My 94 Q45 Bucks...

[30bino09]

Greetings to the forum. I just aquired a 94 Q45, it drove well for the first couple days then one day on my way home from work it bucked a little, I pulled off the free way, then it cut off at the first stop light. Made it home with it bucking intermittently. it's been doing it every day but not all the time. Sometimes it's mild sometimes it's real bad. The only thing I remembered doing when I got the car before this started was to fill it up with 91 Octane gas but also I jiggled what seemed like tubing from the gas tank when I was searching there for the CD changer connectors. I have heard of Mass Airflow Sensors, knock sensors ....waht could be going on here?

[elwesso]

First order of business is to check fuel pressure, has the fuel pump ever been replaced on the Q? Next order of business would probably be the MAF

Welcome to NICO.

[96Qowner]

Yeah, your MAF is misbehaving. Read this:

http://www.q45.org/maf.html

It may not solve the problem permanently - in fact, it probably won't. If you have the time, do a search for MAF in post bodies for both recent and archived threads in Infiniti Online Mechanic and Q45 forum, as well as Infiniti General. That's 6 searches. You'll learn everything you'll ever want to know about Q45 MAFs.

[silver2k2]

Replace the fuel filter. It needs it either way and it may fix your problem

[maxnix]

Please update us with the service history begining with the Infiniti Dealer performed one you inspected before buying the car.

Have you changed all fluids and filters yet? Added an auxiliary ATF cooler? BG44K?

Lots to know and you have come to the right place to learn about your new purchase.
Modified by maxnix at 5:58 AM 5/18/2007

[30bino09]

This has got to be the best auto forum I have ever visited and joined. Many thanks to the people who have replied. I really have to learn all this stuff ATF cooler, BG44K etc etc. This car was purchased from a private seller. Some of the things I know off the top of my head and I can confirm dates later: Tune up 6 months ago, faulty fuel injectors replaced, fuel pump replaced, MAF (purchased on ebay) replaced one year ago when previous owner was having similar problems. I recently changed the air filter when the problem started. I will look at the swervice history paperwork tonight closely.

[maxnix]

And please let us know what a "tune up" involves exactly.

[96Qowner]

... MAF (purchased on ebay) replaced one year ago when previous owner was having similar problems ...

This looks to me like a classic MAF problem. I bet the replacement is failing. Or the harness could also be a problem. It's just SO much like a bad MAF. It wasn't a new replacement, so I'd be sure to rule that out first, before blaming something else. The trouble is, now you have to find a known good one, or take a chance on another used one. Used, about $100, new about $400.

Also, no mention of the FPCU (fuel pump controller). If you do the searches I mentioned about for FPCU, you'll find a bunch of info. Basically, the controller can develop an intermittent circuit that melts and solidifies erratically.

The mention of replacing the air filter is another clue to the MAF. Fiddling with the airbox disturbs the MAF connector. Pull that apart, clean it up and grease it with dielectric grease. Examine the harness and plug for possible failure. Easy, simple, free. Go from there.

[30bino09]

Thanks for the advice. I will start with the MAF. I acquired a used one on ebay. I will install on the weekend and update the forum.

[30bino09]

Guys, I replaced the MAF (a used one $60) on the weekend, now the Q runs sweet. I am glad I found you guys. Saved me a lot of $$$$.

[96Qowner]

Glad we could help!

Heheh, some of this knowledge is hard-won. Been there, done that.