Intermittent engine management light

[Tony]

Dawn's ZR is flashing up the engine management warning light intermittently. It won't come on for a few weeks, then will flash up for around 40-50 seconds and go off again a couple of times in one journey. It seems to be worse in wet weather, but has come on in dry weather too.

I guess we need to check for any stored fault codes to see what is going on, can anyone help?

[Matt Parker]

If its an intermittant flash and the light doesn't stay on then most likely there is a minor misfire being detected either from lambda sensor, a spark plug or coil/coil connection(wiring) This could be from the damp weather getting to the contacts causing a short or a fuel mixture issue which pings thought the lambda sensor.

As its an intermittant MIL the majority of smaller basic 'fault code readers' wont detect an actual fault as it is not current nor pending at the time of plugin. Your need a reader that can go into the ECU history to see any recorded fault. if someone is nice a local and has a code reader its worth a try to see if it'll pick it up failing that your need someone with something a bit more indepth to pick out the fault codes.

In the mean time you can check the spark plugs, condition and gapping, check wiring plugs and HT leads and give them all a going over with electrical contact cleaner/water repellant spray etc. A nothing thing to check is what fuel have you been using? same fuel for all occasions(same fuel as in supplier) you can put a fuel system/injector cleaner in the tank and fil up at a different filling station to see if it makes any difference.

[Tony]

Thanks Matt,

I don't think there's any pattern with where Dawn is buying fuel, it's usually either Morrison's or Sainsbury's. Guess I'll have to get my hands dirty and check the plugs etc.

She now tells me it 'chugs' occasionally first thing in the morning, which I'd guess is part of the same problem.

[Captain Slow]

Tony-give me a shout if you want me to bring my code reader to the meet next week. My reader can see historic, pending or current faults so hopefully it'll pick something up.

I'd suggest the same as Matt-check to ensure all connections to the coil packs are sound and that the leads/coil packs have got a good seat on top of the plugs. Spray the above with water dispersant spray.

When was the last time the plugs were changed?

Also-is it losing any coolant? An inlet manifold gasket leak into the cylinders could cause the symptoms you describe.

[Tony]

That'd be really useful thanks Ian. We'll have to remember to bring Dawn's car to the next meet.

I don't think there is any coolant loss, but will check over the weekend. She had a HGF a few years ago caused by the radiator going porous and ended up with an almost complete engine rebuild with the MLS gasket, so hopefully it's nothing that serious.

As for the last time plugs or HT leads were changed, I have no idea. So they are probably well over-due.

[Tony]

I finally had time to buy some plugs on the way home from work tonight, then found my plug spanner was the wrong size so had to get one of them too.

How tight should the plugs be? I couldn't shift them with the T bar on the top of the spanner so put a small tube on the end to get a bit more leverage. Too much leverage it would seem as the weld at the top of the plug spanner snapped and the plugs are still tight in.
Surely plugs shouldn't be this tight? I was beginning to worry about damaging the head.

Anyway, with a broken tool, which will now have to go back to Halfords, I couldn't do any more tonight so will have to try again tomorrow.

[Sambomonkee]

Shouldn't be that tight at all, should be able to get them out without the use of extensions or breaker bars.

Should only be tightened to 25Nm, which is easily undo-able normally.

Was it the same on all plugs, or did you try it on only one?

I just hope its not been over tightened and the threads damaged when you try to get them out.

PS - was the engine hot, if not warm it up a bit, might help

PPS : if you ever get them out, I also have a spare set of coils (assuming its the 160) if you need to eliminate that from the equation.

[Tony]

I didn't think they were supposed to be that tight and have never had a problem getting plugs out before. The engine was slighttly warm, but not hot. I only tried 2 plugs and they were both the same.

if the plugs don't work (wasn't that a song?) then as suggested by Matt, Iain and other, HT leads will be next. If there's still a problem then loan of some good coil packs to elimate them before spending money on new ones would be really useful thanks Lee.

[Sambomonkee]

I didn't think they were supposed to be that tight and have never had a problem getting plugs out before. The engine was slighttly warm, but not hot. I only tried 2 plugs and they were both the same.

if the plugs don't work (wasn't that a song?) then as suggested by Matt, Iain and other, HT leads will be next. If there's still a problem then loan of some good coil packs to elimate them before spending money on new ones would be really useful thanks Lee.

My coil packs, also have the leads, so use me before spending any money

[Tony]

I'll keep that in mind, although HT leads are about £12 for a set at our local motor spares place and the old ones are probably as old as the car, so it may be worth getting a set anyway.

I borrowed a plug socket and set to work on a warm engine and 3 plugs popped straight out! A complete contrast to last night. The fourth needed a bit of encouragement. Whole job done in under 30 minutes.

The old plugs didn't look too bad to me. (pic shows one new and one old)

[Tony]

A week on and there is small improvement but the warning light light still flashes from time to time and the engine is still coughing.
Dawn thinks she's spotted a pattern with the warning light, It seems to flash mostly on a certain long down hill run.

Putting an injector cleaner in the fuel has been mentioned. Are they any good and what brands are recommended?
Are there any fuel filters that are easy to do and worth checking?

[Sambomonkee]

Fuel filter is a piece of pi$$, just two nuts, get the old one off and put the new one in.  Its at the back of the engine bay just off centre to the right.

But if it does it down hill, could it be related to overun  I would expect it do it on the motorway say at 70 and then just coming off the throttle, should be the same effect.

I suppose or a few quid, changing the fuel filter is not going to hurt, but your in need of a diagnostic session now, as otherwise its going to be guess work.

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