Another P0305 thread

[James Bricken]

Will the pain never end? Just replaced right side head because of a dropped valve seat. Then MAP sensor went out and replaced that (twice). Then the AC hose. Driving back to deliver the car to the owner and the CEL light comes on. P0305. Swapped out out injectors, coil pack, and plugs (which looked normal). Checked compression (160psi or so) Car seem to run normally except a very slight roughness in idle. Cleared the code and light has not come back on, but the code still shows up on the scanner.

I know these motors have valve train issues but I'm hoping it doesn't come to that. Anything else to check before I take the motor apart again? I think the wiring is OK since I can hear slight change in RPM when I unplug the #5 injector, but its not as much of a change as the other cylinders.

 

[James Bricken]

Just tested the leakdown. #5 is leaking 10%, and it seems to be getting by the rings. #3 is only leaking 3% which is normal. I wouldn't think 10% wouldn't be that big a deal, but maybe it is on this motor. I also checked the rockers and springs and can't find any other problem.

 

[James Bricken]

Did some more testing today. Started looking closer at the values on the scanner. #2 02 sensor on left side was reading abnormally low. Turns out the PCM sees this and adjusts the fuel map. I think this is what was throwing the code. I suspect the problem is the CAT but we changed the 02 sensor because it was cheaper. No change in the reading, but the code didn't appear in the scanner till we really romped on it.

 

[Porkchop]

Were did you get the O2 sensor, after markets are not as good as OEM. Just a thought!

 

[ThunderbirdJunkie]

Did some more testing today. Started looking closer at the values on the scanner. #2 02 sensor on left side was reading abnormally low. Turns out the PCM sees this and adjusts the fuel map. I think this is what was throwing the code. I suspect the problem is the CAT but we changed the 02 sensor because it was cheaper. No change in the reading, but the code didn't appear in the scanner till we really romped on it.

O2 sensor or cat won't cause a misfire code. Have you swapped out the coil packs? Don't go a step further until you do.
Are you an actual mechanic?

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[dude1116]

O2 sensor or cat won't cause a misfire code. Have you swapped out the coil packs? Don't go a step further until you do.
Are you an actual mechanic?

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He said he did in the original post. ;-P

 

[ThunderbirdJunkie]

He said he did in the original post. ;-P

He said coil pack, as in he threw one at it as a diagnostic part. He didn't say he moved the #5 coil pack to another cylinder to see if the code followed.

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[dude1116]

He said coil pack, as in he threw one at it as a diagnostic part. He didn't say he moved the #5 coil pack to another cylinder to see if the code followed.

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Hey I was just reading the wording. And being an ass at the same time.

 

[James Bricken]

Were did you get the O2 sensor, after markets are not as good as OEM. Just a thought!

I got a Bosch direct fit from AZ.

 

[James Bricken]

He said coil pack, as in he threw one at it as a diagnostic part. He didn't say he moved the #5 coil pack to another cylinder to see if the code followed.

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I said I swapped out the parts (more than once I might add).

 

[ThunderbirdJunkie]

I got a Bosch direct fit from AZ.

Bosch's parts store specials are not the same as OE.

I said I swapped out the parts (more than once I might add).

But did you take known good ones and put them in the cylinder 5 spot? And put cylinder 5's somewhere else to see if the misfire followed it?
Shit, dude, it's like you don't even know how to work on something without points and condensers. What sort of cars do you normally work on? A modern DIS multiport engine is the same to diagnose no matter its continent of origin.

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[ThunderbirdJunkie]

FWIW, ThunderbirdJunkie recalls the reading should be closer to 190-195.

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[James Bricken]

O2 sensor or cat won't cause a misfire code.

I have read where other people who have had the same problem and ended up with the same solution(s). From my understanding what happens the PCM sees the discrepancy in the 02 sensors and adjusts the fuel map, and that causes the misfire. Like I said: the new 02 sensor reads about the same output, but although slight, the performance of the new sensor is enough to keep the code from popping back up, except under extreme power demands.

 

[James Bricken]

But did you take known good ones and put them in the cylinder 5 spot? And put cylinder 5's somewhere else to see if the misfire followed it?

Yes I did. First thing.

 

[James Bricken]

Shit, dude, it's like you don't even know how to work on something without points and condensers. What sort of cars do you normally work on? A modern DIS multiport engine is the same to diagnose no matter its continent of origin.

I will admit I don't normally have to rely on computers to solve my problems for me. For the cars I do work on its I have much better OBD software, and even at that its a rare occasion that I'm so stumped I actually dig very deep to solve a problem.

 

[James Bricken]

FWIW, ThunderbirdJunkie recalls the reading should be closer to 190-195.

Probably. But the excessive leak down would also explain the low compression.
And although low, its not critically low.