C5 2lt Hdi 51 / 116k hesitation when accelerating

[Jeff]

Hi,

I replaced the mass air flow sensor in january (bought off ebay), this weekend the Engine Mamagement Light came on, then noticed same time car had flat spot in acceleration, assumed MAF as similar symptoms to earlier in year.

I removed and sprayed with unipart switch cleaner which is not supposed to leave any residue, when refitted and started engine EML came straight on - yet before cleaning MAF sensor it came on after about a mile. The MAF wires looked quite clean before I sprayed them.
Could problem be another sensor, loose connection or does it point to the MAF sensor? Does anyone know what are the symptoms with a sticky EGR valve?
Thanks for any advice.

[RichardW]

You can't guess Jeff - you need to get it on a diag computer. Although if you know someone with a similar engine you could borrow their MAF to test. Cheap aftermarket MAFs are, generally, a waste of time and money though....

[Jeff]

Thanks for help.

Has anyone tried one of those cheap diagnostic code readers?

[Stickyfinger]

Yes, there is a reason they are cheap ....

You NEED a Lexia for correct diagnosis

[Jeff]

Drove home tonight with the Engine Management Light off. First hill it crawled up in 2nd after that it drove as normal.

If it was a faulty MAF Sensor would the light be on all the time?

[myglaren]

In my experience a faulty MAF will not put up any lights at all.

[Stickyfinger]

In my experience a faulty MAF will not put up any lights at all.

agreed

[Jeff]

Back in February I damaged the maf by touching one of the wires when cleaning it and the light came on as soon as I put the damaged MAf back - so I ordered cheap maf from ebay and when fitted light went out immediately.

Today the EML came on again. The car runs okay on the flat but struggled up a steep hill, crawling slowly in 2nd. You can put your foot down but there's no revs /power. A friendly garage mechanic put it on the snap on diagnostic scanner (modis elite model)and it showed two faults, MAF sensor and EGR. He knocked out the fault codes and disconnected the MAf and I drove around and the car seemed fine but the area I was driving around was flat. Back at garage it now showed Air Temperature sensor fault. Again the mechanic knocked out this fault and we agreed I would return later in week after running around with maf disconnected. He did think it was a faulty maf sensor though. First big hill on way home car back to crawling in 2nd gear? (EDIT: I just realised I stopped on way home and restarted car when maf was already disconnected before I went up hill crawling in 2nd).

Noticed in week with maf connected first hill I came to it would crawl in 2nd but later in trip, say 5-10 minutes, the engine would freely rev and climb hills???

Any suggestions or idea's please?

[Jeff]

Normally commute 8 miles each way to work and today drove an extra 21 miles lunch time. EML went out and car drove perfectly and this evening on way home. Full torque and power going up hills. No parts changed.

Could a series of short runs 8 miles each way to work be causing a problem with my car?

[myglaren]

They don't like short journeys but I drive four miles to work and four miles back each day with very little variation, and a couple of even shorter journeys at weekends (1 mile each way)
My son takes the car to work at night and follows essentially the same pattern as I do.

It doesn't seem to bother the car too much.

[Jeff]

EML and problem back again. Weird!

[Jeff]

The car is running better now after a shorter run but still lacks power going up the first hill though behaves differently in that it slowly climbs then gets its power/acceleration back on the first hill. Before it would struggle up the first hill in 2nd but fly up a second hill a minute later??

Chap in the garage with diagnostics now thinks its the air intake temperature sensor? (and not MAF sensor) I have rung around scrappies but cant find a C5 2.0lt HDI yet.. anyone else had a problem with the air intake temperature sensor and what were the symptoms? Thanks for help.

[myglaren]

Someone correct me if this is wrong but within the MAF is a thermistor bead that is the induction temperature sensor.
It's usually the very fine platinum wires that get coated with crap so they don't work or burn through that are the problem.

[Jeff]

Thanks myglaren, I may still need a new maf then.

Helpful chap in garage thought it was the denso sensor front right of engine compartment (just under left hand side of plastic cover on battery)?

[myglaren]

This was my MAF when it became unusable. The bead on the right is the temperature sensor.

Have you a picture of the Denso sensor - I think that this is the MAP sensor but my car is away at the NEC currently so can't check that.
When my MAF went down the diagnostics indicated a dud MAP sensor too. I was too stingy to buy one when I bought the MAF and it turned out to be a red herring, MAP is perfectly fine.
In your case it may not be of course.