THP 155 Engine Hesitation

[Chris]

Hi all,

Just experienced hesitation from my engine for around the 4th/5th time it has only occurred when the engine is under load i.e giving it the beans, and only ever in 5th gear (up steep inclines, slip roads, joining motor way etc).

I've done a thorough search on here but am lacking a definitive answer as to exactly why it happens, or how to cure it. Don't get my wrong the hesitation is only for a split second, and is apparent by a violent shudder. I don't get any of the power loss, or engine management light/warnings. Based on what I've red on here it can be one of the following:

(1) - Carbon build up, plenty of threads and posts about this
(2) - timing chain slipping

So if anyone that had had a similar problem and Had it 100% diagnosed & sorted, please let me know I'd be grateful for any advice! Haven't spoke to a dealer yet, simply because it's too hard to replicate or demonstrate to them, as it's only happened 5 times in 3 months of ownership.

Thanks in advance.

[Chris_Blue]

Hi Chris- first of all, what fuel do you use? Premium is best, and has the car used standard stuff for long in the past?
Secondly, I am sure you appreciate there are stacks threads on here about it, but only a few concerning 155 models built early 2012 (Ive counted 3 THP 155s with this issue, so its not common)

The reasons you state are right as far as i know. Carbon build up on inlet valves , with small bits breaking of into cylinders causing hesitation
It could also be a fuel pump issue ? or of course something entirely different, probably fuel related unless the ESP is kicking in momentarily?

Check your oil, and is it dirty and look sort of burnt? Cars always benefit from an oil and filter change, even more often than Citroen dictate
My oil has changed a week ago, and a couple of little noises that I wasnt worried about, seemed to have disappeared.

However, I did tell the dealer about them, and followed my verbal comments up with an email, and they stated they would log it.
My point being, if you are a tiny bit concerned, report it straight away to Citroen, they will log it, even if they dont say you should bring it in. Then if something happens, you can say "I did tell you a while back"

Keep us posted

[Chris]

Hi Chris.

I have only ever used Shell fuel in all my cars in recent years. Albeit the standard 95 Ron.. I do mostly urban driving in my commute, but at least once a week try to give the car a good blow out down the bypass. I've also used bg44k as we've chatted about elsewhere.

I have read Jamie's thread about the carbon build up, and read of a few cases where people have had the high pressure fuel pump replaced too. However recently been speaking to a lady with a DS3R she had the fuel pump replaced, only for the problem to reoccur within a few months. She decided to sell the car so it remained a mystery in her case.

I check my oil regularly, and it is still showing on maximum and I'm not an expert but it looks pretty much brand new. I tend to change the oil every 6k anyway so will have it done in summer sometime. Car had its oil changed when I collected late December.

Thanks for the advice, I will try and speak with my dealer tomorrow, to at least log the problem if nothing else. Just a shame as I had pretty much every common fault of the THP150, on my early 2007 Cooper S! Didn't want to experience any if them again

[Chris_Blue]

The new DS3r Cabriolet states use only 98 RON fuel (I think its 98) so Citroen obvs know lower grade fuel not good for the engine (Just an upspecked THP the Racing engine)
So you may see a difference using better quality fuel- try it for a couple tanks and see. Never used anything other than BP Ultimate, me
How many miles you done?

Ed- you could always whizz it over to SPTuning so he can have a look at the inlets with his cameraa

[BeefMasta]

Just my opinion but if you're joining the motorway in 5th, you're doing it wrong. I was always taught that 3rd is the best gear for this and considering 3rd will go up to 90 (on a private road officer) then it's ideal.

[Chris]

Hi Patrick

Sorry if I was a little unclear - I meant once I am up to speed at around 50/60mph, into 5th gear then accelerate hard..

If I use third or fourth gear to accelerate up to 70mph, then no problem whatsoever and it pulls like a dream

[Chris]

The new DS3r Cabriolet states use only 98 RON fuel (I think its 98) so Citroen obvs know lower grade fuel not good for the engine (Just an upspecked THP the Racing engine)
So you may see a difference using better quality fuel- try it for a couple tanks and see. Never used anything other than BP Ultimate, me
How many miles you done?

Ed- you could always whizz it over to SPTuning so he can have a look at the inlets with his cameraa

Might have to visit Jamie at some point, definitely on my to do list.

I'm on 15,000 miles now after having the car at 12k. I just filled up last night but next time I will try VPower 98 Ron instead, see if it makes any difference.

[BeefMasta]

Hi Patrick

Sorry if I was a little unclear - I meant once I am up to speed at around 50/60mph, into 5th gear then accelerate hard..

If I use third or fourth gear to accelerate up to 70mph, then no problem whatsoever and it pulls like a dream

I understand, but what I'm saying is you still have another few thousand revs left in 3rd

Maybe it's just me but I barely use 5th, even at motorway speeds. Much prefer to drop 6th to 4th and boot it when needed.

[Chris]

Likewise Patrick. I very rarely use 5th gear lol. Maybe this is part of the problem??

[BeefMasta]

Likewise Patrick. I very rarely use 5th gear lol. Maybe this is part of the problem??

Haha, I'll give it a go in mine when I'm out tomorrow evening, see if I get any issues. Hopefully not, although if it does I'll just stop using 5th completely, lol.

[Jonbays]

Is it throwing up any fault codes?

P1385: [BMW] Knock Sensor 4 Circuit or P2336: Cylinder #1 Above Knock Threshold

Mine was doing almost the exact same thing and it was carbon build up that required the head removed and chemically cleaned, new (different PCV)valve cover, replacement timing chain guides and tensioner and replacement turbo!

[Chris]

Is it throwing up any fault codes?

P1385: [BMW] Knock Sensor 4 Circuit or P2336: Cylinder #1 Above Knock Threshold

Mine was doing almost the exact same thing and it was carbon build up that required the head removed and chemically cleaned, new (different PCV)valve cover, replacement timing chain guides and tensioner and replacement turbo!

Hi Jonbays, I haven't had it on a diagnostic yet. Going to try and speak with my dealer this afternoon see if I can get them to look at it.

I can see yours is a THP 155 - was this the same car that you had this work done to?

[Chris]

Booked the car in with the dealer for Thursday - then got a call asking can I pop down this afternoon and they will see if it's throwing out any fault codes. Fingers crossed...

[Chris]

Was aasked if I could call in after work so they can see if it's generating any fault codes. It isn't, which unexpected due to lack of warnings on the dash.

He didn't totally ignore the fact I've got a problem, and told me of a DS3r they're looking at currently, which has the exact same problem as I've described!

Car is being dropped off Thursday morning and I'm making a detailed log for them to send to CUK - wish me luck!

[lfcrule1972]

Good luck mate....