My cossie 4x4 idles high (2k rpm) when warm, disconnect ISCV it drops to 900. Took it to a specialist for a quick diagnostic/fix/rolling road tune, unfortunately we couldn't figure out what was wrong with it by the time my slot finished and there was a queue of other folks waiting already...

Bottom line is that the ecu diagnostics report a fault on the TPS and/or MAP sensor.
We tried a new TPS and MAP sensor, cleaned MAP sensor tube, iscv - no difference.

I have since replaced the bulkhead connectors with a proper soldering job, earthed the plenum chamber to the battery and also earthed the ignition amp back to the battery.
Measured continuity from map/tps to ecu and all is fine with ignition on and off.

What else can it be ? Fooked ECU ?

 

did you tried also another control valve.

 

No, but could a broken iscv result in the ecu reporting a map+tps fault ?

PS: I also changed the coolant temp sensor (blue one).

 

Questions:
1) Is the TPS the correct one? (PF09)

2) Are the 2 earth wires on the plenum cleana nd in their correct and original positions?

3) Are you using Magnecore HT Leads?

4) Are you using Pectel Hardware in teh ECU or STD Ford Board?

 

Stu,
1- TPS is 2wd one with wires reversed (so I have been told) - ran perfectly fine with that before I had the head reconditioned.
2- not sure what you mean here When I took the head off, the inlet manifold, plenum, etc... came with it, I don't remember removing any wires in that area - do you have a pic I could compare against ?
3- Nope - Beru
4- Only ECU change I am aware of is a Power Engineering phase 1 chip. How can I check if the board is standard or pectel ? She's a 1991 4x4 if that helps.

Thanks for your help, this is really doing my head in...

 

Oh - picked this up on another thread - would the ecu report the map/tps faults if I had done the same

"Here’s one for the books. Car went into Power Engineering for diagnosis, and the problem was found to be that the Phase sensor and Knock sensor plugs were connected the wrong way round. (Happened during rebuild by me!!!! wall.gif ) I didn’t bother to check the connections, as I thought the car wouldn’t even run with those plugs transposed, and one would have thought that having two plugs so close together, they would have been made so they weren’t interchangeable. (Well I was wrong!!!) Boy does the car go now, as I was driving it in Limp-home-mode, all the time. Pulls like a train to 4000 rpm, and I’m now dying to push it, but have to show great constraint, as the engine is still been run in. Oh well, only about another 700 miles to go"

 

sounds like the position of the TPS is wrong, as a rule of thumb it should sit exactly half way along its elongated slots, of a 4x4 TPS at idle this should read between 0.2 and 0.25 volts back at the ecu, pins 17 and 30 IIRC (with the ignition on), not sure about a 2wd one though.

 

does it start ok and then after about 10-20 secs suddenly raise the revs to the higher value you said?

 

Starts fine, warms up then idle stays at 2k. Disconnecting iscv drops the idle back to 900. As far as I can remember, if I start the engine when already warm, it goes straight to 2k.

 

Forgot to say that the car runs like crap at the moment, it's not just the high idle, as soon as there is a little load on it (e.g. going up a slip road to m/way), it looses power big time. Before the idle went high, it used to misfire on boost/wot too.

That was all after I refitted my reconditioned head - before then - no problems whatsoever.

 

could be a split in the pipe to the map snesor, allowing it to draw air hence daster idle and then when on boost, not giving the map sensor the correct air pressure.

 

Just been in the garage to check things out. The two connectors at the back of the dizzy are definitely in their correct location. The TPS reads 4.94 volts between pins 17 and 30 at the ECU at idle when ignition is on and drops to 0.38 when on full throttle.
I tried to adjust the TPS to see if it made any difference - the idle just goes higher when I do.

Dave, the chap who looked at the car took a good look at the map sensor pipe and cleaned it. I suppose I could try and replace it just in case.

When the car was warming up the idle is about right, there is a definite and immediate increase when the car is warm. Switch off and back on when warm, jumps straight to high idle.

 

Dave, tried a different MAP sensor pipe - no difference

 

if its a 4x4 ecu, at idle, it is expecting to see the low voltage increasing as the throttle opens, now as long as the chip has been mapped in respect to the 2wd sensor , then ok, but i'd try a 4x4 (PF09) TPS first.

 

Dave, bizarre thing is - it all worked fine before I had the head off.

I haven't rewired anything (Except for the bulkhead connectors which are now gone - and that was after the problem started). The chip and ECU are the same as well.

 

where are these exactly stu ?

ive got similar problems frog

bb

 

Seems a lot of us do m8. Must be a virus going round

 

the ecu earth points (2 of them) on the plunum are located if you are at the front of the car with the bonnet up.... at the back right hand side of the engine on the lower back torx screw in the inlet plenum (there are about 10 around the edge of it holding it in place. these two connections can become corroded and the torx screw can become loose, i ened up recrimping mine and then additionally, running a big new earth lead from there to the gearbox/starter motor earth bolt.

 

Done the same but up to the battery instead of starter motor.

 

Hope you get it sorted mate

These sound pretty obvious but just in case

have you checked that the idle screw adjuster on the throttle body has not fallen out as this is quite common.

Also are you using the cable to alter idle revs, as the cable adjuster should only be used to take up slack in the cable.

If I remember correctly the best way to sort idle is to disconnect iscv when cold, get the engine ticking over then reconnect iscv if the revs rise then disconnect and turn idle screw out a few turns and try again until the revs no longer rise

It sounds as if your iscv is held open far longer than needed, resulting in high revs once warm which is why when you disconnect it that it then idles fine

Another sympton of this is that even when cold and the iscv is disconnected the engine ticks over and does not die which is should do if the iscv is not operating

You may already know all this but thought I would mention it just to be on the safe side and cover all angles.

 

Thanks, idle screw adjuster is still there, there is definitely a screw in there.
Cable is tightened up to the point where the butterfly is 0.1mm off the the throttle body housing (I believe this is how it should me), just nudging the throttle cable is enough to make it move so no slack there either.
IIRC, disconnecting the ISCV when the engine is cold stalls it.

Don't worry about teaching me to suck eggs m8, I am sure there is something simple in all that that I have overlooked.

 

i mainly work on standard cars so please feel free to tell me sod off, but did a cosworth few months back a lot of the problems you describe and it had just had a cambelt, checked the timing and it was a couple of teeth out....................as i say i mainly work on standard stuff but maybe worth a look

 

Thanks chunky, at this stage, any input is appreciated.
Timing is spot on though, it was the first thing the specialist who looked at the car checked.

 

no probs hope you get it sorted

 

Thanks, hope so too, been off the road far too long - it's getting to the stage where I am going to hand her over to someone who knows better than I do. Been round and round the same b***dy roudabout too many times and still haven't found the exit

 

you say the head was off have you checked all round for air leaks boost hoses,plenum gasket, inlet gasket etc

 

Yup, sprayed carb cleaner everywhere to no avail

 

Cable should NEVER be tightened to the point you have no play.. slacken it back off until you have about 10mm play. An assistant will confirm you still get full throttle.

 

Just noticed this, thats a bad start as the 2wd TPS is open circuit at idle and the 4wd has a resistance. This causes the ecu to access the maps incorrectly at idle. However told you that works fine doesnt know as much as he thinks he does.

 

Stu, if I do that the butterfly is fully closed, there no longer is the 0.1mm gap between the body and butterfly plate. Is that what you would expect ?

Either he was wrong or a ghost has been playing with my car - I haven't changed the TPS and the car ran perfectly fine before I had the head off.
Unfortunately I am in France again for three days, so can't take a look until I am back. I'll take the TPS off again and check it's the right one.

 

The gap is set by the throttle stop UNDERNEATH the body and should never be fooked with. Its there to solely stop the alloy jamming / damage when hot and you come off teh throttle sharply.


No Either about it
Dont forget your version of fine and mine may differ, but regardless of any of this, the sensors ARE different and the maps DONT access correctly with the wrong one and finally, FORD didnt change it for nothing, Marelli told em it was a required change to run L8 and they knew a little about that ecu id say so i trust em...

 

Thanks stu, I'll put some slack in the cable and check/change the TPS then see where we are from there.

Can you confirm/do you know what the pin combinations are between the TPS connector and the ECU so I can check the wiring is the right way round, just in case someone messed with it.

Thanks again for your very kind help - mucho appreciated

 

Hi,

That's you need ?



Regards

 

Yey Purfect.

 

Ok, back home now

Taken TPS off, it's an PF09 so it's the correct one for a 4x4.
Wiring is as per above.

Looking at the TPS with the face which goes against the throttle body on the table, and the connector towards the bottom, I read the following off the connectors:
Idle:
Middle and left - Closed circuit.
Middle and right - Open circuit.
Left and right - Open circuit.

Full throttle:
Middle and left - Open circuit, resistance increases as the throttle opens.
Middle and right - Closed circuit, resistance decreases as the throttle opens.
Left and right - Open circuit.

Is that as expected ?

Also, if I disconnect the throttle cable, the plate inside the throttle body is shut against the body, there is no gap, not even a smidgen.
According to stu (above), the screw to adjust this should not be touched. Does this mean I need a new throttle body ?

Any help much appreciated.

 

Try here for resistances etc:
http://www.homepages.hetnet.nl/~pete...ick_check.html

Don't think you need a gap in there m8,the air that goes threw throttle
body on idle goes threw the hole in bottom that the idle screw sits in

As long as butterfly is'nt sticking in the throttle body it'll be ok.
Think the gap Stu was on about will be un-noticeable,that small.

Hope I'm right

 

Thanks CosKev3, one thing I am not sure of, is if the measurements mentionned in the doc you posted a link for apply to both 4x4 and 2wd. If the TPS is different between the two cars, I am not sure the ECU side readings will be the same

Something I completely forgot to mention is that I fitted a breather kit when I put the head back on. Could that have anything to do with the high idle ?

 

What breather kit m8????

What did you do with the small pipe that goes from original breather/valve thing
to inlet manifold???

 

It's a proalloy one, breathes from rocker cover and standard breather on inlet side of engine. Returns to block below turbo.

The small pipe has been removed and the hole in the inlet manifold is blanked off with a nut. Maybe I should check the nut is still there...

 

yep, might need some threadlock or some ptfe tape wrapping around the threads to make it sela properly,