If typical means you need to use your right foot for the gas to keep and running and brake pedal when you stop, then maybe.

[Leviathan]

Looks like it's an intake manifold leak... which is kinda odd for a clean head and manifold. I'm going to pull it off and take a look to be sure.

[Leviathan]

Got it figured out. The gasket they supplied was way off... the bolt pattern was perfect, but it lined up terribly. I must have been half asleep when I put it on. Or maybe I just assumed it was OK.

The pictures should tell it all.





You can literally see where it was leaking. Plus the gasket rose up a half inch into the intake runner.