Fuel System...Maybe??

[cyyoung2000]

Ok this may be a little long, but let me explain whats goin on and hopefully someone can help me out, thanks in advance!!!!

Alright, so the past month or so out of nowhere the ol' 91 Q is acting up.

Now this incindent only happened twice but it may help, I'll start it right up, then a few seconds later, the RPMs flutter up and down like crazy and the car dies. Then it wont start at all until a few hours later, when itll start up just fine. This started it all and it hasnt done this since.

Now, this is where the bigger problem is, I'll start the car up just fine, but at idle the rmps will be about 2 or 300 rpms higher than normal with a fairly rough idle. When i drive, there is literally NO power. i mean, no torque at all. I floor it, and the rpms will shoot up to 3500 and just flutter up and down up and down, the car does go, but slowly. I CAN cruise at about 50 but no faster than that. And after a little while, there is a burnt smell coming from the engine, smells like burnt hair. This only happens every now and then, like once a week maybe. The car does NOT always run this bad. And it only seems to happen when i drop below half a tank. Any other time, the car runs ok, but with NOTICEABLY less horsepower than when i first bought it (about 2 years ago).

So i replaced the fuel filter, had the injectors cleaned, ran some BG44k through it, and changed the oil, just to see if anything helped, which it felt like it did, but i still hav ethe problem. Now, this all feels like a fuel system problem to me. It feels as if the gas isnt being delivered or even worse, like no compression. Fuel pump seems fine, there is no buzzing or loud noises coming from it. So, i was thinking it could be a clog in the lines or something, but if that was the case wouldnt it run like crap all the time and not just occasionally?

Well let me know what you think and ask any questions you need! I really wanna figure this thing out, its killin me. Thanks guys!!!!!!

[Q45tech]

Measure the fuel pressure under load by tee-ing into the rail input after fuel filter. Run test hose out and tape gauge to windshield so you can see while driving. Make sure cruise is 34 psi and WOT 44 psi [throttle position controls psi].

Historically I've replaced fuel pumps every 7 years or 120k. Really depends on the amount of dirt you purchase and whether you change fuel filter annually or not.

[maxnix]

I bet is your fuel pump, but have you replaced or confirmed the replacemnt of your timing chain guides with the newer metal backed ones?

Annual air and fuel filter changes are mandatory! Joe has cheap prices.

[goody90q45]

Tech's advice to check fuel pressure is probably spot on but some of the symptoms you describe make me think that your MAF might be acting up. Have you still got the metal retaining clip on your MAF connector? Is your CEL coming on? Any ECU codes?

Try cleaning up and removing any corrosion from the connector and the MAF pins, tightening up the pins in the connector (see pic), and coating both sets of pins with dielectric grease before plugging it back together. When you're done it should fit tightly and the free play up and down should be minimal.

[cyyoung2000]

Yeah, the guides have been done and the air and fuel filters were done within the last 1000 miles or so. And theyve been done annually, well as long as ive owned the car. And yes i still have the metal clip on the MAF connector. But it was a little loose, fixed that right up thanks goody94q45. No CEL light. So yeah, ill check out the fuel pressure as soon as i get a chance, probably later on tonight, and post up my results asap. Hopefully this will take care of things.

So if it is the fuel pump, how hard are these things to replace? Is it a PITA?

[maxnix]

Best write up in the world on this forum. Be sure to obtain a new O ring and don't confuse it with old one. Verify FPCU is still good.
Modified by maxnix at 4:23 PM 8/3/2008

[goody90q45]

The fuel pump is pretty easy to replace once you remove the back seat and rear deck. The only tools your need are a few different lengths phillips head screwdrivers. The step where you need to be cautious is pulling the pump and sending unit out of the tank so you don't bend anything. There's a good tutorial in the tech help section at Q45.org and lots of help here using the search function.

Just for kicks you can go in through the trunk, pull back the trim and unplug the fuel pump control unit to look for any burning or melting on the connector. That would be an obvious sign that a bad fuel pump is burning out the FPCU or vice versa. While you're there try grounding out the fuel pump to run on high speed only. It's done by running a jumper from the lower right pin (ground) of the FPCU connector to an unpainted ground in the trunk area. If the problems go away you need to replace the FPCU. In the picture the pin to ground has the clip attached and the FPCU is in the background.

What I'm suggesting won't take but a few minutes and if you see a scorched FPCU connector at step one you might as well replace it and the fuel pump. With the mileage on your Q you're due. The fuel pressure test is the best of all since it reads pressure while the problem is occurring. Let us know what you find.

[cyyoung2000]

Yep, the pressure was EXTREMELY low, scary low actually...So... i Replaced the pump, very easy job to my surprise, less than an hour start to finish! and things are back to normal, for now. But i had one little mess up, had trouble getting the damn gas level indicator (the little floating box) in the right spot, but i thought i finally got it. Now my tank reads over a full tank and it wasnt that high to start. Is that normal? Guess i have to go back in and fix that....

I appreciate the help guys, hopefully this takes care of things, ill keep you updated...