Check engine light

Have been searching google along with LZ (although not ideal as all 3 words are very common) but the only advice I can find is get the codes read.
This afternoon my 'check engine light' flashed up, initially with some engine hesitation whilst driving down the slip road, last few times with no effect on the disco at all.
Last night I drained the cooling system (as have been temporarily running with water) and replaced with coolant. Checked the level this evening and it had dropped a bit probably due to an airlock somewhere, so topped it up and went for another drive - wasn't sure if there's a pressue sensor anywhere. Anyway, the light still flashed up
Any advice on things to check appreciated..

No light this morning, hopefully it was due to coolant pressure

I had that the other day but mine was caused by pulling out fuse number 14 in the satelite fuse box, it stayed on for a couple of starts then went out and is still out, so i wondered if it was one of those things that needed clearing by starting a couple of times.

Hi all, I been away from LZ for sometime but this issue with engine cutting out is now getting unbearable. A few return trips to Essex (approx. 500miles) and a day out today has given me some more info on the problem..

For starters it has got a lot worse. Btw I have a 95 ES auto.
- The issue is short bursts of hesitation of the engine caused by revs momentarily cutting out with 'check engine' light coming on.
- This occurs when going over bumps in road although today the slightest ones caused engine to cut out, at one point on m56 every couple of seconds!
- This happens with or without foot on accelerator although is obviously more noticeable with foot on as causes disco to jerk.
- This can be at any speed, so with or without torque convertor locked up.
- Tends to happen on longer distance drives after a high speed run on dual carriageway/motorway after engine has heated up.
- The only way ive found to help the problem is pulling over and waiting for engine to cool down.

It seems to me that there is a faulty sensor that is causing issues with movement, although the fact that it normally happens once engine is hot indicates water or oil related? Unless something else is expanding causing the problem.

One question I've had since doing the rebuild is exactly what the sensor is directly on top of engine, nearside of rocker? The plastic connector on this had corroded so I'd 'temporarily' taped the green and black wires to the spade ends on the sensor. Wondering whether a faulty connection here was causing the issue I completely disconnected today (when broken down on motorway!) and am yet to see the problem, probably because engine had cooled down by then!

SO, any help/advice/pointers/ideas et. al. muchos appreciated as I got a lot of driving to do next week!!

My engine check light came on (98 XS auto) a couple of weeks ago and after a bit of investigation I've diconnected the sensor on the rocker cover. This has kept the light off but the engine is a little harder to start on very cold mornings.

The engine starts fine from cold with the sensor connected but starting when warm sees the engine check light come on and forces limp home mode with hardly enough power to get up slight inclines.

I'm replacing the sensor tomorrow so I'll post back if it solves the problem as it might be a quick and easy fix for both of us.

Nice one hopefully the light is related to this sensor in both cases..

I'm thinking of soldering the wires to a new sensor to eliminate any bad connection.
Can anyone confirm whether it matters which way round the black/green wires are?
If it's a pressure or temperature switch then I would guess it doesn't matter but not sure whether this sensor is on all 300tdi's or is part of the EDC electrickery..

It's reared it's ugly head again.. anyone??

If you can find a place to do it cheaply, firstly get your codes read.

I presume that you have a 300 tdi auto box, which will be EDC control for injection.

I had a similar problem over Christmas after having the head off for the standard blown gasket work. You say that you have also just done a rebuild.

I had the check engine light flash on occasionaly, and was also suffering from intermittent misfire where the whole engine would seem to cut out for a second, you could see the rev counter drop. The CEL didn't come on though.

It eventually started to get really bad to start and I could flatten the battery in cold weather before I could get it to start, previously my motor would start almost instantly.
It ended up where the CEL would come on at start up and then go out at about 1500rpm, but then come back from tickover to about 1500 when pulling up at lights.

The codes came back as "Engine Speed" fault. This pointed to the crank sensor, which I bought. Can't be too difficult I thought, one bolt and a connector. easy job.
When I saw that I needed the assistance of a spider monkey, a vehicle hoist, and probably the ability to drop the engine :5bbanghead: ............I went for plan B.

The crank sensor works with the #4 injector sensor, on EDC models, and controls running and cold start. (along with the temp sensor on top of the engine).
A fault code of "Engine Speed" can point to either sensor at fault.

Plan B was to change #4 injector. A much easier option believe me.

My thinking was, it's easier, it's the only item that had just been disturbed, and my garage had one crank sensor in stock but they'd had that since 2004. So, not a popular repair item.

End result, even after two months, my misfire has gone, the motor starts as it used to, my CEL has stayed off and the missus has her car back.
(and I got my money back on the crank sensor)

My advice, fwiw, if you can't afford to get your codes read, get yourself a s/h injector with sensor wire off ebay (pm me if you want to know where I got mine), it wasn't expensive, and change this first. It's a simple task and could save you a lot of grief.
Make sure you get new washers for the injector though.

Let us know how you get on.

Davee, thanks for the reply very much appreciated.
It's good you mention the electric injector and crank sensor as both of these I have disturbed since before the problem arose.

The #1 injector I (maybe not so now) stupidly bought a replacement one as whilst doing the HG noticed the original was rusty, although later I realised under closer inspection all the valves looked okay. So maybe the 2nd hand replacement is faulty - shall revert back and see.

The crank sensor I guess is the one which goes through top of gearbox bellhousing?
If so yes this is a bitch to get to, but I've recently had to replace the autobox so a possible cause. The replacement came from a non-EDC so I had to remove the blanking cap and reuse the sensor - hopefully this doesn't need replacing as I don't fancy going there again any time

Spending the last 4days driving round snowdonia it seems that this issue is also speed related, as in it occurs more often after driving at higher speeds. This is leading me to wonder weather it could be anything else with the autobox as I never had this problem before changing it. I shall recheck ATF level, but does it have a pressure sensor?

Anyways thanks for the advise, shall make a start with that injector and hope for the best.

Last night I changed the injector with sensor (one nearest bulkhead) and am yet to have the engine cutting out. Shall take the motorway route home from work and give it the real test me's thinks..

Graham, sounds like you may have found the culprit.

I examined my #4 injector wiring before, and after, changing it. I couldn't see a problem anywhere with it. I expected to see a kink, a pinch point or even feel a broken wire internally. Not a thing. :scratching_chin:

I'm driving around now, after nearly 3 months, and still half waiting for the thing to misfire 'cos it was so intermittent initially.

If anyone else is thinking they've got similar, it wasn't a constant misfire like a spark plug failing. I got a momentary lurch from the car and you could see the revs drop, then all was fine again probably for miles. Sometimes it was barely noticeable.

It used to happen at any speed, cold or hot. Sometimes under light acceleration, sometimes just coasting. Sometimes not for several days.

The worst one on the motorway was when the car kept lurching as it dropped the rev's several times on the trot. Then it finally lit the CEL and went into limp home mode, but stopped lurching.
I drove to the farm I was working on, and it stayed like that for about 3 hours as I drove around stopping and starting. Then it just as suddenly cleared and didn't even hiccup on the 25 mile drive home.

As I said previously, it finally reached a point where things were consistent. Starting was a nightmare, pot luck if it caught. It would then also drop in and out of limp home mode as the revs varied.

Changing the #4 injector cured the starting, the misfire and the CEL light all in one go.
Happy days !!

Fingers crossed you've found your faulty item and it's not that unreachable crank sensor.

Let's know how you get on.