I started a thread yesterday, and had my head up my rear when I titled the thread, sorry folks, lol.
It's an automatic 98, with an 01 short block, and it want's to stall at idle, and really want's to stall when shifted into gear. At idle, especially when cold, it stumbles horribly, when shifted from gear to another the RPM's will drop to 300 or so before picking back up and idling roughly around 700 rpm. We discovered several vacuum leaks caused by dry rotted hose's and caps in the pcv system. Here's a few questions though, any help would be appreciated, as I can't find any really good vacuum diagrams
1. The Fuel pressure regulator has a vacuum line coming off of it. This line was just routed through the intake manifold, but did not connect to anything, where is this supposed to go. I think it's the regulator, it sits on top on the intake manifold, connecting the two fuel rails.
2. When a vacuum leak down check is done, it does not hold vacuum at all, should this car hold a vacuum?
3. With the scan tool hooked to the computer, the TPS sensor seems weird to me. When the car is cold, the voltage stays at 1.3v, give or take a few 10th's, gradually as the car warms up, it will drop to .9 and .8, incrementally after a few whomps of the accelerator. The car runs better at the lower voltages, but shouldn't this voltage fluctuate with each individual use of the accelerator? I've never seen this happen in a car, but who knows.
4. The throttle body does not have the coolant hoses lines hooked up, there should be coolant running through here right?

Again, any help would be appreciated, is there anything else I should be looking at? The PCM is dry, no moisture in the carpet at all.
Dan

 

Anyone???

 

Why do you have caps in the PCV system?

 

I'm not sure why it's there, but the rear vent on the passenger side valve cover that is supposed to hook into pcv was capped. Also, couldn't find a port on the line to plug it into, maybe the line was changed at some point? There were lot's of weird stuff in this engine bay from some previous work. We got it running a little better, I won't be able to look at the car again for a week or so, but any tips before then will be most welcome.

 

unless you're FI I believe you should see vacuum at anything other than WOT. if you have no vacuum that could be the issue, it will cause stalling. someone correct me if I'm wrong.

 

When the car is running, I have 15" of vacuum, but if the car is off, it doesn't hold vacuum if I put my pump on it.

 

Your car is running off the idle table until it is in closed loop. Since you are drive by wire, your TPS voltages won't stay constant, so that is normal. Cars that have throttle cables, have Idle Air Control (IAC) valves that control the idle and the TPS is constant. That's not an issue.
What's not holding vacuum? If you're putting a vacuum pump on just the motor that's not running, that's not a valid test. If you are putting a vacuum pump on your brake booster or fuel pressure regulator, that's a different story.

 

Well the installer probably used the PCV setup from the '01 shortblock and just capped off the old setup when reusing the valve covers. At least that's my guess.

 

You really need to get a handle on the vacuum lines and PCV system. I would restore all to stock, and troubleshoot from there...otherwise....you'll just be chasing your tail.

 

Shouldn't the TPS voltage constantly change though? Rather than fluctuating between say, .5 and 4.7, this starts at 1.3, after a few minutes, will drop to 1.2, on to .9 and finally .8, even after the car switches over to closed loop. It doesn't do this constantly, but in slow increments.

 

It's always going to vary, but idle speeds in open loop are programmed higher and go lower as ect increases and you head toward closed loop. It will vary when in closed loop too. If you have vacuum leak issues, it may cause the PCM to " hunt " more. I recommend you deal with the known issues and see what you have left when you're done.