engine revs funny

[ian]

When going down the motor way I had to slow down for a lorry overtaking, I dropped to about 55mph, I left it in 6th and when the lorry pulled in I just floored it, I got to about 65mph then the revs just started jumping up about 200rpm then dropping back then jumping again. The car still pulled away but you could hear the engine wanting to rev up then drop again.
This doesn’t happen in any low gears only 5th and 6th.

It’s a 53 plate golf mk4 gt dti 150, and its been chipped, its runs fine but this just baffles me.

Any ideas fellas ???


ian

[Eshrules]

most obvious thing to me would be the MAF first of all....

besides that, you're looking at the whole turbo issues thing....

do a search on here for lack of power or 'MAF' .... :beerchug:

[ian]

its not a maf sensor issue mate, turbo could be sticking but not sure also think it might be the throttle body.

but im not that clued up on engines.

[bora(ing) nick]

its not a maf sensor issue mate, turbo could be sticking but not sure also think it might be the throttle body.

but im not that clued up on engines.

Hya mine does this also..... i think it is because of the remap / chip, trying to make the fuel pump overfuel the injectors. In my opinion it our own fault for trying to floor it at such a low speed in top gear. I wouldn't panic about it.

4th is probably more suited to them sort of speeds.

Nick

[neileg]

If the revs are jumping about relative to the road speed, then this sounds like clutch slip. Considering this is a chipped 150, it's quite possible.

[Eshrules]

its not a maf sensor issue mate, turbo could be sticking but not sure also think it might be the throttle body.

but im not that clued up on engines.

but how exactly do you know it's not a MAF issue?.... btw, these engines don't have a throttle body ;)


If the revs are jumping about relative to the road speed, then this sounds like clutch slip. Considering this is a chipped 150, it's quite possible.

hmm... that's a good suggestion, do you not think it would be evident in low gears too though? i always thought the clutch would slip when placed under strain?

i'd probably go with nick's suggestion... you really shouldn't be trying to floor it under revved.... if it's not occurring in low gears, it might actually be driver error as opposed to a car fault.

try and keep your revs above 3k before flooring the car.... tdi's have to be at optimum revs, anything below 3k and you really shouldn't be pushing the engine :)

[ian]

Hya mine does this also..... i think it is because of the remap / chip, trying to make the fuel pump overfuel the injectors. In my opinion it our own fault for trying to floor it at such a low speed in top gear. I wouldn't panic about it.

4th is probably more suited to them sort of speeds.

Nick

i have done 18,000 miles with it being chipped and it only started doing this about 2 days ago.

i can leave it in 6th and pull away from 40mph, it seems fine, just really strange it should start doing this now for no apparent reason

[ian]

If the revs are jumping about relative to the road speed, then this sounds like clutch slip. Considering this is a chipped 150, it's quite possible.


yeah i thought along them lines but the clutch feels fine, will investigate further

[ian]

but how exactly do you know it's not a MAF issue?.... btw, these engines don't have a throttle body ;)



hmm... that's a good suggestion, do you not think it would be evident in low gears too though? i always thought the clutch would slip when placed under strain?

i'd probably go with nick's suggestion... you really shouldn't be trying to floor it under revved.... if it's not occurring in low gears, it might actually be driver error as opposed to a car fault.

try and keep your revs above 3k before flooring the car.... tdi's have to be at optimum revs, anything below 3k and you really shouldn't be pushing the engine :)


there is no loss of power in any gear or at any speed so thats why i dont think its a maf issue.

i have done nearly 20k in a year and 18k with the car being chipped, i have not changed anything with the way i drive so i still thinks its funny for such a thing to suddenly start happening.

its never done this before and thats why i think there is somehting a miss.

i love my car i want it to be right !!

lol


ian

[bora(ing) nick]

i have done 18,000 miles with it being chipped and it only started doing this about 2 days ago.

i can leave it in 6th and pull away from 40mph, it seems fine, just really strange it should start doing this now for no apparent reason


I can too leave it in top gear at 40, but just not floor it.

If i do floor it (in top gear) than i get the symptoms you describe. No loss of power at all, just feels like a little blip, or maybe a missfire even.

If it was the clutch, the slip would be more evident in lower gears, so i dont think it's the clutch.

We all love our dubs, it's the reason we sigh up to forums and the like.

I honestly don't think (from your description) theres anything wrong with it. I'm no mechanic, but either both of our cars are fine, our both need attention! :D

I do around 25K a year in the Bora, probably about 8K since the remap. I only noticed it when trying to make the most of the low down torque.

Good luck anyhow,

Nick

[mobitune]

Something happened 2 days ago, if the car was fine before and not now then something HAS changed. What it is will be difficult to diagnose over t'internet

Get it onto vagcom and see if anything shows up, either fault codes or discrepancies with boost pressure or maf reading etc. Also at idle with all accessories turned off and engine warmed up, check engine values block 13, can help show up cylinder specific faults, even camshaft wear.

Good luck

Pete

[ian]

If the revs are jumping about relative to the road speed, then this sounds like clutch slip. Considering this is a chipped 150, it's quite possible.

you were right mate, just had full service and one of the lads took it out for a run and he said the clutch is defo slipping.

vag com never showed up anything, everything is fine, runs smoother with fresh oil in too.

£900 for a clutch and dual mass fly wheel, ouch !!!