C5 2.2HDi 03 poor fuel economy and power loss

mattyh001 · Post by **mattyh001** » 17 Mar 2009, 13:08

Please can someone help?

I bought my 03 plate C5 2.2HDi from a dealer 2 weeks ago with 44K miles on the clock.

the problem I have is that in 2 weeks the fuel economy is sitting at 29.7mpg and which ever gear I am in I am unable to rev the engine over 4000RPM.

Admittedly I only do short mileage journeys of 10 miles a day, however even taking the car for a run on the motorway does not increase my MPG by much, the best I have seen is 30.7mpg.

I have no warning lights or fault messages on the dash, so I cannot say whether it is the dreaded antipollution fault or not.

Can Anyone advise please?

Post by **myglaren** » 17 Mar 2009, 17:54

I would take it back as that is unnaceptable.

It sounds to me as though there is an engine management fault and the ECU has gone int 'bare basics' mode. one step up from 'limp home' mode.

The old Italian Tune up would likely help but as it won't exceed 4000 revs that's not going to work.

You might try the battery removal method but it may get you further in the mire and considering how recently you purchased it I would just let them work it out - if it is a Citroen dealer they will have the diagnostic tools to discover the problem and fix it or clear the fault code if that is all is needed.
If not a Citroen dealer the problem is still there's to sort out.

KevMayer · Post by **KevMayer** » 17 Mar 2009, 23:04

Does the C5 have an automatic gearbox ? I've seen fuel consumptions as low as you say from automatic C5 HDIs.

In 5th gear (manual) my C5 is doing approx 63 mph at 2000 rpm. So, at 4000 rpm I would be doing 126 mph which is roughly the rated top speed.

I can get up to 4500 rpm in 1st or 2nd gear.

I've tried full throttle in 4th and I get up to around 4000 rpm (90mph..ish) and it won't rev any higher. So, it may be mapped to limit at 4000 rpm in the higher gears. It is an electronic throttle after all.

I've heard about remaps being able to increase the max rpm... so, it may be the how it's mapped.

So, if it's an auto and it won't go over 4000 rpm it may be just how it was meant to be.

You could try giving your air flow meter a squirt with carb cleaning solvent. It could just be a dirty MAF sensor which is giving poor economy.

Post by **Peter.N.** » 18 Mar 2009, 08:30

You don't want to be doing 4000 rpm in a diesel they run very inefficiently at high revs. Max torque comes in at about 2000 rpm and that's where you need to keep the revs. If you are trying to drive it like a petrol engine, that could be where your problem lies.