Alias

Ths is my wifes car, a 91' Auto, 212K Miles.

First off what motor is this? The Vg30DE? What the diference between it and my 300zx? Other than the intake.

It has a bad hesitation under 2800RPM, and sounds like abad miss. After 2800RPM it really comes to life, the plugs look fine, normal brownish color. Any ideas guys? It seems to go away when itd cold, once it warms up it freaks out.


It also drinks the gas. 15MPG in the city. It also has a small fuel leak under the front of the intake, near a fuel injector.

jwmaxse

iTrader: (1)

In order to know which motor you have, we will need to know the year, and what trim level. All 89-94 maximas have the VG motor except for the 92-94 maxima SE's which have the VE30DE motor. It sounds like you have a VG. What is the difference between that and your 300zx motor? It depends on the year and trim level of your 300zx. If you think that it has a miss, leave the car running and pull the spark plug wires/coil packs one at a time. If the motor starts idling roughly, that is a good sign that the cylinder works, but if it makes no change at all, that cylinder is bad for some reason.

Alias

Pulling a plug wire isn't going to tell me anyhting in this situation. I know the diference from a misfire and a cylinder not firing period.

Paul89SE

It's the infamous knock sensor under the intake manifold. Either the sensor goes bad because of vibration or there is a lot of corrosion on the wire terminals. Either way it's a pain to remove the intake and get to it. This problem is also called heat soak. Heat soak causes hesitation under 3,000 rpms after the car has been running for a while. Sometimes it starts almost instantly other times it will start only after you restart your car.

jwmaxse

iTrader: (1)

We still don't know which motor you have until you tell us the year and trim level of your car. LOL

Paul89SE

Only engine offered in a 1991 maxima would be a VG.

Jeff92se

iTrader: (82)

You have a 91 auto. That means you have a VG30. Not the DE version. This engine is a 2 valver sohc heads.

A simple check is to clean the red coolant temp sensor connector. If it's corroded, it will send an artifically high resistance value to the ecu and retard the timing. Also a vacuum leak might cause this. As would a bad PCV, EGR valve or bad ign wires, cracked dist cap and the knock sensor.

Maxpwer

iTrader: (7)

Indeed. If your Z is an 84-89 NA then the engines are the same (other than the intake).

Alias

I will clean the conector on the temp sensor. Getting pretty good at it now My RX-7 is riddled with electrical issues.

The 300ZX is a 90', NA 2 seater

bigmax90

Sometimes a crack in the porclein of the plug will cause this or a small pinhole in the spark plug boot. If you think its a miss try looking at night for ignition spark use a spray bottle to pinpoint the spark.

grody

The engine in your Z is a VG30DE, a DOHC motor, and the engine in your Max is a VG30E, a SOHC. They sound similar, but they're pretty different.

jwmaxse

iTrader: (1)

Okay, I need to learn to read.