brycea

Prior to replacing the MAF, I discovered that when I unplugged the sensor, the car ran smoother. So, I bought a new MAF, and I still have issues. The difference now, with the new sensor plugged in: 1. when I start the engine, the engine runs a bit rough. 2. The RPM of the engine goes up and down. 3. When I give the car gas, I am able to rev the engine, although, if I try to keep the rpm at a given level, the rpm will occasionally drop. Have an idea what the problem could be, please let me know.

1990se5speed

Have you checked timing and the o2 sensor are you running ngk plugs the copper no iridium

brycea

When you start the engine, black smoke comes out the exhaust. A mechanic told me, that it was because the fuel mixture is too rich. I have not checked both O2 sensors, and need to know how to check them out. To further, I have not checked the timing, do know that I am using NGK plugs, the three to four dollar version each. Where would you start, maybe the car's computer.

DanNY

iTrader: (14)

does the exhaust smell like gas?

does it happen when the engine is cold? only when hot? hot and cold?

don't just start swapping parts...you need to do some research first.

does it drive normally in gear??

BTW...stop listening to the guy that told you to blindly swap out the MAF...because you just wasted that money on a MAF and it solved nothing.

(EDIT) saw your other thread....
the idle hunts right? (up and down)...does it happen under load only (foot on the gas)? does it happen not under load (foot not on gas)?
again does it drive or does it feel like super slow?

what's the state of tune on the motor...
dist cap and rotor?
ignition wires good?
good plugs?

brycea

91 Maxima GXE
VG30E SOHC

does the exhaust smell like gas? No

does it happen when the engine is cold? only when hot? hot and cold? I take it you are talking about the smoke coming out of the exhaust. When the engine is cold.

don't just start swapping parts...you need to do some research first. Okay

does it drive normally in gear?? From a stop, when you accelerate to go forward, the engine stammers, then runs normal.

BTW...stop listening to the guy that told you to blindly swap out the MAF...because you just wasted that money on a MAF and it solved nothing. No, the guy was right, without the new MAF, when you started the engine, it would run terribly rough, then die. It would take an hour or so before the engine would start again.

(EDIT) saw your other thread....
the idle hunts right? (up and down)...does it happen under load only (foot on the gas)? does it happen not under load (foot not on gas)?
again does it drive or does it feel like super slow? I just drove my car so that I could better explain my situation. The engine now is not reving, nor does it feel super slow.

what's the state of tune on the motor...Replaced plugs & PCV valve.
dist cap and rotor? This is something that I have not done. Is it just a matter of removing the four screws and checking the rotor.
ignition wires good? Appear to be.
good plugs? A mechanic told me that my plugs were being befouled by the richness of the gas.

Thank you so much for your help, what would you do from here?

DanNY

iTrader: (14)

change distributor cap and rotor then report back. try not to get the cheapest part you can find...i like OEM...but even the aftermarket is better than one that's broken/cracked/worn.

just a bit of advice...when you're trying to figure out what's broken start with the cheapest part and work your way up.

don't even look at the O2 sensor right now.

brycea

Will do as you recommend, appreciate all your help.

GluteusMaximus

Next time before replacing a MAF, take it out and douche it real good with some carb cleaner, then put it back in. If the symptom(s) improve, even slightly, then you are barking up the right tree. If there is no change whatsoever look elsewhere for the problem.

GluteusMaximus

Another tip is to tap lightly on the MAF with the handle of a screwdriver and listen for changes in engine speed. If the sound of the engine changes when you tap tap tap then replace the MAF.

brycea

Will do, thanks.

GluteusMaximus

DanNYC is right, do all the tune up stuff first: Plugs, wires (including coil wire!), cap/rotor, fuel filter, air filter, PVC.

Some other things to try out would be to inspect all vacuum hoses for cracking or leaks. Also you said you have black smoke out the tailpipe...this means you are getting too much fuel (or not enough spark) to one or more cylinders. Ohm out your injectors and check your fuel pressure (it's uncommon but the regulator can fail closed meaning your fuel pressure is too high and the injectors are just stuffing it in there).

A cylinder balance test (disconnecting one injector or plug wire at a time) will reveal if the problem is just in one cylinder or systemic to the entire motor.

I don't know if you have it or not, but the Cliltons Manual has ECCS diagnostic flowcharts for 'hunting' and for 'lack of power and stumble' which is what you seem to be experiencing. I would recommend following those - if the basic stuff above fails to reveal the problem - rather than throwing more parts at it if possible.

Good luck and keep us posted.

brycea

appreciate your help, will do the cylinder balance test today

GluteusMaximus

Results?

brycea

To make a story short, I'm taking the car in to have it looked at by a mechanic. Do appreciate your interest.