MPD47

So I'm nearly done putting my car back together (always nice when you've had the coolant, steering and oil systems apart, put them back together and nothing leaks.) and after starting it I've got a terrible idle. I *think* it's vacuum related but I'm not 100% sure as I cant seem to find any leaks anywhere. I just did the venturi delete and replaced my vacuum lines and added Laust's 5 port manifold (which was a very nice piece btw). So when I start the car up the car revs between 950-1500 or so rpms constantly, just revs up, sits back down, revs back up, etc, etc. Meanwhile the vac gauge is giving me a readings between 5-11 vac. I've used carb cleaner and checked for the problem but cant seem to find it. I'm open to all suggestions. The car revs up fairly fine (and sounds incredibly badass with the Vitesse Stage III kit, Lindsey 3 inch exhaust, as I "forgot" to order a muffler for the time being). Oh yeah, and I do not think it's a fuel issue, I'm pretty sure it's vac related. Anyway, all suggestions things to check are welcome! Thanks.

fast951

Check the intake manifold where it attaches to the head? Any missing/misaligned gaskets..
Call me during the day and I'll walk you through few things...
I thought at one time you had a clean idle while we were on the phone... Double check your SMT6 connections.. We can go through them in the morning..

MPD47

K John. I'll give you a call in the morning. Thanks.

Charlotte944

This sounds like a classic case of having the throttle body out of adjustment, causing the DME to see an "Over Run" or "Trailing Throttle" condition with the resulting hunting around idle.

When the throttle plate is closed the TPS sends a ground to the DME. When the DME sees this ground it "knows" that the throttle plate is closed.

If the engine RPM is too high (Over Run) the DME will turn the injectors off. Once the RPM drops back to "normal" the DME fires the injectors. Normally the only time this happens is under deceleration and the DME turns the injectors off to save fuel and reduce emissions.

I would start by disabling the ISV (jumper wire between pins 'B' and 'C' on the diagnostics connector) and then closing down on the idle by-pass on the throttle body.

This problem can also be due to the TPS being out of adjustment, the TB mechanical stop could be out of adjustment, the ISV could be stuck open, or you could have a vacuum leak between the outlet of the ISV and the intake manifold.

jimbo1111

Did you grind down the turbo compressor where it meets the intake. If not. This may restrict the intake from properly seating.

fast951

Good observation. But all turbos have this mod before shipping..

hosrom_951

Fast951: If i am not mistaken, MPD47 ordered his kit weeks before you're mod on grrinding the turbo before leaving??