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Topic: Very poor MPG (Read 1208 times) |
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Nunnspoet
Full Member
I love YaBB 1G - SP1!
Posts: 798
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Very poor MPG
« on: Mar 21st, 2016, 12:36pm » |
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The Beast is being beastly:
The best, very best MPG is 20. The worst is 12.
All 4 HO2 Sensors have been checked and found to be good. There are no driving concerns. I have checked all the airways for leaks and cannot find any
There are no Fault Codes. Not even on "enhanced".
But! There are symptoms:
On tickover the engine revs oscilate between idle to aprox 800rpm.
HELP!!!! I am completely flummoxed and banjaxed, so please let me know what to do.
Best regards
Mike
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Scorpio_Mike
Senior Member
Jeep Grand Cherokee 3.0 V6 & 2.8 Sierra XR4i 4x4
Posts: 2354
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Re: Very poor MPG
« Reply #1 on: Mar 21st, 2016, 1:06pm » |
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Assume this is a 24v ?
Sorry I can't help but your MPG figures make me feel a whole lot better about my Jeep 
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Star sign is Scorpio !
Sierra XR4i's are great...especially when fitted with 4WD 
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a900one
Full Member
A scorpio is for life not just for christmas
Posts: 980
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Re: Very poor MPG
« Reply #2 on: Mar 21st, 2016, 6:34pm » |
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Maf clean ?. Air leak, the t that Matt said about in a post, pig to get at as under inlet I think. Top mpg I have got out of mine was 27 with very small right foot  .
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GrahamT
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I'm a YaBB newbie!
Posts: 108
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Re: Very poor MPG
« Reply #3 on: Mar 22nd, 2016, 1:06am » |
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What are the fuel trims doing Mike?
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Glyn
Full Member
Now an OAP ! 95 cossie and another !and a 12v
Posts: 584
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Re: Very poor MPG
« Reply #4 on: Mar 22nd, 2016, 4:36pm » |
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Had the same problem on one of my 24v's in the past. Turned out to be a crack in the plastic T piece in the vacuum line between the bulkhead and the block below the idle air control valve, which was replaced as the prime suspect. T piece not available so used one from a fuel supply line.
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Nunnspoet
Full Member
I love YaBB 1G - SP1!
Posts: 798
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Re: Very poor MPG
« Reply #5 on: Mar 23rd, 2016, 7:34am » |
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Thanks for your advice everybody. All gladly taken on board. 
I won't be able to follow up on this for about a week as my attention has to be elsewhere. However as the saying goes "I'll be back."
Oh, don't stop sending your advice as I will still be about.......just can't play with The Beast.
Happy day
Mike
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Pegasus
Full Member
24V Cosworth Ultima Born: Sept 97, sold Aug 23
Posts: 741
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Re: Very poor MPG
« Reply #6 on: Mar 29th, 2016, 9:28pm » |
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As said before,
favourite is possible air leak. MAF, fuel trims, are all other readings 'normal'?
Also, what's the inside of the air filter housing like - clean or oil/water at bottom.
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Nunnspoet
Full Member
I love YaBB 1G - SP1!
Posts: 798
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Re: Very poor MPG
« Reply #7 on: Apr 21st, 2016, 11:45am » |
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Thanks for your advice everybody,
As you probably guessed, I have probs. with both of my Cossies,
The Beast is as was: there are no fault codes, mpg is 17.3. I had the plenum off yesterday and can find no evidence of any vacuum leaks, I tested the T piece and it's joining pipes in water - no bubbles also I tried to blow water through, sealing off the exits but none came out.
On the OBD lead I can bring up various fuel trim readings but they mean nothing to me, very frustrating  .
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Nunnspoet
Full Member
I love YaBB 1G - SP1!
Posts: 798
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Re: Very poor MPG
« Reply #8 on: Apr 23rd, 2016, 7:43am » |
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Oookaaay!
In desperation I decided to swap the MAF with the known good one on my other Cossie, with 'icky lights only to find that I had real difficulty unplugging it! The little rubber seal that normally sits at the base of the female connector had slipped forward and was obstructing/interfering with one of the pins - I have no excuses  .
I rectified the situation and went for a drive: Tick-over much improve, kick-down operated perfectly as did the expected surge in power. I set the trip-computer to driving MPG and noticed improving readings: Instead of 2 to 4 mpg at set off I got 4 to 6 mpg. On slight inclines at aprox. 50mph the readings improved from 7,8mpg. to 11,12mpg. Cruising around 30mpg the readings oscillated better, similarly at 60-70mph. Also on deceleration, for the first time in ages she obtained 99.9mpg.
I need to go for a proper run to see just how much improvement there is, but things are a bit more hopefull.
How I did not realise the resistance when plugging the connector to the MAF I have no idea.
Mike
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Nunnspoet
Full Member
I love YaBB 1G - SP1!
Posts: 798
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Re: Very poor MPG
« Reply #9 on: Apr 26th, 2016, 8:29am » |
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She returned 17.2 mph on a 16 mile round trip .
On with the OBD lead and determined to find something relevant I went to "Status." No faults listed. Into "enhanced" and after playing about a bit I found a fault Code: P1153, lack of HO2S21 switches - Sensor Indicates Rich. Yippiee! I have a spare Sensor and as this fault is on the passenger side I should be able to do the job myself (dodgy back permitting).
Peering into the darkness I see that the existing wires from the plug to the Sensor are green, white and two black, one with a white stripe (I think) and the other all black. The wires on the replacement Sensor which is a genuine Ford part are; grey, black and two white.
I need to join the new Sensor to the existing cable as the new cable is way too short so can somebody please tell me how to make the right connections?
In eager andicipation
Mike
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Simmo
Administrator
I'm an OAP !
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Re: Very poor MPG
« Reply #10 on: Apr 26th, 2016, 9:39am » |
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Mike. have a look at This page which I found on Google. I guess if you do a similar search you may get an exact match. If not I'd ring the manufacturers of the new sensor and ask them.
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