1.8 Cav not running quite right - is it just the cold?

[retrogeezer]

So my Cavalier has been faultless since we bought it in May but for the last couple of weeks does not seem to be quite as smooth as it has been.

It ticks over fine and accelerates fine but if you are just using a light bit of throttle like when you are doing 30 through town or sitting at 50 in 5th it seems to kind of 'miss' now and again. It's not bad or anything, just not quite as smooth as has been so is a bit annoying.

I did check the ICV and that all seems clean enough. The only thing I have noticed is that the flap in the air filter box seems to always be open so the hot air is drawn from the manifold. It does open and close properly when sucking on the vacuum pipe.

I have read that these single point injection systems are not known for the smoothness but I just wondered if anyone has had this before?

Thanks in advance folks.

[Cavalier342]

Mine's an auto but same engine as yours and I can tell you that after owning it for over 5 years, any little niggle I can pick up in an instant. From my own experience, you are right, because of the fuel going in through the inlet, it's not as smooth running as a multi-point injection engine. Mine struggles and misfires when hot, i.e. on a hot day, but also on a warm day with a hot engine at idle. Just the way it always has been. Heatsoak. Revs up fine, not a misfire anywhere.

I do notice that it runs a lot better in cold weather as engines should. Can definitely feel more torque as colder air is sucked in. Going out on a cool evening, it still surprises me! Maybe your injector needs cleaning, try a bottle of STP when you next fill up, but don't use the whole bottle at once, do it in stages otherwise it will run lousy as the injector cleaner goes through the system.

Silly question but when was it's last service?

[planetc]

Check the plug gaps, if you have a tight one you get a mild stutter at light throttle. You also get a similar experience if the egr is sticking slightly so that might be worth a clean up or blanking plate.

[retrogeezer]

Yeh, I was thinking it might be the EGR but I went in the local VX dealers and they no longer have the blanking plates available. Is it easy to clean?

I did actually put half a bottle of redex injector cleaner in it before a 200 mile drive back from my parents, I wonder if it's just that still going through the system? I have put in 2 lots of £20 quids worth of fuel since.

It ran faultlessly all summer and I did find it odd that the air box flap stays open all the time at the moment. Even with the engine fully up to temp it is still taking in air from the manifold.

Thanks for the replies.

[retrogeezer]

Oh, and oil and filter change at 92,000 (just gone onto 97,000 but oil still clean) New twin spark plugs at 89k and I just put a new air filter in as the old one was a bit dirty.

[Robsey]

If the air intake flap is not working as it should,
then have you got a crack or split in one of those tiny vacuum pipe elbows?
I've had a few of those in the past.

If my Cav ever ran bad, it was usually a duff oxy sensor or my leads breaking down.
Leads always needed changing around October time.
The SPi engines do have a slight flutter or stutter every now and then.

After converting to 2.0 MPi, although it revs much slower at idle, it is much smoother / even in both feel and sound.


Just another thought - have you cleaned out your breather pipes and the cam housing cover gauze filter recently?
These tend to drag oil vapour into the intake system, which can 'irritate' the running of the engine.

[Cavalier342]

Redex is shite Use STP or Wynns, it'll be more effective. You can't expect much difference from a single injector, but it may improve it somewhat.

Cleaning the EGR valve is easy, only fiddly bit is removing it/re-fitting it. Held on with 2 bolts, 13mm heads. No way you can get a socket on them unless you remove the inlet, so use a 13mm spanner, ring spanner is best.

Don't be shy with the carb cleaner and watch the crap come out! I'll be doing the same to mine next time I service it. It is as simple as that.

The only thing I haven't changed on my C18NZ so far is the ignition amplifier under the power steering reservoir. Not sure where to source them from. But I suspect a new one will help. Changed the distributor cap and leads enough times.


As for spark plugs, I only use single electrode arms. No need for twins on these engines.

[retrogeezer]

Thanks, twin electrode plugs fitted by previous owner. I haven't checked those breathers/gauze thing yet and that reminds me, that short bit of rubber pipe needs replacing that goes to the dipstick tube. Can I just use some generic pipe for that?

I have some of those ratchet ring spanners so I hope that fits, will I need a new gasket or just make my own out of cereal packet like someone else mentions on here.

Such a pain that having a cat means all these silly little things can cause problems.

The flap does work, at least from vacuum anyway. I think it's a temp sensor that should make it move to fresh air from manifold air and it's a bit of a pain to check that. It was half way a few days ago so I think it is working but if someone fancies having a quick look where theirs is when running and warm it might be useful.

Thanks again.

[James McGrath]

Bloody nora! I couldn't disagree more about SPI not being smooth.

My 1.6 is impeccably smooth. It's certainly the smoothest inline 4 I've ever known. Much smother than my C20NE/20NE Cavs, especially at idle. That's with 194,000 miles on it.

Sounds better too, less tapety and more of a purr. Maybe the 1.8 is different from the 1.6 I don't know.

[Cavalier342]

Thanks, twin electrode plugs fitted by previous owner. I haven't checked those breathers/gauze thing yet and that reminds me, that short bit of rubber pipe needs replacing that goes to the dipstick tube. Can I just use some generic pipe for that?

I have some of those ratchet ring spanners so I hope that fits, will I need a new gasket or just make my own out of cereal packet like someone else mentions on here.

Such a pain that having a cat means all these silly little things can cause problems.

The flap does work, at least from vacuum anyway. I think it's a temp sensor that should make it move to fresh air from manifold air and it's a bit of a pain to check that. It was half way a few days ago so I think it is working but if someone fancies having a quick look where theirs is when running and warm it might be useful.

Thanks again.

Funny actually, I got the hose that you mention from Vauxhall, think it cost me £3 something and the length was enough to use it twice. So I have a length left over should I need it. You need special oil-resistant hose, as regular rubber gets eaten away by oil based products.

BUT that was a few years ago now. You can find an alternative, it's not difficult to source one. Just measure the inner diameter and search for an oil hose of that diameter.

I've tested my airbox flap before and it does move when I fit the vacuum hose on, doesn't move to the very end but it does work.

Cat converters are shite, if your's is a K reg like mine, ditch it, and just say it didn't come with a cat as it's the early model. It does improve things!

[retrogeezer]

Like I said James, mine was spot on until a couple of weeks ago. I just read that because of the size of the single injector they can be a bit rough at idle and thought cool, mine isn't like that.

It is only slight but the trouble is there are so many little things it could be. I just took the egr off and that looks fine, would have preferred to find it clogged up.

Are dizzy caps available for less than £25 anywhere?

[James McGrath]

Is it when you're only just using the tiniest amount of throttle?

It could be the fuel cut off.

I think these engines cut the fuel to the engine when you take your foot off the accelerator if the revs are above 1400rpm.

If you have your foot only just on the pedal you could cause the fuel cut off for a brief moment and then for it to come back on again. This can cause a bit of a judder.

Take it for a drive and experiment with it. See if it happens below 1400 rpm, if it doesn't then it might be the fuel cut off that's causing a judder in which case it's probably just a dirty injector.

[Cavalier342]

That valve needs a sodding good clean out in my opinion.

[retrogeezer]

does it? It was all moving freely and only light carbon deposits on the surfaces. The hole is not blocked up or anything?

Never done one before so not sure what it should be like but it certainly wasn't like this one:



And yes James, it is just on the very lightest of throttle that it does it. Take your foot of the gas and engine is smooth again or accelerate and it's smooth. It's just when you are trying to stay at 25-30 through town.

[Cavalier342]

Just keep attacking it with carb cleaner, don't scrape the crud off, keep spraying it until the liquid that comes out is fairly clear. Then refit it and get the engine nice and hot and give it a clear out.

[retrogeezer]

I think I'll just try the blank it off with coke can method and see if that makes any difference.

It's really annoying as it has been fine just running around town for 6 months, I thought I would use it to go to my folks and back as the 400 mile round trip would do it good.

[planetc]

Egr, bad plug or idle valve in my opinion, based on what you described above. Kind of fluttery at very light throttle.

[planetc]

Clean the egr, make sure it is properly closed then refit it but plug the vacuum line instead of reconnecting. If it is shut and disconnected then it can't give you a problem. I did this with mine.

[Cavalier342]

Clean the egr, make sure it is properly closed then refit it but plug the vacuum line instead of reconnecting. If it is shut and disconnected then it can't give you a problem. I did this with mine.

Didn't actually think of that. I've always had the pink hose attached to the valve. So plugging it up helps then?

[planetc]

As long as the valve closes, if you disconnect the vacuum then it doesn't open. If it doesn't open then it can't stick open. Been there lots of times with stuck egr valves, electric or vacuum.... disconnect and beat it with a hammer until it shuts. Sometimes they will barely run but once the valve is closed they are fine, worst case scenario is the eml stays on with electric valves

[Cavalier342]

ok. Will give it a bash. Thanks.

[retrogeezer]

Today's update!

I read what planetc said about disconnecting the egr but re-fitting it after cleaning and thought, if it is closed at the moment and I unplug the vacuum pipe then it should also stay closed surely?

So that's what I did, pulled the pipe off, put a nail in the end of the pipe but just left the bit on the top of the egr.

Been out for a drive to pick the Mrs up from the station and it is running absolutely fine, none of the low rev issues at all.

So if you can just disconnect the pipe why do people bother fitting a blanking plate? There must be something I haven't thought of?

[planetc]

... Because they never thought about it like I did, lol

[retrogeezer]

So I can just leave mine as it is then? Do I need to put anything on the metal pipe on the egr? I suppose a bit of tape over the end will be fine.

Fingers crossed it will be o.k next time I use it and thanks again for the advice so far.

[Cavalier342]

Will definitely do this to mine. EGR, what a load of crap. the 18SV never had one which is why it idled so smooth. Unfortunately my auto was burdened with the C18NZ.