High Idle with slight misfire

[220bhp]

The Idle on my 3b is running at around 1200 all of a sudden, its also developed a very slight missfire at low revs and has cut out a couple of times as I slow down. I done a search on here about cleaning the ISV but I am unsure of its location or whether there could be any other cause for the problem.
thanks Lou

[UrS4boy]

Sounds like its the ISV all right. Its dirty and sticking. Its the silver can with a smallish air hose leading into one end and out the other(side) with an electrical connector attached. You didn't say 3B or ABY but in either case, its very near the throttle body.

Remove from the car (two clamps and the electrical connection). Clean the insides (through the inlet and outlet) with spray carburetor cleaner and air dry before re-installing. Don't forget the electrical connection plug. The ECU controls the ISV.

Dave F.

[220bhp]

Thanks for that Dave, the cars a 3b.Ill have ago at cleaning the isv tonight now I no what is. Its just started to over heat a bit and is running a little eratic, so I hope thats all it is.
many thanks Lou

[220bhp]

I have just cleaned the isv, reinstalled it and the car is the same,pulled the connector of and it is the same. idle 1200rpm a bit lumpy like its almost running on four,so I pulled the plug caps of one by one while the car was running, and each time it made it run worse, so defo running on five, pulled injectors of with the same result. Then I tried pressing the throttle very gently a few revs at a time,and at 1500 revs it suddenly drops to 500 then back up to 1500 without moving my foot; but if I contiue to press the throttle it builds up ok,realy strange dont know what to do next, so if any of you guys have any ideas I be realy grateful.

many thanks Lou

[UrS4boy]

Could be the throttle position sensor (clean the plug contacts) or (worse) the Mass Air Flow sensor. I am guessing the throttle position sensor. (Its on the throttle body).

Its a rheostat and may have dirty or broken segment(s). Just a guess, trying to match your symptoms.

Dave F.

[220bhp]

Thanks Dave Ill try that, and change the maf over from my s6.
chears Lou.

[220bhp]

Done allsorts today , checked and cleaned tps and isv again, swapped maf with my s6,taken throttle body of and cleaned it,replaced with new gasket, tightend a few hoses,checked for vaccume leaks ect,runs a little better but idle still hi,around 1200,no obvious misfire now but still a little uneven
Removed battery lead to reset ecu, still the same. The only other thing is that the tempreture gauge dos;ent work and the car seams to run a little hot as the fan comes on for a minute or two after the car is turned of and I can hear a gurgling noise,no steam or anything just the sound. the thermostate is new but could it be faulty or fitted wrong has anyone any ideas if so I would appreciate your help and advise
many thanks Lou,

[220bhp]

Well the car seems to be getting worse still running at 1200 tickover and running uneven .Is there anyone out there with any ideas

[SilverSquirrel]

crack or some other air leak somewhere along the intake path..?
IC? Do you have normal boost at higher rpms?

clamp the isv hose shut to see if the idle speed drops to normal, if not, then rule out the isv.

[220bhp]

Thanks for that mate I will check for leaks on the inlet side , just bought some new 4mm hose.With regard to blocking the pipe to the ISV.which one do you mean.

[220bhp]

Ghanged the ISV with the one of my s6 today,but te car is still the same.I put the one of the 3b one the s6 and it ran like a dream. One strange thing that happens is whan you gently press the throttle to arrowned 1400 revs and hold it starts to hunt like its being reved up on its own, but foot peddle is being held steady
I have bought some 4mm vaccume hose today to replace some of the suspect ones at the back of the engine, but there seems to be so many, are there any in perticular that might cause these problems
cheers Lou

[twoqu]

Hi!
Not sure what you mean when you say you have checked the tps. You need to measure the resistance of the pins to ensure that the idle signal is ok. Even if you can hear a click, doesen't mean its ok.
You will need a multimeter. Basically you need to measure between pins 4 and 6. This should be 0 ohms or continuity. You then need to open the throttle a bit and measure. This should be open circuit or infinity.
Pin 1 should be uppermost. The ecu needs to know the car is at idle and does this via the tps. As Dave as said earlier, the tracks could be worn!
Other than that try pullling the codes. It might give a clue.

[porkkis]

I'd say this might be the RPM sensor at the bell housing playing up.

You can unplug almost every sensor (except that one) when engine running and see what makes the most difference.

[220bhp]

Thanks again guys for your advice. I will pull the codes tomorrow and see what comes up. I have know idea where the rpm censor is or how to check it.

[220bhp]

I had the fault codes pulled on my car today,and it looks as if you may be right Porkkis,it came up with 00513 Engine speed sender-g28 .
There where 6 other faults but they could of been caused by me pulling wires of while the car was running.They are as follows.

01257 Ideling speed stabilization valve.
Opencircuit/shortcircuit to ground [GND] I have replaced this

01247 Active charcoal filter system soleniod valve1-N80
Open circuit/short circuit to ground [GND]

01262 Solinoid valve for charge pressure control=N75
Open circuit/short to ground [GND] replaced 18mth ago

01250 cylinder 2 injector-N31
Open circuit/short to ground sporadic [GND]

01249Cylinder 1injector N30
Open circuit short to ground sporadic [GND]

Knock sensor1-G61
No signal

I confess I have no idea of the affects the above faults have on the car and would would very much like to hear from anyone who has any ideas

Many thanks Lou