Backfire on startup, long cranking...

[Vett-Klr]

Ok, the car ran 100% fine.
We pulled it into the garage and decided to check the plug gaps. We broke one of the plug wires, gapped all the plugs and installed a new plug wire in place of the one we broke.
Car wouldn't start, it would crank forever then backfire. After much cranking it did start. It ran 100% perfect.
Got it home parked it.
The next week it started fine while cold, but now whenver I try to start the car after it's heated up, it wont start and backfires quite loud. It will eventually start and once it gets started, it runs with zero problems.
Any ideas???? My neighbors are beginning to hate my car.

Dave

 

[83ttypecooled]

Hi,
You said it runs with ZERO problems? No misfires? This is an interexting problem. The simple solution would have been mixed up plug wires, but you seem certain that is not the case. I guess it is also possible that, while changing the plugs and wires, you inadvertently disconnected or jarred a sensor, but I can't imagine which one. You didn't mess with the cam sensor, did you? You probably removed the duct hose to the MAF sensor, but could problems there do what you are talking about? I doubt it. How about MAT or ECT problems? This is about all I can come up with at present, good luck with this puzzling issue!

 

[Vett-Klr]

My buddy has a coil pack laying around, I guess I'll start there....

Anyone else?

 

[SouthernCal GN]

Pull the ECM wire to clear the computer.

 

[turbofabricator]

Pull the ECM wire to clear the computer.

Everytime I just PULL on the ECM wire, it does NOTHING! I then tried a new approach and actually unplugged it. THAT really worked good. So, from now on, I'm going to unplug the ECM connector (the orange wire behind the batttery) everytime I need to clear codes. Pulling on that wire didn't do anything for me. :biggrin:

Your problem sounds very much like a bad timing chain, bad cam sensor or a loose crank sensor. Crawl under the car and grab the crank sensor and try to wiggle it. If it is loose, try to tighten the clamping scew (5/16") with a .020" air gap to the interuptor ring (use a 1/4" wide slice of a spark plug box to set the air gap-- a card board feeler gauge). Your thrust bearing might also be wasted, causing the balancer to move too far forward, or even a loose balancer bolt. I've seen all of these conditions cause your same problems. Tug on the balancer forward and backward. There should only be .009" max movement in the balancer. Try to pull the balancer out of the engine, then try to push it back in. If there is ANY movement at all, then there is a problem. It should only be able to move about the distance of a human hair. It will move, but if you can see the movement, the thrust bearing is wasted, or the balancer bolt is loose, or the balancer hub is cracked. (seen that, too.) Did you change spark plugs of just re-gap? Use AC CR-44TS plugs, gapped at .035" for a 450hp, or under, engine for street use. Get rid of any platnum plugs that are in the engine. They do NOT work in our cars. Stay with AC CR-44TS or Autolite #24's. No gain in fancy plugs and usually a loss with expensive plugs! Might also be time to install a good set of plug wires, too. If I ever break one, I replace ALL of them. I usually replace plug wires every year weather they need it or not. I keep one old set in the trunk. Usually end up giving them to someone at the track, though. Amazing how many guys over look the plug wires.

 

[SouthernCal GN]

Everytime I just PULL on the ECM wire, it does NOTHING!

Ken, ya don't want to be pulling on ANYTHING at your age

 

[Vett-Klr]

I swapped the coil pack, no difference.
I pulled the orange wire and let it sit overnight, no difference...

?????


What causes backfire? Too much fuel, to littel fuel, no spark?

 

[Chris McDade]

Timing could be off. Pull the cap off the cam senor and make sure the cap is not cracked. Pull the cam senor out of the car and make sure it's not broken. They do brake. Report back

 

[Vett-Klr]

Ok, it appears to be ok now. But I'll have to try it again tomorrow to be sure.
First there was a pink wire under/behind the coil pack that was slightly damaged, I fixed it up and all seemed well. Then I played with the cam sensor a bit and was able to make it backfire but them I think I got it adjusted just right (since it didn't run well in all the other positions I tried).

I'm still puzzled as to why it cranks for so long. It did not do that before the cam swap. I went from a flat tapped 206/206 to a roller 212/212. Ever since then, it required longer cranking. It used to start within 2 seconds, now its like 6-7 seconds before it turns over.