Cdrew83942

Hey guys,

I've browsed the forums for some time trying to find a solution here, but haven't seen anything that jives with exactly the symptoms I'm seeing. This has been an intermittent issue, so take everything below with that in mind. So here it goes:

Symptoms
- Car runs fine unless I mash the accelerator to the floor. Sometimes it accelerates fine if I do this...
- CEL comes on with p0303 cylinder #3 misfire and O2 sensor bank 2 sensor 2 code
- Car starts misfiring real bad and shaking almost feels like it's about to stall.
- Sometimes the car will crank but not start until I let it sit for a few minutes.
- Once I restart the car the bad misfire appears to stop, but the CEL remains. I'm not sure about this, but I do feel like it could have a single cylinder misfiring after restart...

What I've tried:
- Fuel pressure checks out around 50-60 psi even during misfire
- Cleaned MAF with purpose built spray
- Unplugging MAF and flooring it. (still reproduces the misfire)
- I switched ignition coils from cylinder 1 to cylinder 3

Results after switching ignition coils:
- Same rough shaking the car misfire
- CEL:
P0100 - Mass Air Flow (expected since it is unplugged)
P0110 - Air intake temp circuit
P0300 - Random misfire
P0301 - Misfire cylinder 1
P0303 - Misfire cylinder 3

I have a new bosch MAF on order since I'm not convinced this is not the culprit. Sometimes the car accelerates fine and I get great hard acceleration. I would really appreciate some ideas or some first hand experience with these issues. Thanks.


Chris

Plutoe

Misfires, you can look all you want, but except for the obvious(plugs wires and coils) they occur for numerous different reasons. We wont work on any misfire issues unless the customer first agrees to pay for a full MB scan. Then we go from there. They are the most difficult issue to diagnose correctly!

Cdrew83942

@Plutoe I've zeroed in on a few likely issues after reading other threads, but I'm open to other possibilities:

- Bad coil, wires, plugs
- Bad MAF
- Bad CPS
- injectors

Maj. Dundee

Codes P0100 & P0110 are for the MAF sensor. Why do you have it disconnected?

When you swapped coils hopefully you switched one at a time on the opposite bank. Meaning make the swap from #1 cyl. #1 to any other coil on the opposite bank then test drive and read codes again. Then do the same for #3 cyl. Do not do both at the same time.

Did you remove the spark plugs on cyl. 1 and 3?

Read the PDF on Misfires.

Cdrew83942

@Maj. Dundee it definitely feels like the selective fuel shut off is occurring, which Would cause the misfire.

I unplugged the MAF to run without it briefly. I was told that the engine will run on default values if the MAF is unplugged.

I’ll try switching the coils, plugs and wires to the other bank and update afterwards.

Cdrew83942

@Maj. Dundee as suggested, I swapped the coils, wires and plugs from cylinder 3 to cylinder 4 on the drivers side bank.

Adding to the mystery, the car is not throwing any codes after several hard pulls, and is accelerating as quick as it should.

the plugs and wires didn't look particularly fouled, but I'm sure they could use a change.

Any suggestions going forward?

Maj. Dundee

How can I suggest anything else when the car is running OK?

Cdrew83942

For anyone interested: I replaced the CPS and have not had any more issues.