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37 Posts
Discussion Starter · #1 · (Edited)
Hi folks,

59 plate M200 (1.0l) here... Being post 2006, it's on the list for fuel e10 OK, but car does not seem to like it....

For the past few weeks starting, especially now its colder often misfires and loses power until hot. Always starts but nearly stalls when pulling away...

Generally (maybe placebo!) feels like its always down on power than before too...

Other than that - I've been nipping around a few trips a week - but with the above symptom for a couple of weeks.

Last Sunday (apart from the above) on morning start; drove 100 or so miles mostly motorway, 16YO son drove about 50 miles at under 17 car club, (varying speeds including motorway!) and returned without any issues... Same as most recent driving.

Up to now no check engine light.

However, this morning - the first outing since Sunday & need to give son lift to college as I take a rare commute to train station...

It starts but instantly feels misfiring with flashing engine light... Thinking it's maybe (a little colder) and slight progression of the earlier symptoms, I let it warm up as windscreen clears etc (revving a bit without load)...But it's still a "bag of spanners" (very rough and still misfiring)... If I rev it - then seems to pick up power and "catch" itself for a while...

I stopped and restarted a few times, even when warm - same. :(

Time pressure: I start driving and it moves but needs high revs / lower gears just to get / keep moving and does misfire even then - especially under any load... Pulling out onto a slightly busy road fun - getting upto about 40-50 very slowly.

Thinking there may be a loose HT lead or some-such, I pulled over and checked (twist and push) all spark-plug leads... That made little / no difference. Coils were replaced within last two years when there was a previous starting / stalling problem.

OK - much against better judgement I continued this "fun" journey and dropped son at college, made it to the station.

(I know, should probably have left in driveway).

Found OBD dongle at station and restarted engine. Now the Engine light is on but seems to be running normally.

Stored code, unsurprisingly, P0300 random misfires.

Do you think it's the fuel or something more omninous? Loath to spend the money on the cheap run-around but will try some super e5 to see if it makes a difference...

Will see what it's like this evening!

Returned to car at station this evening - starting and it's instant misfires again... Tank was half full so topped up with some Untra E5 from BP garage and continued home (approx 5 miles).

Really does not seem to have made any difference - but it's mixed fuels and not sure how much driving would get "new" stuff through the fuel system?

This evening I've started reading the diagnostics for P0300 - I'm really a complete novice - so the "basic checks for leaks / loose stuff etc. is VERY basic... I can't see / hear anything unusual and tugged / pushed a few hoses and connectors under the bonnet... Nothing untoward to my untrained eyes!

I pulled the HT leads, and removed each spark plug in sequence... They're all looking in pretty fine condition (light brown / dry)...
I've not found the part to say what the gaps should look like - but they do look "pretty big" to me! (I dunno 'at least 1mm'?)

Re-fitted the plugs and HT leads... one at a time, in sequence - I would be bound to get those wrong! - looks like 1 - 4 - 2 - 3 & I think matches the manual?

SOOO... Before I take this up to local garage, encounter much sucking of breath, shaking of heads, and extracting money from my wallet... Any ideas what this novice could check?

Does anybody know the correct spark plug gapping? (Diagnostics I've found in manual only says to "adjust to correct gap" without giving any clues what that might be!)

Sean Pearce.

56 Posts

I had been chasing a P0300 code for ages. Didn't seem to affect performance as bad as yours but every now and then tripped the engine light so had to get the odb reader out to reset.

there are multiple causes of this code as shown here . I tend to work from the cheapest fix up through the increasing cost. So you're right to start with the plugs (the gap should be 1.1mm) I think it is listed as a range 1.1 - 1.2 but I always used 1.1 which seemed to work fine. After each fix would reset code and see if it came back, sometimes took days sometimes weeks. Mine seem to go after I did the fuel filter, but before that had changed plugs, air filter, ignition leads. My next stop would have been crank sensor then fuel injectors but didn't get that far.

If I was you would also take filter out and give a good vacuum clean (assuming not too dirty) its only a few screws and eliminates another variable.

good luck...

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