Author |
Topic: misfiring badly at 50 mph (Read 7332 times) |
|
pedropedro
Full Member
Posts: 677
|
 |
Re: misfiring badly at 50 mph
« Reply #40 on: Oct 5th, 2011, 6:57pm » |
 Quote  Modify
|
ive just done a run with vehicle explorer obd and something odd coming up when i play back..maf figures are ok at beginning ie .4 .7 etc then jumps to a reading of 4.9 7.2 then 11.1 intermitently ....shouldnt it run smoothly up to a max of maybe 1.2 at high revs ? if i am right wonder whats giving the high readings ...new maf unit ...that expains why it runs ok when i disconnect maybe....maybe ecu is at fault any thoughts
or would you expect to see readings of 4.0 or higher at high acceleration??
|
|
 IP Logged |
|
|
|
Mike H
Senior Member
Renault Clio
 
Posts: 2594
|
|
Re: misfiring badly at 50 mph
« Reply #41 on: Oct 6th, 2011, 3:02pm » |
Quote Modify
|
The plot thickens!
I don't think so see this page:
http://www.fordscorpio.co.uk/mafdata.htm
According that accepted range is 0 - 4.75V, personally I think it's still dodgy wiring or connectors, looks like 12V is jumping in from somewhere intermittently so may be a short somewhere or damp. Or could be the MAF sensor ground lead is going O/C. This is brand new MAF sensor so shouldn't be anything wrong with that.
There's 4 wires to the MAF, I think 2 are for the heater element and the other 2 are the thermistor part.
|
|
IP Logged |
Mike H
|
|
|
pedropedro
Full Member
Posts: 677
|
|
Re: misfiring badly at 50 mph
« Reply #42 on: Oct 6th, 2011, 4:32pm » |
Quote Modify
|
well it must have 12v on the supply to the maf although output seems to be up to 5v or so......the ground measures 8r to battery which i guess is ok ish would expect to be zero need look at circuit and see where its grounded
|
|
IP Logged |
|
|
|
Mike H
Senior Member
Renault Clio
Posts: 2594
|
|
Re: misfiring badly at 50 mph
« Reply #43 on: Oct 6th, 2011, 6:34pm » |
Quote Modify
|
You might have to examine the wires from end to end, see what state they're in. Dodgy plug connector on the PCM box is another possbility (this happened to someone else just recently, was it the 24V that conked out and wouldn't restart from April?)
|
|
IP Logged |
Mike H
|
|
|
Cosray
Full Member
8th Scorpio, 2nd Cosworth: currently '95
Posts: 569
|
|
Re: misfiring badly at 50 mph
« Reply #44 on: Oct 6th, 2011, 9:05pm » |
Quote Modify
|
Hi John,
your ground resistance measured from MAF connector pin 3/Black to battery NEG pole must be a solid near-zero ohms on a Ohmsmeter in the 10 or max 100 ohms range.
In an LHD the G10 ground distribution point sits next to the battery on the engine bulkhead -RHD may be different.
If this point is rusty or oxidised it might create the funny values you are recording on the signalwires, making things go haywire.
Try locating the crowded G10 point and wiggle it to see if the connection is "floating" and make your Ohms values fluctuate.
Connector pin 5 is straight to the batt PLUS 12V on the Battreyr junction box C621 to Fuse F37, acc. to diagrams.
Pin 1 & 2 signalwires lead to the PCM/EEC-V pins 36 & 88.
Might be wise to inspect/cleanspray the big ECU multiplug as well and measure connectivity since cases of water intrusion have been reported. It sits under/behind the glovecompartment lid (remove) and can be retracted after removing one security rivet.
HTH
Ray
|
|
IP Logged |
|
|
|
pedropedro
Full Member
Posts: 677
|
|
Re: misfiring badly at 50 mph
« Reply #45 on: Oct 7th, 2011, 7:35am » |
Quote Modify
|
Hello Ray
thanks for that ..will work on that and figure why the ground is not zero
rgds john
|
|
IP Logged |
|
|
|
Mike H
Senior Member
Renault Clio
Posts: 2594
|
|
Re: misfiring badly at 50 mph
« Reply #46 on: Oct 7th, 2011, 12:27pm » |
Quote Modify
|
Note also for a real chance of measuring very low resistances your meter probe tips must be absolutely clean and points of contact absolutely clean, double-check first that you can get a true zero between the probes themselves. (Analogue meters have a zero adjust, DMM's don't.) Aerosol switch contact cleaner is very useful in these cases.
|
|
IP Logged |
Mike H
|
|
|
pedropedro
Full Member
Posts: 677
|
|
Re: misfiring badly at 50 mph
« Reply #47 on: Oct 7th, 2011, 3:13pm » |
Quote Modify
|
Ok ground ok.......drove 100 miles today...with maf connected jerky lumpy and fuel consumption at steady 70 mph level ground was 25mpg...pulled maf pefectly smooth engine and consumption went to 38 mpg....when checking maf stationary looks fine on ve obd2 ....i am at a loss where to go now...it runs perfectly without maf so thats how i guess will have to run it without maf a mystery
|
|
IP Logged |
|
|
|
Cosray
Full Member
8th Scorpio, 2nd Cosworth: currently '95
Posts: 569
|
|
Re: misfiring badly at 50 mph
« Reply #48 on: Oct 7th, 2011, 3:30pm » |
Quote Modify
|
.... hmnmmm not encouraging... generally not employing the MAF should make things worse, not better...
1) ...do you still get this unusual 12V reading where 4,7V should be the max.? Pls confirm -
That would explain why things are better w/o MAF .
If so, following this reasoning, knowing your MAF is new AND assuming it's 100% THEN somewhere in the loom there's a voltage leak between some wires with brittle isolation and some humidity... not uncommon 
So IF this voltage leak is supposed to originate in the loom then you should be able to measure its presence (with a high resistance Voltmeter)
at the MAF connector, at either pin 1 or 2 towards the EEC-V (since ground 3 nor 12V line 5 would be affected by leaks)
with KEY ON and Engine running.
2) How did you measure the zero-Ohms-ground?
I do hope between MAF connector pin 3 and Batt NEG pole? (thereby including discovery of a bad G10 Ground distribution) with
Key ON engine running NO MAF?
What do you think?
Ray
|
|
IP Logged |
|
|
|
pedropedro
Full Member
Posts: 677
|
|
Re: misfiring badly at 50 mph
« Reply #49 on: Oct 7th, 2011, 3:36pm » |
Quote Modify
|
Ray...where in the loom are there likely to be breaks ? ive had a fuel shut off loom fitted 12 mths ago...i will do a run with obd hooked up again.....yesterday i got some 11v and 7v readings so will work in that area..rgds john
|
|
IP Logged |
|
|
|
Cosray
Full Member
8th Scorpio, 2nd Cosworth: currently '95
Posts: 569
|
|
Re: misfiring badly at 50 mph
« Reply #50 on: Oct 7th, 2011, 4:06pm » |
Quote Modify
|
on Oct 7th, 2011, 3:36pm, pedropedro wrote:| Ray...where in the loom are there likely to be breaks ? |
|
... impossible to say... with the 2.3 I am not sure... the usual suspect locations are close to Heat - causing isolation to brittle, come loose and cause crossleaks between arbitrary wires/strands... also looms affected by cooling lquid and oil... and heat.
Over the top of the engine toward autobox, front of the engine, exhaust shield side of the engine are the worst sites.
HTH
Ray
|
|
IP Logged |
|
|
|
rich170361
Newbie
I'm a YaBB newbie!
Posts: 49
|
|
Re: misfiring badly at 50 mph
« Reply #51 on: Oct 7th, 2011, 4:19pm » |
Quote Modify
|
I might be wrong I had a problem a bit like this on my cossie ultima changed the fuel pressure regulator has run fine ever since.
|
|
IP Logged |
|
|
|
Cosray
Full Member
8th Scorpio, 2nd Cosworth: currently '95
Posts: 569
|
|
Re: misfiring badly at 50 mph
« Reply #52 on: Oct 7th, 2011, 4:21pm » |
Quote Modify
|
Hi rich that's very plausible however it does not explain away the erratic MAF behaviour I am afraid...
Ray
|
|
IP Logged |
|
|
|
pedropedro
Full Member
Posts: 677
|
|
Re: misfiring badly at 50 mph
« Reply #53 on: Oct 7th, 2011, 4:32pm » |
Quote Modify
|
ive just run another scorpio with obd2 and the maf readings are the same as my one...ie accelerated hard up to 2700 rpm and maf reading went up to 8.7 on the the graph ..so despite the data page showing it going to 4.5 or so it seems it goes much higher....so i think red herring ...so now have to figure why it is lumpy at 50-60 with the maf plugged in and why fuel consumption doubles....beyond me for sure .....john
|
|
IP Logged |
|
|
|
Mike H
Senior Member
Renault Clio
Posts: 2594
|
|
Re: misfiring badly at 50 mph
« Reply #54 on: Oct 7th, 2011, 4:33pm » |
Quote Modify
|
Circuit diagram here, page 20
https://skydrive.live.com/?cid=eb36f845ea9b8fb6&id=EB36F845EA9B8FB6% 21146#
Seems MAF has electronics inside and uses +12V from fuse 37. Ground is via 'ground distribution, G10' which seems common to engine / transmission management, VSS etc. 2 separate wires go to PCM only brown/blue & white/blue.
Have you looked at the actual PCM yet? Maybe water's got in and is messing with the plug block connections? The higher Voltage could be bridging across from another pin like Ray says, I still suspect something of that sort as well. Leccy gremlins!
|
|
IP Logged |
Mike H
|
|
|
Mike H
Senior Member
Renault Clio
Posts: 2594
|
|
Re: misfiring badly at 50 mph
« Reply #55 on: Oct 7th, 2011, 4:39pm » |
Quote Modify
|
on Oct 7th, 2011, 4:32pm, pedropedro wrote:| ....so i think red herring ...so now have to figure why it is lumpy at 50-60 with the maf plugged in and why fuel consumption doubles....beyond me for sure .....john |
|
OK so boils down to what's the difference between closed loop & open loop fuelling, or, what else is not being used for open loop mode (?)
EGR is one I believe....
|
|
IP Logged |
Mike H
|
|
|
pedropedro
Full Member
Posts: 677
|
|
Re: misfiring badly at 50 mph
« Reply #56 on: Oct 7th, 2011, 4:40pm » |
Quote Modify
|
not convinced when maf disconnected goes to open loop...the lamdas still switch and seems to stay in closed loop
|
|
IP Logged |
|
|
|
Highlander
Moderator
Expert
13 Scorpios, XR4x4, Suzuki SJ413 for off road :)
Posts: 8244
|
|
Re: misfiring badly at 50 mph
« Reply #57 on: Oct 7th, 2011, 4:47pm » |
Quote Modify
|
New MAF faulty?
Is the other Scorpio a 2.3? can you swap them temporarily?
|
|
IP Logged |
on Oct 17th, 2011, 12:35pm, Simmo wrote:I give up !  Too much for an old boy!  |
|
|
|
|
pedropedro
Full Member
Posts: 677
|
|
Re: misfiring badly at 50 mph
« Reply #58 on: Oct 7th, 2011, 4:53pm » |
Quote Modify
|
ive done exactly that pulled that one and exchanged no difference
i have x1 new , x1 from the other scorp and x2 others (x1 you sent me some while ago) all do the same thing......dont think its the maf ! so why does it run perfectly and fuel consumption low when maf pulled...the data readings i am convinced are fine........if it were a wiring short that would have produced symptoms with maf unplugged ? confused
|
|
IP Logged |
|
|
|
Mike H
Senior Member
Renault Clio
Posts: 2594
|
|
Re: misfiring badly at 50 mph
« Reply #59 on: Oct 7th, 2011, 4:55pm » |
Quote Modify
|
I'm only going by what I read on here, unless I remember it wrong, but something is different +MAF vs –MAF.
Ah this is the page:
http://www.fordscorpio.co.uk/maftest.htm
|
|
IP Logged |
Mike H
|
|
|
|
Home
Help
Search
Members
Login
Reply
Send Topic
Print