OK so this has been going on for a couple of months now. BUT now it seems to do it when ever it wants. The weather when i first noticed it was alot warmer but now today and yesterday it is quite cool and seems to be whats causing it to do it when ever.

With the car warm and after sitting for a few minutes. It will run rough for a few miles. It holds Idle just fine @about AFR 13.3, but when i go to give it gas to drive,it goes way down into the 18-19s and bucks and kicks. If I give it some more gas it smooths out and is fine. BUT then while driving, say 35@2500rpms it goes lean and bucks again. Usually it will sort itself out after about 3 miles. But yesterday and today (cold here now) it just seems to do it when ever it wants to.

If i leave the car, and come right back to it (1-2 mins.) she runs fine. If I leave it for about 5 mins. is when it starts having problems. I check the temp on my Rtek and its is usually at or above 180.

I did a couble of Logs when it was fine and when it wasnt' and the injector pulses seem about the same on both. Intake temps, map sensor is showing about the same vacuume. but thats about all I can think to check.
I'm going to try and warm it up tommorow and pull the IC and have a look in the TB to see if maybe that stupid wax pelet is casuing my butterflys to close.
OH and my TPS doest go above 93%

S4 Turbo
720x4 injectors (set right)
BNR stage 2
Racing Beat turbo back.
Walbro pump.
Rtek 2.1

 

Fuel pump? Could be the fuel pump giving up.

Ken

 

My turbo VW does this time to time, it is most def fuel press. In the vw (yes i know piston) fuel pressure drops under boost when the fuel reserve is pressed.

best way i can explain it, fuel press reg makes sure there is enough pressure to meet the demands of the engine. If fuel demand > fuel pressure you get the same problem, and only seems to happen under boost. Combined with high intake temps you should be getting a lean code.


IMO- i'd check/change the FPR and start off with a fuel system check

 

Vdub you mis-understand. It runs fine under pressure. If im just running down the street she bucks and surges and reads lean. As soon as I give it more gas it runs normal.
My walbo doesn't have to many miles on it. Unfortunatly i don't have access to my other car (91 turbo) to pull and test the pump.

Seems to be getting worse.

 

ahhhhh, then hmmm... it reads lean at low rpms before boost? or at idle? it would seem its starved of fuel at idle so i would check your injectors to start with. also for a vacuum leak.

 

The car idles perfectly.
After sitting for a few minutes (10-15) it still idles perfectly BUT when i try to drive down the street she runs lean and bucks. If I give it boost she goes back up to decent AFRs, but will run rough again when i go back to cruiseing. This USUALLY last for about 3 miles.

 

Almost sounds like AFM problems since it's intermittent. Vacuum leaks aren't usually intermittent. Either it exists or it doesn't. I would check the volts/resistance against specs while moving the flap. Also check TPS volts for smooth rise as you open the throttle. Boost sensors can be erratic as well and don't always set a trouble code. Coolant temp sensor can be suspect although not usually intermittent.

 

wow same exact syptoms in my car, everything to the exact word..runs fine in boost and at idle, but trying to daily drive is almost impossible bec. i have to get to 0 vac. or into boost jst to cruise..
:/
i'm thinking it might be the coolant temp sensor cause i've done NEARLY every dam thing to my car to make it go away and still..i'm thinking the Coolant temp sens. cause it runs great wen its cold in the morning until about 10 min. of driving and it gets a little warmer it starts running like that! and its pissing me off already...any luck for u?

 

My coolent temp reads about what it should BUT i noticed today that my Temp Switch isn't ever reading above 70. I'm going to swap it out and see if that helps. It definatly ran better when the temp outside was in the 80s. Now that we dip into the 40s at night its alot worse.