Help with 99 QX4

[ArmyGuy45]

Long story short I had an old friend (no longer that and you will see why) move in with me who was down on his luck. So I bought him a car (99 Infiniti QX4 with an 01 Engine/Trans, or so the mechanic I bought it from says) and gave him some cash with the promise of paying me back. He did make some payments to me but never fully paid me back. When I kicked him out I kept the keys to the SUV as a final payment. Now I am trying to sell it and in the short 4 months he was living here he never really took car of it. That is why I am here. I have a bit of mechanical knowledge but I am lost on this last one.

I bought a 99 QX4 with 240k on the frame and 120k on a rebuilt engine/trans from an 01 (or so he said). There is no paperwork on the engine/trans since he bought it from a junk yard and installed it himself. The reason why I believe him is because I had the replace the Throttle body Sensor and the 99 threw codes but the 01 did not. I have replaced the radiator and a few hose since those blew on him while going to work (extreme summer heat here in AZ). As stated before there was a check engine light and it was the TBS as per the computer, swapped that out and the error went away.

Now comes the real problem, when I got the keys back it was shifting really hard and really late in RPMs, around 4k. I checked the fluid and it was about 1.5 quarts lows and low fluid can cause shifting issues so I topped it off with some Dex III as Autozone recommended. The shifts did smooth out a bit but it still shifts hard an only after 3.5k now, unless I come completely off the gas pedal after 2k it will shift. Sucks having to act like this thing is manual and time the gas for each shift. I am trying to sell it and get my money back so I am hoping there is something that could be an easy fix (bad sensor somewhere). As of right now I have no check engine lights and haven't since I swapped out the TBS.

Any thoughts on where to start?

[MisterH]

I think you're going to have to get it evaluated by a transmission specialist, but there is a relatively low-risk experiment you can try:
- Buy a bottle of SeaFoam Trans tune and follow their procedure for a clean out and flush. ($12.00) . Put at least 200 miles on it before you go to the next step.
- Drain the transmission and pull pan. After you completely drain the fluid in the pan look for metallic fragments and sludge at the bottom of it. A lot of metallic fragments is cause for concern. A few is not a problem. Thoroughly clean out the pan.
- Remove and replace the transmission filter and install new pan gasket. ($30.00)
- Refill transmission with a good Synthetic trans fluid (30.00)

Make sure your fluid is topped off correctly and then drive it and see if the behavior is improved. If no improvement you will need to either replace the transmission or all the shift actuators. Good luck

[ArmyGuy45]

Thanks for the reply MisterH. That was my fear that this transmission is going. How much dose these go for if the transmission is going out, if I were to sell it as is?

I will try your experiment and see if it improves the transmission life.

[04pathse]

Thanks for the reply MisterH. That was my fear that this transmission is going. How much dose these go for if the transmission is going out, if I were to sell it as is?

Maybe around $1000 - $1500

[ArmyGuy45]

Thanks for the reply MisterH. That was my fear that this transmission is going. How much dose these go for if the transmission is going out, if I were to sell it as is?

Maybe around $1000 - $1500

Well to break even I need to sell it for 1200 now, or 1300 if I drop 100 bucks in fluids, filter and gasket.

So I am about that range. I will give it a shot. Thanks all!

[04pathse]

Well I may have been a little high on my numbers.

I just checked KBB.com and they value the vehicle for trade-in to dealer around $700, and that is in "fair" condition which is in running condition with no major issues, they don't give estimates of value of vehicles in poor condition.

Furthermore, they estimate private party value around $1300, again that is in "fair" condition.

[atraudes]

Quick first question: is this hard shifting a new behavior, or did it always do this?

You said you replaced the TBS; I'm assuming you meant the throttle position sensor, correct? If so, did you calibrate it per the FSM after installing? The reason I mention this is that the transmission makes shifting decisions based on input from this sensor and if it's not relaying the correct position of the throttle, that could certainly explain the late shifting you're describing.

If you weren't referring to the TPS, can you describe the TBS more? I'm not familiar with that acronym.

I'm also surprised there's an 01 motor in that 99; I would think there would be too many differences that would make the swap financially challenging. I don't have any doubt it's possible by someone determined enough but it's not a straight swap. The signal from the 01 TPS may be different from the one on a 99, so perhaps that could also explain what you're seeing.

The quick and easy test to see if you have the 3.3L (99-era) or 3.5L (01-era) engine is to see if it has a distributor. If it does, you have a 3.3. If it doesn't and uses coil packs instead, then it's a 3.5.

[ArmyGuy45]

Quick first question: is this hard shifting a new behavior, or did it always do this?

You said you replaced the TBS; I'm assuming you meant the throttle position sensor, correct? If so, did you calibrate it per the FSM after installing? The reason I mention this is that the transmission makes shifting decisions based on input from this sensor and if it's not relaying the correct position of the throttle, that could certainly explain the late shifting you're describing.

If you weren't referring to the TPS, can you describe the TBS more? I'm not familiar with that acronym.

I'm also surprised there's an 01 motor in that 99; I would think there would be too many differences that would make the swap financially challenging. I don't have any doubt it's possible by someone determined enough but it's not a straight swap. The signal from the 01 TPS may be different from the one on a 99, so perhaps that could also explain what you're seeing.

The quick and easy test to see if you have the 3.3L (99-era) or 3.5L (01-era) engine is to see if it has a distributor. If it does, you have a 3.3. If it doesn't and uses coil packs instead, then it's a 3.5.

It was the TPS, Throttle body Position Sensor and I did not know there was a tuning required after you install it other than checking your idle RPMs. It has been shifting crazy after the first TPS. It was shifting fine before the swap.

It does have a distributor (circle device near the front of the engine that has all the plug wires connected to it) but the previous owner said it was a motor from a 02 and a trans from a 1997. Is that possible? He did get it them from a junk yard and two different vehicles.

Update. After a fluid and filter change on the transmission, it smoothed out a bit on the shifting but still waits until 4k to shift.

Could it be the speed sensor from the transmission?

[ArmyGuy45]

Update: So the TPS sensor I threw on there was from a 2001 and didn't throw codes but causes the crazy shifting. Now I put a 99 TPS sensor on there (I am being told the ECU is a 99) and it throws the engine code for the TPS sensor but shifts a lot lower in the RPMs (normal ranges, around 2k) but it goes 1st, 2nd, back to 1st and them seems like OD.

So I don't think my problem is from the transmission since it shifts differently when the two different sensors. With that said. I have tuned the 99 TPS by checking the idle on a warm engine. I have not tuned it with a voltmeter (looks like it needs to be .5 V between the middle pin of the bottom connector and ground as per youtube) but only by listening. Could a not tuned TPS cause codes and this crazy shifting pattern?

[MisterH]

Faulty TPS would change the shift points but I would follow all the normal diagnostic procedures for a 99 model year. It is extremely unlikely that any part of your engine and related components are from a later model year. The DOHC 3.5 was a complete redesign from the ground-up.

[ArmyGuy45]

Faulty TPS would change the shift points but I would follow all the normal diagnostic procedures for a 99 model year. It is extremely unlikely that any part of your engine and related components are from a later model year. The DOHC 3.5 was a complete redesign from the ground-up.

Do you think it is the transmission though? With a 99 TPS (only tuned by listening to the idle) I throw a code and get the 1st, 2nd, back to 1st then OD shift patterns, but when I put in a 01 TPS I get no codes and get really high shift points.

One thing I did notice is that the variable resister in the 01 TPS spins the opposite direction as the 99. That could explain the high shift points since the computer has no idea where the throttle is at but then why no codes?