Engine hunting/surging - Citroen 2.0HDI

funkey_monkey

Hi,

I've got an old 2.0HDI engine and I've noticed that at steady revs (usually around 1750rpm) that the rev counter flucuates and I can feel the car accelerate/decelerate as a result of this.

What could be causing this and is it something I could have a go at fixing myself?


Thanks.

Hal1

That could be caused by a variety of issues. There's no positive way to know for sure unless you bring it to a mechanic with a scan tool, one that can read live data. It could be anything from a crankshaft position sensor to a vacuum leak, idle control valve, engine temp sensor, or a clogged egr valve.

Row

Have seen a few fuel regulators on the hp pump causing this but like Hal1 said it would be best get a diagnostic scan carried out otherwise one could end up firing parts at it..:)
My guess its the older 2.0 hdi 99-2003..?

rex-x

Hal1 wrote: »

That could be caused by a variety of issues. There's no positive way to know for sure unless you bring it to a mechanic with a scan tool, one that can read live data. It could be anything from a crankshaft position sensor to a vacuum leak, idle control valve, engine temp sensor, or a clogged egr valve.

Vacuum leak, icv on a diesel? OP on these engines its going to be the fpr on the back of the pump or an injector/multiple injectors

funkey_monkey

Row wrote: »

My guess its the older 2.0 hdi 99-2003..?

Yes, 01.

funkey_monkey

Digging this up again as the issue has resurfaced, but this time at idle.

What happens is that at times (randomly, no pattern) it will hunt quite badly at idle and then when I attempt to drive off and put my foot on the accelerator there will be no response for between 1s - 4s and then it all comes in a lump.

This morning I was driving out of a side street onto a main road (30mph in town thankfully) when the car bogged down and did not respond to the throttle for an uncomfortable few seconds before it accelerated. It done it twice today.

I use a decent fuel and have been putting Redex Injector Cleaner through the tank. Servicing is regular and thorough.

I've been told it might be the pressure regulator on the back of the HP pump on another forum.
Edit: just realised Row also mentions it above!

Do I need to take this to an auto electrician in order to get the fault correctly diagnosed - there are no warning lights on the dash, so I assume that there might be some codes that can only be detected by a diagnostic tool and a decent operator?


Thanks.

funkey_monkey

How much is a diagnostics scan roughly and would they do it without getting the corrective work?

rex-x

funkey_monkey wrote: »

How much is a diagnostics scan roughly and would they do it without getting the corrective work?

Where are you located? You don't want a diagnostic scan, what you want is a proper diagnosis which involves checking for codes and then using live data and actuation functions alongside physical testing to determine the cause of the problem

Anywhere will scan the car but it won't be of much if any benefit to you

quinla

funkey_monkey wrote: »

Hi,

I've got an old 2.0HDI engine and I've noticed that at steady revs (usually around 1750rpm) that the rev counter flucuates and I can feel the car accelerate/decelerate as a result of this.

What could be causing this and is it something I could have a go at fixing myself?


Thanks.

Change the fuel filter and see how it goes then. No need to get complicated. Inexpensive part and at least its done. if it doesn't cure it, i Then get a diagnostic done.

funkey_monkey

Hi, resurecting this thread.

I've replaced the HP Fuel Regulator with a genuine Bosch item and it has definitely improved the situation. However, it has not been fully resolved.

Without taking it to a main garage (local does not have a Lexia) I'm trying to figure out if the fuel pump in the tank could be starting to fail. There has been a few instances of the car starting and hunting badly before dying - even though I can hear the pump priming. There are also instances of the fuel guage not registering when ignition turned on.
Primary intermittent issues of slight hunting remains and poor acceleration, but definitely not as pronounced as previously.
Injector cleaner has been used and car has recently (with 200miles) been serviced.

When I removed the old regulator it looked like shown in the attachements. Is this a standard wear pattern?

biko

funkey_monkey wrote: »

Hi, resurrecting this thread.

Since you started it that's fine.

Liberta Per Gli Ultra

Hal1 wrote: »

That could be caused by a variety of issues. There's no positive way to know for sure unless you bring it to a mechanic with a scan tool, one that can read live data. It could be anything from a crankshaft position sensor to a vacuum leak, idle control valve, engine temp sensor, or a clogged egr valve.

Best piece of advice in the thread and still stands by the sound of it. Scanning the computer for trouble codes with even the most basic generic diagnostic tool is a better idea than buying parts which may or may not be relevant to the problem.

zilog_jones

funkey_monkey wrote: »

There are also instances of the fuel guage not registering when ignition turned on.

Not sure which car it is, but if the instrument cluster is any way similar to my 406 there was a known issue with a dodgy solder joint within the cluster that caused the fuel gauge to stick or not work at all. So it could be unrelated, but it could maybe also potentially suggest dodgy wiring to the tank? Don't know if it's related to the wiring to the lift pump, mine had the later Siemens injection system so no pump in the tank at all (I assume yours is Bosch if it's an '01).

I got the diagnostic cables and software at reasonable cost on eBay (Lexia/PP2000 is the old software, it's now called DiagBox), but it was a pain in the balls to get working on my laptop so I wouldn't recommend unless you're handy with computers.