Need Help...Q RPM's Drop @ 3,750...video clip to show problem

[rsiwicki]

hey all....I really need help figuring out what is wrong with my 95 Q. The problem is the following:

RPM's drop by 50 to 100 rpms right around 80 mph @ 3,750rpm in 3rd gear only under medium acceleration

I can't get the rpms to drop in any other gear besides 3rd gear

The rpms do not drop while under WOT...or at least I can't see nor hear a change in the rpms (the engine sounds good and strong under WOT..but when under medium acceleration the rpms always drop at 3,750rpm in 3rd gear)

Check out the video clips and whatch the rpms when they approach 3,750 under medium acceleration....they drop for some reason by 50 to 100 rpms...again this only happens in 3rd gear and at around 80mph. I can keep accelerating until redline again...110+ something...and all is good...no mysterious rpms drop.

The car idles smooth as slick

I can put the car in park/nuetral and rev the engine all the way to redline steadily and the rpms don't miss a beat...nice smooth progression in response to the gas pedal movement

This only happens in 3rd gear right at about 3,750rpm or 80mph...it does not do it under WOT or in 1st or 2nd gear.

I was with the dealers top mechanic running the consult and duplicating the problem and no codes were displayed at all. The dealer said that the only thing odd was that torque converter (TC) was at 94% right when this happened and thought that it was due to a faulty TC. Well I just had a new LevelTen transmission & TC installed this past week and the problem still exists.

Also I have run a 93 TCU & 95 TCU in my car and the problem still exists...so it is not the TCU, nor torque converter, nor transmission.

Any help is much appreciated. I don't know if it is some weird glitch in the speed sensor or what? It is a very controled drop in rpms...just like if I raised my foot off the gas pedal for a split second and the hammered it back down again.

I just had the fuel pump and filter replaced...so I don't think that it is this either and if it was I don't know why it would only do this in 3rd gear @ 3,750rpms only.

Thanks again for reviewing my clips and watch how the rpms drop right around 3,750 and then start going up again for no reason at all.

Rob

http://www.nissaninfiniticlub....1.asf

http://www.nissaninfiniticlub....2.asf

this last clip has some LevelTen shifts in it again and at the end is the damn rpm drop problem

http://www.nissaninfiniticlub....p.asf

[HeavyDuty]

I've only had this car for a few months, most of my miles are around town, but I think mine does the same thing.

I've noticed that lug when on the highway (which your speed would indicate) and I try to pass someone without first pulling the selector into 3 instead of D.

It feels to me like the converter is lugging down the engine. If I muddle through that area it eventually gets better, but performs much better starting out my pass in 3.

Did you also change the filter next to the battery?

Stupid question perhaps.

Lord I sure hope I'm talking about the right thing. It's been a couple weeks since I was under my car starting all the P/S & trans line stuff.

[rsiwicki]

the dealer thought also that it was like the converter was trying to start a shift to go into overdrive...but then the car realizes that it should not be going into overdrive and continues to accelerate without any more problems. Only happens once in 3rd gear under medium acceleration right at 80mph or 3,750rpms. I can be at any other speed/rpms in 3rd and never haver a problem. Also it does not matter if I start from "d" or "3rd" in the selector...it does it regardless. this only happens for that split second that you see on the video clip.

I don't know which fuel filter was replaced. I had the dealer do the fuel pump and I just told them to change the fuel filter also so I don't know how many or which one they changed.

[rsiwicki]

the dealer said that it was definitely not the engine itself as it was not "missing"...but that some sensor or something else was telling the engine to do a very controled rpm drop by about 50-100rpms and then start accelerating again without any problems.....I have wound the speedo out to 110+mph,5000+rpms after it has happened at 3,750rpms and it never does it again...just perfect smooth acceleration from the time it does it all the way up to redline

[elwesso]

That is very strange, as it looks like its makig a mini shift...

If its in 3rd (selector) it shouldnt even try OD.....

Ill be interested to see what Dennis has to say about this, as I can say that most of us here are stumped...

[1qckser]

My G20T does the same thing, if you are in 3rd and want to rev past the point where the computer would normally shift into OD, the rpms drop for a split second then continue to accelerate, kinda annoying but after 8 years im used to it:)

[HeavyDuty]

I don't know which fuel filter was replaced. I had the dealer do the fuel pump and I just told them to change the fuel filter also so I don't know how many or which one they changed.

I'm not talking about a fuel filter, but rather what appears to be an inline transmission filter that looks like an oil filter suspended in air towards the pass side of the fan shroud. It's hard to see unless you're looking for it.

One line comes up from the DS frame rail, across the front of the engine to the filter housing, then returns on the same path back to the trans, or so it appears. I could be smoking crack, but I believe we traced the lines from the trans to the filter, then back.

I could post a pic, but I'm not at the shop. When I did my trans, it looked as though it had never been replaced.

[rsiwicki]

I will check it out heavy...but I don't think that it has ever been changed either unless they did it at the 120K service or when they rebuilt my transmission last year. I know that they installed the cooler when they did the transmission, but I have no idea about the filter. I will check it out...probably should be changed anyway with the new transmission.

1qckser......that is wierd about the G20 doing the same thing. I can't believe that after owning the car for 6 years that I am just finally realizing it. Maybe it is something with the ECU/TCU programing?

I am dying to hear Dennis's opinion on this one.

[elwesso]

Youll want to take that filter out. I have pictures of it on my website when I did my transmission cooler!

[HeavyDuty]

I didn't plan on removing it, but rather relocating it to the area that used to be occupied by the stock lower airbox in the front bumper, to gain easier access.

Why did you remove it, Wes?

[rsiwicki]

I spoke with Wes about the filter...he said that he did not think that it did all that much good as when he opened it up after over 100k that there was barely any metal shavings. Nothing wrong apparently with leaving it in. It looks like the transmission shop bypassed my filter when they installed the transmission cooler last year as I just have two lines running from the transmission straight to the aftermarket cooler and no interface with the OEM filter or OEM cooler.

[elwesso]

by how my transmission was treated, what I found inside the filter, its obscene complexity, and the openinings in my aftermarket cooler, I see no reason to leave it in..

I also used hacksaw to open the filter so I could have gotten some shavings from that.....

Its under enough pressure and the way I maintain it, it wont have a chance to tihnk about clogging!!!!! Thats its only purpose, to prevent the stock cooler from clogging.....

[sijoko]

rsi,

Maybe what you are feeling is the converter going into lock-up under part throttle.

Because of the high stall, you would notice the lock-up more than before.

-sijoko

[elwesso]

Even at that, the TC should only lockup under little or no throttle, as it cant handle that amount of HP.....

[Jesda]

My 92 wouldnt have that auxilary filter, would it? The transmission was replaced under warranty in 1995 at 50k.

-Jesda

[rsiwicki]

sijoko...thanks for the tip, but it was doing this before I had the new transmission & TC installed. The dealer ran the consult monitoring everything when the problem occured and only thing that came back was that the TC was at 94% at the exact moment the rpms dropped...all the other parameters remained the same so that is what the dealer thought as well that it was something with the TC. The car does feel as if it is about to go into overdrive or make a little upshift.

[1qckser]

RSI if you put the selector in the OD position and go for a spin see if that is the point the car would shift into overdrive:) I just did it in the G and that is what is going on, goodluck.

[rsiwicki]

sounds like a good idea...I will try that tomorrow. If this is it...then I can't believe after owning the car for 6 years that I am just finally noticing it. I guess there is always a little something new to learn no matter how long you have owned it.

[maxnix]

Youll want to take that filter out. I have pictures of it on my website when I did my transmission cooler!

That is so patently FALSE!!! This transmisssion filter is a prime reason the transmissions on 1994-1996 have a much better life if properly maintained.

[1qckser]

I think Dennis said some of our 91s also recieved this filter as a upgrade from the factory, isnt it the round canister on the passenger side next to the radiator? If so leave it, its just more thing that will help transmission life.

[rsiwicki]

1qckser....I tried it and I it did not work...I actually got it to act up at 85mph this time at a higher rpm. Sometimes right after it acts up I can see the rpm needle wobble ever so slightly back and forth as if after it does it something in the engine gets out of sincronization...but still accelerates.

Dennis.....you have been too quiet for us.....any thoughts???

[Q451990]

You're running a 90-93 transmission in the 95, right? I don't know if it would work, but you might try a 93 ECU with the 93 TCU. I think it's a conflict between the two systems. With the LAN, and different sensors, I have no idea if it would work, or if it would potentially damage something - so try this at your own risk.

The car has a spark timing retard at the shift points to make the shift smoother. I'm not sure if the ECU or TCU is responsible for the spark timing retard. If it's the ECU, and you're running the 95 ECU, maybe it's putting the spark timing retard in there at it's expected shift point, even though the transmission isn't shifting.

The "mini-shift" description sounds like the torque convertor locking and unlocking but I don't think the behavior you're showing is normal.

Heath

[rsiwicki]

Thanks Heath....but this problem existed with my original transmission as well so it can't be a combo of the ECU/TCU different year conflict. This problem existed with the OEM setup and no mods at all....and now it still exists with a new TC, transmission, 93 TCU. I had originally thought that it was knock sensors...but now I don't think that it is knocksensors.

I don't know what the problem is but it drives me nuts...more so now than before.

[elwesso]

http://www.nissaninfiniticlub....ilter

This thread seems to indicate (to me) that its not that imperative...

[rsiwicki]

okay...enough thread hijacking and transmission filter stuff

Dennis...are you there or does anybody else have an idea of what this could be. I can do it at other rpms as well...such as at 95 mph...it will do the same thing but to a lesser degree.

I will try to get a few more video clips at different speeds to show you all what it is doing.

And as always...your comments are much appreciated as this thing is really pissing me off

[Jeff Williams]

Rob, my 1994 does a similar thing.

If I leave the car in 3, and drive normally (not hot rodding), the car hesitates, where it would normally shift into 4th. then goes back into 3rd. It feels like a shift gone wrong, or the TC trying to lock. I am usually decelerating, or not pushing it hard, at all. It sometimes jerks the car a very little, even. Usually, I am downshifting, for a stop light, and forget to put it back into "D", when I continue down the road. This reminds me to put the car in "D".

When driving around in "D", I can feel the car "shift" in to (what I call) OD, almost like a 5th gear. It usually drops the RPM about 100, or so.

When I get on it hard, it seems to shift O.K., but it takes a long time to get from 3rd to 4th. It feels like clutch slippage, to me.

Is there any way you can get a pressure gage in the transmission line, and monitor this pressure, while you are experiencing the problem?

Good Luck. Let us know what you find.

[elwesso]

Well in that case, mine does the same thing, except not on acceleration.

I always drive in 3rd unless im on a stretch where it will lock the TC for a long time.

I can usually go 2000rpm, at 45ish mph, after the TC has locked.

I think the TC locks at certain RPMs under light acceleration, and doesnt matter if its in D or something else...... Just speculation?

[maxnix]

Rob, I tried to drive in 3rd at 80mph in my stock 1995 Q45 at ~3500 rpm (15-215/65 Michelin XVGT) and did not notice any drop. I will try on longer stretch when the opportunity arises.

Your video confused me as I saw rpm changes of greater than 1000 rpm, so I assume shifting was involved.

Wes, I think you need to tell those Nissan engineers how much time they wasted in college and in apprenticeships in engineering departments at producing manufacturers. Never have seen a car produced by a forum. Think carefully!

[rsiwicki]

thanks guys for your help...but it all just does not make sense why it would be doing this. I can do it from the 3rd or "d" drive selector and can do it in 4th gear also. I have not been able to do it in 1st or 2nd and under WOT it seems all is good.

I just don't know and Dennis is too silent for some reason. Come on Dennis....got any clues...give me a little bone to pick at or something to chew while I try to get to the bottom of this problem.

[maxnix]

OK, I thought it was under constant speed. By medium acceleration, do you mean a constant 3/4 throttle acceleration?"__________________Brian1995 Q45 & Q45t & 2000 Q45

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