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Ford Explorer SOHC 4.0 2000 - Weak mixture, hesitation under acceleration #

Posted by Stuart MacKinnon on December 11, 2012, 12:48 pm

Year of Manufacture *: 2000
Engine Size and Code *: 4000cc, SOHC
( Optional ) Scanner Used: IDS

Hi Chaps,
Engine is subjected to weak fuel mixture under acceleration and therefore a serious hesitation, both lambda's are reading a weak mixture at this point. Both lambda's switching are normal at tick over and on fast idle. EGR blanked off with a plate by us a while back so this isn't the fault. Fuel filter relatively new, but does anyone know what the actual fuel pressure should be, I've got 45psi on tick over (at the rail), when you rev the engine and it flutters/hesitates/falters the pressure drops slightly (as expected) to 35psi, does anyone know if this pressure is acceptable? I’m unable to blank off the fuel return to increase the fuel pressure as this must be built into the pump it’s self. Using IDS I can see the fuel injection opening time increase as you accelerate and demand the power, this opening timing does not back off so I can only assume the injectors are fully open. Your thought please. Thank Stuart

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by Chris Angus <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5111' width='330' height='300' border=0 style='border:none;'> on December 11, 2012, 1:30 pm, in reply to "Ford Explorer SOHC, weak mixture, hesitation under acceleration"

I would be happy with that fuel pressure.
Have you checked MAF sensor?

Chris

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by Stuart MacKinnon <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5451' width='330' height='300' border=0 style='border:none;'> on December 11, 2012, 4:39 pm, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"
Stuart MacKinnon

Hi, thanks Chris, just been on road test and took a snap shot of the data, see the image, you can see when I floored the accelerator

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by Chris Angus <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5111' width='330' height='300' border=0 style='border:none;'> on December 11, 2012, 4:55 pm, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"
Chris Angus

Looks like MAF output is low, if I'm reading it correctly you have a maf output of 2.5v at wot which is too low, did you log all the way to redline?
Can you scope the maf in the workshop, also try disconect it and see if it revs ok.

Chris

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by Craig Hewison <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3409' width='330' height='300' border=0 style='border:none;'> on December 11, 2012, 7:17 pm, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"

I'm with Chris on this one, MAF looks low! Can you see fuel trims at idle? Have you checked for a vac leak?

Hth
Craig

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by Stuart MacKinnon <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5451' width='330' height='300' border=0 style='border:none;'> on December 11, 2012, 9:33 pm, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"
Stuart MacKinnon

Hi Guys, forgot to mention already passed air leaks test with the smoke tester. Will get back on this MAF sensor then in the morning, stay tuned for an update! Thanks for the input, Stuart

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by Stuart MacKinnon <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5451' width='330' height='300' border=0 style='border:none;'> on December 12, 2012, 9:29 am, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"
Stuart MacKinnon

Hi Chaps, please view the latest, this was in the workshop, I reved the engine up to the limiter, 6000+, I think the MAF looks OK on the live data, also scoped it at the sensor and got the same readings.

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by James Eardley <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3143' width='330' height='300' border=0 style='border:none;'> on December 12, 2012, 10:44 am, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"
James Eardley

Hi Stuart

Can you scope the Lambda sensors along with the MAF doing the same test.

The MAF output seems to be better in this capture I wonder what the lambda sensors were reading during this test.

Does your live data provide you with fuel trims?

If you can, graph LT fuel trims, ST fuel trims for both banks.
Lambdas for both banks.
MAF and throttlposition.

James

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by Chris Angus <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5111' width='330' height='300' border=0 style='border:none;'> on December 12, 2012, 12:14 pm, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"

Just checked on bosch esi, fuel pressure is 2.5 to 3.1 bar, so you are ok there.

As Maf does look ok now, I would probably think about removing the injectors and testing the flows on a bench.
If it's not too much work for you I can test them if you send them

Chris

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by Stuart MacKinnon <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5451' width='330' height='300' border=0 style='border:none;'> on December 12, 2012, 2:36 pm, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"

Hi chaps, latest screen capture, just squeezed onto one page! MAF low because on full throttle the revs will not go above 3000 and is very hesitant.

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by Stuart MacKinnon <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5451' width='330' height='300' border=0 style='border:none;'> on December 12, 2012, 5:14 pm, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"
Stuart MacKinnon

See 2.36 post ???

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by chris Angus <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5111' width='330' height='300' border=0 style='border:none;'> on December 12, 2012, 6:52 pm, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"

Yes, looks like you've checked all you can now and is looking like a fuel supply problem.
Can you get fuel pressure gauge on and check while on the road, just to confirm?
Another test is to measure injector duty cycle while under load, this will confirm if they're fully opening, not an easy test though.

Then last thing is checking injector flow rates, they just might not be flowing as much as they should be

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by Alan Kane <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=alankane' width='330' height='300' border=0 style='border:none;'> on December 12, 2012, 11:43 pm, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"
Alan Kane - Administrator

Is the exhaust blocked?

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by Mark Carter <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1428' width='330' height='300' border=0 style='border:none;'> on December 16, 2012, 8:46 pm, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"
Mark Carter

Has a fuel flow test been carried out on the vehicle?

Mark

Modern cars, Its all wizardry and witchcraft

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by Stuart MacKinnon <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5451' width='330' height='300' border=0 style='border:none;'> on December 18, 2012, 11:22 am, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"
Stuart MacKinnon

Hi Chaps, update, found bad fuel, water and muck, removed tank and washed out, cleaned out fuel lines, currently also got the injectors out, Chris Angus can you assist in checking/cleaning these, they are a Bosch units, call me on 01889 563448, thanks Stuart

Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration

Posted by chris Angus <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5111' width='330' height='300' border=0 style='border:none;'> on December 18, 2012, 6:04 pm, in reply to "Re: Ford Explorer SOHC, weak mixture, hesitation under acceleration"

Hi Stuart, I did ring but it was a bit late.

If you want them checking, just send them.

Exhaust Discounts
1A Wellington Road
Leeds
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