Engine going flat between 3-5k rpm

[MNBoxster]

Originally Posted by 986Jim

All it takes is for the air fuel ratio to be out slightly (and it alwasy goes rich when it does) and you will lose a lot of power. Normally at WOT the car will run 12.5-13.0:1 (air to fuel) which is great for a normally aspirated engine. When the maf gives wierd readings the ecu will compensate with extra fuel as it's the safe way to keep the motor from blowing up. A lean air fuel ratio is very hot and burns out pistons and valves. A rich condition really robs the engine of HP however the ECU may not consider that a fault as it's not out far enough to trigger a CE light.

Most CE lights are maily for emissions related items, as long as it things emissions are ok the light stays off. HP is not the computer concern, but it is ours and when the car is rich the CAT will take care of the emissions but hp is lost which the ECU doesn't car about. We sure as hell do, so thats a big problem.

Eventually the reading will get so far out that CE light will come on and you have your problem.

Hi,

I agree with you and this is what I meant by a Masked MAF problem. IIRC, the Bosch DME ME 7.2 has something like 27 different A/F Maps. So long as the DME can switch to a different, compensating, Map and the 0² Sensors don't throw an Emissions Fault at it, it's happy and won't trigger a CEL. But I still suspect there's more going on here than just tainted Gas...

Happy Motoring!... Jim'99

[Brad Roberts]

Fuel pump.

I would suggest having a volume test done on the car if this power issue continues. Your cleaner may have freed up the pump temporarily.

I have seen this 2-3 times this year on mid to high mileage cars.

The K+N stuff is myth. I sat with the independant 3rd party firm who tested ALL the filters. You can dunk the MAF in oil...

Bottom line: The dealers dont want to warranty the MAF. There is a VERY large lawsuit against the dealers from K+N right now.. and K+N will win.

Now.. if you want to chat about the "air boxes" available and how they can run up against the threshold for MAF failure...LOL


B

[oversteerdawg]

I had a similar issue with a comical ending. The car was idling at 1200 RPM, the ce light was on, and i had a big flat spot from 3-4k. Also, I had a lot of part throttle hesitation/surging. Turns out the celophane from a cigarette box somehow got past the filter and was blocking the maf. I think when it was last serviced it may have fallen in without anyone seeing it. Worth taking a look if you just had your car serviced.

[johne4]

Saw that my original post resurfaced, car is running great, took several long road trips since post, odometer shows 68,000 now, yikes. The only problem I had was when I spent a couple of week in Missourri, for whatever reason the highest octane I could find was 91, a bottle of octane boost help. I have been sticking to one gas company, Sonoco, they have 93 octane down here and the car runs great.

John

[Adam]

Originally Posted by Brad Roberts

Fuel pump.

I would suggest having a volume test done on the car if this power issue continues. Your cleaner may have freed up the pump temporarily.

I have seen this 2-3 times this year on mid to high mileage cars.

The K+N stuff is myth. I sat with the independant 3rd party firm who tested ALL the filters. You can dunk the MAF in oil...

Bottom line: The dealers dont want to warranty the MAF. There is a VERY large lawsuit against the dealers from K+N right now.. and K+N will win.

Now.. if you want to chat about the "air boxes" available and how they can run up against the threshold for MAF failure...LOL


B

"Dunk" the maf in oil and it will still run properly? Gimme a break. Oil on the maf will not allow it to properly interpret air flow. Oil and contaminates on the maf will compromise the system.

[johne4]

Since the air box subject as come up, what about it?

As anyone tried one?

I see one in the ******************************************** porsche catalog for about $380, seems to appear to be a alternative to desnorkeling.

Thoughts, comments, experiences.

Thanks