Problem with Transmission, I think. Car chugs up slight hills sometimes

[carlosinseattle]

I wanted to post this thread to keep from invading other threads, or otherwise confusing myself or other people.

I have a 91Q with 113K on it.

Here's the problem: When driving up slight hills at 40-60 mph I get a slight chugging type of motion from the car. It's a vibration that feels like a train chugging rapidly. It feels like a rapid engaging and disengaging of the torque converter. In some ways it feels like driving over the "rumble strips" on the side of the road. The noise is pretty bad too! Some people have said it might be caused by the Throttle Position sensor malfunctioning. And others have said it's because the transmission needs a flush.

I did the full transmission flush at a local Grease Monkey with Mobil 1 synthetic ATF, the filter change, and added Lubeguard Red into the transmission fluid. The problem decreased at first, but still happens with regularity.

What else can I do to fix this? The transmission shows nothing when putting it in diagnostic mode. Is there an easy way to put the ECU in diagnostic mode? How do I perform a diagnostic on a 91Q?

[CrimsonQ]

ECU TEST

turn ignition to "on" position

Turn test knob on ecu clock wise fully, the ccw.

Should start the light flashing after a second. 55 is all clear.

Ecu is located on passenger side kick panel to the right of glovebox.I had to remove the glovebox and plastic panel piece on my 90 to get good access to it. Yours may be different Im not sure.

Good luck on the diagnostics.

EDIT: here is a more in depth guide on the ecu test.

zerothread?id=60332

[Q45tech]

Important to make sure engine is able to produce sufficient power [torque] to avoid lugging [chug] at low rpm high load. Is problem worse with AC compressor on at 45-55?

Knock sensors and dirty injectors, induction \TB dirt?

[carlosinseattle]

Important to make sure engine is able to produce sufficient power [torque] to avoid lugging [chug] at low rpm high load. Is problem worse with AC compressor on at 45-55?

Knock sensors and dirty injectors, induction \TB dirt?

The car has plenty of power. It's not losing power at all. It's not lugging like a manual transmission car does when the RPM<'s are too low. It's not that. But thanks.

[maxnix]

If the vibration occurs in 3rd at ~45-50 mph and in D at ~65-70 mph, then one has to suspect the third engine (transmission) mount.

Lugging up any grade in D at 40-50 mph should be avoided.

[prsfan]

My auto 240sx also does this under light braking from time to time. I had thought it was my diff...maybe it's something else? Anyone have other thoughts.

[carlosinseattle]

It only happens when coasting while holding speed or slightly accelerating. Otherwise it never happens. If I leave the car in 3rd gear it never happens. That’s why I know it has to be something in the transmission or transmission control.

It seems to happen more when I use octane boost. I sometimes add octane boost, fuel injector cleaner, and a little Marvel Mystery Oil to a tank full of gas. That’s what I did this time, and it seems to be doing it more frequently. I’ll try to see if I can obtain codes from the ECU tonight in case it's my knock sensors.

[Q_SHIP]

Sounds like more of an engine problem under a load to me.

[elwesso]

I think its something like a TCC lockup shudder... Does it only happen when the torque converter is locked???

Disregard our email, i thought of something after i replied.

[carlosinseattle]

I think its something like a TCC lockup shudder... Does it only happen when the torque converter is locked???

Disregard our email, i thought of something after i replied.

Exactly...It is definitely the TCC lockup shudder. I did the flush, and added the lubeguard, but it still happens. Is there some sensor that will make this stop? Or can I use the Transmission Control Unit from a 94Q?

[elwesso]

SO, if yours is like mine, if you put it in 3rd and the TC locks, it doesnt want to shudder, right???

[louiegz]

Yea, mine does the same thing. Always happens when I hop on Route 46 going to the GW Bridge. Slight uphill and the trafic only allows you to do about 40 or 45mph. I put it in third and it goes away. I wish it didn't happen. It's a real pain.

[elwesso]

IN EITHER case (Lou or carlos), does the problem go away if you DO NOT DOWNSHIFT but you allow the torque converter to unlock?

[carlosinseattle]

IN EITHER case (Lou or carlos), does the problem go away if you DO NOT DOWNSHIFT but you allow the torque converter to unlock?

I think I understand your question. It only happens when I hold my foot steady on the gas pedal. If I let off or increase, evem slightly, the shudder goes away. I can even tap the gas pedal and it will stop. I think racers call it "feathering" the throttle. Again, it only happens on slight hills, not steep hills, and not on flat ground or downhill, only when I hold the gas pedal steady. By rapidly tapping the gas pedal, even very very slightly, the problem goes away.

When you look on MSN Autos' reliability ratings it mentions something about a faulty "Torque Converter Turbine Sensor". It says there were frequent problems with failing torque converter turbine sensors on early Q's. Has anyone ever replaced one of those before??

Here's the write up: "An occasional problem on this vehicle is failure of the Torque Converter Turbine Sensor.The cost to repair the Torque Converter Turbine Sensor is estimated at $98.00 for parts and $526.50 for labor.All prices are estimates based on $65 per flat rate hour and do not include diagnostic time or any applicable sales tax.Here's the link: http://autos.msn.com/research/...l=Q45

[maxnix]

When you look on MSN Autos' reliability ratings it mentions something about a faulty "Torque Converter Turbine Sensor". It says there were frequent problems with failing torque converter turbine sensors on early Q's. Has anyone ever replaced one of those before??

Documented in Infiniti Online Mechanic Forum. Usually evident by leak along wires connecting sensor to trnamission along driver's side.

No symptoms on mine when I had a leak, but maybe I got it early.

Problem sounds like you are on verge of insufficient power in gear to maintain TC lock-up. Intake path and IAC and EGR valves and TB have to be pristine and fuel system as new to not have a problem at low rpm on incline or at altitude. Why you have no problem in 3rd. Well documented in Q45tech's posts and replies to others who have TC lockup problems at low speeds and low rpms.

[louiegz]

IN EITHER case (Lou or carlos), does the problem go away if you DO NOT DOWNSHIFT but you allow the torque converter to unlock?

Yea, if I don't downshift, it goes away. It just might be that the incline is over. It's not something that happens all the time on other places, but as I metioned, when I'm on Route 46 east heading to the George Washington Bridge, I'm sure James know where I'm talking about, it happens more than not. It's a minor problem since I don't take the highway too much. Hell, Wes, when I drove to Ohio and to Indiana 2 years ago to hook up with you, it didn't happen once in the whole trip. Also in the Winter, the Q is the car I take to the Poconos because it's the only car I put the snow tires on. Don't happen then either. This has benn going on for a couple of years and I've lived with it but it would be great if I could solve this.

[TXCumtrensh]

When is the last time youve replaced your fuel filter?

In my camaro (back in the days) i had a exact problem like your describing, turns out the fuel filter was OEM (150K miles) and was rusted horribly... after replacing it, everything was fine.

just food for though.

[Peterofdevon]

I hate to tell you this but this is a common G50 problem that no one has diagnosed.

It happens to my 94, had it real bad on my 91.

I think its an ECU issue and that when your are going up hill in 3rd gear just before the downshift point the computer is giving false codes to the engine fuel mixture causing a sputtering and resulting in intermitant power transfer to the torque converter.

It is not repairable.

You just have to lift off the gas and punch it a little to initiate the downshift--then back off the gas and ease into the hill.

It is a quirk of the car. Yes, it causes us madness!!! I sold my 91 due to it---Infinty replaced its transmission twice and the MAS---it still did it.

Peter 91 Q 90K93 Q 217K94 Q 140K94 Q 45K

[Q45tech]

You must keep the engine perfect [as in creating the as new torque ouput at low rpms] because the economy gear ratio [2.45 from 0.694 x 3.538] is just on the ragged edge of functionablity at low rpm in 4th gear.

Extra drag from misalignment or tires or weight in trunk or AC or just 10% down on torque at under 2000 rpm and it shows up.

US gasoline has declined in BTU since these cars were designed so the preprogrammed amount for 14.7 AF doesn't create the same torque as it did in 1990...............study BMEP.

Fresh spark plugs seem to make it better as does BG44k and a pristine clean intake/plenum system for a few months...............every single pound foot counts on some inclines.

The lighter Q41 used the same transmission gears and they had to go up to 3.694 vs 3.538.........4.4% increase because of the lower torque at 1500 rpm.

This instability is a perfect test to warn of needed maintenance.

[maxnix]

This instability is a perfect test to warn of needed maintenance.

Just to repeat for those who think it is a design problem. It is not. It is a mechanical condition problem.

Think of it as an early warning symptom that not everything is up to as new OEM specifications.

[carlosinseattle]

You must keep the engine perfect [as in creating the as new torque ouput at low rpms] because the economy gear ratio [2.45 from 0.694 x 3.538] is just on the ragged edge of functionablity at low rpm in 4th gear.

Extra drag from misalignment or tires or weight in trunk or AC or just 10% down on torque at under 2000 rpm and it shows up.

US gasoline has declined in BTU since these cars were designed so the preprogrammed amount for 14.7 AF doesn't create the same torque as it did in 1990...............study BMEP.

Fresh spark plugs seem to make it better as does BG44k and a pristine clean intake/plenum system for a few months...............every single pound foot counts on some inclines.

The lighter Q41 used the same transmission gears and they had to go up to 3.694 vs 3.538.........4.4% increase because of the lower torque at 1500 rpm.

This instability is a perfect test to warn of needed maintenance.

OK...WOW...OUCH!!!

I wish this weren't the case. I believe you, but I wish I didnt have to, and there was another cure. I did have a ton of extra weight in my car, two 15" inch subs in seperate boxes, and another twelve in a seperate box. Last night the car drove almost flawlessly when I took everything out. That was before I read your post. My only question is what bout the guys who performed a transmission flush, used the mobil 1 and other additives, and had their problem corrected? Was there some magic to that?

[Q45tech]

Different things the TC lockup clutch can only hold a tiny bit of power.......why the transmission goes in and out of lockup to save the clutch from burning up.

We have an incline on I285 [ATL] where trucks slow down if it's very heavy traffic the average speed gets down to 45- 50 mph instead of 70-80 mph in Summer AC on even mine misbehaves sometimes...................I just drop down to 3rd and the problem goes away, when it opens up after the incline back to overdrive.

[Peterofdevon]

It is good to see Dennis explain this. I was incorrect on it starting in third gear---its 4th.

Thanks Dennis!

Peter

[maxnix]

We have an incline on I285 [ATL] where trucks slow down if it's very heavy traffic the average speed gets down to 45- 50 mph instead of 70-80 mph in Summer AC on even mine misbehaves sometimes...................I just drop down to 3rd and the problem goes away, when it opens up after the incline back to overdrive.

For the newer members, I will repeat that in town, below 60 mph, or up an incline, my cars stay in 3. Only downhill, dead level at maybe 55 mph, or more likely over 60 mph is car in drive.

Mine will do the low rpm lugging without chuggling, but it is not good for the engine to be pulling below 2K rpm, so I don't allow it. More transmission fluid heating and more loading of the plugs with excess fuel to foul them.

[louiegz]

Well, I understand what's happening now, but I find it sad that a car that cost $50k back in 95 should do this. Most people that bought this kind of car usually put it in D, which is the way an automatic should be. This is the only car that I've ever driven that this happens to. Does this happen to your Y33 Brian?

[Q45tech]

Is it Nissan fault that owners don't maintain to standard or that US refiners are allowed to produce gasoline that is so way below BTU standards to compensate for rising fuel prices.

Ever wonder why diesel is so much more than gasoline yet is much easier to refine or home heating oil .....................normal pricing [not tax] is a pure function of BTU per gallon.

See these type of things all the time on older LS400 [in 1998 they lightened the model by 300 pounds and went to a 5 speed to solve some problems] when the plug wires begin to fail or the 2 rotor buttons dist cap get pitted or the plugs need changing.

The LS 3998 cc engine had the same overall effective 4th gear rate as the Q so you can see both engines had to move the same weight........just that the LS was signficantly weaker in acceleration until 1998.

[maxnix]

This is the only car that I've ever driven that this happens to. Does this happen to your Y33 Brian?

Well, I have been pursuing the stumble problem and replaced a coil pack so far.

Since my wife drives it almost exclusively at 80K miles, no it doesn't. None of my cars do (seldom drive fully loaded, either). But I still don't drive them that way.

The way the VH45DE is tuned (for low end torque while preserving high rpm power output), the OD gear is really just that, Overdrive. Driving any VH like a diesel is just wrong, as the VH is really just a detuned racing V8.

I wonder how many of the owners who have this trouble run their cars to redline at least once a week? Q45tech's admonition to blow off the plugs regularly should not be lost on members.

By the way, as another indication of how the engine is tuned, I can find no discernible fuel economy penalty for keeping it in 3 for all but high speed highway driving in either VH car.

[louiegz]

Is it Nissan fault that owners don't maintain to standard or that US refiners are allowed to produce gasoline that is so way below BTU standards to compensate for rising fuel prices.

Well no, Dennis, it's not Nissan's fault on how people maintain their car or the BTU in current fuel, but I do blame Nissan for how hard it is to maintain some things on the Q. Things that should be simpler to promote people to maintain their car better. Of course, Nissan's objective is to sell new cars and not have us run our cars for 10-15 years. Anyway, you really shouldn't assume that everyone doesn't maintain their Q. Most don't as well as you do, but I've don't a better than average, at dealer prices keeping my Q tip top. I have about 90k on my 95 and the plugs were done for the 3rd time about 2 years ago and they even cleaned the intake and the injectors. I still run with the original injectors. The only thing I haven't done is the under plenum work, but I guess there isn't anything major going on there because I'm sure the dealer, as incompetent as they are, are always looking for something to repair. I'd like to have it done but I'm afraid to see how much they would charge me for that.

[elwesso]

My Q has never done this... for 2 reasons.

1. My high stall torque converter.2. Never sees 4th gear except when cruising...

sometimes ill be cruising at 80 right after Ive left my on ramp -- its perfect straight and slightly downhill with great visibility, usually take it sideways after the left turn and take it up to about 85 on the ramp... From there, i have driven probably 5 miles or so bfeore i actually notice its still in 3rd gear!!!! When it gets really hot out, ill sometimes put it in 3rd so the trans gets a litlte extra fluid running through the cooler.... My 4th gear/torque converter clutch is really weak, so i have to baby it in 4th....