9Shenandoah

iTrader: (1)

I have a 98Maxima in very good condition.

Today we had it on Route 18 off of Maple Valley in Seattle with 3 adults in in it and we noticed that when we shifted gears the RPM would rise and drop right after the shift. For instance, when we were shifting from 3rd to 4th, the RPM would go from 4000 to 3000 and the suddenly float to 3200 and the drop off to 2700.

No OBD II codes on the computer. Is it a worn clutch or a sensor problem..?The car has plenty of clutch beef in 1st gear. I am suspecting:
(1) fuel pressure
(2) vacuum leaks
(3) worn clutch?
(4) fuel pressure regulator
(5) coil packs

Am I looking in the correct places?

wirelessdude04

iTrader: (24)

Check your TPS closed throttle .500 ohms open should be about 4000 ohms there is a write up on VQ power.

9Shenandoah

iTrader: (1)

Thanks Do you know how I can find the VQ power write up>

njmaxseltd

iTrader: (19)

If you have a manual transmission and the engine rpms increase while your driving, but the car isn't accelerating, your clutch is slipping and needs to be replaced. This is always more noticeable in higher gears, 3rd 4th etc. The additional weight (3 adults) allowed the problem to show itself.

What you describe is not an engine related issue.

asand1

iTrader: (1)

This. Manual trannies create a solid link between engine and wheels, one cannot change without the other. 1st gear will always slip less due to the mechanical advantage of lower gears. The rpm fluctuation you see is a result of more weight in the car and a tired clutch.

9Shenandoah

iTrader: (1)

Thanks everyone--You guys could be right... but I have her up on stands and I was checking the MAP, MAF, TPS--and she does the same thing at idle.

When I race the engine by raising the throttle and release it, she doesnt bounce back rock solid like before. There is a funny sounding drop off before she goes into idle, almost like a vacuum leak.

The TPs reads .63 ohms to 3.9, bit I don't think thats the isuue.

Also I am getting a yellow light on my OBDII scanner, not green like i used to get-- and the O2, Cat and Evap read as not vaild--however no trouble codes.

Now I dont mind doing the clutch--I was going to put a heavy duty ceramic clutch in anayway, but I still have to solve this.

njmaxseltd

iTrader: (19)

O2, Cat and Evap are not valid - Did you clear any TDC's lately? That would cause the ECU to go into a not ready state until a set of normal drive patterns have been completed without the ECU detecting any errors.

A manual's throttle should "hang" slightly when you come off the gas. This aids in shifting by not allowing the RPM's to drop so fast. Older Carb fed engines used a device called a dashpot to do this. Todays electronically controlled engines use the IACV to do this. Do check for any vacuum leaks, clean the throttle body and IACV. Make sure the intake piping is all intact with no cracks.

Most importantly, replace your worn out tired clutch.

cashoit

Agree with NJ.

There may be 2 problems here. One is the worn clutch. The other is a bad IACV. Test the IACV per the FSM. A bad or worn clutch will cause the RPMs to rise a bit when shifting before settling down to the correct RPMs. Both issues are unrelated but both CAN affect RPMs

I am going to advise against the heavy duty clutch. Stage 1 is ok. stage 2 is unnecessary unless u going to FA and then still may be overkill IMO. Stage 3 or 4 is NOT intended for street use. Just stick with OEM or reputable brand.