Amabile

Me and my b/f are about at wits end trying to figure out the culprit in this situation, was hoping I might get some help in here. Car in question is a 95 Z28 M6.

Last week, it started running real crappy. It was ok if you rode the clutch and didn't give it too much gas. Try slamming the accelerator down and it'd stumble real bad, almost die. We thought it might be bad gas (that's what it was running like), so we tried some Heet. Didn't make much difference and it stayed parked all day. The next morning it wouldn't even start, it would turn over, but wouldn't fire.

We were trying to do some troubleshooting on it from tips some friends had gave us... and in the process, he pulled a plug wire off to check for spark, which we couldn't see it, but thought maybe it was just to bright outside and we missed it... the funny thing is, with the plug wire off, the car starts up just fine! Put the plug wire back on... it's back to not starting.... We were both quite baffled, and didn't know what to make of it, but was told to try replacing the coil... He exchanged the fuel filter we were going to try for a coil (yeah, that broke ) and put it on to see if it fixed it... He didn't mount it, just unplugged the old one and hooked the new one in (so if that wasn't it we could take it back) and the car started up just fine, revved fine, and he was all excited thinking he had it fixed so ran upstairs to get me and the 2 year old. I got outside, he tried to start it, it sounded like it was going to start, then flames shot out the throttle body...

We're back to square one... any ideas what it could be?? I just really don't have the funds to start replacing things until it's fixed... really don't have the time either! We're trying to find a good shop nearby that would be reliable and not just try to replace everything on a whim... but, I thought I would come by here and see if anybody had any ideas!! I'd really appreciate it
Thanks a million to anybody who even read this far
Tara

Bobbys_97_Z28

Try opti? how many miles?? looks like you have taken a look at the main things except the opti...

Hotwire

Hey Tara,

The car won't start unless the intake is securely fastened onto the throttle body, it needs air going through the MAF to run right.

rent a fuel pressure regulator from autozone to try that. like bobby mentioned, have you looked at the opti? I know a lot of people point fingers to it, but maybe just pull it and check to see if it's carbon tracking inside, clean it w/ dish soap and hot water, dry it real good, and reinstall it, sounds like it the way you describe the car not firing w/ the plug wire removed.

good luck.

Amabile

We'd actually been avoiding even thinking about the opti due to $$/hassle. Iwas actually told that it'd cost upwards of $300-$400 dollars to replace. I see that's quite high, may have to look into these Autozone reman.

How bad are these to replace?

Tara

TechCam97

When my opti went out, it did that exact same thing. I'd do some checking around the hood though, make sure all the spark plug boots are on all the way, especially the boots at the opti. They can come off easily if the wires are stretched too tight. Make sure all your electrical connections are secure and tight...make sure you check out the coil and the coil wire, sometimes people forget about that. Also be sure to check all the vaccuum connections and make sure nothing has any tears in the lines. Everything! If there still is no improvement, then I'd look into replacing the opti. I know it seems hard, but it's not too bad. Just take your time and have the proper instructions and you'll get it done just fine. When I replaced mine, I replaced the coil, plugs and wires. Just to be certain the whole spark part of the system was good. Good luck with your problem though!

Amabile

Well, we decided to just bite the bullet and take it to a shop for diagnoses. Neither of us has time right now to do it (we need it back on the road days ago), so we decided "Screw it!".
Well, in spite of the fact that the plugs and wires were changed under 10K miles ago, they're "confident" that what it needs is a tune-up (specifically plugs-wires). I'll be talking to them soon to see how in-depth their inspection was, but in the meantime, anyone else buy that? I hate to take a gamble on that being it when it's gonna run us $571. I know from when we changed them before that their price isn't THAT awfully ridiculous, but it's still a fair amount of money to gamble with.

Opinions?

Thanks,

Tara

Billz28

I wouldn't buy that. $500 to change wires and plugs? Seems kind of high. Did they show you any wires that were damaged or fouled plugs? Did he scan for trouble codes and sensor problems?

Maybe I'd let them do the change only IF they guarantee that the problem will be solved, in writing. If not, then its their responsiblity and cost to keep working on it until it is. I've know people who know how to work on cars to get hard to fix/diagnose problems done this way. Replacing plugs and wires is the definitely the thing to try. Next would be the coil and ignition module. After that comes the optispark, that is if it is an ignition problem.

Several weeks ago, mine did some serious stumbling when more than just a little gas on the way home. At home I turned it off and then it wouldn't start up again. My first thoughts were that it was the new optispark which I had replace 2weeks previously along with the waterpump. After getting set mentally to pull it all apart again, I put my coil and ignition module, which come off real easy, on a friend's engine and found it to be the coil. A $40 part and <15min fix.

You might do your own inspection when the engine is cool. Look for discoloration or burn spots on the wires; it's possible for the wires to arc; in this is the case you might even see arc it at night or see the manifolds glowing. Are all the wire connections secure on their plugs? secure on opti-spark. If you pull any of the wires off the plugs, check for corrosion inside. Are any of the plugs loose, you shouldn't be able to turn them by hand. Definitely check the wire which goes from the coil to opti-spark.

S8ER95Z

I did the Napa Rebuid for 160.00 and it solved all my problems. After I tore the opti apart I discovered the cap was melted partially and the rotor looked like an army man stuck in the microwave for a little too long. Over 8 months of heavy driving (I frequently race, bury the speedo, etc) and its running perfect

Hotwire

I would listen to Billz28.

Sounds like this shop likes plug and play. I would ask them if they ohmed out any of the wires end to end to check for higher than normal resistance, measured resistance to ground to see if any plug wires are shorting out. Ask them if they checked the spark voltage to the plugs, good shops have meters, make them work for that money.

I had problems with mine, turned out to be a ton of rust in the injectors from where the truck sat outside w/ no front end and no covers over the fuel line for 6 months. My water pump went out and truck was missing, so I automatically thought opti, replaced it, wires, coil, ignition module, plugs, etc...

good luck.

Amabile

Well, I wanted to thank you guys for the advice. I think we tracked down the problem. Apparently when the plugs/wires got changed last time, they weren't securely routed. Once the shop got it up on the rack and could actually see the routing of all the wires (which we couldn't), there's massive arc going on down there, and damaged wires.

That would seem to make sense to me on all fronts. Even if that's not what cause it, it sure isn't gonna run right till that gets fixed anyway.

What do you guys think?

J