Vauxhall Zafira won't run after oil change

[James k]

Hi,
I've got a car but not minor related problem (hence why it's in off-topic). I changed the oil, oil filter and air filter on my dad's 2002 Vauxhall Zafira today. I drained the old oil out, replaced the filter, and refilled with new oil. I used 10w40 oil and a can of STP. I unplugged the coil and turned the engine over until the oil light went out and a bit longer before reconnecting the coil and starting the engine. The engine runs extremely badly, it just revs up and down between stalling and about 3000rpm. It's impossible to keep the revs steady and if you give it any throttle it flies up to about 5000rpm. It's also backfiring occasionally through the intake. The Green Flag man came round for about an hour and a half and tested everything he could think of before giving up. I have absolutely no idea what could be wrong with it. Can anyone think of anything? I can't understand how an oil change can do that to an engine.

Thanks,
James

[SteveClem]

I don't think it can. Probably a coincidence unless something got disturbed during the oil change,but your Green Flag man should surely have spotted that. Did he plug it in to the devil machine that they all seem to depend upon these days? At least it didn't catch fire...

[panky]

It must be something to do with unplugging the coil and turning the engine over, must have confused the ECU somehow. Try dis-connecting the battery for a few minutes, that used to do wonders for odd little problems on my Ford Focus.

[SteveClem]

Good idea. You might find that the radio packs up unless you keep power to it,though. Not a problem if you've got the reset code.

[James k]

I hadn't thought of that. I'm reluctant to try it though as I don't want to not have a radio any more (naturally I don't know the code!) My immediate thought was that the STP has jammed the valves somehow, is that possible? If so, is there anything that can be done about it?

Thanks

[panky]

I wouldn't have thought so, has it had STP in it before?

[James k]

I haven't changed the oil on it before so I don't know, I assume not. What sort of stuff can a confused ECU do?

[James k]

I should add that it makes a terrible crunching sound when the revs drop low, the same sort of sound you get when you engage reverse gear when you're still rolling a bit.

[panky]

Crikey
I can only suggest you have a look on the Zafira forum, yes there is at least one

http://www.zafiraowners.co.uk/

[panky]

I haven't changed the oil on it before so I don't know, I assume not. What sort of stuff can a confused ECU do?

On my Focus the central locking stopped working, the speedo was all over the place and the battery said it wasn't charging, but I've heard of other issues like the engine going into 'limp home mode'

[bmcecosse]

Did the air filter change go smoothly - any odd pipes disconnected...Try without the filter.

[irmscher]

Try an old trick and take the battery leads or positive lead off for a few minutes resets the ecu .Worth a try has worked for me in the past

[James k]

It seemed to, I checked all the pipes afterwards. It seems be steadily improving with time. My dad sat and rand the engine, keeping the revs up for about ten minutes. At first it wouldn't idle at all and was making that crunching sound as the revs dropped. It wouldn't rev steadily either, basically all or nothing when you put the pedal down. It's now stopped the crunching and is idling, it's still bad and the exhaust is popping but it's loads better than at the start. You now have control over the revs too and can hold it steady. We took it round the block and, apart from idling, it's okay. In fact, it's noticeably more powerful than before the oil change! Still, the idle is very rough and it's revving up on it's own.

It does give the impression of something that's clearing out the more the engine is run, does this hint at what the problem is?

I do want to try the battery check but I don't know what I'll do about the radio

[bmcecosse]

It's much more likely to be an air cleaner/pipes problem than anything to do with the oil...... Is the air filter clipped in correctly - no air leaks, anything like that?

[beero]

You may have disconnected or disturbed the wiring to the air flow meter when you changed the air filter.
It is usually a black box with a multi-plug and wires between the air filter box and the inlet manifold.
Google it for a picture to identify it.

[M25VAN]

Don't these modern ECU managed cars need a good blast on the open road to get the computer and sensors etc. all set back up? Although I thought that was after a power reset. For your radio code have a google, you'll probably find a cheaper way than paying a dealer/manufacturer, there are loads of links including a 3,500+ thread on moneysavingexpert.com

[olderisbetter]

I had a Ford do this after a service, and we ended up taking off the battery lead off to cure it, then as normal we had no radio and someone suggested it maybe written on the radio so i used the prongs and slid out the unit and there was a hand written code on a sticker, i am guessing the previous owner had the problem a few times.

[kennatt]

Had the same problems on a Nissan primera, Was reliably informed that on most moderns if you make the mistake of spinning the engine over,or running it ,even briefly ,with any of the ecu connections disconnected ie Coil MAF sensor, then when you connect up and start the car, the system is now looking for a new unit, it doesn't recognize the old one,so is waiting for the system to be re set. With the Nissan was advised to take . it onto a main road where I could get it up to 60mph and hold it there for 25 to 30 miles I did this and virtually at the 30 mile mark ,the engine cleared,and it picked up and accelerated to 90 and has been fine since. Don't know about the zafira,may need a diagnostic and reset. Typical modern madness. Stick to the old classics,can't go wrong with them.

[James k]

Hi,
I just tried the ECU reset. I disconnected the battery for about fifteen minutes and then tried running the car again. No luck unfortunately. I've tried looking for air leaks around the intake and sprayed WD40 around the area. I did hear a bit of a sucking sound when I sprayed the WD40 and I think the idle was changing slightly when I fiddled around with it although nothing significant. I wrapped gaffer tape around the part of the intake pipe that I thought the noise was coming from but that didn't work. The engine management light hasn't come on so there aren't even any fault codes. Any more ideas? I'm not really confident that a mechanic will be able to work it out either

[olderisbetter]

After a chat with a long suffering zafira owner he mailed me these links, he had a problem after an oil change and he had what he called a noisy back firing engine, his was caused by a faulty coil pack and blocked pipe, the coil packs seem to be a well known problem, hope you find something from the links and get it sorted.
http://www.honestjohn.co.uk/forum/post/ ... m?t=100446
http://www.pistonheads.com/gassing/topic.asp?t=841299