My '99 ls1 m6 has had a rough idle, hesitation, been back firing and running really rich for the past few weeks since I installed an slp catback. I've changed plugs and wires, O2, tps, and maf sensors. Had it scanned today and the scanner read the maf was faulty, but that's all it showed and it was a cheap scanner. Gonna get another new maf and see if that cures it. Any other ideas of what it could be?

Mods : Lid, pacesetter lt's, 3" ory, slp loudmouth 2

 

I'd try cleaning and re-installing you original maf. Just use isopropyl alcohol and some q-tips.

 

It looks like it should be the maf..since you alreadlt replaced all other possible causes

 

Use maf sensor cleaner not q tips.

 

No luck with a new maf sensor, although it did stop most of the hesitation. Could it be the IAC or a vacuum leak?

 

Iac should trigger CEL. Yes, vaccuum leak is likely.

 

Cleaned the iac and throttle body yesterday, still no luck. All vacuum lines look good from what I can see though. Anyone know where I can get a vacuum line kit, or some sizes at least? SES is on, but the MAF was the only thing the scanner showed, and it was replaced.

 

You weren't having any issues before the exhaust mods? I would check for burned o2 harness. Can you scan and see if the fronts are switching properly?

Also, double check you have all plug wires snapped down on the plugs and coils.

 

You could try a new coolant temp sensor.......

They cause all your issues when they are failing.

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Everything looks good on the scanner though, exhaust back pressure shouldn't have anything to do with it, should it? Or could it just need tuned?

 

I can't see why in the world it would be your exhaust back pressure! I'd keep looking for a different solution. Spray a can of carb cleaner over all vacuum lines and there connections to check for a leak, you'll hear the car will want to choke out.

 

Did you check the intake bolts? Did you test for vacuum leaks around the intake seals?

 

Check the fuse for the MAF.

 

Sprayed carb cleaner around vacuum lines, injectors, and intake, didn't do anything. Which fuse is for the maf sensor? And is there only one coolant temp sensor or two?

 

lol you can't tell anything doing that.......check the intake bolts.

 

This may be a stupid question, but did you put the maf on in the right direction? There is an arrow on the case that shows the direction of air flow.

 

Yep, the maf is on the right way lol

 

Finally found the issue, scanned it again. It said it was the maf, wiring was bad going to it. Thanks for the input though guys.