recon fd

Hey Guys,

I have searched this one, but no joy yet. I didnt know if anyone else has experienced something similar. Havent drivin the car in about a month because of this issue.

Here we go:

Ok so the other day I was driving down the street with absoutly no issues. Boost was fine, vacuum ok, fuel pressure good. I got into some traffic for about 5-10 min. and the car started to basically bog down. It would idle fine, but if I went to give it gas to take off it would bog like it had no power and buck. Vacuum and fuel was still fine though...so was temp. I had her towed home.

The next day I went out and started her up and drove her around. No problems. Started right up, and no problems cruising around. Hmmm wierd. So I decided I would bring her to work the next day. On the way to work no issues, but one the way home I got in a little of traffic again. About 10 min into traffic it started again. Brrrapp brllllrap brapapap. Luckly I was in the right lane and able to rev it up enough to get it off the interstate and directly home.

I let her cool down for about 2 hours,a nd went to start it back up. AGAIN no problems riding around. Plug wires are tight, temp is good, fuel is good, vacuum is good.

I havent driven her anymore because I dont want to be stranded anywhere.

Anyone have any ideas?

thanks for the help,
-josh

dubulup

here's my guess.

failing AIT sensor...heatsoak makes it crazy and it causes the ECU to dump fuel.

Mahjik

iTrader: (1)

Did this start happening out of the blue, or did you do some work on the car and it started right after that?

recon fd

No it just started out of the blue. I had not driven her for about 2 weeks because I was out of town on business. When I took it out for the first time when I got back it started. No I did not change anything before this happened.

DaveW

This is just WAG, but, back in the days of carburetors, heat soaks would cause the fuel to get too hot and vaporize in the fuel lines (usually in the non-pressurized line between the tank and the pump), causing fuel starvation. The car would buck on acceleration as only vapor would get to the carb and starve it for fuel. This doesn't usually happen in pressurized lines, so I was wondering if something is letting your fuel pressure get too low, and, thus, cause vapor-lock at the injectors, or something similar.

Dave

recon fd

Yeah this was sort of my thought, but my fuel pressure is staying steady on the gauge. Of course this could happen past the sensor, but how likely is this on a fuel injected car dave?

DaveW

IMO, not very likely if the fuel pressure reads OK. I wonder, in my ignorance, if the Fuel Pulsation Dampener could cause this.

Dave

recon fd

Ok, let me elaborate on my fuel pressure.

Fuel pressure is fine at idle, and is fine when I drive around normally, but when it starts to bog down is will stay steady at idle, but right after the bog happens it will drop with the rpms.

DaveW

So it does sound like a fuel starvation/vaporlock issue.

How about the fuel filter - how long since that has been changed? Any chance some water got into the gas tank? Water will swell the filter element and restrict fuel flow.

Dave

recon fd

I changed the filter about a year ago. I really dont think I got water in the tank, but why would the problem just start in traffic (heat soak)?

DaveW

I don't know. Is it an aftermarket fuel pump? Any chance it might be malfunctioning as it gets hot?

Dave

recon fd

nNo the fuel pump is stock, but I have a walbro 125ml in the garage I have not gotten around to installing yet. May be worth a shot. Do you think this cold be the case?

Monsterbox

iTrader: (6)

recon,

dont forget. your fuel pump is only supplied with 9V at idle!.....this could be your problem...your pump is either worn out or the electrical wiring is worn out (resistance increases with heatsoak) so what may be happening is your pump cannot maintain the fuel pressure at only 9V..try the dale clark rewire its EXTREMELY easy as see what happens...when I did this i had an instand 12+ volts all across the rpms and my pressure raised about 1psi at idle...FP is now 42

existanzrx7

iTrader: (8)

My seven does some thing like that in traffic. When it sits for to long in traffic with hot weather and as you go to take off it has trouble gaining speed like it has no power or some times even during take off the rpms drop to much and dies so what I due is start her back up and I must keep it in high rpms to get it to move some where and as I go threw the gears in high rpms after I get to my desired speed I shift to 5th gear and just cruse and it seams that when you just cruse after a while without stopping the engine cools with all the fresh air coming in and gains back its power I also been asking my self what the fck is going on with my seven. What I thought it could be is the intercooler just gets to hot and all the piping with it and the engine needs cold air and as it sits in traffic it just starves it self with all that extremely hot air. What do you guys think?

fd0

iTrader: (8)

Oh my, please use periods at the end of each sentence. It helps with the reading.

Now to your issue, any chance it could be the map sensor or the hose connected to the map sensor?

1QWIK7

iTrader: (33)

Hmm, my car has been acting similar to that past couple of weeks.

Only after its been warmed up (not even up to operating temp yet). When i would turn a corner, the rpms sometimes drop down to like 900-800 pretty fast and makes me bog sometimes.

Or when i would be in gear (say like 2500rpm), then i drop to neutral, the rpms shoot down to like 900-800 fast sometimes. It only does this like couple times during a single trip. I dont think it was the dashpot because i havent touched it in a long while and car never did this before. I turned it i say a 1/4 turn in so i hope that helped a bit. I didnt drive the car yet since that day so i hope that was the cure.

recon fd

Alright I am going to give it a shot.

thanks guys,
-josh

existanzrx7

iTrader: (8)

Sorry I was an a hurry and as to my problem everything looks good it only happens when sitting in traffic in hot weather thats when it acts up. But when I finally get the car up to speed and put it in 5th and just cruse than some how it gains its power back I guess its all the cool air flowing in that gets it going again.

recon fd

^ same issue

Not the map sensor. Mine is almost brand new, and has no cracks, splits, etc. Only when the car is hot.

But not running hot.

CantGoStraight

By any chance are you throwing any codes ?

recon fd

No....... nothing.

1QWIK7

iTrader: (33)

How about grounds??

Did you check your stock grounds or added any new grounds?

Its cheap and at least that would rule out one possible factor.

kash

What are the condition of your plugs and which type are you running? I know that colder plugs will run like crap at idle as they get fouled easily and same with old plugs ?

jmadams74

I'm in way over my head here, but it seems I recall one of the solenoids controls some kind of fuel pressure regulator who's specific job it is it ensure extra fuel pressure when things get hot such that vaporlock and other bad things don't happen. Just a thought. . .might check that solenoid for proper operation.

djseven

iTrader: (56)

Is it doing it only in boost. Can you accelerate if you stay out of boost. Your symptoms sound a lot like limp mode which can be caused by a number of different things.

However, with your situation it does sound like it could be the AIT sensor if it only happens during heat soak.