QuestionVon:
Well, have cleaned everything I could clean. Throttle body, etc. Carb and choke cleaner in "mechanical" areas, and electronics cleaner near and around sensors. Replaced suspect vacuum hoses with new. Also a new air filter. Engine runs fine for a while, then stumbles (misses) erratically under load, and stumbles and sometimes stalls when dropping to idle at a signal light. But not always. It runs as it should, until it doesn't. No consistency to it. I raised the idle a bit, via the "big plastic screw" on the IACV-AAC unit. I have made sure the throttle body valve does not slam shut at idle. Adjusting the screw on the IACV - AAC unit stopped the stalling, but not the stumbling. Haynes manual says the 1995 Nissan Maxima is OBD II. Nissan dealer says it is OBD I. I can purchase an OBD I code reader for less money than it costs to have the vehicle diagnosed. An OBD II reader is about 100 bucks. With all the troubles as written about above and below, the check engine light STILL never comes on. It works (the bulb is not burned out) because it does light when turning on the ignition, when all lights light, and after the engine stalls, again when all the lights light up. But it does not light when the engine is running, or after it is re-started - which it always does without a hitch. No one in town (including the dealerships) has a fuel pressure regulator in stock. Nissan dealership parts department stated they have never had a problem with one, so never had to stock one. I have ordered an OBD I code reader and will see what pops up after I check the codes. I hope it isn't a broken wire in a harness somewhere. Boy, I'm glad I don't drink!
The fuel pressure regulator appears to be nothing more than a spring loaded mechanical diaphragm device that doesn't open until and unless a particular amount of pressure is present, keeping the necessary fuel volume and pressure inside the rail for the injectors, and returning the excess volume to the tank. How much trouble would it be to have added sensor capability to the device, with a min-max spread to light the light if it is malfunctioning? It sure costs enough to have a built in sensor included!
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The text above is a follow-up to ...
-----Question-----
Hi, Von:
This is my daughter's car. Began surging (bucking, actually) and stalling. No power. Replaced fuel pump, strainer, fuel filter.
Ran fine for about fifteen minutes, probably because the battery was disconnected during repairs and maybe the computer reset? Removed and cleaned mass air sensor with electronics cleaner. Ran great, so I replaced mass air flow sensor with a new one. Ran great for a week or so. Now it stalls after warm up when releasing the foot from the accelerator. My daughter swears it acts up after a fill up. I'm not so sure. Check engine light has never come on. I have not had the opportunity to drive it since this second acting up stage. Any ideas? I appreciate your help in any way. Thanks.
-----Answer-----
Bob,
I would check the fuel pressure as the regulator might be going out and if the filter was not replaced change it too. Sounds like it is fuel related so let me know if the pressure is out of wack. And, if so, replace the regulator. The reason I say to replace the filter is that it acts as a restriction and the regulator has a hard tome compensating for a dirty filter. You already replaced the mass airflow sensor so that should be fine. Check to make sure the air inlet temperature probe is installed and there are no leaks between the air meter and the intake. If the hose is cracked or the clamps are loose unmetered air will enter the engine and make it do strange things like a bucking idle. So, check this too.
AnswerBob,
1996 Was supposedly the first year of OBDII for Nissan. Have you taken the car to Autozone or Checker and had them read it? This would let you know for sure which you have. Transition years could mean that yours has the OBDII connection. But, no codes lead me to think the problem would be with fuel delivery like the pump, relay or regulator. A Haynes Manual would be helpful as would a fuel pressure gauge. Check it out and email me back.
