I was all stoked to start it up, it started up the first time (which is cool considering all the work I did, and how many pieces my engine was in…) Anyway, my question - when it started, it idled at 4200 rpm… wooow, not good, i know that… my first guess was the throtle cable was holding the throtle plate open (if anyone remembers I put a STR manifold on). My fix, to disconnect the cable… No good, idle still high. Checked all vacuum lines, sensors, fuel pressure, everything I could think of; Now I am totally at a loss for possible causes.
Please note - there are no c.e.l.'s
If there are any members close by, the pizza and beer are on me!!!
What do you guys think about spraying some starter fluid around suspected leakage areas. It should prove whether air is getting in… Right? The idle would drop… Right?
Haber : I used all new seals the injectors, that really doesn’t mean anything.
FORMZ : I think it would have to be post TB. But I am not sure.
Would a failing O2 sensor cause this, just a thought.
qwkteg125 - it makes about 25"hg at idle (4000 - 4200rpm this is the lowest idle I have got).
I have also rechecked the bolts on the intake mani and all are tight. I have no other thoughts right now. I am going to work on it today when I get home. I have no direction to take so I will again recheck all of the rechecks that I have rechecked. :bang:
That sounds like the same problem I had when I started mine. Do you still have the stock throttlebody on the car? If so, does it have that round flat UFO looking thing hanging off to the side( it attaches to the top by 2 star headed screws and has a vaccum line going to it? Take that vaccum line off and plug it up with a srcew. Dissconnect your battery for 1 min, then start it up. I would take that piece off and tune it with the idle screw on the throttlebody and the throttle cable. Once you have that idle screw set to where she idles decent then cover your idle screw with silicone (leeks like crazy there for forced induction when the screw isn’t all the way in). Hope this helps.
Mike is talking about the dashpot diaphragm. I don’t run one on my car. I’m not familiar with the STR manifold but are you sure all the ports that are in it are plugged?
MIKE - I tried that on my lunch hour, it only made a marginal difference in the idle speed. It now idles at 3800rpm. I think we’re makin’ progress…THANKS!!!
HABER - I believe that all ports are either used or plugged… I’ll try to snap a pic showing vacuum lines and where I have them attached. Maybe I’m am over looking something, that will be obvious…
I will double check to ensure there isn’t a open vacuum port
This happened to buddy mine also and we could not fing the problem to save out lives. So just to check things out we pulled off the intake manifold and there was little piece of the old gasket stuck on the head. We scraped it off put the intake manifold back on and voila the idle was back to normal. Might wasnt to check it out. Godd luck.
What ecu are you using? Another thing you might want to check out is your throttle plate. Take off your pipe to your throttlebody and look to see if its stuck open. Did you change your map sensor or are you running the stock one? To give you a more accurate advice post all your mods right down to your spark plug gap.
Originally posted by nosintegra92 This happened to buddy mine also and we could not fing the problem to save out lives. So just to check things out we pulled off the intake manifold and there was little piece of the old gasket stuck on the head. We scraped it off put the intake manifold back on and voila the idle was back to normal. Might wasnt to check it out. Godd luck.
Ya…I was thinking along these lines too. Maybe the manifold isn’t flush against the gasket/head?
OK guys, i’ve snapped a few pictures of the engine trying to show vacuum line routing, however, it looks pretty messy.
There are only 4 vacuum ports on the manifold. I using one of those ports for the map sensor, one is Y’d to the b.o.v. and the f.p.r., the other goes to the vacuum purge silenoid, and the last is for the brake booster.
nosintegra92 - As a last resort I’m going to pull the mani off and check for remnants of the old gasket. :argh:
MIKE - ecu is stock, I check the throtle plate after i read your post and it is closed. As for mods, i’ve got a ton the engine is basically fully built (low comp.) ignition system consists of al MSD products, fuel system is all SX (pump, filter, regulator) injectors are RC 440’s with a climax fuel rail and -6AN lines… Other stuf i can’t remember.
What kinda of map sensor are you using? I don’t see any check valves on your vaccum lines??? Another thing I would do is to run your vaccum line from the intake to the fuel regulator seperate from your blow off valve. I am willing to bet your leek is with your direct port setup. I had that same problem when I was N/A. Take off your NOS line to the distribution block. Your solenoid could be stuck open creating your leek. Better yet take off the direct port fogger nozzles and plug the intake with a alan key screw and start her up. When I had my direct port on my car one of my fogger nozzles cracked where it bolts into the intake but you would never know because of the steel lines are so strong its hard to move them when they are all bolted up together.
MIKE - I am using the stock map sensor and I have a missing link installed between the sensor and the manifold. I will definitely try what you suggested with the direct port setup. That is a lot easier than removing the manifold.
Thanks to everyoned who has offered their suggestions, they have been very helpful. I’m hoping to have the problem fixed this weekend.
I have also noticed that you have pluged up the vaccum line on the throttlebody. Take that blk cap off it and run your map sensor line there. Also double check your wiring for your for your MSD.
I am not exactly sure what it was, it possibly could have been a combination of things. I removed the direct port, and I also pulled the intake mani off. After plugging the holes in the mani where I drilled and tapped (for the d.p.), and reinstalling the mani it started and idled at 900, with a little tweaking of the idle screw on the t.b. it now purrs like a kitten.
Now, all I have to do is tune it a little - and enjoy!!!
Thanks again to all of the members that offered their suggestions, they were all very helpful!!!
Danm, I know this thread is old as dirt but I’m having the same exact problem. The only difference is that I dont have NOS just turbo and my car is idleing at 2500 rpms not 4200 rpms. I will try some of the suggestions and let’s pray that it works
I’m hoping to have the problem fixed this weekend. 
