The Joy Of 240's, with issues...

[CosmicBike]

I am sick of decorating! Sanding doors and making dressing tables got tiresome, so a bit of a fiddle.
A workmate of mine is also a car nut (Stag and Astra GTE), and on a shift last week we got chatting about stuff and he found an interesting bit about Idle Air Control Valves on a Mercedes forum. Never knew they were proportional, and varied based on input voltage, though it does make sense. Whilst I was confident mine was OK, I did a little test with a battery from one of my lads RC cars, circa 9-10v. ICV positioned differently to on 12v. Whilst it was off the car I checked both hoses to and from the unit, all OK. Also check the resistance of the ICV, 8 Ohms, exactly as it should be. Started car with valve removed, 2000 rpm idle!! Tested voltage at connector, steady 12v regardless of throttle position, so figured ECU needs to see the 'load' of the ICV. Refitted, and 'back-probed' the connector. Engine started and I got 8 Volts, steadily decreasing as the engine warmed up. According to the MB data, a warm engine idle seems to be about 4 Volts. Mine got down to 5.9 Volts just sitting on the drive, temp gauge just off the bottom, so I'd say it's fine.

Changed air filter, and noted the hot/cold airbox flap was on the hot intake. Removed airbox (along with more knuckle skin, again..). Interesting little thermostatic plunger actuator on the flap. Took A LOT of heat to move the flap, holding the actuator in the flame of a lighter until too hot to touch. Now I figured it would move at about 20 Degrees? Anyway, I've removed the flap and actuator which rather handily just clips into the airbox. Also blocked off the hot intake. I read somewhere on here I think that these can stick on the hot inlet and damage the MAF, so I'll leave it as is I guess.

Also a quick MAF test, disconnected whilst engine running. Engine stopped instantly.

So no nearer the fix, but learning the car. And it beats decorating

[Clifford Pope]

Originally Posted by CosmicBike

Never knew they were proportional, and varied based on input voltage, though it does make sense.

If it was just an on/off switch it wouldn't need to be so complicated. It's having the rotating actuator and the sliding shutter that enable it to control the idling speed so finely, but also makes it very vulnerable to dirt. In my experience at the first sign of an odd idle, or the speed sticking before dropping to normal idle, I remove the IAV and give it a clean inside. It's interesting that the rest position has the shutter very slightly open.

When running properly and freely the device works like an engine governor, making it very difficult to stall the engine accidentally. If you are gentle letting the clutch in it will pull away at idling speed without touching the accelerator, even allowing a change up into 2nd gear.

What I've never understood is what actually varies the voltage. The throttle position sensor is not proportional (although I have read that the very latest LH 3.0 system is, unlike the usual LH 2.4), simply clicking on and off a fraction of a turn after opening. So which sensor is it that picks up engine speed? The CPS?

[CosmicBike]

Painting woodwork today, so with 2 hours between coats, fiddle time.

Seeking a quick win, so off with the centre console and I replaced (or fitted, since 2 of them were missing) the diddy little lamps for the heater etc panel. Result, something that works! Also fitted a new clutch pedal rubber as the old one kept falling off.

New spark plugs fitted, lots of Verdigris on the No.3 connection, cleaned but new leads needed really.

Getting back into the technical stuff, and I found the ECU. Actually on the drivers side, that'll teach me to read American sites and will entirely explain the nonsense readings I was getting last week, from the EZK...…

Much measuring, and I'll put numbers up later as waiting for her to cool down. Same behaviour, terrible cold, warm up a bit and fine with a hint of a misfire low down.

[CosmicBike]

Originally Posted by Clifford Pope

What I've never understood is what actually varies the voltage. The throttle position sensor is not proportional (although I have read that the very latest LH 3.0 system is, unlike the usual LH 2.4), simply clicking on and off a fraction of a turn after opening. So which sensor is it that picks up engine speed? The CPS?

I have no idea, I'm going to go digging for LH2.4 logic as it may help get to the bottom of my issues. I would imagine that it gets it from the EZK, since the CPS feeds into this.

[CosmicBike]

Numbers, interspersed with painting, dog walking and cooking.

COLD (as in not started, ambient circa 10 degrees C)

Sensor only, measured directly on sensor terminals: 9.04k Ohms

All other measurements taken at pins 5 & 13 on ECU.

Sensor connected: 4.57k Ohms

Sensor disconnected: Open Loop (infinity Ohms)

Sensor plug shorted: 860 Ohms

And after re-connecting the ECU and battery, followed by a 14 mile drive to the dump and to fill with petrol. Temperature gauge just below mid-point when I returned to the driveway.

Hot to start with at least

330 Ohms @ 1236hrs
690 Ohms @ 1310hrs
1425 Ohms @ 1410hrs
2142 Ohms @ 1510hrs
2768 Ohms @ 1630hrs
3100 Ohms @ 1730hrs

I have yet to back probe the pins to check voltage, but on the surface it would all suggest the ECT to be working correctly.

Interestingly large difference between measuring the sensor directly, and then again at the opposite end of the cable. Nearly half the resistance, perhaps due to multiple ground paths? Likewise interesting to see that just the cable is so high.

[CosmicBike]

Well more painting, which means more fettle time. Couple of bits arrived from ClassicSwede yesterday, nothing too exciting, dizzy cap, rotor, inlet manifold gasket and an O2 sensor as home work suggests it may be 'lazy'.

After removing the plastic guard I jacked the front end up on the crossmember and axle stands under the jacking points. Left the jack in too, you never know....

Old sensor was hot following a 20 mile run, and came out with a little encouragement from a mallet. New one had a different part number and the cable was 6 inches shorter, but nothing that created a problem. Old sensor was very coked up.

Since the car was already warm I have no idea if it has gone any way to resolve the problem with cold running. I also swapped out the dizzy cap and rotor as routine, new leads will go on tomorrow. Car runs OK with new O2 sensor in, I'll check specs on Bosch site later as they are both from them.

Lets see what the morning brings, I'm off to the driveway to jet 26 years of oil and general muck off the underside of the block before re-fitting the plastic guard.

[CosmicBike]

Well the storm didn't deter a run out. My Halfords jack was slowly self lowering yesterday, and whilst I always use axle stands I figured a new jack was in order. Last night the roof rack was refitted, and all the junk various from the garden chucked in the back, with the Christmas tree bungeed to the rack.

This morning, well she started OK, and seemed a little better, a little faster. Still spluttering a bit. Off to the dump, then M25 - M3. Cruising at 60mph as any more and the thunderous noise from the rack was unbearable. Smooth as you like and just about to come off at Sunbury the engine warning light came on. No change in running.

New jack collected and home, quick code read, and 113 is back, 'Fault with injectors'. Cleared no problem and hasn't returned after a run out for paint.

[CosmicBike]

I've been using Grace to commute the past couple of nights, far too windy for the bike, on the way home at least!
Seems to be running a bit better, I have not experienced a cold start/idle stall which is a move in the right direction. Maybe the under bonnet clean has made her feel a bit loved again....

I have been a little miffed by the row of holes underneath the plastic door trims, along the top edge of the sills. A little internet digging and it appears there should be some trims in there, so something else to hunt down.

I reckon post storm Dennis I'll finally do the big service, got the new cambelt, all other belts, filters and so forth, will grab a new water pump too. LHS engine mount wants doing, likewise NSF lower arm and bushing. Then she's in use whilst I get welding on the Capri through the Summer

[Othen]

An interesting journal - I enjoyed reading it, thank you.

Did the house decorating get finished yet?

Alan

[CosmicBike]

Originally Posted by Othen

An interesting journal - I enjoyed reading it, thank you.

Did the house decorating get finished yet?

Alan

It had the danger of becoming a tale of woe, but perseverance is paying off...

Decorating, no danger of that being over for a couple of years yet, the cars and cycling are my 'outs'.