z24 won't run - need advice

[pappyl]

1999 2.4 l chev cavalier 200 000km

Wife took a trip, car running just fine, stopped to shop, was hard to start, finally started - drove for about 15 min - went into campground, car wouldn't stay idling, eventually stalled - couldn't restart.
Can put to floor, will start, feathering throttle, but will stall (running very rich)

Brought to garage to diagnose - said it was ignition coil or module. Got a "tested" unit from wreckers (whole ignition assembly w/housing) Dropped it in - same problem - garage full of shit.
- Checked all vacuum (and Map sensor) all seem good
- NO Codes on computer (have an actron scanner)
- Fuel pump charging (I changed filter - no effect). No valve to check pressure.
- When I am able to start
- eventually stalls (too rich - fuel in muffler)
- can can get it too level out smoothly for a few seconds - coils ok...

- I dont think its fuel supply (unless regulator shot)
- I dont think its ignition coils/module
- Timing?
- Computer?

Simply not sure what to try next....

Any ideas greatly appreciated.

Thanks

[pappyl]

Well, since no one has a clue out there... I guess I'll need to work this myself.

- So far
- visual inspection all vaccum lines, ignition wiring, and pulled all fuses/reseated (engine compartment)
- pulled ignition coils & module housing - swapped out with a junkyard unit - same results - not sold that this is ignition problem
- attempted to get components tested at a few places - no luck - seems garages can do a test - when they are in the car - not useful...

- So I bought a fuel pressure meter and a schrader valve kit - need to BE SURE the fuel pressure is around 10-13 lbs - so pressure I'll test
- next step pull the throttle body, IAC, TPS and clean them.
- Pull the plugs, clean them, drop some oil in the cylinders for compression
- Put her all back together and try to start it

- If it runs, great, if not.... need to get this electronic test complete... I do not want this to be a PCM problem.....

So if anyone else has this type of problem, hopefully my posts will help.

[Blue Bowtie]

Perform a fuel pressure test and check the leakdown rate when the fuel pump shuts off.

[TRINI55]

pappy
check for plugged cat, disconnect exhaust from manifold, start and re-check

hami

[mcclunet]

Dont feel bad I am currently working on a 96 z24 2.4 quad4 with the same issue, The car has 35,000 miles, was only drove 5 mils a day and a older layed owns it. so it has never seen abuse, rough housing of any sort. So far I have changed coil pack, fule pump, crank & cam sen, pcm, nothing has changed. I have a cirt gm guy look at it, he told me it was security locked, tryed to reset it. nothing, changed key switch, ipc (gauge cluster) and still the issue remains. I am running out of things to change/ try myself. I am unsure if the cata is pluged, that is my next step in the morn along with testing injector wireing, tps, and changing injectors all together. Be rest assured if i find the problem on that car i will let you know the next place to check.

[pappyl]

Hi Guys - here's an Update

As per my plan, went to the fuel system to check pressure, part of which is a vaccum "behaviour check" on the regulator. I pulled the vacuum line off the regulator and low and behold, full of fuel!

This explained all the behaviour.

I pulled the injector rail off and replaced the fuel regulator ($126.00) and we are back up and running!

note: I could look right through the bottom of the regulator - a pinhole in the diaphragm.

IF you are on the road and this happens, disconnect the vacuum and plug with a bolt, use a spare/small length of vacuum line blocked off at the end and a small hose clamp to seal the regulator. That'll get you home...

So, here's a breakdown of my specific steps.
- Pulled the fuel pump relay, cranked the engine to depressurize the fuel line
- Removed the TBI plastic intake
- loosened the supply line on the right of the fuel injector rail
- Undid the bolts off fuel line clamp in the back, then the intake, then the 2 bolts holding the rail
- Undid the accelerator cables... Just pull the plastic tabs up with a screwdriver on the housing, and the clips come out. Rotate the accelerator back to rotate out the cable end.
- Unclipped the injectors (little blue pastic tabs - depressed with small srewdriver, then pulled them out a bit, then they unclipped. Undid the cam sensor. Pulled wiring harness aside. Carefully wiggled the rail/injectors out and pulled the fuel rail up to rest on top the intake.
- Undid the torx screws off the regulator and return line clamping plate.
- wiggled the regulator off the return line, and out of the fuel rail (both pressed/sealed with O rings) NOTE: used rag to catch gas in rail.
- Cleaned the intake ports (stuck fuel line host in injectors and cleaned each with WD40) as there was plenty of crap buildup which I didn't want to get on the injectors when I put back in
- Cleaned the injector Orings (all were good) - BTW best to replace - BUT I couldn't get any in time - reused old ones - put dielectric grease on each
- Did the same with new regulator Orings - pressed in return line, and rail.
- Reassembled injector rail, intake (make sure to every injector connector clicks in, and don't forget cam sensor). Connected regulator vacuum.
- Pulled the plugs and cleaned them, them put ignition housing back on, connected ignition plug
- Double-checked all connections - then restarted engine
- Fired up then died, fired up again, ran a bit rough as system cleared the excess gas (exhause was a smokin). Note: came up with a map sensor error - it eventually cleared.
- let her warm up and then took her for a run - all good.

As for the cat, since I've run too much gas into it, I do expect I'll need to replace the cat before my e-test in October. That's a job for my mechanic - a PITA without torches and a hoist.

Thanks for the input guys. Hope this helps anyone else who has this problem.

[pappyl]

Mcclunet,

Not sure if you are having the same problem - maybe so. I assume you've checked all the fuses and relays.

You should be able to put a stethascope on the injectors - they click when they turn on (even an old broom handle on the intake should hear them click). Should hear them when you turn the engine over.

btw: I had a GM dealer tell me I had to replace my computer on my Bonneville to fix my AC. I found a blown fuse on passenger side to be the problem. Take what they say with a grain of salt.

The only other thing I could think of to check - the PCM (should be a box on the right fender). Check for compromised wiring. Hope not the box. It's a dealer switch as it needs to be programmed. Was in my Haynes manual.

Best of luck.