Scrooge

Try removing your air flow meter and cleaning it with a spray solvent, e.g., carb cleaner, or the like. Be careful not to drop it or get any of the solvent into the electronics as this is a $1200 part. This fix has worked for me on multiple occasions, though the problem returns after a year or so. While I'm in there, I usually remove the idle control valve and give it the same treatment, and clean out all of the hoses in the intake area with a rag to remove any oil/moisture residue that has collected thereabouts. To be honest, I don't know which part of the foregoing treatment is the real cure for the "power loss" problem, so I suggest doing everything and testing the results.

Best of luck to everyone!

Heirsh

Thanks for the tips Scrooge,

In my case I've had the entire intake off, cleaned everything, new seals under the trumpets, cleaned the maf, cleaned the isv, cleaned everything I could find. I have some bad track on my maf's wiper, so I bent the arm for it to run on fresh track. There is an old thread of mine detailing out everything I have done, if you are truly curious. I finally gave up trying to fix it because it was driving me crazy. I just adjust how I drive to not have the problem. (of course with cruise on I just have to live with it)

dougn

i bench tested my MAF last night and it seems to be fine....nice progressive voltage out. my car has poor throttle response right off idle. it's good when it's stone cold right after i start it. makes me think the slow response has something to do with the fueling.

i know my fuel pressure is good under vaccum and increases properly when i stab the throttle. about the only thing nobody's talked about is the injectors themselves. I can't see how they could cause this ....however

Heirsh

I had my injectors flowed and cleaned. they were as perfect as anyone could expect.

I too suspect my MAF. I, unfortunately, never found anyone willing to test mine. Surely someone has the ability to check the calibration. I am not willing to part with as much as one of these costs as a shotgunning technique though.

DarrylH

Some part, when tilted nose-down, doesn't work right. Is the MAF door more likely to stick in a given position when tilted?

JasonAndreas

Is this happening on your other 964 with Motec or Motronic?

What happens to the O2 sensor "Actual Value" when this problem occurs? Is the sensor output still bouncing back and forth on either side of 0.5v or is the voltage sticking high or low? If you have Doug's software, delete all the actual value entries except for the one for the O2 sensor and the AFM. This will increase the update rate for those values and give you a better idea of what the O2 sensor is actually doing.

Geoffrey

Motronic with a stock chip. If it were MoTeC I'd be able to fix it.

Heirsh

Jason,

The actual value pegs in either direction. one direction for the barely cracked throttle and the other direction when you get back on the throttle.

It has been too long and I dont recall which direction for which condition.

rennmax

I have had this happen twice in the 3 months I've owned the car and it is very slight when it happens.
I think this problem maybe more to do with the idle position switch being a bit flakey and the problem is only apparent when the car is allowed to coast longer than you would normally in gear. ie going down a hill.
If the switch isn't registering that the throttle is closed then it will still be feeding fuel through the injectors which would probably create a rich condition and the DME would compensate by leaning out the fuel map and when you get back on throttle the fuel needed isn't there because of the leaner map (or trim) the DME has gone to.

This is just a theory and not knowing the complete ins and outs of the motronic system means I maybe way of the mark.
As I understand from Adrian's book the motronic system has no throttle position sensor, just a idle switch and WOT switch.

JasonAndreas

So the O2 sensor voltage actual value is pegging/sticking to one side?

springer3

Have you checked for diagnostic fault codes? It is a complicated engine control system, and multiple sensor failures or actuator failures can cause strange behavior.

Heirsh

Jason,

Yes. I looked at the actual values coming from the ox sensor and they are doing what I described. If it matters what the numbers are I could resurect my laptop and do another test. I liked watching the trim bar myself as glancing over at the computer while driving wasn't the safest or easiest thing to do.

Springer,

No fault codes for anything in the dme. None the times I've looked and none the times my mechanic has looked. Well, thats not exactly true. When I ran it w/o the ox sensor for a while it threw up that fault.

dutchcrunch

i think this is normal as my toyota 2004 coroola does this too. now i know the cars are not the same but i think it has to do with the load of the engine and the fuel management system.

i bet when you are going slightly down hill and you were to accelerate to go faster there is going to be a slight heasitation till the engine loads up and the systom should go away. the car will accelerate smoothly!!!

if you do not believe me try it in any other car that is not carburated as it will do the same.

put your car or any other car in cruise control for the speed limit just before you approach a known down hill and let it continue all the way thru and watch as the car gets confused and starts to act wierd, and soon as it levels out the car act normal.

i think this will have you chasing your tail for nothing. this is a normal glitch in the system. the fuel mapping was not done or designed to go 50 mph with no laod or just coasting. and that moment of hesitation is the computer catching up .

Heirsh

Thank you for the followup Dutch,

It is not a moment and it cannot be normal. The car will actually buck sometimes forcing me to either peg full throttle (bypassing whatever trim values it is using) or giving it just slight throttle (still not good as its fed the wrong mixture until the ox sensor figures it out and corrects).

It can take 5-10 secs to clear up under the worst cases. Surely your corolla wasnt bucking and complaing for 5-10 secs?

garrett376

Also if it was normal it would happen all the time... One of my 964's did this a long time ago, but none of the subsequent ones ever have.