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Matt, Engineer
Category: Car
Satisfied Customers: 20375
Experience:  Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.
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1995 Nissan altima: acceleration..Replaced the alternator..cap..rotor

Customer Question

1995 Nissan altima bogs at low idle, little acceleration until 3300 rpm then it has power, occasional backfireing, has issues on warm start. Replaced the alternator (due to low voltage (11.4v), distrubutor cap and rotor (due to common oil leak issue) and coil (due to not starting with warm and was getting very little spark from coil). Still having all of the same issues! HELP PLEASE! The previous owners told me they had the fuel system replaced about a year ago (looks all new). Car drove fine for a little over a month then it started having issues.
Submitted: 4 years ago.
Category: Car
Expert:  Matt replied 4 years ago.

This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.
As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.
Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Might also be worth cleaning out the idle speed control motor / valve as these get clogged up with carbon and some brake cleaner washed through helps free things off.

Might also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.
if the engine condition is the same then chances are the meter or the connection to it is faulty

Air leaks are very temperature dependent as gaps can open or close up as things expand with heat, so the weather and engine temperature can effect them.

This leads them to be quite intermittent in the case of mild leaks

its also worth cleaning the airflow meter by removing it from the car and spraying the exposed sensor wires inside the tube with a brake or switch cleaner - ensure that the cleaner is one of the old fashioned, non Eco type that does not leave a residue

On no account touch the sensor wires with anything physical as they are extremely fragile
Customer: replied 4 years ago.
I got new plug wires today and it is running much better still not completely right. I will try the mass air flow idea tomorrow!
Expert:  Matt replied 4 years ago.
Glad to hear that there's been some progress
just get back to me on this post
Matt and other Car Specialists are ready to help you
Customer: replied 4 years ago.
It seems to have fixed it for the most part! Still an ocassional issue will check for leaks when it's not raining!
Expert:  Matt replied 4 years ago.
Glad to have helped

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