WTF, I am stumped

[lmnhed]

OK, my car idles way too high. The previous owner had the idleadjustment screw adjusted all the way and the car still idles at 1200-1700 rpm. I was wondering what you all think the problem might be. I am leading towards the timing belt being off some teeth at the cam gears, ie cam timing off. the reason I think this is because my powerband is copped up. It is pretty laggy for an RB20DET IMO, even with a z31 turbo, and then it'll fall out of power from 3.5-4.5k rpm's and then pull from 4.5-6.5k and then kinda fall off to red-line. I could be wrong maybe the high idle is a wiring problem, I have yet to pull the previous owners wiring job out and clean it up. Do these problems sound like it could just be wiring or are you with me on the whole cam timing thing? Let me know what you think. Maybe I am missing something entirely. Le tme have it. TIA

[JonPowell]

MAF and it's wiring, TPS and it's wiring, IAC and it's wiring, vacuum leak from the manifold.

[lmnhed]

I know its not a vacuum leak. So it looks like my next course of action should be to pull the engine harness out and redo the whole thing. Its just that with the powerband acting weird it makes me believe timing to be off. Do any of you know where I can find info on doing a timing belt for the RB20, I guess I could at least check and make sure the cams are lined up pretty easily.

[Ramius83]

I KNOW that it cannot be your timing belt being off a tooth or two.

I know this because on my VQ (Maxima), even with the one single exhaust cam on the front bank being off ONE tooth, the car would almost not run. When I gave it 1/2 throttle, the engine would shake. Any higher and the engine would cut off.

If you think the timing belt is off still, you can take off the front cover and the crank pulley, and check it. Hell, you could just even take the timing belt cover off and keep turning the motor a good couple revolutions and wait until the belt and the marks on the belt get to the alignment marks on the cams. If, and when it does, you can then eliminate that as another reason for your troubles.

I agree with Jon about the MAF, IAC, and the TPS. One, even two combinations of any of those would result in a horrible untuned engine that would describe your lack of power and rough running engine.

Get your multimeter out and get the FSM out. Test your wiring and test the sensors for functionality. After this is done, then you can eliminate those possibilites and we can go from there.....

[FrostyRB]

You would deffinatly know if your cam timing was off because it would not want to idle, and the car would run like a bag of d!ck.

[Nameless EJ6]

I've never heard a bag of d!ck before.. but I also don't think you're belt is off.

How do you know you don't have a vac leak? What methods did you use to check?

Check voltages and specs on all major sensors that determine idle speed. IAC, CAS, Water temp, etc.

If they are all within specs, then look elsewhere.

[lmnhed]

Thanx for the replys guys, glad to hear that you all don't think I have a cam timing issue. Some reason that made since in my head. I'll probably still pull the top cover and just make sure both marks line up to feel a little better. As far as the wiring goes, I have a huge task ahead of me. The previous owner didn't take that much time in wiring things properly from what I can tell, I have already found and fixed the MAFS wiring, and the cold start wire wasn't hooked up so the car would crank forever. I am guessing that this may not be all of my wiring issues, so I am gonna have to pull the entire engine harness out and go to town on it. Don't worry about me though, I am very familiar with a multimeter and how to use it, I have done a few different swaps on S-chassis before this. This car I bought with problems, not my swap but it was a good deal, and I won't have time to really tear it apart for a while cus I am still building a Z32tt. Right now I am just trying to get ideas from others that know more about Rbs than me. As far as following the FSM, where can i find an FSM for the RB20DET, I swear I have found it before but I can't seem to find it now. If any of you have a link that would be awesome. As far as testing for a vacuum leak, I have a pressure tester that i built from home depot supplies that allows me to pressurize my piping and intake manifold, hence all I have to do is listen for air leaking out. It is the handiest tool ever when you own a boosted car.

But yeah, if you could link me to an FSM I would be obliged, forgive me for i am not as good at the internet as all of you. Thanx again guys.

[Nameless EJ6]

I'd still question that vacuum testing you're doing.

Are you using a gauge with it? Engine vac is very strong, usually 20-30 in-HG. If you're not pressurizing it to 20-30 psi it won't tell you much... especially without a gauge to monitor.

I've never measured with that method, considering pressurizing the system probably wouldn't be acurate - air seeps in and out of open/slightly open valves.

Just pinch or bypass vac sources to test for leaks. I do this all the time at work.. usually with old american carbureted vehicles with cracked *** lines.

btw, you don't need to take your valve covers off to check for camshaft alignment. The cam gears only go on one way, and there are markings on both of them, as well as the harmonic balancer. Line up the engine to TDC and visually look to make sure they are all lined up. If you keep rotating and rotating, not seeing them line up, then your belt is off.

g/l

[lmnhed]

Well I didn't feel like going into too much detail on my pressure testing kit but I should have mentioned it has a boost gauge on it so that you can test it up to a desired pressure. I usually test up to 20 psi because my tester pops apart after that. And yes I know that air will escape past the valves but that is a very quite drone, nothing like the sound of air leaking outside the engine. But I will try your method cus it can't hurt.

And I never said I was gonna take the valve cover off to check the timing belt, when I said top cover I was reffering to the black-plastic-front-top cover.

So does anyone know where I can find an FSM?

[krayton]

i got a few i can throw on a disk.

let me know