restoring the performance to my 94Q

[motorbobb]

I wanted to solicit the members opinions on a problem that has been effecting my 94 Q45t. Here is my issue:

The car just does not accelerate like it used to a few years ago. Over the years, I have had all the normal induction parts cleaning done, and during a recent service check-up, had the plugs replaced. The car doesn't miss or display any obvious characteristics but its just so flat / unresponsive, particularly at low rpm's. If the engine was an old, pre-computer / electronics / vtec motor, I would be playing with the spark advance and / or the vacuum which opens the big venturi's on the 4 barrel carb.

The car has 125k gentle, well maintained miles. I am not looking to add any aftermarket performance, just trying to restore performance close to OEM. Is there any obvious thing I should have someone look at (ie are there any adjustments to valve or spark timing) or is this just normal old age performance? (or maybe the fact that my performance benchmark is warped since my daily driver is an E55?).

A couple people have suggested to me so far the anti-knock sensors or the fuel pump (the pump does whine). Any other ideas? Also, any estimates of the cost of replacing the pump or the anti-knock?

Thanks a bunch. rgds kc

Any advice from the board would be appreciated. rgds motorbobb

[vicQ45]

how much would the fuel pump effect performance? i too have noticed really sluggish performance at low rpms and i need a new pump...

[elwesso]

The fuel pump can cause that sort of thing, and its best you replace it..... If its on its way out it could do that.....

$250 for a new pump, plus maybe 2 hours for install.....

Knock sensors cost a lot of money to replace, probably 9 hours to replcae and $300 in parts ($200 from me)..

Id suggest to do a consult diagnosis on the car, unles you are ready to dig right in... We'll help you out, but if your unsure of what your doing

[Jesda]

What are your driving habits? Lots of slow stop and go or do you mostly fly down the interstate?

[DAEDALUS]

Throwing $250 at a problem on a hunch isn't recommended. For $35 you can buy a fuel pressure gauge and verify whether you really need a new pump. If the knock sensors are bad there'll be a code in the ECU that you can retrieve on your own.

[elwesso]

Well he said the pump whines and it will need replaced either way, eventually.....

[maxnix]

Describing your maintenance history, especially of the fuel system, will help the experts here a lot.

If the pump is whining, it is time to replace before it takes the FPCM (and many more of your $) along with it.

As always, read the previous posts, especially by Q45tech (mandatory).

Tangalora has written the definitive fuel pump replacement post.

[DAEDALUS]

Well he said the pump whines and it will need replaced either way, eventually.....

Agreed it should be replaced because it's humming, but I wouldn't expect a performance gain from it.

[maxnix]

Agreed it should be replaced because it's humming, but I wouldn't expect a performance gain from it.

Unless the fuel pressure test you suggested indicated below OEM specification pressure at the mid or highest pump speed.

[elwesso]

Indeed.. No offense to her, but she has made the "Q45 repairs for dummies" writeups on many things... not to insult her intelligence, but to show that her writeups are very thorough..

If you can dodge a wrench, you can dodge a ball... wait, if you can turn a wrench, with tangalora's writeups, you can fix a Q45

Like I said, unless the pump is failing (car would be hard to start, and it would "chug", but be "normal" on WOT), then thats the case...

Another thing to check is timing... After I replaced my KS, my timing was still off about 5-6 degrees.. I had done about everything i could that would affect performance, and the timing was still off... I attribute 125-130k worth of chain stretching to throw it off.. The car was "normal" (sans sludge) in every other aspect, plus im certain that the CAS wasnt messed with... I seem to recall some paint marks, to show it wasnt messed with.....

on Q45.org, we have about 3-4 writeups on fuel pump replacement......

[texasoil]

It may well be deposits on th eintake valves causing your low performance problems. Very common. BG44 in the fuel will remove them, as will Techron. The new gasolines that advertise 'clean-up' ,or 'drive clean' will also--they HAVE been tested and WILL clean up a dirty intake system. B4 throwing money at a undiagnosed problem--try the easy way out and let a little time and cleaning solvent do their things. High probability that deposits are your problem.

[Jeff Williams]

Lola came from California. She was sluggish as well. I attribute it to the Bosch plugs, poor quality of California gas, and dirty throttlebody. Since getting to Alabama, and using only Techron Supreme from Chevron, putting the NGK plugs in, and cleaning the TB throughly, she has picked up a lot of pep. My next step will be a fuel rail flush and timing adjustment at the dealership. Hopefully that will get her up to the performance of Layla.

It sould like you are getting some great advice. Definitley replace the fuel pump ASAP. I waited about 8 months on Layla, and was nervous. The Buzz got so loud people in the back seat were commenting on the noise. It is really a simple process. It took about an hour, since I removed the entire back seat, and rear deck, and all the panels and mat in the trunk. The plugs take about 2 hours, and the engine needs to be cool. Clean the TB and intake pipes at the same time, since you have to remove them, to get to the plugs. Replace the fuel filter after the pump, so any dirt or crud shooken loose in the pump replacement will be caught in the old filter.

Try 4 cans of Techron FI treatment, every other tank full.