I have a 1988 Maxima with 238K on the clock. Recently the engine stumbles when it is hot outside (90+). When it is cooler there are no problems. It starts fine, but then stumbles and somtimes even stalls. The stumbling prevents me from driving, and it can last several minutes. I thought it might be the fuel pump, so I replaced it, and I also replaced the fuel pump relais. The problem however did not disappear. I have measured the voltage at the connecter of the fuel pump, which should be 12 volts for 5 seconds after the ignition is switched to on. It is only 0.4 volts for 5 seconds most of the times (sometimes 6.2), and only after 5 seconds it switches to 6.2.
My feeling is that this is causing low fuel pressure, which causes the stumbling.... Can anybody help me fix this? Or am I completely off with my analysis.....

 

Do a mode III diagnostic of the ECU. You can do this by removing the passenger seat with an 8mm socket. Then you remove the ECU cover and loosen the 10mm nuts that hold it down. Next turn the ignition to ON (don't start the engine) and turn the dignostic screw fully counter-clockwise (IIRC) once both LED's flash 3 times together turn the screw fully the opposite direction. Don't over turn the screw either . Now count the number of times the red and green led flash. For example if both flash 4 times that is code 44 and all is well. if the red does 1 flash and green 2 that is code 12 for example and that would indicate a problem with the MAF. You can find the procedure in a haynes or chilton repair manual.

 

I ran the diagnostic, and I get 2 green and 2 red flashes, which is the fuel pump circuit being open or shorted according to Haynes.... However the manual does not really help me much further.

 

buy new connectors

 

Thanks a lot....it worked, she starts fine again!