Intermittent power loss during steady driving

[Snarks]

I've been searching through this forum trying to find someone with a similar problem to mine.

Basically, during steady driving, i.e. constant speed not flooring the throttle, the power seems to cut out for a fraction of a second and then come back to normal again which produces a jolting sensation especially at lower speeds in first or second gear. It does it a few times a week and has been doing so for several months.

I waited until the service was due but the engine did not report any faults when connected to the computer.

I also notice that when starting from cold, the engine can sometimes "shake" for a second or two but then the revs go back to normal. I don't mean a rattling noise but from the driver's seat, it feels like the engine is trying to break free from its mountings.

Anyone any ideas?

 

[Big_daddy]

does it occur between 2 to 3 rpm?

 

[D3DNA]

No to sure but sounds like the dv valve. if the problem is more persistant around 2 to 3k rpms then its very likely.

 

[Saul]

im having this exact same issue at the mo, and yes big lad between 2 and 3k

no solutions as yet, but im on the case

 

[Snarks]

does it occur between 2 to 3 rpm?

Yes, it would be about that range. It's a standard 180bhp 1.8 petrol cupra, 50000 miles, 4.5 years old.

 

[Big_daddy]

Hi think the problem could be similer to my mates golf. the problem he used to have when he is driving normal, the car jus dies out and the revs dies as well for 3seconds. Then all sudden a quick boost of power.
The problem was with oil pump, that its keep playing up. later as it got worser and the oil can symbol starts flashing but when check oil level every thing is fine.

the problem was the oil pump, get yours checked.
check for oil loss,
when was it last serviced as blocked can some times build up causing pressure in the pump
Regards

 

[RikH]

is this not also a possible symptom of the MAF sensor

 

[Big_daddy]

MAF should not cut jerk the car, like this did.
when my mates golf when in for a diagnostic, all the sensor where fine and nothing was coming up on fault screen.

 

[YerMother]

Could be DV sticking open slightly . Get a new OEM one or service it if you have a Forge one!

Could also be throttle valve sticking too!

 

[DPJ]

Would a fuel pressure problem throw up a fault code?

(I had a similar problem on a previous car with a very intermittent electrical feed problem to the fuel pump.)

 

[Big_daddy]

there possible chance but we had the whole fuel tank treated and a new fuel filter put in. still the same.

Once on the motorway, the car started dieing again, then the oil symbol started beeping/flashing. Thats how i figured it. had AA on the side in the case of the worst

 

[cordobabrendy]

Recently ive been having the same sensation, ill not call it a problem as such.
I noticed today that my dv was a bit gunged up even though it was serviced a few k ago, luckily ive still got the old piston as it was replaced early anyway so im going to grease it up tonight and fit it, Im not convinced that this is whats causing it though as its not happening on boost (ie above 0 on the boost gauge) or if it does its not as noticeable. I suspect its the n75 or n249 fooking around, if i can get a lend of a spare n75 to test it out im going to try that then get rid of the n249.

 

[Big_daddy]

i have the same forge dump vale - the one with logo printed on the side and vacum nozzle that spins around.
do these require servicing? i also got some additional spring included when i bought it

 

[cordobabrendy]

yup they do need servicing, you can do a pen test first or just remove it, clean it and re grease it and refit, ive been doing mine every 8-10k.

 

[Big_daddy]

how do you do a pen test?
whats grease do you use or do use oil instead?

 

[cordobabrendy]

castrol,mobil etc any sort of decent branded grease, dont use oil. searchy for forge service.

 

[Snarks]

Thanks for the replies.

There's a company called Frank Massey Automotive Diagnostic Solutions in Preston. They seem to be recommended by some on these forums. I'll get in touch and see if they can diagnose any problems.

 

[Nathanio]

I have had similar problems before but on a 1.2 Punto and it was a misfire on a single piston. ECU was playing up and messing with the timings. Exactly as you described it.

 

[davebnly]

I have this exact same problem between 2-3K RPM, always have done since fitting the Forge DV from brand new, so i doubt its an issue of the DV needing service. Mine also has a remap though and it seems to make the juddering slightly more severe than one without.

Since it started happening i always assumed there will be no cure as its only happening under slow speed equaling vacuum in the manifold to open the DV slightly (as it is supposed to under vacuum).

 

[cordobabrendy]

I managed to fix mine temporarily with an ecu reset (battery disc for 5 mins) but it seems to come and go again after a load of miles, its not a problem as i mentioned before just a minor oddity, maybe the 249 removal might fix it.