40-50mph transmission "chuggle"

[Q45Viper]

I have been having a persistent "chuggle" or faltering upon gentle acceleration through the 40-50mph range. It does not seem to happen if I hold the car in third gear. I had the car evaluated by some mechanics I trust, their opinion was a problem with the torque clutch converter. That diagnosis was from driving it only, they are not a transmission shop. They also say there was a TSB on this from way back in the early 90's. Car is a 92Q with 135K on it chain guides done lot's of other stuff done, new O2 sensors but the plenum has never been off, and it is throwing knock sensor codes but other than than it shows no codes, it is due for spark plugs in 1k . The transmission was replaced at 88k with an Infiniti reman under warranty and was flushed by the dealer at 128k or so. But it was not a full flush with a pan drop and filter change. The dealer convinced me it was not neccesary. Ironically that seems to be about when the chuggling started. Opinions please???

[PalmerWMD]

Not an uncommon problem.When your dealer convinced you to not do it, he was gravely mistaken.

However this chug is not teh kiss of death.

Do a chemical flush with Mobil1 ATF and drop/clean out pan prior to flush.add new filter as well.

It mitigated that symptom slightly for me.

In town I usually kept the car in "3" anyway.

I had a 91 with that problem sold it to a good friend 2 years ago, gets driven <hard>, transmission still runs strong.

Fred..

[Q45Viper]

Thanks for the reply. What do you mean by chemical flush? And I assume that Mobil 1 ATF is the recommended fill? Do you have to put the new filter and the pan back on to flush after drop and cleaning? I've always been a little confused on these steps and I would like to insisit that it is done exactly right this time.

[PalmerWMD]

There is s simple replacemtn flush you can do and/or a chemical flush with extra detergents offered by some locations (Firestone)

That one is likely a good idea as some have speculated that a contributing source to your problem can be varnish on the TC.

But in any case a regular replacement is also likely to help.

Fred..

[Q45tech]

"it is throwing knock sensor codes but other than than it shows no codes"

Definitely the knock sensor!!!!!!!!!!!!!!

This is the clue you look for........funny light acceleration and greatly [10-20% worse than spec] diminished 50-80 mph acceleration.

Time for a plenum pull and the $1,000-$1,500 worth of R&R. Hoses /KS and harness.

So common I can tell by watching the car idle [mental telephathy]. I hear it begging for service.....maybe just sensitive to the ecu clock frequency 8 MHZ and the bursts of pain.

Dealers just don't see [understand] the problems of old Q on a daily basis.Some don't see one in a week or two vs if we don't have 15-30 [a week] we get worried about the owners.........maybe they are sick or something.

[Q451990]

Dennis is right... I had that exact issue with "Q1" and it was a bad knock sensor harness. With bad knock sensors, your ECU retards the timing as much as possible (kind of like holding your hands out in front of you when it's dark) because it can't tell for sure what's going on with the engine in regards to spark knock. This is designed to proctect the engine. Very few technicians and mechanics understand the incredible impact knock sensor faults can have on the performance of the Q.

You'll be amazed at the difference in the way your car drives when the ECU lets the timing run where it's supposed to!

Heath

[Q45Viper]

OK, I was about to go under the plenum anyway to do the knock sensors and harness....But why the heck doesn't it do it when you hold it in third? That's the only reason I've been buying the transmission theory.

[PalmerWMD]

When meaning chuggel dont you refere to the jerking of a locking and unlocking TC?

Fred..

[Q45Viper]

Yeah.

[maxnix]

But why the heck doesn't it do it when you hold it in third? That's the only reason I've been buying the transmission theory.

I would venture a guess it is because the power is not quite as marginal at the higher rpm. Hence, the engine is less sensitive to ignition retardation at the higher rpm. Advance and fuel delivery with cam timing advance is a tricky balance, especially with an intake exhaust path like the VH45DE which is optimized for high rpm operation. Easy to bog the engine if anything is out of specification.

[PalmerWMD]

The TC sees torque has varnish on it so its less able to "decide if it shouild be locked up or ont.

In "3" higher rpms= no uncertainty.

Of course part of that uncertainty can be the knock sensor issue which lowers the torque available at low rpm cruise.

Still at least a a couple Q onwres have reported a lesser problem after flush, myself included.Our imagination?

maybe, maybe not.

Fred...

[nuQ]

Q45viper, i'm going through the same thing. i thought it was the trans at first too, but after reading the posts here, i think it's the KS too. i'm getting a consult soon.

same thing though, at 40 to 50, and trying to keep a steady speed, i get slight "chugging". can't imagine the Q with more performance with new knock sensors, but i'll hopefully be seeing for myself soon. long live the Q!!!!!!!!!! jeff