shadow993

On my jag xfr, I have a rough idle with misfire on left 2,4,6 cyl code at startup.

The dealer cleaned injectors, reprogrammed throttle body, and checked injector & coils.

While watching my O2's I noticed my left bank is at .012 and .08 at idle and jumps with throttle but will settle down around there. While the right bank that doesn't show a misfire shows .750 and .350.... and jump around with throttle, but settles around those numbers.
The indi mechanic thinks its injectors.

Thoughts ? Ideas?

pp000830

Air intake leaks after the MAF can cause misfires. Misfires on multiple cylinders suggest a shared source of the misfire, not a plug, wire or injector. If your oxygen sensor was a problem you would get an OBD Code directly related to it. I noticed the cylinders involved are even numbered, are they on the same side of the engine, this may be a clue to look for the problem.

nine9six

...Or dying, yet not yet failed O2 sensor.

shadow993

Would they both die at the same time? Im thinking it's bad could or plugs causing the car to run lean.

shadow993

Thanks. It has dual mass sensors , but a shared intake. I may swap the MAFS and see if that helps. However that usually has its own code. The intake tube is fine, as the dealer had to replace it, bc they cross threaded the mounting bolt.

NC TRACKRAT

Even though they replaced the intake tube, squirt a little starting ether around the left bank and see if the idle raises.

pp000830

+1

nine9six

You're getting a code on one bank (2, 4, & 6) correct? How many O2 sensors control this one bank of cylinders; one, yes?

If your O2 sensor has failed you'll get a bad O2 sensor code; but since you're getting a lean condition code on one bank of cylinders, I'm thinking it could be a failing, but not yet dead O2 sensor.

If the dealer was the last one messing with your car and the issue was not there prior to the dealer touching the vehicle, then go with the most likely cause, first.

Granted, I know nothing of your specific vehicle but I was just trying to help since you're posting in a Porsche 993 forum.

shadow993

No worries... in asking here bc most guys here are gear heads.

I have 2 O2 sensors on that bank(4 on the car)and both show lean.

The independent that did the timing when the issues wasn't there, keeps saying injectors. That's a big $$$ bill. Before I start throwing money at it, I wanted a 2nd opinion. Dealer cleaned injectors do the de carbon technique. They said injectors fine, could fine, and reprogrammed the throttle body (jag tsb).

I'm going to swap out the coils and plugs. If that doesn't work, back to the independent.

nine9six

If it's like a 993, it's got one pre cat O2 sensor, and one after cat O2 sensor per bank; for a total fo 4 O2 sensors.

Why not switch one bank of O2 sensors with the other. If the problem shifts banks, its the O2 sensors. Elimination of potential variables.

I don't believe plugs, if the right heat range; would be the cause of the lean condition.

More likely, vacuum leak or O2 sensor issue. Or possibly a MAF related issue.

shadow993

My gut says vacuum leak, bc it idles better once warm. However, I covered that motor with carb cleaner and no fluctuation.