Bad mpg and low speed judder

[DC5RLY]

Trying to diagnose what's causing this issue.

I average at 14mpg town driving and 20mpg motorway. It's shocking for how light I go on the throttle with no Vtec at all.

I've only used vpower since owning over the last year. It's had a major service and oil/filters/plugs/valves all done.

So far I've changed the the secondary 02 sensor (after cat) and cleared fault code pointing to this P0141 - the code hasn't come back.

Has anyone experienced mpg like this?

Performace is fine car pulls well for stock apart from at low speed, on/off throttle has very noticeable judder.

I'm looking at
1.primary sensor - waiting to test again don't have my jack/stands at the moment

2.TPS - unable to fit multimeter pins into plug to test. I unplugged and nothing changed while driving.

3.fuel pump - not sure how to test if poor flow although this was check at the start of the year with grinspeed and all was fine.


Any ideas what would this give such poor mpg. ???

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[CW05TEG]

Did the mpg get noticeably worse after any of the work was undertaken? Or did the problem arise beforehand? Does the car feel sluggish?

Just starting with the basics...

1. I'm assuming the O2 sensor was the correct one? They are around £150-200 for the dc5, not like the ones that go on the ep3.

2.Who did the valve clearances? Are you sure they were done correctly? If they are too tight you will experience blow-by past the valves, which lowers the compression and burns out the valves over time.

3.Are the brakes in good shape? A seized caliper can cause drag which will affect performance and mpg. Usually its quite noticeable as a wheel will be getting hot.

4. What oil is in the engine and gearbox? Is it possible somebody has used a thicker grade than recommended?

5. What condition is the air filter in? I have heard of people having issues in ep3s and it turns out the air filter was well overdue.

5. If all of the above are OK, it might be overfuelling. I'd imagine you will notice this as it will smell noticeably rich. It could be simply a gunked up injector or incorrect spark gaps.

 

[DC5RLY]

Thanks for the reply

O2 sensor was the correct one for the dc5 went with NGK. Also fuel consumption was poor before this was changed.

valve clearances were done with the major service at grinspeed. This was done at the start of the year so all good there

The fuel consumption and judder has got noticeably worse in the last month.

brakes are in good shape and nothing seized.

oil in engine and gearbox is all honda spec

Air filter/box is Mugen which is kept clean

It's definitely running rich can smell fuel from the rearend big time.

Would you recommend checking injectors and spark plug gaps?

Come to think of it, I put some fuel cleaner in a few months back. Maybe this has pushed a load of gunk through and blocked an injector?



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[abbey132]

was there a problem before you decided to put the injector cleaner in?

 

[DC5RLY]

was there a problem before you decided to put the injector cleaner in?

Fuel consumption was around 350 miles full tank with city driving and a few country roads.

This has dropped to around half that if I'm lucky.

Have you used injector cleaner ? It was RedX, think I did 1 or 2 full tanks with it.

Can't imagine this causing an issue :s ?




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[moody_mage]

Did you get any resolution on this? I have the same.

 

[bennn]

I'm thinking maybe you've got an air leak somewhere which is causing over fueling.

I had similar years ago on a 106 gti and it was a cracked inlet manifold.

 

[DC5RLY]

Here's the update, apologies for the delay!

Took out the primary oxygen sensor, cleaned and re fitted.

I replaced the secondary oxygen sensor with new.

Then cleared fault codes.

It took a few days of driving after doing this to see that my MPG is back to where it should be.

Looks like the fault was down to the oxygen sensors, with the secondary been goosed.

Hope this helps anyone with similar issues. I'd definitely check/eliminate before buying sensors, I was lucky to get some decent discount at the time of buying.

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