I just bought a 1990 Maxima GXE for $400. I had to replace a leaking injector o-ring before driving it home. All new gaskets went on the manifold. I also went ahead and replaced the plugs with BKR5-ES NGK's gapped at .44 and put in new wires as well.

Now onto the problem.... The car runs great while the engine is cold. Smooth at idle, part throttle and WOT. Once the engine is hot, it's a different story. I have made a couple of ~10 mile trips in the car. On the way to the destination it runs great. On the way home it runs poorly.

When it's running poorly the symptoms are: erratic high idle at times (1200-1800 rpms), surging and sputtering while accelerating/under a load, engine will barely rev past 3k and general low power. CEL is not on.

Another symptom the car has even when cold is it takes 3-4 seconds of turning over before the engine start.

Things I've done: cleaned coolant temp sensor connection, cleaned KS connection, cleaned TPS connection, cleaned MAS connection, checked plug wires to be sure they are seated well, checked all hoses for vac leaks and replaced as needed, pulled plugs from hot motor and they are pure white (indicating a possible lean condition...)

I'm hoping someone has had a similar problem, this thing is driving me crazy. Any suggestions are greatly appreciated......

 

I have a 96 and it sounds like we are having similar problems. When cold runs great. Gets to running temp and I put it in gear, everything seems to be ok until i let off the brake and go to leave a stop. RPMs drop to 500 sometimes even as low as 300. If i let of and feather the gas it catches and i can then leave. driving it runs great, just leaving a stop is my problem.

I have found that cutting a hole in my vacuum line right on top of the intake manifold in the center towards the firewall it runs amazing all the time. What im not understanding is that hose runs form the intake to the valve cover. How is that helping. All I know is that it does and its going to stay that way until I can find and fix the problem.

Also, that small round black canister has no vacuum going to it or leaving it neither the large plug with two vacuum lines on it. I have no idea what that is.

 

The round black thing is a vacuum canister. That hose sounds like the pcv. Sounds as if you got some vacuum issue. Is everything hooked up in the correct order.

 

Mine never clears up once it starts after the engine warms up. It surges and hesitates while driving and has erratic idle.

The black canister in the front of the car is the charcoal canister (emissions junk). Cutting a hole in a vac line will make the car run more lean so sounds like something is causing yours to run rich when hot. Mine seems to be just the opposite (judging by my white plugs).

 

Im lost to all of this.

 

Me too, my thread got hijacked. See Post #1. lol.

 

You have an air leak on an emmission vacuum hose or etc....your coolant temp sensor/wiring is defective...

 

I have all emissions related stuff bypassed and plugged off now (no smog tests here).

There seem to be two coolant temp sensors? One in the front and another behind it. Unplugging the one in the front makes the coolant gauge to stop functioning. Is this the same one used by the ECU for fuel calculation?

 

Yeah there are two sensors. The one in the back is connected to the ECU. As you noticed, the front one is only for the temp gauge.

 

Thanks for this bit of info. I'm hoping this will be the culprit.

Anyone know the proper ohm readings for the coolant sensor?

 

This should help you look for your issues

http://www.nicoclub.com/FSM/maxima/1994/ec.pdf

 

There one temp sensor that other item is a thermobulb/sending unit for your water temp gauge.....it has one wire! Make sure your solenoid vacuum lines are in good condition if this is a "VG", they're locate on the driver's side slightly under the intake manifold....Try this once it gets up to temp again, unplug your EGR valve and plug the line it could be a leaking EGR valve which is gonna come online once the car is warmed up!

 

I have the EGR/power valve solenoids and EVAP disconnected and their ports plugged. I think the only things I have left with vac hoses going to them are the heater/ac valves,IACV and the FPR. PCV and brake booster are still connected as well. New hoses on everything.

I think I've narrowed it down to either the o2 sensor or the coolant temp sensor. I saw a diagnostic procedure for the o2 last night, I'm gonna try and find it again. That or I may just hook a meter to it and see if it cycles properly.

It would be nice if someone could OHM out their known working coolant temp sensor while motor is cold then ohm it out again while the engine is warm. Then let me know their #s so I can compare

 

Page 141 (EF & EC 143)

 

ptu a suction tool on the EGR to ensure it's holding vacuum then, You can also push up on the bottom of the EGR valve while the car is running to ensure the plunger is seated!

 

by any chance can you respond to this... My car runs fine until it warms up.. once it warms up it will not allow me to push the gas pedal like normal use. I have to apply light touch to the pedal to pick up speed if I mash on the peddle the car gets hesitation... how did you fix your problem ... bigcee352@yahoo.com (cleveland ohio 44122)