Weird engine load surge on idle & throttle

[Connor H]

for the past week i have been trying to figure this out.

every 10 or so seconds (sometimes couple in a row) the engine load will surge about 3-5% like i just blipped the throttle

happens when idling and when on throttle, at any revs, i can feel the surge. so its not a vac leak i can tell of.i used vcds lite to chedk my voltage and that seems fine. no idea where else to check.

anyone got any ideas? its driving me up the wall!

 

[Connor H]

unplugged the maf, FPR, oil cap off, keeps doing it either way. no codes except brake switch that wont ever leave but my brake lights work fine

also checked fuel pressure, recently changed fuel filter, changed fuel pump...no bueno

 

[Alexis27]

Brake switch doesn't just control brake lights, it confuses the ECU and messes with the combustion mixture if it's broken. Sounds like that is your issue - I had the same problem a couple of years ago.

 

[Connor H]

Brake switch doesn't just control brake lights, it confuses the ECU and messes with the combustion mixture if it's broken. Sounds like that is your issue - I had the same problem a couple of years ago.

Really? I figured it wouldnt affect the fuelling. the code > http://wiki.ross-tech.com/wiki/index.php/16955/P0571/001393
its been there for well over a year before n after the tune. but maybe its finally **** the bed?

ill seek one out. what were your symptoms?

 

[Alexis27]

It would really cut the power at random intervals. So you'd press down on the throttle and it would then suddenly lurch forwards. Then it would be normal for a few minutes before doing it again.
It's a cheap replacement anyway, so worth doing first.

 

[Connor H]

It would really cut the power at random intervals. So you'd press down on the throttle and it would then suddenly lurch forwards. Then it would be normal for a few minutes before doing it again.
It's a cheap replacement anyway, so worth doing first.

yeah ill pick one up either way. those symptoms sound different tbh though, this is literally surging every few seconds even in neutral ticking over.I dont get power cuts, im sure thats down to not being able to brake and gas at the same time and a dodgy sensor.

i was wondering if a TB alignment would help but i dont have the option in vcdslite to try. does the old wives tale of disconnecting the battery work

 

[mty12345]

i was wondering if a TB alignment would help but i dont have the option in vcdslite to try. does the old wives tale of disconnecting the battery work

You could try disconnecting the power, and then leaving the ignition on for 30 seconds without starting the car or touching the pedal. I've heard people claim that has worked before, but i'm skeptical and AFAIK the only way is with VCDS.

Not really sure on the issue tbh. Hard to say without seeing data logs or live data. What is your long term fuel trim? (LTFT %)

 

[Alexis27]

Yeah, throttle body worth checking next.

There is also an earth cable under the battery tray that can cause all sorts of weird symptoms if it's corroded.

 

[Connor H]

You could try disconnecting the power, and then leaving the ignition on for 30 seconds without starting the car or touching the pedal. I've heard people claim that has worked before, but i'm skeptical and AFAIK the only way is with VCDS.

Not really sure on the issue tbh. Hard to say without seeing data logs or live data. What is your long term fuel trim? (LTFT %)

This is what i heard. You're supposed to be able to hear some telltale clicking in the TB which i have heard before tbh. ill give this a go today n see what happens. The TB itself is pretty immaculate inside since i last cleaned it. Earth under the battery is good.

i only have shareware vcds so i cant see blocks over 024, think i should probably fork out and register it at this point.

im more than happy to log what i can and bring some data back

 

[mty12345]

This is what i heard. You're supposed to be able to hear some telltale clicking in the TB which i have heard before tbh. ill give this a go today n see what happens. The TB itself is pretty immaculate inside since i last cleaned it. Earth under the battery is good.

i only have shareware vcds so i cant see blocks over 024, think i should probably fork out and register it at this point.

im more than happy to log what i can and bring some data

Ah right, i thought vcds lite could do obd2 data, but I just looked it up and i see it can't.

Torque app or any cheap obd2 reader that supports live data should be able to see long term trims if you have either of those

 

[Connor H]

Ah right, i thought vcds lite could do obd2 data, but I just looked it up and i see it can't.

Torque app or any cheap obd2 reader that supports live data should be able to see long term trims if you have either of those

Oh yeah i just had a closer look on rosstech and i cant even go above block 33 in lite registered. Ffs glad i didnt go for it then. I dont have a generic reader as it got stolen. ill have a look around for an app that works for iOS, know of any ELM dongles that aint trash?

Also as expected the budget TB adapt did nothing


thanks for ya help

 

[mty12345]

It's a bit of a gamble with those ELM327, i had to buy 3 until I found one that worked, and even that one doesn't always boot first time

 

[Connor H]

havnt had the time to do any more diagnostics but heres a video of it. only found one other person with this issue and they changed everything but was told its likely the cam chain itself?

 

[MoToJoJo]

Umm... sounds like mine... but mines a TDI. Does sound top end, dunno if the 1.8 has tappets but it sounds tappety

 

[Connor H]

Umm... sounds like mine... but mines a TDI. Does sound top end, dunno if the 1.8 has tappets but it sounds tappety

yeah it sounds kind of choppy. stinks more than usual too. ive got a rocker gasket here so ill open it up soon and have a look at the tensioner and chain.

 

[mty12345]

havnt had the time to do any more diagnostics but heres a video of it. only found one other person with this issue and they changed everything but was told its likely the cam chain itself?

Most times when you get that sort of surging, it's usually some sort of intake leak somewhere.

It does sound a little tappety, (so does mine) but not too bad at all. No harm in opening the rocker cover and having a check round, especially the chain, but doesn't sound concerning tbh.

On a side note we certainly lucked out with the 1.8t. I find it amazing that so many of us are still driving modded versions around, 20 years after they were built! Most modern engines are scrap or not worth repairing after less than 10 years!

 

[Connor H]

Most times when you get that sort of surging, it's usually some sort of intake leak somewhere.

It does sound a little tappety, (so does mine) but not too bad at all. No harm in opening the rocker cover and having a check round, especially the chain, but doesn't sound concerning tbh.

On a side note we certainly lucked out with the 1.8t. I find it amazing that so many of us are still driving modded versions around, 20 years after they were built! Most modern engines are scrap or not worth repairing after less than 10 years!

i thought intake leak , but when you're on throttle the engine load surges too which is making town driving lumpy.

 

[Connor H]

New brake light switch didnt fix it but finally got rid of that code after a year lol. , also changed the rocker gasket and had a look underneath, cams dont look badly worn, chain was tight and tensioner pads fine.

gonna take it to a garage at this point and get a camera in the bores, compression test etc. cant find anything else that can cause it to surge forward. heres to hoping i havnt toasted my block or bent a rod lol