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Hey guys, so its day 60 of ownership for me and my 4.2 D4. Sometimes i feel the engine skipping a beat on cold start ups and lately i notice some hesitation when i accelerate from a stop. The drive seems fine for the most part and one day I accelerated a bit harder for an overtake on the highway then my engine light lit up (static light and not blinking). Good timing since I just ordered my OBDeleven and it was picking it up that night. So i scanned the car and it indicated the codes written below;
I took it to my independet mech and he said its due to the carbon build-up in these engines and recommended having it cleaned using compressed air with a media (crushed walnut shells). He has to take out the manifold in order to access the intake ports and valves to do this. Its about grand ($) and 12 hrs to do this but before I say yes to this should I keep in mind that if the carbon build up is the culprit, wouldn't it affect more than one cylinder and have random misfires occurring on more than one cylinder? The spark plugs were recently done @ 85k kms by the prev owner and I'm at 120K kms now. A bad plug? 35k kms life for a spark plug should still be okay, right? Im assuming at this point that a bad gas mixture from a misfire triggered the error code. Should i swap the coil packs first and observe if the misfire migrates to another cylinder before anything else? I need some guidance for those of you who have experienced this before. Thanks in advance!
With symptoms given out by codes you're getting, I would suspect upstream O2 sensor. Cylinder 1 & 2 are on the same bank, so makes the O2 sensor on that bank more suspect.
Moving coil packs is an easy way to see if it’s the coils.
plugs are 35k mile intervals but might be worth it to do iridium plugs and then now worry about it for a bunch of miles.
What TheoRR said about an O2 sensor makes sense though.
Thanks for the reply guys. Where can I find this o2 sensor? It should be near the cat-converter towards the front, right? If it's underneath the car then I may have to find a shop to hoist the car up. I think I'll start with the coilpack since it's more accessible to me. Maybe start from small diagnosing this one by one before doing a carbon clean.
Access to O2 sensors (both upstream and downstream) is from the top of the engine compartment. Interestingly, in the D4 setup, upstream and downstream O2 sensors are literally located right next to each other separated only by matter of inches. For reference purposes, the left hand side O2 sensors can be easily observed from the top of the engine compartment near the back of the engine. On the right hand side, which you're having problems with, downstream O2 can be easily observed, but the upstream O2 is under the clutter of various hoses and tubing.
Access to O2 sensors (both upstream and downstream) is from the top of the engine compartment. Interestingly, in the D4 setup, upstream and downstream O2 sensors are literally located right next to each other separated only by matter of inches. For reference purposes, the left hand side O2 sensors can be easily observed from the top of the engine compartment near the back of the engine. On the right hand side, which you're having problems with, downstream O2 can be easily observed, but the upstream O2 is under the clutter of various hoses and tubing.
Okay thanks. I'll take a look at it today. Last night wasn't a good time and I already broke a tab on coilpack #1. The cold weather makes these plastics brittle. Btw, what would cause the misfire though? Does the upstream sensor go before the engine and followed by the downstream sensor?
Last edited by collantes_C6; 04-28-2019 at 05:18 AM.
Just the upstream O2 sensor sending bad info, and downstream O2 regulating the engine assuming the info from upstream is correct. When the upstream O2 sensor goes bad, symptoms are often miscellaneous misfires and not a code for the upstream O2 sensor itself. Misfires are a result as the engine runs too rich. A typical upstream O2 sensor issue starts by intermittent slight rough idle, then after awhile constant rough idle which would register a check engine light as running rich may potentially damage the catalytic converter. O2 sensor going bad is a fairly random occurrence. I wouldn't look at it as a harbinger to something worse to come.
04-26-2019, 12:14 PM
A misfire and engine hesitation.
