Hi,

I have a 2007 GTC with under 5,000 miles.

The car runs ok at cold startup. After it comes off the start up cycle of higher RPM it runs rough for three seconds. Sounds like it will die but it doesn't. It will idle around 500 RPM.

I used my universal tester.

It gives me:

"Intake Air System Leak P2279"

When I delete the code on the running car it runs rough for three seconds again. Sounds like it will die but it doesn't. Just like it does after the cold start.

Five seconds later P2279 is back.

Initially I also had P050A, Idle Air Control System Circuit Low. This code has not come back after I cleared it.

I checked the connections from turbo to I/C and I/C to throttle body. They look ok.

There is a vacuum to overcome when removing the oil filler cap.

Is this the dreaded split hose problem? Or is there a diaphram on the valve cover like on Audis that could be torn? If there is, where do I find it?

Where should I check? I do not hear any air escape. Car has low power and is rough.

 

Could possibly be anywhere from the inter cooler inlet tubing back. I would inspect connections beginning at the inter cooler to turbos and work my way up and back. Also may want to inspect air filter box for cracks and bad connections.

 

I just did another cold start.

Got four codes:

2 x "P0101 Mass or Volume Air Flow Circuit Range/Performance"

2 x "P2279 Intake Air System Leak"

Upon reset only P2279 comes back. Just like before, causing rough idle then throwing the code right when idle gets stable at 500 RPM.

When the car is idling I can hear some persistent faint knocking. It sounds like a solenoid is trying to move or a valve is trying to open/close.

 

Sounds exactly like the symptoms of the 07 GTC here minus me knowing the code. Am sure you've seen the 'Rough Idle' thread about a month ago. Smoke test found it and was an engine out hose R/R affair.

 

hi Zbird.

please see the pm i left you also that faint knocking is probably the purge valve it sits on right side inner fender behind headlight,check and make sure that is on its mount ok and see if you can hear vacuum pump running constantly,if the things i put in the pm check out then as Enjoythe music wrote a smoke test is next on the list.

 

bentleytech,

Thank you for your reply and help.

The air pump inside the left front fender only runs if I hit the brakes three times and shuts off after three seconds. Does that mean I do not have split hoses?

The engine tray is off. I checked all the large hoses from turbo to intercooler to TB on both sides. They look good.

The MAFs are a pain to get to. I just pushed on the connectors. I also spraycleaned both MAFs with electrical contact cleaner.

I found the purge valve, the 1" hoses seem to have a tight fit.

I let the car idle again, deleted codes.

"P2279 Intake Air System Leak" came right back.

Then I raised RPMs to 1,400. The code does not come back while at higher RPM. Only after I dropped down to 500 did 2279 come back.

What do you think about the other two codes?
P0101 Mass or Volume Air Flow Circuit Range/Performance
P050A, Idle Air Control System Circuit Low

At cold start this morning I got two each P2279 and P0101. Does that mean on both banks? My tool does not specify the banks.

 

OK, I did some more work.

I looked at the purge valve some more and noticed that it can be flipped back and off the hose.

When I drive with the lower part removed and the hose open the car has its power back. That is a relief. While driving at 1,500 RPM I do not get code 2279. But I do get 0101 when driving. Keeps coming back. When idling at 500 RPM I still get 2279.

Does all this point to a faulty purge control solenoid, one or two faulty MAFs, or both?

Or something entirely different?

Oh, and the exhaust stinks like rotten eggs.

 

i think you really need to do a smoke test and find out which bank is giving codes,like i said we used to experience severe running issues with bank 2 mafs,at the electrical connector,can you look at the pig tail and see if it hjas been renewed ever and please make sure both mafs are sitting in the rubber seal correctly. just for interest you said car has been sitting,have you had any work done on it recently or was it like this just after you started it for the first time after 5 months.

 

Which side is bank 2?

US driver or passenger side?

My driver side has the MAF going towards rear of car. This one is pretty hard to get to. The passenger side has it pointing to the fender. This one is much easier to get to.

 

Bank 2 is the left hand side,by the dipstick you should be able to apply a little pressure to connector to see if it changes engine revs etc. have you tried soaring a little throttle cleaner around all the hoses at the firewall end to see if it changes engine revs ?

 

Thank you for your continued help.

I have used carb cleaner. No soaring anywhere. That would also point to the MAF.

I'll try to unplug the MAF to see if that changes anything. If it doesn't that would point to the MAF as well.

What is procedure to remove the MAF?

 

I got both air boxes removed. The MAF pipe is just plugged into the intake pipe. That is some design. Can't really appreciate it. That leaves room for so many issues. What a shame. Most likely what caused my problems.

After removing and cleaning both MAFs with electric contact cleaner the car finally started to run right after I cleaned the second MAF on the right side.

Let's see if it still runs OK tomorrow.

It is strange that the right MAF has four wires and the left MAF has five wires.

Bentleytech, thank you for all your help with this issue. You had pointed to the MAF early on. If the problem comes back I'll buy one or two new MAFs. Thank you again.

 

glad you got some progress,but before you condemn the mafs,check the pigtail on both sides,they are gold plated connectors in there i believe and we have had awful issues with them,some places even use tie wraps to secure them tighter ! you can buy just the pigtails from the bentley dealer.

 

Glad to see you seem to have solved the problem. For your reference, what we (on this side of the pond) call Mass Airflow Sensors, the manual refers to them as Air Flow Meters. You mentioned that one connector has five wires and one has four. When I chased a problem somewhat similar to yours, I was concerned about the different wire count. The difference is correct. Here are the two wiring references for the Airflow Sensors. If you want the schematics, please PM me.

For what it is worth, the mistake I made was to replace both MAFs before I discovered my problem was only with the connectors. Anybody need two used (but fully functional) MAFs?

 

Do the new pigtails have a better updated design?