mgf

[Rob Bell]

What year is your car Mykel? Does it have an OBD2 socket? If it has, you can probably get one of those readers that provides the sensor data in real time (engine speed, water temperature, oil temperature, inlet air temperature, lamda etc etc). A bit of overkill perhaps, but I think it would be very useful to understand what is going on to make the car want to idle fast? Perhaps there is an intermittent fault, or a wire whose resistance increases with the heat due to a break, altering the correct sensor value? It isn't unheard of for the Lambda sensor to rest up against the manifold and melt, for example...

[Mykel]

Thanks for the idea, Rob, yet it's a 2000 VVC, the last one with MEMS 2J, not OBD-II compliant. So no Scangauge II or other gimmicks, unfortunately. Otherwise I'd have gone for one of those anyway, if only to know the correct temperatures. But that won't work

Last night I gladly received the workshop manual (thanks Kim!) and there is one more VVC-only sensor, the MAP thing sitting on the inlet manifold head. I have no idea what a faulty one would actually lead to, yet I think I will simply take it off and look if it neads a good cleaning, as I presume it breathed the same air as the IACV (which was awfully dirty).

The lambda would be my last resort and I won't touch that one before replacing the complete exhaust system.

[Rob Bell]

That's a shame (although the last of the pre-OBD2/ EU2 cars were actually MEMS3).

I am still wondering about that water temperature sensor and perhaps either a dirty connector or a dodgy wire to it... and hence being able to see what the ECU "thinks" the water temperature is would be very helpful!

[Mykel]

If the problem persists (has been quite okay today) I could hook the sweetheart to a Testbook, couldn't I? Yet unfortunately they can't be taken along the way on a test drive and usually when you arrive at the garage, everything is normal. Always. Inversion of Murphy's Law actually.

[lsparrow]

I had a sticking revs when I replaced the plastic throttle body for a metal one on my 1998 VVC. I loosened the bolts ever so slightly and found an instant result compared to when bolts were fully tightened. I also sanded the edges of the butterfly valve in the body to take off any rough edges that were catching on the inside of the body. That was about 7 years ago, no issues since. Hope that helps add to the pot of possibilities.
Liam.

[Mykel]

Thanks guys, yet I'm afraid the real cause of the problem may be found. Although nothing any of us would have ever thought of.

I have to go back in time a bit ... after having changed brake disks in February, I was puzzled to find an M8 nut on the driver's floor mat right after returning from the DIY workshop. I checked everything around the pedals and fusebox, but nothing was missing there. So I guessed the little bugger must have been sticking to my shoes. Yet the thing looked quite MG-ish, so I kept it in the lost&found box.

Yesterday I removed the MAP sensor from the inlet bridge to clean both the sensor itself and its connector. This allowed me to have a look at some of the mounting points of the manifold to the head. Guess what, one of the studs was completely naked and in desperate need of something to cover this shameful nudity, possibly an M8 nut might suit?

I actually almost jumped out of my trousers ... after the issues with the alternator fixing and the completely open airbox, this is the next (and obviously most serious) piece of crap the garage guys have delivered when changing the head gasket in December. Obviously I'm not letting them have another go at my precious, so now i will have to quote Lady Thatcher: "I want my money back!"

by the way, a somewhat "farting" sound while accelerating has developed over the last weeks. Might also result from this, mightn't it? How dangerous is this situation in respect to coolant loss or other serious faults?

Really p***ed off at the moment,
Mykel

[redarrow]

manifold bolt, to engine head not a massive fault, but a old farting manifold gasket is annoying lol.

sounds like you got bad gasket some where, you can replace the bolt.

these so called car mechanics are a joke,hope the hgf was repaired properly.


^^ He tried the throttle, no luck.that why he stripping his own engine parts, to find the real reason off high revs.

[Rob Bell]

by the way, a somewhat "farting" sound while accelerating has developed over the last weeks. Might also result from this, mightn't it? How dangerous is this situation in respect to coolant loss or other serious faults?

Fortuantely, nothing diasterous Mykel. Just replace the nut and torque it up tight, and there should not be any problems

[Mykel]

That sounds soothing actually, thanks a lot Rob! Yet the thing is to get to that bl**dy thing, could hardly take a photo to proof it, even with the MAP sensor off again:

_IMG_0120.jpg (94.33 KiB) Viewed 824 times

And that was only with the Phone. Somebody has to suffer for this, I demand severe punishment! Mailed the blokes a registered letter today, summing up all the lousy work they delivered, backed with a series of photos and claimed back 500 Euros of the 1.700 Euro bill. We'll see how that works out.

[redarrow]

You tell them mate.

dam idiots, sorry but it bad workmen ship.

what if you took the car back and get everything done again properly.

surly you got a guarantee. ((let them stop all other problems )(not you!

[Mykel]

Yes RedArrow, that is what I had to do. Normally I didn't want to have them touch my car again, but under terms of guarantee I unfortunately had to give them another try to fix it. Left the car there this morning and got her back in the late afternoon. They gave me a courtesy car for free for the day but I had to pay 15 Euros for the CDW to minimise my obligations in case of damage, which was "totally free to choose" obviously.

The first thing I noticed when I drove home was that I seem to have a completely new engine in the back. Not the slightest "fart" or Beetle sound anymore ... I actually had to switch the radio off to listen to the car's heartbeat.

I went for a short test drive, again warming the oil up thoroughly and then starting the usual 0-60 (or rather: 0-85) run towards home. No high idle probs anymore, only when approaching our house I went at say 30 mph in 2nd gear and when parking, she remained at 1.600 rpm. One Aston-Martin-ish push on the throttle (my name's Bond ... ) and down we were at 850.

So time will tell if this nasty, involuntary intake bypass created by Germany's Workshop Idols was really the cause for the high idle revs. I'll keep you posted.

[redarrow]

well done m8, get your money worth out off them i say.

lets us no about the high revs, in the mean time, hopefully fixed now.
mykel = bond lol

[Mykel]

Blimey,

the idle rev problem has actually not really improved after the inlet manyfold was properly fixed now. Yet I think that I found a kind of replicable way to actually provoke the needle to stick at 1.400 rpm. And it's two possible ways to achieve the dreaded thing.

Situation 1:
I drive on country lanes from cold for - say - 10 to 15 miles, easy-peasy cruising style, keeping the engine around 2.000 rpm, never exceeding 3.000. Water and oil gauges have come to normal operating temps. After having reached my destination without any sign of problems, I turn the car off and go at whatever I actually drove there for. Shopping for example. After half an hour I return to the car, her still being warm, engine starts normally and off we go. At the second or third roundabout or traffic lights the idle stays up. I can also feel this coming when approaching the stop, as there is little to no effect when releasing the throttle pedal, no engine brake. Sometimes (rarely) it works to rev up in neutral, but mostly it takes loooong for the needle to come down and the only solution is to reset the stepper (ignition off/on, 5 steps and so on). That works always, yet she is very reluctant to fire up afterwards. But runs fine from then on usually.

Situation 2:
I go for a motorway ride, normally around 80 - 90 mph, occasionally a bit faster. Oil heats up, sits around 130°C (oh, these crappy MY2000 gauges!). When taking the exit, everything is fine, again until the second or third stop. Then everything continues as described before.

When the car is allowed to run on A-roads only and to completely cool down after ride (2 hours or more), everything is perfect.

From all this, the things I have done so far (and my measurements) I would rule out:
- the brown ECU coolant temp sensor (quite new, reads correct values)
- the HT leads and plugs (both new and correctly fixed)
- any air leaks on the inlet manyfold (thoroughly checked now)

From my driving experience, it actually feels as if the IACV doesn't close correctly when over a certain engine temperature, thus allowing too much air into the hot inlet, and (after resetting it) is too tightly shut as to allow the engine be fired up properly without pressing the throttle when hot. So I'll have to take the bugger out again and check movement.

Other things that came across my mind are:
- inlet air temperature problem (would want to leave out the resonator and connect the air filter input directly to the n/s air intake)
- throttle body sticking, though it's a 48 mm alloy one (VVC) (cable is known good)
- lambda sensor faulty (MEMS 2J, only one of them)
- air inlet temp sensor faulty
- ignition coils rotten
- ECU broken

So, all you wise people dwelling on my car's island home, from your vast experience, which would be the most likely cause for this dreaded issue?

Thanks a lot
Mykel

[Mykel]

Okay everybody, this hopefully is the final update on the issue.

After another two weeks, here's just a brief summary of the actions carried out so far:

The previous owner had:
- the temp sensor changed twice
- another "switch" changed, probably the one for the oil pressure

Afterwards I had:
- fitted new spark plugs (NGK iridium)
- fitted new ht leads
- cleaned all connectors to sensors, switches and so on
- dismantled, cleaned thoroughly and tested the IACV twice
- removed and cleaned the MAP sensor
- had the poorly fitted inlet manifold refixed
- took off, checked and cleaned all breathing hoses on the manifold/throttle body
- replaced the throttle body -> brand new 52 mm with new TPS
- modified the air intake and replaced filter element with a K&N panel filter

None of this worked in the end, the revs kept settling at around 1.400 rpm virtually all the time now.

After I realised a whiff of petrol in the morning when I had the car in my mums garage over Easter, I thought maybe the connection to the purge valve has come off somehow. I checked this and to my big surprise the valve kept on clicking while the engine was idling at 1.200 rpm. Normally the valve mustn't open below 1.800, so something seemed to be wrong here, which was proved as the car immediately got back to normal idling after I disconnected the valve from its wire.

To me this meant, that the engine ECU simply didn't get the information that
a) the engine revs at less than 1.800 rpm and
b) the throttle body is closed


At first I was quite afraid that this may point to a faulty ECU in the end, but it simply turned out to be a connector problem with the black multiplug on the ECU. The cable tie securing the engine loom to the ECU bracket had broken, I replaced this and now the loom has less pull on the connectors, but none of them had come off anyway (like Dieter had it with his car). But even the slightest force seems to be problematic in that area so this has to be checked obviously. Giving all of the connectors around the ECU a good wash in contact cleaner has solved the issue completely. Smooth running, needle goes straight back to 850 rpm when I take the foot off the pedal.

Cheers
Mykel

[redarrow]

well done m8, you really worries me some times, glad you sorted that,

just shows how a bit of dirt, and connection can do insane things.

i love the diagnostic example above,and the written explanation, so well written.

was it maplin contact cleaner cheapest i found lol.