Please help. 91 nissan maxima GXE engine miss

Hey everyone,

First of all, sorry for the cross posting but I believe it's relevant in all groups posted to. I have a 91 nissan maxima GXE with 190k, V6,

5sp. This car has driven great until 2 days ago. All of a sudden (literally overnight)it developed a miss that is noticeable throughout the entire RPM range. Car ran great Friday and then Saturday when I started it, the miss was noticeable. The idle is down to about 600 vs 800 it was before and power is down. I checked the plugs, wires, cap and rotor and they all look good. They are about 2 years old with roughly 15k on them. The miss seems worse when the engine is cold. I can't see any wires arcing and have verified that there is spark at every wire using a timing light. The check engine light is not lit. The car shakes mildly at idle and has kind of a pfft pfft sound at the exhaust pipe. Anyone have any ideas on what else to check? I am at a loss and need to get her running right again asap.

Thanks in advance

Derek

Reply to
genius
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Could be a bad fuel injector, or much worse- a burnt valve. If it's not ignition-related, it's either fuel or mechanical. You'll need to narrow it down to one cylinder if you can. If not one offending cylinder, could be a bad O2 sensor. Others here will probably offer more accurate diagnoses, but that's where I would start. Good luck.

Chris

90 & 94 GXE's
Reply to
Chris H

Chris,

Thanks for the quick info. Do you have any suggestions on how to narrow this down without throwing random parts at it? I did unplug the battery for 30 mins, reconnected and same issue. I suspect something electrical as the vehicle literally developed this problem overnight while parked. Thanks again for the input.

Derek

Chris H wrote:

Reply to
genius

If one cylinder is not working (either because of fuel or spark for example) you could run the car and pull the spark plug wires for each cylinder one at a time - when you unplug the bad cylinder - the engine should not run any differently. Once you have figured out which cylinder is not firing, you can diagnose further.

As an aside, you can get a piece of rubber tubing or a long screwdriver and use it as a stethescope to listen to each injector - you should hear distinct clicking for each injector pulse... see if find a dead injector. You can confirm that cylinder is indeed dead with the method I described above.

Cheers Nirav

96 Max GLE, 118k
Reply to
njmodi

How old is the fuel filter? Replace it if it's old. Since you have spark at each plug, the other necessities are fuel and air. Check the air filter, and then check the injectors.

You can use a piece of rubber hose to listen to each cylinder as the engine runs, and each injector should make a "pfft pfft" sound. Another test is to unplug each injector (engine off) and put an ohm meter across the two leads. I don't know what it should read, but they should all be the same. If one is wildly different, it's probably bad. But, you should have a Check Engine light if one of the injectors has failed. You could also unplug each injector and see if the car's performance changes. If one is bad, and you pull another cable, you'll probably stall the car.

Bill G '91 SE Auto

Reply to
Bill G

Ok, it sounds like one cylinder is not igniting properly. If the pfft pfft sound is pretty regular like it's the same cylinder, then it must be ignition or fuel injector to that cylinder. Pull each spark plug wire and note the wire that does not change the misfire characteristic. That's the one you need to completely diagnose. Pull the spark plug, check resistance to that wire, check the distributor cap for cracks, contact points for pits, any moisture inside of dist cap and any dirt particles in the Crank Angle Sensor disk inside the distributor. If there's any moisture in the dist cap, replace it and the rotor cap. (Both my Max's had cracks in the dist caps which allowed moisture in. They were REALLY old, but your's still could have a defect, so check them anyway.) Also, check the fuel injector wires to make sure there are no cracked or loose connections to the fuel injectors. That would definitely cause a regular misfire. Did you wash your engine compartment or did it rain last night? Water and moisture can cause a short in the ignition by allowing the spark to jump to ground, and moisture in the dist cap will also cause a short.

Chris

90 & 94 GXE's
Reply to
Chris H

Thanks to everyone who replied. Mysteriously the miss is gone and the car runs good now. No idea what caused it. Friday it was fine, Sat & Sun had a miss, Monday was fine. I imagine some moisture might have been somewhere it wasn't supposed to be and when it dried out, it was fine. I am going to throw a new cap, rotor, plugs, wires and fuel filter just as preventative maintenance since I have no idea how old they are. Thanks again to all who replied.

Derek

Bill G wrote:

Reply to
genius

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