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Greetings and thanks for your time, I have an 02 Nissan Altima 3.5 with a manual gearbox. For the past few months I’ve had slow acceleration, reduced MPG by about 5 miles, a few stalls after long drives (starts right back up), and a noise under load that I’m wondering if it’s spark knock. I can rev the car in neutral and the rpms will quickly raise and I do not hear this noise. The car starts and idles fine, it is drive-able as long as I do not use more then about a quarter throttle.
I’ve replaced plugs, cleaned the MAF, compression tested two cylinders(150psi), checked the exhaust back pressure on one side of the engine. I’ve also hooked up a scanner, no codes or pending, fuel trims stay below %10, O2’s are switching within normal voltage. This car does use a quart of oil about every 1200 miles and has done so consistently for the past 40k.
Any suggestions on what I should look at next? Maybe fuel pressure? but wouldn’t I have symptoms during starting, idling, and in neutral? No fuel filter just the in tank strainer.
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Fuel pressure may be a good next step. Given the oil consumption, how is your PCV? Might be worth checking it if you have not changed it recently. My only other thought is possibly something causing teh clutch to not fully release (throwout or pilot bearing), I would exhast other checks before going dpwn this read.
In the case of our old Altima
We had a bad cruise control switch, brake pedal switch or maybe a pedal clutch switch. Some of the symptoms you mentioned happened. It turns out the switches at the pedals needed adjusting. They weren’t releasing properly. Once they were properly adjusted the problem went away.I grabbed a fuel pressure tester but my car requires a special tool as there is no where to hook up the gauge without it. Question: If I was having fuel problems wouldn’t that show as high fuel trims when the ecm calls for more fuel?
PCV valve is brand new, I’m not thinking its the accelerator petal at this point because I do see on my scan tool the throttle position go all the way up.
Just an update, I checked the fuel pressure and it was 49-50 psi, spec is 51 psi. I also did a flow test which seemed to indicate good flow. I also found 2 coils soaked in oil so I replaced them along with the valve cover and seals on that side. I’ve also taken it to a local mechanic who claimed he identified the problem, a dirty throttle body. So he sold me a fuel system cleaner and a calibration on the throttle body which did nothing, other than it may have resolved the stalling issue. Performance under load is becoming increasingly poor. Currently the car will not go over 70 mph and slows dramatically up hill.
I’m going to try a dealer to see if they have any luck. This has been such a frustrating ordeal.
All sounds a very ignition related issue from what you have said and also sounds like the engine is on the verge of misfiring when under load.
So you found 2 oil soaked coils. In any event with the issues you have I would have replaced all the coils on that engine.
2. If not done yet I would be checking the condition of wiring and alternator performance.
3. Given the age and likely high mileage on that car , if also not done yet, I would be checking the performance of each fuel injector.Exhaust restriction maybe? Might have a fuel filter in the fuel module but is not replaceable. But you mentioned pressure & flow were good.
[quote=”zorexjonny” post=192767]I’ve replaced plugs, compression tested two cylinders(150psi)…This car does use a quart of oil about every 1200 miles and has done so consistently for the past 40k.[/quote]
What did the plugs look like? And, you really need to do a compression check on all the cylinders.
Both the Nissan dealer and an exhaust shop diagnosed plugged exhaust. I guess the exhaust back pressure test I performed was flawed. I would have preferred to run the test while driving under load but my gauge and connecting hose got hot quickly. I’m also perplexed as to why my vacuum gauge test looked good but again it was not performed while driving under heavy load. In hind sight I should have just removed the O2 sensors and then drove the car to pinpoint the issue.
Anyhow I’ve ordered cats from Eastern which I should have installed in a couple of weeks. I’ll report back the fix.
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