FactoryFreak99

I sold my 99Z M6 about a year ago. I loved this car, I almost cried when I saw it like this. It got destroyed by the new owner... I bought it back for a $1000. I sold the car originally with these bolt ons...

Ported FAST Intake 90mm, FAST TB 92mm, new plugs and wires, SLP lid, Pacesetter LT's no cats, TSP True Dual w/ Mufflex race mufflers, new TPS, emission delete, new o2 sensors and extensions, new fuel filter. 98,000 miles. STOCK TUNE!!! I repeat no tune... The car ran fine though, needed a tune obviously, but I went FRM, and sold it. Never had a problem like this when I had it.

Okay, well now that I have it back... It will not run right. I drove it 200 miles like this so hopefully that's a good sign. Here's what it's doing... As soon as I turn the key it revs to about 2500rpm. After 1 second (literally) with no driver input, the engine loses all power and shuts off. Like the ignition/fuel just turned off, and dies. However, I can keep it running with a little foot feed action. It misses terribly when I'm keeping it running like this though. It misses A LOT... The rpm's jump around too while I keep it going, it might stay at 1800rpm for 2 seconds then die, or rev to 4000rpm, then die. Without me touching the gas, its dies instantly. With a little courage I drove it like this. However, above about 2000rpm with a load, the car "runs" decent. Some sputter around 2000rpm, but no missing. WOT, it runs decent too, pulls okay still. Confusing already for me... While driving fine on the interstate, if at any time I push the clutch in, or put in neutral without hitting the gas, it will die, immediately. So while driving 60mph in 5th gear, running decently with cruise, push in the clutch or put it in neutral, the car dies withing 2 seconds, literally. Its ran like this for about a month he said. One day he just got in it and it started doing this. He said it sounded like a cammed idle for two days, then this, no idle ****. Good news, no knocking, and not much smoke that I can see really. It always does this, never changes. Not when it's warm out, cold out, warmed up car, cold start etc...

So after digging a little... The o2 extensions are shredded. Which shouldn't make it die immediately. I unpluggged the MAF and it idles at about 3000rpm, with no missing. Cleaned the MAF, no help. Unplugged all the sensors that didn't change anything. Tried to check for vacuum leaks, but it wont idle, and it's very, very loud. I don't see any fuel leaks. Getting a fuel pressure gauge tomorrow, let you know what that is. I can hear the fuel pump prime.

I don't know where to start. It still has no tune, and the o2 sensors are not hooked up/ working. The MAF is stock. Fuel Pump is stock, 100,000 miles now. I don't understand why it will run WOT, but not even idle for 3 seconds. I don't know what to look for for codes, cause its going to throw a bunch already like this.

Please, someone help me. I sold this car after a bad breakup, regretted it for a year. Now I got over the b**** and bought it back. I can't not love this car. Any wisdom will help.

VandykeT/A

Check all the battery connections and ground wires. Are you getting any codes?

FactoryFreak99

Yeah all the connections are good. Throwing lots of codes because of how jacked up everything is. I'll have to see what all codes it's throwing. Definitely misfire and o2 sensors.

VandykeT/A

No chance someone messed with the 02s and plugged them in the rears or even crossed them (not sure crossing them is possible). I cammed a C5 and accidently crossed the upstreams and it wouldn't run at all. Died at idle, cutout continuously until the CEL came on and then ran perfect until you turned off the car. Probably not the problem but something to look over. Scan the codes and report back.

FactoryFreak99

The o2 sensors are in the bungs on the header only to prevent an exhaust leak at this point. The extensions must have dropped down after i sold it. They came unhooked and aren't even able to be plugged in anymore. I dont have rear o2 sensors either. So its def going to through a code for that.

VandykeT/A

A friend of mine had some home made 02 sensor extensions that he just spliced with electrical tape and his car would spit and sputter and sometimes completely die when it rained or had been raining. I'd fix the 02 sensor and go from there with the codes.

Sail Hatan

id fix the O2s first, then go from there. pics of the car?

LS6427

iTrader: (2)

There's no reason to even try to fix this problem till you fix the the 02 sensor wires and check them with a scanner to make sure the 02 sensors are switching properly. Don;'t be surprised if all your troubles end after you fix the wires.
02's cause misfires at all rpms levels.......and rough running engines.

If its still idling high on start up after the 02 sensors are back online.....but runs good at WOT, you probably need a new IAC valve (Idle Air Control). If you have no vacuum leaks.....for sure.....the IAC valve acting up is the ONLY thing that can increase engine rpm's with your foot OFF the throttle pedal. No other way for an engine to increase rpms........period.

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FactoryFreak99

Alright guys little update. Waiting for the o2 sensors to come in a friend stopped by a scanner. O2 sensors was one code, egr another, and MAP sensor was the other code. We also noticed that timing was jumping from 14 to 39 degrees while I was running it. Also had a misfire on cylinder 5. Friend drives 02SS, so I was able to eliminate MAF. IAC was dirty, still moved. Removed it, plugged it, unplugged it, ran the same every time. Backfires and smokes now, smell really rich.

The timing degrees seemed a bit extreme. Every time I blipped throttle to keep the car running it spiked over 35 degrees but yet fell to 14 degrees at points. Crank sensor..?

No clue on how a car acts with a bad map sensor...

LS6427

iTrader: (2)

Disconnect battery for 30 minutes to reset the PCM and clear the codes....then Install the new 02 sensor and re-connect the battery....if it doesn't IMMEDIATELY fix the issue(s), remove it and return it for a refund. Clean it up and tell them you don't need it that it was something else that was wrong and you never even installed it.

Then its time to check the ground connections behind the passengers side head...2-3 bolts depending on year. Most important one is the PCM-to-Head ground wire. If they are tight, then with the engine running and the scanner connected, grab the wiring harness thats coming right out of the PCM, the big thick wire bundle, and move that bundle left-right-forward-backward and see if there's a change in idle, misfiring, sanner readouts, while the engine is running....

If that checks out and there's no change for the better or any changes at all........you're PCM could have taken a ****. You can pop off both PCM strip plugs (loosen one bolt on each plug) and look at all the pins, see if any are burnt looking. Even with no burnt pins though, the PCM could be bad.

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FactoryFreak99

I cant even keep it running so I cant check the harness. I'll wiggle the harness...

FactoryFreak99

Also, what are the symptoms of a bad MAP Sensor? Im throwing that code, and its the only code that didnt really make sense. Are those timing parameters normal?

FactoryFreak99

Here it is the day before I sold it. It has a bra cause the paint chipped off the cheap urethane bumper. I'm gonna repaint it pearl white again, with either black Manta stripe or Sunuco hood, black Berger panel, grill delete. The blue stripes I have on it are a really nice blue, with ghost flames in the stripes. They are ruined though... It has Caddy Pearl white on it now, but the whole car needs to be repainted due to damage everywhere as you can see. New qaurter, new door, new front and rear GM bumpers are going on it after I get it running good.

midnightbluS10

And this guy did all this in 2000 miles of driving it? Seriously?

Fix O2's, replace MAP sensor. If you still have EGR, remove the EGR valve, clean it, make sure the pintle isn't being lodged open by a chunk of carbon, and reinstall it. An EGR valve that's stuck open could cause the no-idling issue.