rough idling, C18NZ

[Cavalier342]

Hey guys. I keep trying to figure out whats causing a rough idle on my Cav, but i'm never certain. basically from cold, it starts fine, but idles like it's on 3 cylinders. (tu tu tu tu tu tu tu) there's a lot of engine vibration, especially when in Drive with the brakes on. When i drive off, it pulls away fine, its only rough at tickover. When it warms up it still does it but not as bad. Plugs are pretty good, changed them last xmas, i regulary WD-40 the leads and the connections to the distributor. battery is good, alternator is good. I checked the EGR valve the other day, it was surprisingly clean. Air filter is good, no hoses/pipes as far as i know are blocked. Could it be the idle control valve? I've noticed it a while ago, but its been doing it more noticeably now, and it doesnt sound very happy. I've been using STP fuel treatment regulary too, so i doubt it would be the injectors or intake valves, but then again i'm not positive. Any help is appreciated
Andrei.

[shox1991]

hey i had a similar problem on my cav c18nz, does it do it from start up but then after a bit calm down, and does it start easily or does it take quite a while to get it to start?

[Cavalier342]

Hi mate. Ye, like i said, it turns over fine, and as soon as it starts, the rough idling begins. When it warms up, its not as bad, but still not smooth. I know its probably something simple but i cant figure out what thanks for the reply mate

[Envoy CDX]

There is a crude form of ICV on the bottom of the injector, this can get cruded up - easier to replace off a scrap car 2x T10 from memory and it pops out. Sorted my rough idle.

:edit:

Could be the EGR valve too.

[Cavalier342]

Thanks Gary. i have my suspicions about the injectors too. Never checked them, but i have been using a fair bit of STP additive. On my SPI, how many injectors are there? i was never sure

[Envoy CDX]

1, Single Point Injection SPI
If I see the bit I'm refering too, I will drop it in the post with those other bits

[Cavalier342]

oh right. cheers Gary.

[Cavalier342]

Well i checked my plugs just now, they seem ok, slightly fuzzy electrodes, but no sign of severe corrosion/suttiness, etc. The starter motor sounds perfect, i cranked it over with no leads in, cranks over fine, with the odd "cough" as if it wanted to start. A guy i know suggested this trick, start the engine several times, each time with a different lead disconnected. And see when it sounds roughest. Mine sounded roughish on all attempts, including after, with a bit of WD-40 and all the leads on. I think it might be worth checking the injector now.

[Envoy CDX]

Well i checked my plugs just now, they seem ok, slightly fuzzy electrodes, but no sign of severe corrosion/suttiness, etc. The starter motor sounds perfect, i cranked it over with no leads in, cranks over fine, with the odd "cough" as if it wanted to start. A guy i know suggested this trick, start the engine several times, each time with a different lead disconnected. And see when it sounds roughest. Mine sounded roughish on all attempts, including after, with a bit of WD-40 and all the leads on. I think it might be worth checking the injector now.

It maybe that with all the injector cleaner, you've pulled crap from the fuel lines into the injector, even then it should clear eventually.

I'd block off the EGR valve, Adam posted the kit number for Vauxhall, costs about £10ish might be worth giving that a go first.

[Cavalier342]

Well i checked my plugs just now, they seem ok, slightly fuzzy electrodes, but no sign of severe corrosion/suttiness, etc. The starter motor sounds perfect, i cranked it over with no leads in, cranks over fine, with the odd "cough" as if it wanted to start. A guy i know suggested this trick, start the engine several times, each time with a different lead disconnected. And see when it sounds roughest. Mine sounded roughish on all attempts, including after, with a bit of WD-40 and all the leads on. I think it might be worth checking the injector now.

It maybe that with all the injector cleaner, you've pulled crap from the fuel lines into the injector, even then it should clear eventually.

I'd block off the EGR valve, Adam posted the kit number for Vauxhall, costs about £10ish might be worth giving that a go first.

I think youre right gary. As soon as i get a bit of cash together i'll try it. As for now though, i think i'll keep sticking plenty of STP in. Eventually, as you say, it should clear itself.

[Envoy CDX]

Well i checked my plugs just now, they seem ok, slightly fuzzy electrodes, but no sign of severe corrosion/suttiness, etc. The starter motor sounds perfect, i cranked it over with no leads in, cranks over fine, with the odd "cough" as if it wanted to start. A guy i know suggested this trick, start the engine several times, each time with a different lead disconnected. And see when it sounds roughest. Mine sounded roughish on all attempts, including after, with a bit of WD-40 and all the leads on. I think it might be worth checking the injector now.

It maybe that with all the injector cleaner, you've pulled crap from the fuel lines into the injector, even then it should clear eventually.

I'd block off the EGR valve, Adam posted the kit number for Vauxhall, costs about £10ish might be worth giving that a go first.

I think youre right gary. As soon as i get a bit of cash together i'll try it. As for now though, i think i'll keep sticking plenty of STP in. Eventually, as you say, it should clear itself.

I'd lay off the injector cleaner for now,(for the price of 2 bottles you have your £10 too! lol).

Gary.

[Cavalier342]

ok mate, advice considered. thanks.

[Cavalier342]

here's something worth pointing out...
I ran the engine today, and plucked off each lead at a time, (gently by the rubber end to avoid electric shock) The first 3 made the engine idle worse ( as expected) but when i took off the 4th lead, it made no difference I reconnected it several times, but there was just no difference. the leads were still sparking as normal inside when disconnected. So it would seem like the first 3 cylinders contain the problem. Would the injector still be worth checking or would i be looking at something else?
cheers.

[Envoy CDX]

Sounds like its only running properly on 3 cylinders to me.

Check the plugs against pot 4. If it doesnt make a difference when number 4 is off, then I'd say your issue is there.

Could be the inlet manifold gasket has let go and your not getting fuel to pot 4. Best way to try this is to spray something like WD40 around the inlet manifold and see if theres a change in the engine note.

[Cavalier342]

thanks. will give that a go

[toptune]

could be map sensor feed hole is slightly bocked

[Cavalier342]

Just as an update everyone, i've had the inlet manifold gasket replaced and she is now running like new
I forgot how smooth she was until now

[Squig]

Glad you hear it sorted mate... been reading this on the sideline but no clue sop haven't commented

[Envoy CDX]

Just as an update everyone, i've had the inlet manifold gasket replaced and she is now running like new
I forgot how smooth she was until now

Simples when you find out what it is ain't it

[Cavalier342]

Ye i know, i thought the injector was to blame, although it might need cleaning anyway, but its all down to a poxy gasket the guy who replaced it, a very good mechanic, friend of my dads, he said that apparently they mostly always let off at the 4th cylinder for some reason. As it was in my case, from the 1st to the 3rd cylinder area, the green gasket came off in one piece, but around the 4th, it crumbled off in little bits, so that just proved it really. hopefully this is a good tip for others who have or may have the same issue.
Andrei.

[Cavalier342]

Glad you hear it sorted mate... been reading this on the sideline but no clue sop haven't commented

Cool, thanks anyway buddy

[carlos_canter]

Funny you should say that with cylinder 4 going first.

I bought my old nova and the head gasket went on it at cylinder 4, you could see the lip of the gasket that sits on the edge of the block weaping oil and water, banged an e-bay special in it, then the inlet gasket went, at number 4.

Then the head gasket showed signs of weeping again at, you guessed it, number bloody 4!

Been told that all the 8 valve engines do this with the head gasket any way. There all very similar blocks(if not the same), bored out to size required.

[Envoy CDX]

Can't remember seeing any big block Nova's.

[Cavalier342]

Oh right. Must be just a design thing then Well i guess this is a good tip for other members who may share the same 3-cylinder idle problem.

[carlos_canter]

Can't remember seeing any big block Nova's.

I mean the 8 valves mainly my astravan had the 1.6 SV, the belmont had the 1.4 and the nova had the 1.2 - The cylinder heads are either identical or very similar as are the main blocks. So its just the bore and capacity thats changed. Thats as far as i know, i could of course be completely wrong.