THP Judder on partial throttle

[Tim451]

Just got my car back yesterday having had the timing chain, guides, tensioner and camshaft oil seal replaced and have noticed a new issue. On partial throttle when maintaining a steady speed at around 1500rpm I have noticed a judder. It feels as if the engine is going to cut out. Also, when applying hard throttle there is a slight jolt before it then continues to acellerate smoothly as normal. The car is just shy of 27000 miles so I'd imagine carbonisation could be a factor but I'm concerned it could also be related to the HPFP. I've also had slight hesitation a couple of times under hard acceleration in 5th gear as if it momentarily loses power before picking up again like normal. Anyone have any advice as to what to look for in torque pro with regards to fuel pressures?

[victoryo]

Hmm difficult to say. I also had judder while accelerating.
Luckily the engine had a fault in it and my HPFP was not good.

But unlucky for me after replace with new HPFP it still judderd sometimes.
Did a wallnut blast after all and all judder was gone.

So in short terms, it can be HPFP but it can also be carbon build up or in my example both, haha.

[Tim451]

OK, a little bit more to add to this. I've been running torque pro this afternoon to see if anything looks amiss. Fuel rail pressure at idle fluctuates between 4500 to 5500kpa and seems to raise linearly under acceleration which I believe is normal. I did check the LTFT value and it's sitting at 0% although the dealer did update the ecu with the latest software while the car was with them so presumably this value could have been reset. I also monitored the timing advance which at idle fluctuates between -3° to -8° but I'm not sure what would be considered a normal range. This seemed slightly erratic under acceleration peaking at around +10 but again I'm not sure what would be classed as normal. It certainly feels like a missfire and the jolt when applying throttle is such that I initially thought the issue was transmission related. I'm thinking that new plugs and a walnut blast are on the cards but it's just strange that this issue has only begun since having the chain replaced. It's going back to the garage tomorrow for a test drive with one of their technicians so I'll see what they suggest.

[V3nn3tj3]

Did they replace the variable cam phaser and the cam gear? They must have checked the timing when the rocker was off using a tilt meter. I did when i replaced all the timing gear myself. If they did timing has to be spot on. Whats the max fuel pressure you got when driving under load ?

[Tim451]

Quick update to this. I have replaced the plugs and coils which have helped but the issue is still there. The misfire codes have stopped appearing but it still isn't running right. There is still juddering at low rpm and on partial throttle I can hear the exhaust popping to the extent that it sounds like I'm running anti lag. I also have a persistent pending fault code which confirms that it's running too rich. I've been keeping a close eye on the fuel rail pressure and I haven't seen anything to indicate that the pump could be at fault. The issue seems to get worse as the engine warms up too. Myself and a local mechanic I've since taken it to are well and truly stumped. I'm thinking lambda sensor (although unlikely being that the issue is present from cold), map sensor or coolant temp sensor possibly. Anyone know how to test these or have any other suggestions?

[Jamie@SPTuning]

THP Judder on partial throttle

Have timing rechecked. An inoperative dephaser will give you P&B but it will also be down on power especially low rpm.

[Tim451]

The timing was my first thought but citroen have had it back twice and they say that the timing is fine (although I don't fully trust their judgement since they initially advised me that the issue was probably because of my induction kit). Is there any way to check the operation of the dephaser myself? I'm currently on holiday and the car went into limp mode 4 times on the way, once on the M5 which wasn't particularly fun. Codes suggest it's misfiring on 3 out of 4 cylinders. Interestingly after the last 2 occasions the juddering stopped completely upon restarting the engine, as did the machine gun style backfiring from the exhaust on partial throttle. I also noticed the the temperature gauge didn't rise above a quarter of the way up for the entire 4 hour journey and upon stopping the fan has continued to run for a good 5 minutes after switching the engine off. Not really looking forward to the journey back up country.

[d_darko]

The timing was my first thought but citroen have had it back twice and they say that the timing is fine (although I don't fully trust their judgement since they initially advised me that the issue was probably because of my induction kit). Is there any way to check the operation of the dephaser myself? I'm currently on holiday and the car went into limp mode 4 times on the way, once on the M5 which wasn't particularly fun. Codes suggest it's misfiring on 3 out of 4 cylinders. Interestingly after the last 2 occasions the juddering stopped completely upon restarting the engine, as did the machine gun style backfiring from the exhaust on partial throttle. I also noticed the the temperature gauge didn't rise above a quarter of the way up for the entire 4 hour journey and upon stopping the fan has continued to run for a good 5 minutes after switching the engine off. Not really looking forward to the journey back up country.

Did you check spark plugs and coils? If they are OK, check electrovalves. And also check throttle body.

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[cyclone]

The timing was my first thought but citroen have had it back twice and they say that the timing is fine (although I don't fully trust their judgement since they initially advised me that the issue was probably because of my induction kit). Is there any way to check the operation of the dephaser myself? I'm currently on holiday and the car went into limp mode 4 times on the way, once on the M5 which wasn't particularly fun. Codes suggest it's misfiring on 3 out of 4 cylinders. Interestingly after the last 2 occasions the juddering stopped completely upon restarting the engine, as did the machine gun style backfiring from the exhaust on partial throttle. I also noticed the the temperature gauge didn't rise above a quarter of the way up for the entire 4 hour journey and upon stopping the fan has continued to run for a good 5 minutes after switching the engine off. Not really looking forward to the journey back up country.

If the temp sender is screwed could be giving false info engine computer.

[Tim451]

Yeah that's what I'm thinking at the moment. Does anyone know where the sensor is located? Mine's a 62 plate so I'm presuming it was made after they switched to one built into the thermostat housing. I've had a quick look under the bonnet but I can't work out where it is.

[cyclone]

Both models are in the thermostat housing, Just one you can replace the sensors and the other you have to replace the whole housing.

[Tim451]

Thanks Cyclone, any idea where the housing is located? I'm told it's somewhere down to the left of the oil filter but after an hour of googling and messing around under the bonnet with a torch I'm still none the wiser.

[cyclone]

toward back of car from oil filter, under the 2 air ducts (from inlet to filter and filter to turbo) and above transmission.