FSI Hesitation - Finally got VCDS
- Thread starter Topsie
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Topsie
Member
So a bit of an update...
Rocker cover replaced - I was a little worried about replacing the rocker cover, I used Elring 300 degrees silicon sealant (I'll update a little later with the exact details) which was relatively easy to work with, albeit a little expensive. I placed a thin bead on the area's as shown in the A2 service manual (found online) and then spread with an old bank card. I then cleared from any areas that shouldn't have any and ensured oil galleries were clear. I didn't use a torque wrench for the rocker cover bolts (10Nm) but relied on my trusty calibrated arm!
Timing was checked and double checked upon replacement, turned until the chamfered tooth met the marker on the bottom pully and the timing tools (1/4" extension bars fit nicely) are free to be fitted.
She took a while to start (HP Fuel Pump was empty) but fired up quite nicely, however it seemed like there was no noticeable difference, though I no longer have any codes for the inlet cam timing.
However, upon receipt of a second hand solenoid valve (£7.50 opposed to £68!!) and a quick swap, i'm happy to report a vast improvement - I really didn't expect the intake flap to make much of a difference - but it really does.
I've gone from an average of 28mpg to 37mpg and the car now feels much more responsive in lower rev ranges - however i'm still suffering from hesitation, there are no fault codes however if you goto the measuring blocks for misfire counting, cylinder 3 (and only cylinder 3) is counting up misfires at an alarming rate (just not enough to throw a code)
I've got a week off in May when i'll whip off the inlet manifold and send off the injectors for testing and ultrasonic cleaning.
Nick
Topsie
Member
I think people underestimate (including myself) how integral the intake flap is to the FSI engine...
My A2 has now developed a misfrie on cylinder 2 & 3, I've swapped over the coils and checked the plugs - all fine. Carried out a compression test and had 18-17-17-17 Bar (1-2-3-4) so it's got to be the injectors, nothing else it can be!!
My A2 has now developed a misfrie on cylinder 2 & 3, I've swapped over the coils and checked the plugs - all fine. Carried out a compression test and had 18-17-17-17 Bar (1-2-3-4) so it's got to be the injectors, nothing else it can be!!
Topsie
Member
Dicky,
Did you replace wires or just tidy up? I do remember the wires on my Seat Leon Cupra were brittle and breaking up because of the heat, but I just sold it before it caused any issues.
What fault codes did this give you? Just Random multiple misfire or coil pack short to ground?
Nick
Did you replace wires or just tidy up? I do remember the wires on my Seat Leon Cupra were brittle and breaking up because of the heat, but I just sold it before it caused any issues.
What fault codes did this give you? Just Random multiple misfire or coil pack short to ground?
Nick
S2Dicky
Member
I just cleaned up and insulated were needed. I would get various misfires and it also could cut the car out and blow the fuse and this also took out the OBD port?
One of my coil packs wiring had been turned through 360 degrees which had caused the worse short.
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Topsie
Member
Well...
My A2 started showing some strange symptoms, all reminiscent of an vacuum leak with one exception;
My brake pedal goes rock solid on idle!!
I'm assuming the brake servo has failed, it's not easy access at all so diagnostics are difficult, I was going to pull the vacuum hose, blank it and re-test fuel trims, but I'll have to remove the wiper mechanism to get to it, if I'm doing that I'd rather have a new/spare part to go in.
normal misfire fault codes coupled with a fuel trim - air leak fault code. Fuel trims at idle after code reset is between 20-30% so a considerable air leak. No hissing from the car but there is faint hissing under the bonnet which sounds like it's near the servo. Pipes look in good condition which i'll confirm once the work in wake is out the way. Fingers double crossed this is a long standing problem that has slowly got worse over time and solves my misfire issue!!
Nick
My A2 started showing some strange symptoms, all reminiscent of an vacuum leak with one exception;
My brake pedal goes rock solid on idle!!
I'm assuming the brake servo has failed, it's not easy access at all so diagnostics are difficult, I was going to pull the vacuum hose, blank it and re-test fuel trims, but I'll have to remove the wiper mechanism to get to it, if I'm doing that I'd rather have a new/spare part to go in.
normal misfire fault codes coupled with a fuel trim - air leak fault code. Fuel trims at idle after code reset is between 20-30% so a considerable air leak. No hissing from the car but there is faint hissing under the bonnet which sounds like it's near the servo. Pipes look in good condition which i'll confirm once the work in wake is out the way. Fingers double crossed this is a long standing problem that has slowly got worse over time and solves my misfire issue!!
Nick
steaman
A2OC Donor
Check the links i attached to post #28 in: http://www.a2oc.net/forum/showthread.php?32407-FSI-erratic-uneven-running/page3
Last edited:
Topsie
Member
Well, there wasn't any issue with the brake servo, the car was legitimately loosing vacuum somewhere else...
now I have a few idea's, but one thing stands out.. When i removed the hose to the brake servo and blanked it, the lean condition remained. When I released the vacuum hose and allowed it to leak, the engine obviously nearly stalled, but, to my surprise, the fuel trims did not change... hardly at all!? I found this a bit strange.
I put the hose back into the brake servo, put everything back together and tried an old trick. I removed the connector from the MAF sensor and went for a drive. (To force the engine into limp mode)
She drove flawlessly, no hesitation, no lack of power, no strange idle, no hard brake pedal, which leads me to believe a sensor, somewhere, isn't functioning correctly, but also not causing a fault code. This should be fun.... Obviously this isn't a solution, fuel consumption will go up (I hope) and you run the risk of permanently damaging your catalyst (engine will run rich) but for now, it's much nicer to drive.
Time to start diagnosing the many sensors that make up the engine management system.
Nick
now I have a few idea's, but one thing stands out.. When i removed the hose to the brake servo and blanked it, the lean condition remained. When I released the vacuum hose and allowed it to leak, the engine obviously nearly stalled, but, to my surprise, the fuel trims did not change... hardly at all!? I found this a bit strange.
I put the hose back into the brake servo, put everything back together and tried an old trick. I removed the connector from the MAF sensor and went for a drive. (To force the engine into limp mode)
She drove flawlessly, no hesitation, no lack of power, no strange idle, no hard brake pedal, which leads me to believe a sensor, somewhere, isn't functioning correctly, but also not causing a fault code. This should be fun.... Obviously this isn't a solution, fuel consumption will go up (I hope) and you run the risk of permanently damaging your catalyst (engine will run rich) but for now, it's much nicer to drive.
Time to start diagnosing the many sensors that make up the engine management system.
Nick
steaman
A2OC Donor
When i removed the hose to the brake servo and blanked it, the lean condition remained. When I released the vacuum hose and allowed it to leak, the engine obviously nearly stalled, but, to my surprise, the fuel trims did not change... hardly at all!? I found this a bit strange.
What was the starting level for the STFT? If it already was running lean (you have a vacuum leak) you might not se any big increase?
What was the starting level for the STFT? If it already was running lean (you have a vacuum leak) you might not se any big increase?
Topsie
Member
STFT ~22% which didn't really change when the I allowed air to enter the vacuum hose. I would expect STFT to go >25%, if not that than at least go out of range...
Just to reinforce, with the MAF disconnected I no longer get any issues with my brakes - Obviously I'll reconnect, clear codes and go for a drive to see if the conditions still exist or if I've nudged something and miraculously fixed the problem.
Just to reinforce, with the MAF disconnected I no longer get any issues with my brakes - Obviously I'll reconnect, clear codes and go for a drive to see if the conditions still exist or if I've nudged something and miraculously fixed the problem.
Topsie
Member
Mysteriously the problem is fixed 
I went and topped up with some Tesco momentum with VCDS connected and monitored fuels trims as I was driving, and was happy (and surprised!) to see the λ go sky high as she dropped into stratified mode. (30 mph in 5th gear just feathering the throttle). Is it a bit sad that I was a bit excited? lol.
It didn't last long anyway - a couple of roundabouts and then I couldn't get it to drop back, read the codes when I got home and had an inlet cam over advanced fault code which probably prevented stratified mode.
No idea what was causing my lean condition and solid brake pedal...
I went and topped up with some Tesco momentum with VCDS connected and monitored fuels trims as I was driving, and was happy (and surprised!) to see the λ go sky high as she dropped into stratified mode. (30 mph in 5th gear just feathering the throttle). Is it a bit sad that I was a bit excited? lol.
It didn't last long anyway - a couple of roundabouts and then I couldn't get it to drop back, read the codes when I got home and had an inlet cam over advanced fault code which probably prevented stratified mode.
No idea what was causing my lean condition and solid brake pedal...