Fuel starvation or clutch problem? (Or something else?)

[Gareth-j9d65]

Hi all,

I'd appreciate any thoughts anyone could share on a problem I'm having with my Citroen diesel (manual).

When accelerating in anything above 3rd gear, when it reaches about 1800 rpm, the revs will suddenly increase very quickly up to about 2200, before dropping back down to 1900-ish, then continuing to accelerate as normal.

Changes to the engine note are consistent with what is shown on the rev meter (i.e. it sounds like it's racing then slowing down again), which suggests to me that it's not an instrument problem. Throughout the sudden increase in revs and the subsequent decrease, the car will continue to accelerate, i.e. even while the revs are decreasing from 2200 down to 1900.

My assumption was that this was a clutch issue. Given that the car continues to accelerate while the revs decrease, I don't see how the clutch can't be slipping.

However, when I took the car into the garage, they said the clutch was fine (which was a relief - the car's only don't about 32k miles) and that, having run diagnostics, the car was experiencing fuel starvation at high speed. They gave me a fuel additive and told me not to use supermarket diesel. So far, the problem continues.

What do you guys think? As I say, given that the acceleration increases even as the revs fall back, it seems to me that the clutch must be slipping, but it's more than possible that I'm missing something. It could well be that there's a fuel starvation issue as well, but I don't see how this could be the whole story.

Many thanks in advance,

Gareth

[littleredrooster]

Clutch. It's the only possible reason why the revs can increase out of proportion to the car's speed then fall back. Clutch slip always starts in the higher gears before it fails completely.

[Demelitia]

Have you tried the standard stall test on the clutch to see how much slip there is on it? High gear, try setting off from a standstill and see if the car stalls; it should if the clutch is ok.

[E-bmw]

Clutch 100% all day every day.

[stevieturbo]

If the garage actually drove the car and experienced the same rpm rise...with no change in road speed that you have described ( assuming of course you arent spinning the wheels....lol ) and said clutch is fine

Then it really does make you despair at how bad some garages can be.

From what you have described...and assuming you are not causing this slippage due to driving style ( ie resting foot too heavy on clutch etc )....then it can only be clutch slippage.

[Gareth-j9d65]

Thanks, everyone. You've eased my nagging doubts and confirmed my suspicions (albeit the answer isn't great for my wallet! 😟).

Demelitia, I did the clutch test last night and it pulls away in fifth on a slightly uphill driveway without ridiculous revving, which seems pretty conclusive.

stevieturbo, to be a bit fair to the garage, it's in the city centre and I've only (so far - noting littleredrooster's point) had issues above about 45mph, so it probably won't have happened when they drove it. That said, I had explained the issue to them (albeit perhaps not in as much detail as above) so they surely could have done something on rollers and/or carried out Demelitia's test. It's disappointing, as it's a pretty well-regarded local garage.

(For the avoidance of doubt, no clutch riding! 🙂)

Thanks again,

Gareth