Car misfiring, random misfire code, constant knock counts, oh my.

**Toni** · 07-31-2014, 09:49 AM

Alright so my car has developed some misfiring problems.

[Update 1] Halfway fixed, misfiring ended up being a bad PTU but the knock/dogging not fixed yet[/Update]
[Update 2] knock issues seem to be fixed with a new sensor.[/Update]

Cliffs:

Started misfiring the morning then went away never to return all day.
Could drive for 2hrs no issues once it went away
Throwing random misfire code
Multi-bank issue, front/rear afrs peg at 20-22
Also sometimes 7-9 Knock counts as if knock sensor was disconnected but went away never to return
Seems to be getting worse
New plugs did not fix
Swapped coills didn't fix.

First instance:

Started the car in the morning, went a mile and stopped at a light. Check engine came on and the car ran rough. It completely went away and the car was fine the rest of the day.

Second instance:

Car was fine in the morning to work, at lunch it did the same thing but this time, it wouldn't go away quickly. I pull over and check ignition related connections. I was only a mile to my food place so I started limping it. Then all of a sudden it came alive. It had a "random misfire" code stored.

Car ran fine the rest of the day and took it on a 2hr trip.

Third instance:

Did it again on the way home from 2 hr trip a couple days later of the car sitting. It took a few miles for it to clear up.

Decided to change the plugs. This didn't fix anything.

Fourth:

Happened one more time on the way to work and went away but I turned around and parked it. This time the check engine light was kind of flickering. I figured it was just the misfire code.

Fifth:

This morning the car started up just fine, went maybe a mile and the check engine light popped up. I pull over and checked the code, no code? Put up the logger and it's 7-9 counts of knock and my knock light is triggering. I check the knock sensor (it's <20kmi old) connection and all seems good visually. Start the car back up and a couple hundred feet and it goes away and the car come alive again. Odd...

A mile down the road the misfires start to happen. Both banks run lean 20-22 so it's not just one cylinder. No code right away. This time I drive for 4-5 miles and it's not going away. Pull over and check connections etc so I drive it home.

I have a spare coil pack, luckily I can reach all the connections so I plug it in. No changes. I also unplugged my DLI just in case that was messing things up. No change.

**Boost4VR4** · 07-31-2014, 09:52 AM

Sounds to me an intermittent injector... Or a bad signal wire from the O2s to the ECU...

**Jimvr4** · 07-31-2014, 10:24 AM

Sounds like fuel issue. Check fuel pump and hotwire?

**Toni** · 07-31-2014, 10:32 AM

Was talking to Hans and he linked my ECS issue with my misfire issue. Could be a possible bad ECS unit. I replaced the bad caps like 7 years ago but maybe it finally gave up the magic smoke.

**Toni** · 07-31-2014, 10:31 AM

Fuel pressure was good on the gauge.

**green-lantern** · 07-31-2014, 02:04 PM

damn, I hate intermittent problems like this. Did you make sure the MAF sensor is plugged in well? I had a gasket that was pulled out in the plug a little bit and was keeping it from plugging in all the way.