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[05omegav6]

Had the codes read and cleared yesterday. Emission control light now back on

Only 3 codes this time:
1. 0300 random misfire
2. 0306 misfire on number 6
3. 0704 clutch switch malfunction

The clutch switch is not the problem, a new one is on order and we knew yesterday that it was suspect. Does explain why the cruise stopped working on the way home  .

The car has recently, ie in ther last 8k/3months, had both coil packs replaced with nearly new s/h ones, 6 new plugs, number 6 injector swapped with number 5 injector(made no difference).

Basically engine is idling a bit rough, though it still goes wot like it should  :-/ Thinking that it might be a wiring issue, although everything is plugged in as it should be.

Fast running out of possibilities.

Al.

[Kevin Wood]

The ECU normally picks up any breaks in the wiring and flags up a fault code, even if it's an intermittent problem. :-/

I know we went over loads of possibilities before..

I would say on the face of it either faulty ignition components, poor mixture control - MAF sensor / lambdas perhaps? or maybe the crank sensor on the way out? I think we covered all of these before, though.

You said it often gets worse after a long period of idling. I wonder if the lambda sensors are cooling off? Then again, IME the ECU will pick up problems in this area and flag them up before they affect engine running.

I suppose if the MAF was also faulty, so open loop running was poor?...

Do you have access to a code reader that can report live data? Would be interesting to see if anything is noticeably different when it starts misbehaving? (MAF output, fuel trims, O2 sensor behaviour, coolant and air temperature, injector duration, battery voltage, etc.).

Kevin

[Lazydocker]

And as a quick addition Al, don't even contemplate the LPG conversion until you've got this issue sorted and had a few clear weeks with no issues

[05omegav6]

Maf sensor was also replaced. Best I can do is the pedal trick I'm afraid. :-/

Very valid point, Paul. Whilst LPG is definitely on the to do list, it is not iminant, I've got other bits to do first such as tax bill looming, and trying to get time to do my Hgv test. The car is an ongoing project. It's taken me a few years to work out that life is easier in bitesize lumps.

If I can break down the collecting of parts etc ready for the conversion, then once the car is behaving itself, I'll be ready to get cracking.

[feeutfo]

Was the air leak on pot 6 confirmed and rectified? ( working from a poor memory of old posts  :-/. )

[Kevin Wood]

Next time it starts acting up, might be worth unplugging the MAF. See if the idle improves.

Failing crank sensors are also generally worse after when a bit of heat soak has set in...

[05omegav6]

might be worth unplugging the MAF. See if the idle improves.

Give me 2 mins

[05omegav6]

Right. Unplugging MAF made no difference. just re read codes and in order:

0300
0306
0704
0303
0304
0305
0100.

If left idling it starts getting really rough quite quickly. If you then try and drive the car it bogs down at approx 1800-2200 rpm, just wont accelerate. Ignition off then on again and it drives fine until you next leave it idling for more than 30 secs. :-/

[05omegav6]

Was the air leak on pot 6 confirmed and rectified? ( working from a poor memory of old posts  . )

Compression test on pot 6 was within 10% of the other 5 pots iirc. Both sides (above and below) of the intake manifold had new seals fitted, as did the plenum. Seals were all genuine vx.

[Kevin Wood]

After it starts idling rough, does it improve if you hold it at, say, 3,000 RPM for 30 seconds and then let it idle again?

[05omegav6]

Don't know. :-/  I'll try that when I go back in to work this evening.

Generally, I just switch it off and back on again, and even this doesn't entirely sort it.

Thinking out loud mode: ON.

You mentioned about residual heat possibly affecting the crank sensor. The sensor was replaced approx 50k ago, by vx with a genuine one. Not sure about the routing though. Was the modified route a vx suggestion, or was it an OOF solution?
Two things happened around the time of this issue beginning. Firstly the aircon stopped working, secondly, the car had a full service plugs/filters/cambelt/wp.

The aircon condensor was fubar - chunks missing. Have replaced with a tidy 2nd hand one and the car is being regassed tomorrow. I usually leave the aircon switched on, which would cause the fans to run almost constantly, thus reducing the engine bay temp :-/
I wonder if this might be the thing that is causing the gremlins  :-/

Thinking out loud mode: OFF

[Kevin Wood]

It might be worth a look at the routing of the crank sensor wiring. Normally, the alternative route is a matter of necessity as it's all but impossible to use the original route up by the oil cooler lines. They may have managed to route it the original way, though.

In addition, however, tying the cable to hot oil cooler lines isn't a great idea from a point of view of reliability as the cable insulation breaks down with the heat.

Normally, crank sensor issues cause a code to be raised (P0335 on these IIRC), and normally the engine just stalls and refuses to restart until it has cooled a little, but, as we're clutching at straws...

[05omegav6]

After it starts idling rough, does it improve if you hold it at, say, 3,000 RPM for 30 seconds and then let it idle again?

Sadly, no. If anything it's a bit worse for it.

Although whilst up at that speed, it only spluttered once, one miss on one cylinder. :-/

[05omegav6]

Aircon regassed. Nice and cold inside 8-), still idling like a 3.5 pot . Runs and drives fine provided I keep it above 1500rpm. :-/

[TheBoy]

Thinking about it, joshwyatt had a 3.2 manual that was exactly the same...  ...we never did get to the bottom of it before space demanded he sold it as spares or repairs...