JimmyMur

My boxster has started to occasionally throttle when I press the clutch in while coming to a stop. The revs do return to normal slowly. However, when the AC is on then car performs much worse and will actually stall when coming to a stop due to the revs dropping so low. At higher revs with the AC on or off the car performs perfectly normal.

CEL shows p1124 and P1126. So far I have replaced the MAF and AOS. Smoke test booked for Friday.

Any ideas would be appreciated.

Macster

P1124 is oxygen sensing adaptation range 1 (cyls. 1-3) at enrichment limit.

P1126 is same error for cyls. 4-6.

If DTC P1124 or P1126 logged then fuel/air mixture is too lean.

Possible causes: intake system leak; fuel pressure too low; fuel injectors contaminated; volume supply of fuel pump too low.

You have replaced the MAF and the AOS. That leaves a possible intake system leak. (This ignores, for now, low fuel supply or low pressure or contaminated fuel injectors.)

Some thing you can check easy. With the engine idling check that the oil filler tube cap is not leaking. See if you can move the cap around even lift it up and if the engine reacts.

It was a leaking oil filler tube cap that had me diagnose a bad MAF and replace same only to have the error codes come back again afterwards. wehn I was looking into this again a co-worker heard the oil filler tube cap leaking while the engine was idling.

Might mention the replacement cap eventually failed the same way. At over 310K miles on my Boxster I have worn out 2 oil filler tube caps (and 3 AOS's). That is I "get" around 150K miles out of an oil filler tube cap.

Otherwise I guess smoke test to test for an intake air leak. If that turns up no leaks then you will have to confirm there is sufficient fuel in the fuel tank and then check fuel delivery supply and pressure.

JimmyMur

Thank you for your reply Macster, really appreciate the help.

The oil cap comes off easy and there is little to no change in the idling.

Macster

Sorry, didn't make myself clear. I did not want you to remove the oil filler tube cap.

I only wanted you to check that even though the cap was tightened down properly if you could move it about or or even lift it up some and cause a leak at idle.

However, it is kind of suspicious that removing the cap results in little to no change in the idle. A healthy engine with a healthy intake system at a hot idle should react rather dramatically when the oil filler tube cap is removed.

It should recover in just a few moments. And when you put the cap back on the engine should react again -- though not as dramatically -- and recover in just a few moments.

With the engine up to temperature -- cold the engine is more richly fueled and this can partially compensate for an intake leak -- see if you can move the oil filler tube cap about and the engine reacts or you can actually hear air leaking past the cap. But do not unscrew the cap.

JimmyMur

Thanks again Macster. I was not able to move or lift up the cap.

The strangest thing is that it only really plays up when I have the AC on.

San Rensho

Check what the air flow is with a durametric. I believe it should be around 13-15. If it's significantly lower then you have a vacuum leak which could be the problem. If it doesn't show a vacuum leak I wouldn't waste the money on a smile test.

JimmyMur

Thanks San Rensho, unfortunately I do not have access to a durametric. I could probably ask the garage to do a quick check before they start the smoke test tomorrow.

mikefocke

Up at the top of the page listing all the thread topics in a dark band and in the middle is a command button called "Search". Press it and in the box enter "P1124" and you will get displayed 47 threads of others having the same symptoms. Read those and see what their causes/solutions were.