Rough idle/no rev problem

[tada]

Originally Posted by Need_for_speed

Just throwing this out in an attempt to be helpful: any chance that the variocam solenoid on that bank has failed? And if it did, would it throw a code or light the CEL?

I think it's a good idea. No CEL is being thrown. The only codes the Durametric is picking up is a low battery failure (when I disconnected it to reset the DME) and a P1541 when I jumpered the fuel pump relay. There should be a way to test the solenoid. If anyone knows, it would be appreciated. Thanks, Tom

[tada]

It's been a while since I updated the post. I've been working a lot of OT at work and haven't had much time for the Box. Today I cleaned the IACV and reinstalled it with a new gasket. I cleaned the throttle body first. Installed a new gasket between the throttle body and intake manifold. Reinstalled everything.

Went under the passenger front fender and smoke tested the lines from the evap canister. Fired it up. No change. Still running only on bank 1.

I've been reading posts about vacuum pressure at the oil filler cap. While running (barely) I checked for a vacuum. When I take the cap off and place my hand over the opening, I feel a little suction. Actually it ran better without the oil cap. Reinstalling it just caused the engine to stall.

So have I found all my vacuum leaks? I've inspected every component and replaced all the rigid hoses. Otherwise, I'm down to replacing the fuel injectors. And that looks fun. Do you have to pull the air box and the secondary air injection fan to get at the rails and injectors?

Thanks, Tom

[tada]

I think there still must be a large vacuum leak. My next suspect is the brake booster vacuum line. Does anyone know how to disconnect the white round connector in the engine bay, or is it necessary to remove the screws securing the flange to the intake plenum?

[jdraupp]

Originally Posted by tada

I think there still must be a large vacuum leak. My next suspect is the brake booster vacuum line. Does anyone know how to disconnect the white round connector in the engine bay, or is it necessary to remove the screws securing the flange to the intake plenum?

Not sure, but the brake booster lines are a big one as far as vac leaks are concerned.

[tada]

I removed the vacuum hose for the brake booster and sealed over the opening with duct tape. Same results. Running on bank 1 only. So I have chased the vacuum leaks. The only thing I can think of now is to remove the fuel injectors and send them off for cleaning and flow matching. I may be wrong about the flooding of bank 2. It may just be too lean. The plugs have a slight smell of gas, but look brand new. So maybe I have three stuck injectors? The car did sit for months. I have tried running techron through them.

[jdraupp]

Originally Posted by tada

I removed the vacuum hose for the brake booster and sealed over the opening with duct tape. Same results. Running on bank 1 only. So I have chased the vacuum leaks. The only thing I can think of now is to remove the fuel injectors and send them off for cleaning and flow matching. I may be wrong about the flooding of bank 2. It may just be too lean. The plugs have a slight smell of gas, but look brand new. So maybe I have three stuck injectors? The car did sit for months. I have tried running techron through them.

The only thing with the techron is if you can't get it to run it won't do you any good. It works by passing the fuel through the injectors. So it's possible I guess that if you have a stuck injector that the techron can't get there? Good luck, hoping it's this. You've tried all else.

[Smallblock454]

Hello tada,

did you get my wiring plan for the car? Did you check the wiring loom?

3 broken injectors at once? Hm, implausible.

Regards, Markus

[tada]

Originally Posted by Smallblock454

Hello tada,

did you get my wiring plan for the car? Did you check the wiring loom?

3 broken injectors at once? Hm, implausible.

Regards, Markus

Got the diagram, thanks. I ohmed the harness out and found no problems. I was hoping to find a short to ground. I used a noid light and saw the harness working correctly. But I can't get my meter leads into the actual fuel injectors themselves because the air box is in the way. If one of the three injectors is shorting to ground internally, it could cause a failure on all three.

[Smallblock454]

Originally Posted by tada

If one of the three injectors is shorting to ground internally, it could cause a failure on all three.

That is correct. OK, pull them an check them.

Maybe they can also be checked if you measure the resistance of the fuel injectors at the ecu - if you diconnect the wiring plug. I don't know the resistance value that should be measured there, but they should be the same as on the other bank.

Regards, Markus

[tada]

Sorry to revive my old thread, but I’m back to trying to get the 986 running. On advice from a mechanic, I changed out the camshaft position sensor on the offending bank that was not firing up. I then tried to drain my old fuel out of the tank by removing the fuel pump relay and jumpering it. I could get no fuel out of it. So then I checked my battery and found it to be 12.14V. The battery was still in warranty. So I got a new battery today and tried to fire it up. It’s turning over and trying to start, but just won’t catch. I jumpered the fuel pump relay again and listened for the pump with the ignition on. I heard nothing. Now as part of this project, I had earlier replaced the fuel pump and measured the fuel pressure in the fuel rail and it was fine. Hard to believe a fuel pump died without ever being run. I also checked the fuel pump fuse and it was good. When I try to crank the engine, the tach barely registers. I mean not even a tick and no real movement of the needle. Could it be the crankshaft position sensor? I don’t get much time to work on the 986 as I work out of town and am only home a day or two a month. So I didn’t have time this trip to check the fuel rail or spark to the plugs. Just looking for ideas. Thanks, Tom

[Gelbster]

Crankshaft Position Sensor?
Fuel Pressure regulator?
Fuel Filter?