Reply With QuoteNot sure about the BOSCH engine but with gems at least the MAF is so far away (at the beginning of the air intake) that misfires are not likely to hit it.Just to check: did you erase the error codes after replacing the O2 sensors?
Cheers,
-P
Master
SupporterHi all, a few weeks ago I noticed my 2001 P38 HSE 4.6 thor hesitating now and then, was struggling up hills occasionally, I couldn't quite put my finger on what the problem was as I could not recreate it.
Other times it ran perfectly.
Then one morning it lost power, I managed to turn around and baby it home, the fuel pump had died.
I replaced that with a new Bosch one and it started straight up, all was well again.
Then I noticed it was idling a bit rough and smelled like it was running rich, I took out the plugs and they were carboned up, classic overfuleing sign.
Checked the fault codes and one of the O2 sensors was at fault.
As the O2 sensors are now 19 years old, I thought it was probably time to replace them both.
So with new O2 sensors installed, it was running very well while driving, but the rough idle and overfuelling is persisting.
I checked the fault codes, there are 5 codes present.
*P0135=Oxygen sensor heater upstream catalyst Bank1 Drive cycle C persistentely present
*P0155=Lambda sensor heater upstream catalyst Bank 2 Drive cycle C persistentely present
*P0175=Mixture adaption factor FRA Bank 2 drive cycle C (signal too high) persistentely present
*P0134=Lambda sensor upstream catalyst Bank 1 drive cycle C signal invalid intermittent
*P0175=Additive adaptive mixture correction TRA Bank 2 Drive cycle C (signal too high) persistentely present
I doubt I'd get two new faulty O2 sensors, so I'm thinking that's all pointing to a faulty MAF, but I'd be interested to know your thoughts on this.
The MAF I have is about 5 years old, I'm wondering if missfiring due to the old fuel pump has damaged the MAF in some way.
Thanks, Pete.
Wizard
SupporterNot sure about the BOSCH engine but with gems at least the MAF is so far away (at the beginning of the air intake) that misfires are not likely to hit it.Just to check: did you erase the error codes after replacing the O2 sensors?
Cheers,
-P
Master
SupporterHi Prelude, thanks for the response, yes I did clear the fault codes a couple of times.
The codes don't re appear straight away, it needs to be driven a bit for them to show again.
It could just be a failed MAF sensor regardless, as the MAF and the O2 sensors work together.
Wizard
SubscriberDo you need to do an adaptive reset as you would with a D2 after replacing O2 sensors?
2002 D2 4.6L V8 Auto SLS+2" ACE CDL Truetrac(F) Nanocom(V8 only)
Master
SupporterI did attempt to do an adaptive values reset, my faultmate worked really well with my old serial port laptop, but I have tried and tried to get it to work with my new USB laptop with no luck. I have updated drivers etc with no success.
While I can read and clear fault codes in stand alone mode, I can't do anything more advanced without it being connected to a lap top.
It is my understanding the adaptive values would adjust themselves over time anyway, it's been 3 or 4 weeks now with no noticeable improvement.
You are probably right though, I might keep trying with the new lap top, pity the old one died!
Wizard
SubscriberAfter replacing one of my sensors, I had a 1000km trip with terrible economy and bad fueling ratios. As soon as I did the reset, it all came good immediately, so worth a try.
2002 D2 4.6L V8 Auto SLS+2" ACE CDL Truetrac(F) Nanocom(V8 only)
Master
SupporterThanks biggin, you were spot on!
After a bit of mucking around I managed to update my serial to usb drivers, got it hooked up and what do you know it connected.
I reset the adaptive values and it instantly started idling better.
I think that's done the trick, thanks for your help!
Saves me the cost of a new MAF.
Cheers, Pete.
Master
SupporterI have an update, it is idling better now and running well, but I'm still getting the error codes popping up for the 02 sensors.
I have cleared the codes twice and they keep returning after a drive.
Any suggestions on a next step here?
Thanks, Pete.
YarnMaster
SubscriberHi Pete
have you checked for vacuum leaks?
the following URL has a fairly comprehensive approach to testing the O2 sensors... including checking voltage fluctuation with a multimeter..
(O2) Oxygen Sensor - Function - Failure Symptoms - Testing
hope it helps
cheers
Hoges
MY99 RR P38 HSE 4.6 (Thor) gone (to Tasmania)
2020 Subaru Impreza S ('SWMBO's Express' )
2023 Ineos Grenadier Trialmaster (diesel)
Master
SupporterThank you for that Hoges, interesting read!
I have not checked for vacuum leaks, that will be my next step, I'll check that today.
Interestingly, the plugs on the drivers side bank are full of carbon, the passenger side plugs look pretty normal.
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