Rough Idle/Hesitation/Backfire

[Gary Yarbrough]

Thanks for all the advise! At idle the spark sounds "loud and clear"... Does anyone know if there is a way to test the ECM before I send it off to have it rebuilt?

[XfireZ51]

Originally Posted by Gary Yarbrough

Thanks for all the advise! At idle the spark sounds "loud and clear"... Does anyone know if there is a way to test the ECM before I send it off to have it rebuilt?

Is the motor running? Is this just a miss at idle? Why would the ECM need to be rebuilt? Is there a code?
Seriously guys, the ECM and ignition module are core systems not just for running the motor but even more importantly, from an OEMs perspective, emissions. So these components are pretty robust with other peripheral components more likely to fail first. I just see many here jumping
to the ECM problem as a conclusion for an idle miss etc. Particularly if the motor hasn't been scanned and datalogged. I'm not doggin anybody but just my .$02. I'll get off my soapbox now.

[Pete]

What brand of plugs are you using.

If i had to guess by your symptoms,Bosch.

Also where did you gap the plugs?

Also why in gods name would you wanna put it in 6th gear @ 40mph and floor it.

Pete

[Gary Yarbrough]

The issue is deeper than rough idle. It is a hesitation in the ~1500 to 2200ish RPM range.

Pete, you guessed right about the plugs. Am I correct in assuming that I've gone wrong with these? As for the gap, I don't recall off the top of my head but I set them at whatever the stock gap was.

[secondchance]

I agree w/ XfireZ51. Before going into ECM based on my personal experience;

1. Check for cracked insulation on plugs. What the heck! Try a new set of standard Delco plugs - only $30 top.
2. You said MAP hose is fine. Is it factory? Factory hose is a hard plastic with rubber boot at both ends only. I thought my MAP hose was fine but found out it was collapsing at low RPM (high vacuum condition) after aging w/ fuel vapor and heat degradation.

I apologize if this had been discussed already.

[XfireZ51]

Originally Posted by Gary Yarbrough

The issue is deeper than rough idle. It is a hesitation in the ~1500 to 2200ish RPM range.

Pete, you guessed right about the plugs. Am I correct in assuming that I've gone wrong with these? As for the gap, I don't recall off the top of my head but I set them at whatever the stock gap was.

I doubt hesitation is spark related. If you are hitting the accelerator and its "bogging" that's a sign of air but not enough fuel. As for the backfire, is it in the exhaust or the intake?

[Gary Yarbrough]

Originally Posted by XfireZ51

I doubt hesitation is spark related. If you are hitting the accelerator and its "bogging" that's a sign of air but not enough fuel. As for the backfire, is it in the exhaust or the intake?

Backfire is on the intake end of things.

[secondchance]

Originally Posted by Gary Yarbrough

Backfire is on the intake end of things.

That sure sounds like one of the cylinder firing during intake stroke - possibly arcing?

[Pete]

Originally Posted by Gary Yarbrough

The issue is deeper than rough idle. It is a hesitation in the ~1500 to 2200ish RPM range.

Pete, you guessed right about the plugs. Am I correct in assuming that I've gone wrong with these? As for the gap, I don't recall off the top of my head but I set them at whatever the stock gap was.

Bosch will do all the symptoms you describe above.

Change them with a set of regular resistor AC-Delco 41-602 plugs $10 gap them at .035 and enjoy.
Lesson learned, more doesn't always mean better.

Pete

[secondchance]

Originally Posted by Pete

Bosch will do all the symptoms you describe above.

Change them with a set of regular resistor AC-Delco 41-602 plugs $10 gap them at .035 and enjoy.
Lesson learned, more doesn't always mean better.

Pete

Very well could be. Corvettemasters in Orlando tried a set of Bosch Platinum 4 (I think) in my car back in 2000 and they hated it. Went to stock plug which was FR2 LS? It has been a while...