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Ross
Ross, UK Car Mechanic
Category: UK Car
Satisfied Customers: 837
Experience:  licensed Honda technician and general car mechanic
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My 07 honda crv i-ctdi is giving my 31mpg on average (200 miles

Customer Question

My 07 honda crv i-ctdi is giving my 31mpg on average (200 miles on motorway, 50 miles around town , where on motorway we maintained speed at around 70-75 mph, sixt gear). On top of it it has strange pinging noise between 1500-2300 revs - any gear. My local honda dealer has no clue what is going on - no faults on diagnostic computer. Any ideas?
Submitted: 1 year ago.
Category: UK Car
Expert:  Ross replied 1 year ago.

techmachine :

Hi, welcome to Just answer! My name is Ross and i will help with your question

techmachine :

What brand of fuel do you use?

Customer :

Hi. It's shell diesel

Customer :

car was fine when I picked it up from a dealer. Then it went for service with honda dealer - that's when problem started

techmachine :

Do you know which service was carried out?

Customer :

Bought second hand from cargiant week ago on Sunday and was absolutely fine. Then it went for service with honda dealer week ago....it sounds terrible since then. It was service after 75k miles

Customer :

sounds like petrol car when you change gear too early i.e. from 2nd to 5th instead of 3rd.

Customer :

and also day after service I had engine management light on the dashboard after cold start - dissapaered after 200 miles :(

Customer :

are you there?

techmachine :

Right, ok on the 75k service the fuel filter would have been changed, the fuel filter is really the only thing they would have changed that would directly effect the running of the engine to create the noise you hear.

There was a very commonly asked question on these engines about a "knocking" or "Pinking" noise at the RPM range you describe, this was caused by the pilot injection which is completely normal.

Customer :

was no noise before the service - I have a very senitive ear - I'm musician....and technician as well

Customer :

and fuel economy is just shocking

techmachine :

Ok, the fuel filter is a possibility, if the water float was left loose or the seal not fitted it can leak fuel out, this will effect fuel delivery to the engine which can cause the combustion noise you hear and obviously reduce the fuel economy, however I would expect you to see a small amount leaking onto the ground.

The only other possibility, which is more likely is the rear brakes. The handbrake is operated via "inboard" shoes in a drum as part of the rear disc, these will have been adjusted during the 75k service and often they are tightened a little too much which alowes the brakes to get hot and expand by which time they will be locking on quite tight. This will bind which makes the engine work harder to keep you moving, the added strain on the engine is making the pilot injection noise much louder (so its not a fault of the engine, but is normal operation becoming more pronounced) And of course the fuel economy will hit the floor!

Customer :

there is a leak onto the ground - but it's water - seems like condensation from air-con. Rear brakes don't get hot and also on neutral gear car rolls without problem - doesn't seem like it was on brake.

techmachine :

Yes water will be from the Air-con, If the brakes are not the problem this leads us to the fuel delivery which is heading more towards fuel pump or control problems, If this is the case we really need to find out why that engine management light came on. Although the light went out the fault code WILL have been stored on the ECU.

techmachine :

Was the car scanned for faults after the light came on?

Customer :

It was. They deleted the fault...but I don't know what the fault was:(

techmachine :

Ah, they should have printed out a record from their HDS system for you to keep, if not they should have written the code on the job card so it might be worth speaking to the dealer to see if they have the code.

Customer :

Ok - I will ask them tomorrow - car was left with them for a day - I will pick it up tomorrow. We will see if they can find a problem.

techmachine :

If its not one of the usual causes such as fuel leaking or brakes, which are the common ones I deal with regularly its going to be caused by a fault on the fuel system or with a sensor, with there being so many sensors and possible causes of the light being on the first step will be looking at the code and working from there. Unfortunately parts are to expensive to risk taking a guess on so its worth following the correct steps.

Customer :

well..they are main honda dealer.....so I was under an impression they should know what they doing.

Customer :

OK....let's wait till tomorrow - maybe they will find a solution. I can't accept 31mpg....I get 29 on my 3.5 tonne LWB van....with 200k miles on the clock:(

techmachine :

They are the best people to deal with this, there is definitely a fault and they should be able to find the problem. These engines are very reliable and don't commonly suffer with issues so they take a bit of investigation to get to the bottom of it

Customer :

they already tried once - but even having all their diagnostic equipment they couldn't find a problem. They als agreed that my pinging nose is above normal. But no solution was found after 2 hour investigation and few test drives..so I'm getting a bit nervous:)

techmachine :

It sounds like they have checked all the basics, The next step will be to get out on a test drive with the HDS drive recorder, this records all of the engines data which can then be analysed, even if the dealers are stumped they can always send the data off to the Honda headquarters where the master technicians will take a look and help them out. The engine management systems are very complex on these.

Customer :

ok....thanks for advice. We will see how it goes tomorrow. what should be right fuel economy on these diesels - I don't drive like a maniac:)

Customer :

?

techmachine :

Its difficult to say, I personally drive an Accord with the same engine and i see 40mpg on short trips to work and back, on a good run i see 50MPG + if I'm careful, the CRV is a bit heavier but you should expect to see anywhere between 38mpg in town and 50mpg on a longer run when being careful. 45mpg as an average will be perfectly acceptable.

Customer :

yep...but not 32 on 200 miles motorway run. and 35 on 700 miles trip to Belgium. And 45 mpg is what people say. I would personally accept 43. I had mercedes c class automatic 220 CDI before honda. Even on fast trips via germany (driving like 120 mph all the time) I always had 35 mpg. And thats 5 speed auto gearbox.

techmachine :

Yes 32 is not right, I have driven my car very hard and still it remains at above 37 so im certain the low MPG is not normal and should return to normal when the fault has been found and repaired.

Customer :

OK, thanks for your help for now. We will see how it goes tomorrow. Bye for now...thanks

techmachine :

No problem, keep me updated and if you need any further assistance just ask!

Expert:  Ross replied 1 year ago.
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Ross
Ross
UK Auto Mechanic
837 Satisfied Customers
licensed Honda technician and general car mechanic