Lately, seemingly when I am at or near idle with a warm engine, I get a pretty frequent Restructed Performance. Car has new plugs and I replaced one coil pack when the car was having issues earlier. It throws a P0172 and P0175, both banks running rich. Do you think I have more bad coil packs and should replace the other 7? Possible dirty MAF sensor? Vacuum leak? Any suggestions?

 

Are you running the original 02 sensors?


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You really need to get an ODBII code reader and see whats going on. Or go to a place like AutoZone and they will read it for free.


Dave

 

If you can measure the fuel trims you might try this to narrow it down,
Diagnostic Tip:

For a suspected vacuum leak, note the fuel trims at idle and increase engine speed to 2500 RPM and hold. If the STFT immediately decreases and moves to acceptable levels and the LTFT slowly starts to come back down, you have a vacuum leak. After the repair, reset the KAM and start the vehicle. Monitor the fuel trims to make sure they are within the normal ranges. It could take up to 10 miles of driving for an accurate LTFT reading.

ps, op supplied codes

 

I'm running original O2 sensors at 90k miles

I may need to upgrade to a scanner capable of reading fuel trims.

 

With rich codes it's unlikely to be an air leak.

Still worth looking at the trims in hope.

Maybe a dirty MAF.

If both codes flagged together then a common cause is most likely - and both O2s going bad together is unlikely.

 

Are you an XK8 or XKR? I had a similar situation on my R (simultaneous onset of 172 & 175 codes) and found it to be a disconnected little vacuum(?) hose that ran from the top right side of the s/c to what looked like a pressure regulator on the front of the right fuel rail. Reconnected the hose and the problems went away instantly. Good Luck!

 

the tube to the TB can become can become brittle and leak air near the corragated portion. Pull it off and check I wrapped mine with electrical tape. Also while you are at it check vacuum lines and clean the maf.

 

+1 from me at 90k miles on original 02 sensors on at least checking them!

They may not necessarily throw any codes but even a failing 02 sensor will cause all sorts of trouble.

Rough uneven idling / hesitation / surging / increased fuel usage and others

 

So far I've checked the intake tube and it looks perfect . I cleaned the MAF sensor while I changed oil today and it seems good so far, but I'm not sure it can be that simple since it looked very clean to start, but I guess we shall see

O2 sensors are probably the next thing to look at. I haven't looked, do these cars have 2 or 4?

 

I had those codes and cleaned the Electrical Connector to the MAF/IATS, cleared the codes and have not had a problem since.

 

We have four O2 sensors. Two at the tops of the Catalytic converters and two at the bottom. It's a pretty typical set-up these days.

 

That is what I figured.

Day 2, about 75 trouble free miles with MAF and MAF connector cleaned, so we will see if my luck holds.

 

Well my luck didn't hold out, so on to the next step. I am going to try to clean the back side of the MAF and my filter needs to be changed, but I'm thinking the problem is more than that.

 

I hope the fresh air filter and subsequent MAF cleaning fixes it for you. Keep us posted....

 

Me too, since cleaning the front seems to have helped a bit despite not noticing much of a visual difference before/after. I'm laid up with the flu right now so it will be a couple of days before I get to it.

 

Well today I was chasing TPS issues and replaced the gold contacts (with no luck ) so I had the hold intake elbow off. I had looked over it before, but today I noticed one little bad spot. Could this be enough to cause issues? Right now the Restricted Performance takes a back seat to the failsafe engine, but it does make me curious.

 

Yes that little leak can really confuse things for sure....



Dave

 

Agreed. Any cracks in the accordion section of the intake air duct can cause havoc. Tape it up or replace it. I replaced ours in October 2012. No codes have been thrown since....

 

I patched the leaky intake hose with some blackjack [black roofing caulk I had sitting around] (there was just a pinhole through), cleaned the back side of the MAF (still looked clean to me) and replaced the air filter. So far, so good, but still too soon to tell.