Lack of smooth throttle / acceleration after driving car for 1hr+.
04-17-23, 04:01 PM
#1
Lack of smooth throttle / acceleration after driving car for 1hr+.
Experiencing an issue for the first time over the past few weeks. Symptoms are that after about an hour of driving when I'm on the throttle I get little or no acceleration. I will have been driving the car just fine, runs smooth, pulls great. Hitting typically close to 1-bar on the turbos.
During this issue my A/F gauge doesn't light up... car chokes and stutters, pops. After some feathering for a few seconds I can get enough acceleration and all of the sudden turbos spool up and I accelerate and the A/F reads correctly. If I keep it under throttle it will pull fine, and I get strong boost. Moment I shift gears I start all over again. It's an absolute nightmare and now on two drive's I have had to limp the car home for almost an hour.
Turning the car on and off and sitting for 10-15 mins didn't solve the issue. Leaving the car overnight the first time it happened did resolve it "temporarily". I say this because I was able to get it to the nearby shop fine. We cleaned the injectors, and tried to diagnose. At a glance all checked out, I took the car for a shorter drive and it was fine. Until I went back out for another longer drive this weekend and at almost the same distance / time on the road the problem kicked back in. That could be purely coincidence but that was really bizarre.
Some sensor data which may or may not mean anything. I noticed that when I was on throttle the PFC showed that the FPD is always on and FPR was not on until the moment that I get normal acceleration then the FPR lights up. HWL is always blinking once I'm in gear on the road. O2 sensor showing 00-.01V until you get normal throttle response and then it's up around .74-87 ish.
Other notes, car idles smoothly even during this issue, turbo is strong (running twin 99's in sequential on a street ported motor with 850cc's all around). New-ish plugs, wires, fuel filter was just done in the past 5k. It was sitting for the winter and some of the first rides this season were just as long and all checked out so this is just starting to happen.
Appreciate any thoughts pointing me in the right direction.
During this issue my A/F gauge doesn't light up... car chokes and stutters, pops. After some feathering for a few seconds I can get enough acceleration and all of the sudden turbos spool up and I accelerate and the A/F reads correctly. If I keep it under throttle it will pull fine, and I get strong boost. Moment I shift gears I start all over again. It's an absolute nightmare and now on two drive's I have had to limp the car home for almost an hour.
Turning the car on and off and sitting for 10-15 mins didn't solve the issue. Leaving the car overnight the first time it happened did resolve it "temporarily". I say this because I was able to get it to the nearby shop fine. We cleaned the injectors, and tried to diagnose. At a glance all checked out, I took the car for a shorter drive and it was fine. Until I went back out for another longer drive this weekend and at almost the same distance / time on the road the problem kicked back in. That could be purely coincidence but that was really bizarre.
Some sensor data which may or may not mean anything. I noticed that when I was on throttle the PFC showed that the FPD is always on and FPR was not on until the moment that I get normal acceleration then the FPR lights up. HWL is always blinking once I'm in gear on the road. O2 sensor showing 00-.01V until you get normal throttle response and then it's up around .74-87 ish.
Other notes, car idles smoothly even during this issue, turbo is strong (running twin 99's in sequential on a street ported motor with 850cc's all around). New-ish plugs, wires, fuel filter was just done in the past 5k. It was sitting for the winter and some of the first rides this season were just as long and all checked out so this is just starting to happen.
Appreciate any thoughts pointing me in the right direction.
04-17-23, 06:04 PM
#2
Racecar - Formula 2000
WAG - doesn't fit all your symptoms, but - Fuel tank air inlet in cap plugged? Could create a vacuum after a longer time driving.
Last edited by DaveW; 04-17-23 at 06:07 PM.
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fstfwd (04-17-23)
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