Highpox1

Owned for 6 years, mileage 53K. About a month ago, when driving to work at a steady 70 mph, I began to feel motion sickness..the car was surging back and forth. The tach was not moving, but clearly I was feeling this push from behind, then a let off. Air temp was 50F. Since then I have experimented and found the following: Does NOT do it when air temp is > 60F. Surges at any steady speed, from 30 to 80. Will not do it on acceleration (still smooth). Does it w or w/o the A/C being on, or cruise control. Many tanks of different gas, so not a fuel issue. When stopped, the idle can't hold. It jumps from 600 to 900 rpm (target is 700 rpm). After 5 min of idle, it settles in perfectly at 700 rpm. No code is thrown, no pending code is showing. This HAS to be a MAF sensor issue? It seems like the cold air (<60F) is causing the MAF to vary the fuel mix (leaning), but no one will work on it until it shows a code. Should I gamble and replace the MAF, or do you have another suggestion? THX!

Verboden

I have no experience with the problem but since you think it might be the MAF it would be a simple job to clean it before trying a replace. They actual make MAF cleaner but you can also use electrical contact cleaner (ingredients very similar half the price). I have done it on mine, I had the intake out at the time but I am not sure if removal is actually needed. Not a particularly hard job if you have basic hand tools and the required Torx drivers.

North Shore 911

Just spitballin' here, but have you had any problems with starting your car (taking longer crank time to fire up)? The High Pressure Fuel Pumps on our 997's are a typical problem (I had mine replaced at 40k under CPO), and at 53k I wonder if you're starting to see that manifest itself in what you're describing...?

Highpox1

North Shore- no issues starting. That's still normal and quick. If the HP fuel pump was acting up it wouldn't be temperature sensitive? The facts here tend to rule out mechanicals since it's a cold air issue and sure acts like a sensor of some kind. A mechanical failure would (a) likely throw a code and (b) repeat no matter the air temp. Fuel pump, clutch, plugs, etc all would be continuous. Plus the unstable idling for several minutes then going back to a steady idle suggests it's reading an air flow that -once settled - eliminates the problem. Keep the ideas coming please.

docdrs

HPFP will usually shoot a reduced engine power warning due to lack of adequate fuel.

Linnm

What is rpm range when you feel the surging ?

Cbst09

I agree that cleaning the maf sensor should be the first try before replacing. I use the CRC stuff.

Highpox1

When I am holding a steady speed the rpm is between 3K - 4K. I tried varying the steady rpm when it was surging and it didn't seem to care. Once it started it seemed to occur no matter what the gear or rpm. I slowed to 30, then 40 mph, all the way back up to 80 and at flat speed, it was rocking me.

Highpox1

Can you clean a MAF sensor w/o removing it? I watched a You-Tube on changing one and it seemed fairly straight forward on pulling it. Before I replaced or even cleaned it I was hoping I was on the right track here. It could be an O2 sensor too (don't we have 8 of them?). Thx

Cbst09

The MAF sensor is so easily accessible and is just two screws and lifts right out so just remove it. Should literally take about two minutes to take out. Be careful not to touch any of the wires inside, hold the maf sensor by the outside only and spray the cleaner on the wire inside. Mine is a 997.2 Carrera S.

Highpox1

You still have to pull out the air intake and flip it over, correct?

DC911S

You read the ECU for any codes or errors. If it's surging that bad a fault should be triggered.

Highpox1

That's the frustration. It isn't triggering a code or even a pending code. Nothing. The dealer won't touch it w/o a code. Too many options. Given the evidence I've collected it seems to be a sensor of some kind. I live in Texas, so we are warming up here. There is a cold front coming late week, and the morning temp is supposed to be 54F. That should get it going again. I may try to get over to a mechanic to have a look, but we are just guessing w/o the code.

Cbst09

No, you dont have to pull out the intake at all. The maf sensor is right on top. It is located right on the side of the intake (where I have the red arrow placed) Like I said, just two screws

Highpox1

Thank you-- I saw a video of the intake having to be flipped. Yes your engine and mine are the same. I will pick up some cleaner spray and give it a shot. Would a dirty MAF cause these issues in colder air only? Maybe. We have a cold(er) morning coming late week so that will be a good test.