After replacing MAF and getting new battery - no changes!

[FarFetched]

I suspected faulty MAF, also batt was a biot weak. So, I replaced both.The car (97 Q45) still does the same. Intermitten stumble at idle and hesitation at very light throttle (variuos speeds) just before transmission kicks down! It seems to happen when TCC locked up (i can see slight RPM drop). Dealer said that they might spend entire day diag this problem and never find anything because there is no MIL light or any codes that I know of!

I read an article (web site) regarding hesitation!Here it is!Quote »Hesitation has been decribed by several auto owners as a surging of power or a hunting for power while attempting to accelerate in a smooth fashion. The car lunges and hesitates all while the gas pedal is being pressed ever so gently or even held in one position. The car can't seems to find a place where it wants to take off smoothly. It seems to hunt for a sweet spot. It feels like it may be starving for fuel, air, or spark.

In the case of my car's problem, the hesitation felt was this:

The ignition advance that normally occurs during accelereation was being hindered by engine management, the computer. The computer was hearing some noise through the knock sensor that it had interpreted as engine pinging. The engine was not pinging, but try to tell my computer that!

So the result was varying degrees of ignition timing advance during acceleration. Everytime the ignition advanced, the power surged and every time the ignition retarded, the power level fell. [/quote]I appreciate any input!Thanks?!

[elwesso]

Dealer said that they might spend entire day diag this problem and never find anything because there is no MIL light or any codes that I know of!

I read an article (web site) regarding hesitation!Here it is!

I appreciate any input!Thanks?!

At least they were being honest!

when was the last time you checked your codes?? maybe the car is running a touch warm (tstat) and causing engine retarding.....

[DominickJ30]

So your replaced the MAF with a good one and still get hesitation? Next thing I would check is the TPS response. Do you have or have access to an Osciliscope? If so then hook into the middle wire of the TPS and do a slow sweep with the KOEO , if there is a problem there will be dead spots in the waveform where the signal is climbing but suddenly drops to zero. If it proves good then check your timing at IDLE. Then if possible(and if you have a scan tool available) make a movie of data on hard acceleration when this happens. I know this equipment is not readily available to everyone but it really helps narrow down the problem. Next thing I would check is 4-gas readings and do an Ignition Scope.

[FarFetched]

The thing is that TPS would have a "dead" spot at one or more positions. In my case it happenes at any throttle position only when car goes up a slight uphill either cruise control or manual throttle. Also, how would I explain idle stumble? Idle stumble feels the same as cruise stumble/hesitation. I have checked spark plugs, no complaints, look pretty good It feels as if IAC has a hick up or something like that. I am in aprocess of cleaning auxilary air valve, PCV (will replace it) and other things that could cet carboned up!

[maxnix]

I am in aprocess of cleaning auxilary air valve, PCV (will replace it) and other things that could cet carboned up!

I bet that does it, provided the intake plenum and runners are clean.

No EGR on OBD II, right?

[FarFetched]

I disabled EGR, (that dreaded EGR) WHY do we have to have this evil device on cars I had Jeep Cherokee, no EGR no auxilary air pumps, Simple speed density system. Engine worked like a ROLEX watch!And this "lux" car is giving me grief with that intermitten hesitation.I am checking into T-stat, because aluminum engines don't like run hotter than they should!I have dealt with a few Mitsubishi (warped heads) because of overheating!I can see temp gauge move a bit, especially after freeway run.Another weird observation, it will not stumble or hesitate when very first start-up even if I drive prolonged time. As soon I shut it down (on occasion) and than re-start (wait approx 5 min) it will do it. I think am looking at termal influence on fuel trim. The hotter, the leaner fuel mixture - right !So will se, what t-stat looks like!Cheers!

[DAEDALUS]

that dreaded EGR) WHY do we have to have this evil device on cars

because aluminum engines don't like run hotter than they should!

Question answered! Helps improve mileage too.

So with the new MAF, is the voltage reading the same as well? Make sure the input voltage to the MAF is 5.0V.

[911/Q45]

Could the disabled EGR be causing the problem?

[FarFetched]

I desabled EGR only for test purpose. It is back to normal now. I thought that intermitten hesitation and idle stumble were caused by faulty EGR/EVAP valve or EGRC-BPT valve(last one is vacuum operated).Disabling all that didn't give any positive results.I have completed t-stat replcmnt, will test it tomorrow!I also noticed when cold (gauge in mid 1/4 range), car takes off like a rocket. Then as temp increases, car becomes a bit "slow - read retarded"The t-stat was ORIGINAL 08/1996. It had some wear marks on one side (rubbing marks). It seems to be working ok, got temp probe, 180 and up water, t-stat opened up. then at higher temps it opened up more i would say 10-12 mm . Will see. Cheers!