Questions and Answers

Nissan Altima Stumbles When Cold Q. Dear Vincent, I would first off like to say I love the web site, there is a lot of good information on there. However, I am writing this e-mail to tell you my problem with my car. I have a 1993 Nissan Altima automatic transmission. The car is having a problem upon acceleration. It is stumbling, when you try to push the gas the car just wants to flood itself and almost dies, sometimes it does.

It doesn't seem to do it after the car gets warmed up all the way. But, until that point the car really acts up. I have replaced distributor cap, rotor, spark plugs, spark plug wires, fuel regulator with adjustable one running at normal pressure. I checked the injectors by listening to them through a screw driver, all the injectors pulse fine. Fuel pressure stays stable. I also have replaced the intake filter so I'm am stumped at what else this could be.

After the car gets up to full operating temperature it only stumbles if you try and floor it from a stop, sometimes while rolling as well. Also I sprayed some carburetor cleaner through the intake filter while the car was at idle and the car died. So I'm guessing that the car is flooding itself, but my fuel pressure is at normal, and I don't understand how his could happen then. My air/fuel gauge shows that it's at normal operation, not to rich or lean. Could you please help me out with this.

Thanks,
Shawn

A. What kind of air/fuel gauge do you have? Mine is big and expensive and not easily moved around.

The first thing you need to do is check the PCM for any stored codes. That will tell you where to start looking for the problem. How to display and read the Diagnostic Trouble codes stored in your vehicles computer.

Unless there is black smoke coming from the tailpipe that you didn't tell me about, I really doubt the engine is "flooding out". Unless you shoot small measured squirts of carburetor cleaner into an engine, any engine will stall when sprayed with it.

I think it far more likely the Coolant Temperature Sensor (CTS) is bad and causing the engine to run lean. A bad Air Flow Meter (AFM) can cause a vehicle to have these symptoms as well. Intake valve deposits will do it too.

I would install a set of NGK spark plugs, BKR5E-11, gapped between 0.039" and 0.043". Then I would give the throttle chamber a good cleaning. A lot of times cleaning the throttle body cleaning will solve many driveability problems.

After that, I would do a fuel pressure and fuel volume test. This will determine if the fuel pump is operating properly.