MY 94 Q45 HESITATES WHEN I GET TO ABOUT 60MPH WHAT COULD IT BE?

[joneil1129]

I have a 94 Q45 the car runs fine when the engine is cold, but when it warms up it starts to buck bad, when im on the high way and get to 60mph. now I have done nothing yet because i don't where to begin.. If someone out there can help me I thank you........

[Epod]

1) Has the fuel filter been changed since the factory? It's about $12 and if it's not part of this problem, it will be part of a problem soon enough.

2) Have you tried some fuel injector cleaner? Same rationale applies - it's cheap to try, and you probably need to anyway.

3) If you want to do something more targeted, you could measure the fuel pressure under load. A search of the board will show you a cool scheme for adding a T fitting so you can do this in a slick way.

4) Does it make a difference if the fuel tank is full or empty?

5) Do you hear a buzzing sound from the area of the fuel tank? You might park at idle and check. If you hear one, that suggests bad (but fixable) things involving the fuel pump or the controller.

Good luck - and you might mention the current mileage of your car.

[joneil1129]

Yes I do hear the buzzing sound. before I start the car again after driving it I release the pressure from the gas tank by taking the fuel cap off after i do that the car some what wants to act right.. The car has over 200k on it.and yes all I ever used was the BG44k.

[joneil1129]

And if I do have to replace the FP do I have to drop the tank???

[Epod]

I have not had this issue, and I have a 2nd generation Q, but from reading the board I'll suggest:

1) The received wisdom here is that you'll want to keep your tank at least half full while you are diagnosing this problem. The theory is that the pump is better cooled when it is immersed in gas.

2) As a minimum, it would be worth measuring the fuel pressure. If you want to go beyond the mere minimum, the more technically savvy on the board would suggest that you splice a T fitting into the rubber fuel hose downstream of the fuel filter and snake a few feet of fuel line hose from the T to the windshield, where you can tape a fuel pressure gauge so that you or your trusty assistant can read it while the car is in motion. If you do this, be sure you use fuel line hose and that you route it where it won't get cut by anything, or else you'll be driving a fireball down the interstate, and it's brown trousers time when that happens. If I were measuring fuel pressure that way, I'd keep the windows and the sunroof closed.

3) If I were you, I'd change the fuel filter...it's cheap and easy, it's not going to make anything worse, and it may relieve some strain on the system while you are diagnosing and dealing with other issues.

4) In addition to the fuel pump, there is also a "Fuel Pump Controller Unit". It is referred to on the board as FPCU. I suggest that you search on the terms "FPCU" "bees" "buzz" and "buzzing" (in addition to more obvious searches like "fuel pump")...those searches should lead you to posts about diagnosing the fuel pump and the FPCU. The received wisdom here is that if you ignore a bad fuel pump long enough, it will start to draw too much current, and damage the FPCU, which costs more than the fuel pump does.

5) You have downloaded the factory service manual, right?

6) If you conclude that it is your fuel pump, here's a write up a member did that is applicable to your year:

http://www.nicoclub.com/articles.php?id=164324

Good luck!

[Epod]

Also, check out

zerothread?id=6268

[joneil1129]

I ordered a new fuel pump today will there be anything else that I may need?

[Epod]

If you haven't already done so, download the factory service manual ("FSM") and read the procedure for diagnosis/replacing the pump.

It's all worth your attention, but in be sure to notice the step for removing pressure from the system (as memory serves, it involves pulling the fuse that powers the fuel pump then idling the car till it dies of fuel exhaustion).

If I were you, as long as I was in the neighborhood and playing with fuel hoses and clamps, I would change the fuel filter unless it's been done recently.

Here's a thread worth reading since it describes accessing the stuff you want to get to and a "gotcha" about reassembling it.

zer...ouble

Good luck!

[joneil1129]

Yeah Epod, I've just got the pump, im going to have it put in tomorrow. because the buzzing sound is getting nothing but louder, and the car is bucking more I have over a half a tank of fuel in the car.. I've downloaded the instrut yester day on how to install it the do's and not to do's... so I should be covered on that... well wish me luck... I'll let you know how everything went... Thanks again....

[joneil1129]

The fuel filter was the first thing I done when the problem first occured.. about a month ago.

[japaneseq]

Did FP fix problem?

Please let me know.

Thanks,

[Q45tech]

Use Consult to check for knock sensor codes.

[joneil1129]

KNOCK SENSOR???? i THINK i NEED TO GET AN ODB 1 SCAN TOOL.... IT DID WELL FOR ABOUT A WEEK NO THE SAME THING WITH THE BUCKING.... IM ABOUT TO JUST GIVE UP ON THIS Q.... AND BUY ANOTHER CAR..

[Infinitiguy19]

Did you test your knock sensors or read the codes off the ECU with a consult or manually?

Respectively:http://q45.org/ohminjectors.htmlhttp:// ... p?id=60332

If you don't have the money, knowledge and time to replace the knock sensors then please sell your Q to a NICO member.

Do you have any service history on this car?

Can you type any better too?