XLR8NSS

iTrader: (4)

Alright heres the scoop.

A while back(in the summer) I thought my transmission had went south. I had just put my supercharger on and I thought it blew up the trans. This is an A4 by the way.

I would go WOT and the car would just fall on its face like it was in between a gear or something. The rest of the trip I would have to drive with very light throttle or the car would sputter. It would do this after I had been cruising on the highway for a while. It would only happen on the really hot days and the car was fine after it sat for a couple of hours. I figured the trans. was getting hot and going into some protection mode. I decided to see if I could record what was happening with ATAP. Well, of course as soon as I hook ATAP up it stopped doing it. <img src="images/icons/rolleyes.gif" border="0"> I literally drove around for weeks with my laptop in the car trying to capture the problem in a log. No dice.

Well one very cold Fall morning the car decided to do it again. (I did not have my laptop) :figures: The next morning it wasn't so cold out but I took the laptop and tried again. No dice again. It never did it again until this morning.

It was about 26° out this morning and half way to work I decided to pass a car about 3/4 throttle. <img src="gr_stretch.gif" border="0"> I pressed the accelerator and the front of the car dropped like a rock. I'm thinking great. I noticed out of the corner of my eye that the fuel pressure guage was kinda moving in tune with the accelerator pedal. I looked at the fp guage and its about 3-4psi low and drops off as the load on the motor increases. I'm thinking man thats strange. If I'm just cruising the fp is just a little low but, any attempt to speed up with more than just a tiny bit of pedal results in the fp dropping off.(drops to around 20psi very quickly)

The fuel pressure was fine when I started the car up this afternoon. It never showed any sign of doing it again on the trip home from work.

It doesn't seem to do this during moderate weather. The car has done it several times now when it was extremely hot out or very cold.

My fuel system consist of the stock intank pump and a 255lph inline pump. I have 42# injectors now but back in the summer I had the stock injectors so I don't think it has anything to do with them. The inline pump has a relay triggered by the stock pump relay so it comes on with the stock pump and has its own power run from the front of the car.

I'm thinking that the intank pump is quitting for some reason and the inline is able to draw enough fuel to keep the pressure up under light load. What do you think of this?

Also what could be causing the stock pump to quit? Can the computer shut the stock pump down? If the computer shut the stock pump down then the relay for the inline should open and shut it down?

Do you think the intank pump is bad?

Let the ideas flow. <img src="gr_stretch.gif" border="0">

Sorry this is so long. I just wanted to include as much info as possible. I know I probably forgot some things.

Johnnie

[ January 02, 2002: Message edited by: XLR8NSS ]</p>

Z2802

I'm new to late model F-Bodies but I'll throw my $.02 in. Could it be some crap in the fuel filter or in the bottom of your tank clogging the pickup?

MIGHTYMOUSE

iTrader: (59)

do you have a fuse going to your in-line... can you hear your inline running?

i have had an intank/inline pump before and if i had one pump running and the other just sitting there.. it would have normal pressure until i gave a load. then drop off like a rock

i bet that your inline pump is no longer running.. and it is just impeding flow.. either remove it (now just a restriction) or make it work again.

good luck

XLR8NSS

iTrader: (4)

Hey thanks for the replies.

Z2802 - I don't think its a filter problem because it is very intermittent. I mean the last time it did it was back in mid summer. Oops, actually that was the first time. The last time was a couple of months ago. <img src="gr_stretch.gif" border="0">

Thanks

MIGHTYMOUSE - Yes the inline is running. You can hear it come on when you first start up the car. Its pretty quite though and you can't hear it while driving over the road noise. That sounds exactly like what is happening to my car. Pressure will be normal under very light throttle but as soon as you try to accelerate it drops(very quick).

I'm starting to think it might be a gound problem on the inline. The weird thing is that it has only done it three times in like 6 months. The first times it did it I thought it was trans. problems though, guess not. <img src="images/icons/rolleyes.gif" border="0">

The car has acted normal since yesterday morning. I'll test out the inline and check all the grounds later today.

Thanks

Johnnie

[ January 03, 2002: Message edited by: XLR8NSS ]</p>