1997 Maxima backfire on starting

[maxfirst]

I recently got my first Nissan, a 1997 Maxima with 163K miles. All was fine until recently it started backfiring through the exhaust when starting the engine (one "pop"). Once started it runs fine, fuel economy, performance are all OK. Twice it has not wanted to start, but did start after holding accelerator pedal down-almost all the time it starts, just with the backfire. Thought I should try to track it down before something gets worse. Thanks.

[loystock]

Welcom to NICO - the best car forum in the world.

FAS - Fuel, Air and Spark must come into the combustion chamber at the right timing for smooth combustion. Your problem may be as simple as water in your fuel tank, low fuel pressure (fuel pump, filter, etc) and/or ignition system (coils, pugs, timing, etc.) issues.

From the info provided looks like you have a dirty fuel filter (starting problem) and water in the fuel tank (backfiring). Water in the fuel tank us due to condensation which forms when the tank is kept below half full most of the time.

We'll start with the simple one - remove water in the fuel tank and replace the fuel filter. Before replacing the fuel filter, ensure the fuel line is empty - FIRE HAZARD, by pulling the Fuel Pump fuse (15A, fuse panel below dash board, driver side) until the engine dies. Crank the engine at least once to ensure line is empty. Remove and replace the fuel filter (on firewall besides brake booster).

Once fuel filter has been replaced, buy a full tank of Tier 1 gas (Shell, Chevron, etc) and at this time, Premium is preferred though regular gas is Ok. Add a bottle of Iso Heet Antifreeze and Water Remover into the fuel tank. Check the air filter - it may be dirty and needs replacement.

When you have time, clean the MAF (Mass Air Flow) sensor and connector. and throttle body. Use zero-residue Contact Cleaner on the MAF sensor and connector. When cleaning throttle body, be gentle with the throttle valve and never spray cleaner directly into the throttle body (can damage TV actuator/sensor). There are other things that you need to do to keep you car running smoothly by doing a SEARCH as well as reading the FAQ sticky in this forum.

OEM parts fuel filter can be bought from NICO sponsor, IoS - everythinginfiniti.com, @ 25% off MSRP. Aftermarket fuel filter can be obtained from AutoZone and the likes as well as Iso Heet, MAF Cleaner, Degreaser, etc.

Rod

[maxfirst]

Thanks. I had already replaced the air filter; will get started on fuel filter, etc. as you've suggested.

[maxfirst]

Well, after half a tank of gas with isoheat and a new fuel filter, no noticeable change so far-still a backfire on startup. While the filter was not plugged, the gas that came out when I drained it was not clear-a bit milky yellowish. What's the next step?

[loystock]

Looks like you have contaminated fuel. Good fuel should be clear and not milky-yellow. I hope it's just the fuel but it's possible that the tank itself may be contaminated. The milky-yellow color could b e an indication of RUST inside the tank. Another possibility is that somebody could have played a prank on you (added something in the fuel tank).

Rust could have formed from years of driving with the fuel tank near empty and/or leaving the fuel cap open, allowing water vapor inside the tank, leading to corrosion.

You have to siphon the contaminated fuel from the tank and replace with a new one. If that one does not work, then you have to remove the fuel tank for through cleaning. The fuel pump may need cleaning, too. Fuel tank cleaners are available from car parts store.

You can also take the car to a shop for a 2nd opinion, cleaning and probably rust removal. Fuel tank cleaning may cost you $300 more or less (more expensive in dealership). A special acid treatment is needed to remove the rust. Another option is to get a new or used replacement tank.