Cable's Thread of Ongoing Misery

[Cabletwitch]

In the words of a co-worker of mine... Phucktybollocks. (thank you, bonkers swear filter)

So, the new ICM started out at 3000RPM, then dropped slowly until it was back in the horrible zone of poppybangbangphut. I really thought I had that figured out, but the gods of Cavalier have decided to stick two fingers up at me again. Thought I DID take a good listen to the engine as she's running, and heard something a little odd, at least to my limited knowledge...

The injector makes quite the ticking noise as it fires, and can easily be heard (through the nice amplifier box thoughtfully screwed to the top of it). Mostly, it's firing fairly slowly at idle, but every now and then speed up quite a bit for around a second or two, then drops back to the slower speed. Now, I understand there is a lot of feedback from various sensors around the engine (I know this, because I've replaced almost all of the bloody things), but even with one or two not playing ball, you'd think things would still be fairly even. I'm now more inclined to go down the 'ECU is having a stoke' route, and look at changing that out for one off Ebay. Tomorrow though, I'll give it a good check over and see if there is any damage, as there IS some rust on the drivers side A pillar which may allow for water ingress, and causing all manner of wonkiness to happen.

I'll report more as I find it!

[Robsey]

Sure is a saga of woe.

As you say - nearly all sensors have been swapped out.

Assuming all rotor, dizzy, amplifier, coil and leads are in good fettle.?

Induction and exhaust are okay and leak free.

T'is a really confusing state of affairs.

[Cabletwitch]

After a bit more inspection, checking as much of the ECU as is visible and giving all the plugs a good wiggle, I'm happy that's all fine on the physical side of things. Taking the neg off the battery for a few hours (partly for good luck, partly because I forgot I did it) didn't seem to do much... while the idle was fine after putting it back in again, the moment I moved the car a little to get it back off the driveway, she started thudding and being erratic again. This time, I'm wondering if it could be the throttle position sensor, as if that doesn't move, everything stays fine. I'll need to run longer on idle and see if that's the case, but I figure something isn't quite reporting the plate position correctly, and the engine isn't scaling back on the fuel being administered. Besides, I'm starting to run out of theories at this point, and at 7 quid on ebay, it's not going to break the bank to get one and change it.

I get the impression this post is starting to span both mechanical and the electrical section now, with a good dose of fuel systems thrown in. I'm going to need my own section just for me and my godawful bad luck after this, I think...

As usual, I'll report back once I have any results!

Oh yeah, I forgot to ask... where the water temp sensor joins the loom, there is another wire that buggers off down beside (and in my case, probably inside) the timing belt case... I'm guessing this is the oil temp sensor, right? Could that possible have any effect on the running of the car... would it use that over the water temp to assess the engine state when warmed up?

[Robsey]

Are you sure it isn't the wire that runs down the back of the engine to the oil light pressure switch?
(SIngle wire).

If you have a thick wire with a black insulation that runs into the timing belt cover pastics, this should be the multi wire cable for the crank angle sensor.

Any faults with this will put the engine fault light on.
Invariably it will either not run at all or you may get an intermittent mis-fire.
As it does not do anything until you "blip the gas", I am pretty sure the crank angle sensor is not your fault.

Neither is the oil pressure switch.
Any problems with this will only put the oil can light on.

[Cabletwitch]

Yeah, sounds like it's the crank sensor wiring bundle, multiple wires in a sheath. Oil pressure is fine, is there no oil temperature sensor though? Or is that present only on other models, I'm sure I saw something along these lines when looking through the Bog Book of Lies. I'll double check and have a think, although I'm kinda hoping it's this bloody throttle pot that's playing up. I'm going to guess the ECU uses whatever it finds at startup to calibrate the 'closed' position, then as you open it up, it uses the increase in proportion to a lookup table and does it's voodoo magic with that in regards to fuel in. If mine is somehow not dropping back to zero, then it'd continue to put more fuel in than needed, and thus causing the over-rich mixture and misfires... Is my guess anyway.

We shall see. Why can't anyone own one of these things near me, so I can swap parts to check?!

[Robsey]

Oil temperature sensors were not used on Cavalier engines.
Just oil pressure on all engines.
And oil level on 16 valve sumps.

Hmm - we shall see what effect changing the throttle position sender has.
At £7 it is probably the cheapest thing you could replace.

[James McGrath]

And oil level on 16 valve sumps.

It was part of the check control system package.
So GSi, Turbo, C20XE and X20XEV SRi and X20XEV and C25XE CDX.
So not all 16v Cavs had it but it was only fitted to 16v 2.0 or V6 models.

[Cabletwitch]

Well...

I got back from being out and about, and some thoughts had crossed my mind, some lingering from a suggestion my tame mechanic friend had told me to try, so I figured I'd give them a try while I still had daylight. First up was taking the servo vac line off the intake manifold, and covering the hole to see what happens... apparently some interesting noises and no good results. That was replaced, and I made a point to check for any hoses leaking (again), and any intake leaks. Seeing as I'd tried taking the filter out of the system to improve air intake for the duration, I held my hand close to the angled hose and found there was much less air passing my hand than expected.

Poking my fingers down the hose, again I was surprised at how little air was apparently being drawn in... not a good sign. So mostly for giggles and maybe a little hope at finding an issue, I covered the end of the hose with my palm and waited to see if the engine would choke and stop.

It did not.

So, SOMEWHERE is a rather nice hole letting air into the system after the map sensor port, thus dropping the pressure and causing my ECU to go a bit cuckoobananas. It was certainly a novel thing to watch the air feed pipe concertina up as much as it'd go and still have the engine running on as if nothing happened. There was a substantial vacuum present in the pipe when this happened, so it was still drawing from that side, but weirdly, no hissing or other noises which would indicate any induction leakage further down the system.

I'm kinda baffled at this. It's a pretty short route for the air once it's in the intake pipe... through the injector, past the throttle plate, then into the manifold and then the engine. A couple of joints, yes, but I can't for the love of me figure out where it would be... I wonder if the top hat seal is a bit leaky, I'll have to bung some gasket crap on it and see if that solves it somehow. I can do that while I'm at work or something. Otherwise, it's going to be a disassembly job on the throttle and manifold to find out where the sodding thing is leaking from.

Any obvious places to check first, lads?

[Cabletwitch]

Anyone perchance have a photo or able to get photos of a C18NZ intake manifold? Trying to do some research as to where it could be leaking, but weirdly, the internet isn't very helpful on this part.

Anything helps, cheers!

[Steven715]

What I would try is with the engine running use a propane touch without it being lit and put it near the vacuum hoses especially near any bends or where the vacuum hose terminates, your looking for a change in engine note this would indicate that there is a vacuum leak of some kind I hope this makes sense. You can also check where the air intake if you have an airflow meter any air or vacuum leak wouldn't be accounted for by the ecu and the engine will be running lean.

[Robsey]

On the C18NZ, the main source of air leaks is the vacuum hoses.
There are loads - some hidden.

General list is as follows: -
Carbon cannister to tank vent valve.
A blue plastic hose on the bulk head from the drivers front wing (above the arch liner) to about 2/3 the way across.
It will meet a funny round disc thing. This is your vent valve.

My memory gets blurry from here but -
I think there are two pipes from here.
One links further across the bulk head to the MAP sensor. (Manifold Absolute Pressure).
This is normally hiding behind the thin black plastic scuttle panel cover.

There should be one hose from either the vent valve or the MAP sensor to the throttle body.

Okay - there is a fine red tube from the air filter intake control flap across to the back of the throttle body.

Then next to this pipe on the throttle body should be another that which goes to the egr valve - I think. (It has been a few years)

The only other vacuum pipe I can think of is the big fat black pipe for the brake servo from the top of the intake manifold.

If you are thinking of a vacuum pipe pressure error, then this can only be from the MAP sensor, but I am sure that when mine went, I got the MIL light and a code 1-5.

The top hat should not make a difference as the car will run happily with this removed.
Just like a carb engine one.

In all honesty the Rochester Multec throttle body is just an electronically controlled / glorified carburetor.

[Cabletwitch]

That's the thing... no warning light, and given the engine can draw in enough air when I block off the main intake with my hand (palm across it) to continue idling. So that to me means more of a problem possibly just below the throttle body. If it were drawing from say the brake servo pipe, then only one cylinder would get that air, and the whole thing would stop. Same with any of the other hoses, they're just not big enough to pass enough air to run the engine. The only thing I can think of is either the rubber seal on the hat has stopped being effective, or there is a gasket leak below the throttle body itself.

I would imagine the mech used a new intake manifold gasket when putting her all back together, so the only real thing to my mind is in the throttle section. I may be utterly wrong, but everything seems to make sense when you consider it.

I can try and replace all the hoses, anyone got the inner diameter of the pipe itself so I can do so?

[cavalier1990]

Is there anyway of posting a video of this running problem that would help a lot? The intake on the 1.8 is not really dependent on the airflow through the intake pipe as much as say the 2.0 inj, pull the intake pipe off the 2.0 and it cuts out, the 1.8 you can lift the "hat" right off the carb and it will run as it done before.

Have you pulled a plug to see what colour it is?

Have you checked for fault codes using the paperclip test?

Here's some pics of my engine if it helps:

[Cabletwitch]

Soooo... I may have neglected to check something while I was looking at damn near everything else...

this morning, not 5 minutes ago, I was trying to discover the source of the air leak still. I had the bright idea of covering the air intake as before, and listening for any hissing. And boy, did I find some. Turns out that the hose to the MAP sensor had indeed split, and was causing the pressure drop itself. Also, it proved I'm an idiot, because for some demented reason I thought the MAP feed was before the throttle, not after. So, aside from finding the damned issue, I've learned a very valuable lesson - Don't try and do any of this work in the dark, because you'll miss everything.

I cut the end off the hose, refitted, and everything seems a lot better, albeit not perfect yet. I think the entire hose is a bit leaky, so I'll be sourcing some later today with luck (why is there NO mention anywhere of the inner bore sizes of these hoses? WHY?). I tried a couple of other things too... I noticed the seal on the top hat was indeed a little crap on one side, either overcompressed or just worn, so with the aid of an old bootlace inner, I was able to pad it out a little and get a better seal. I'll let you know how that goes. Also, the throttle cable itself seems to have a clip on it that allows for manual idle RPM adjustment, so I opened that up some to allow for a slightly higher idle RPM in either case. So far, so good.

So, after having replaced nigh on all the sensors, undone and redone just about everything that has a hose (except the knackered end of the MAP line, evidently) and invented several new and interesting swearwords, I think I've finally cracked it. Or just cracked up, whichever is the most likely.

I'll keep an eye on things for a while and let you guys know if it's worked, but fingers crossed this is it! Learning some very valuable things doing all this, chief of which is "Hoses are your worst enemy..."

[Robsey]

Don't beat yourself up over it.
All car owners have moments where they do not see the obvious.
Sometimes even when nudged in the right direction.

It happens to us all.
Those who say it didn't happen to them, have obviously not yet found the bonnet release lever.

Hopefully it is all good then - yayy

[Cabletwitch]

I'm starting to think I shouldn't have been allowed to find the release lever! Not yet been able to change the pipe on it, and the only hose I can get locally right now is fuel hose with a 4mm diameter, but that should work with some luck.

If I don't get it sorted between now and Saturday, it'll be done over the weekend. One thing I have noticed when sorting the pipe to its semi-knackered state is that I have a strange smell coming from the exhaust... smells not great, like something is burning or melting, but from the exhaust gas itself. Plus, it does seem a little more visible on cold days than usual, but could just be me being a bit assumptive. No water loss, so can't be drinking coolant at least. It could just be residual crap from the pipe burning off, but I'm not sure. I did whack the bottom of the car on a verge the other day when I slid off the road (not fun, do not recommend), so could be the centre box finally doing stupid things. I'll get that changed once the misfiring is cured properly though.

So yes, hopefully all will be well, and I can finally breath a sigh of relief... and then move onto the next issue!

[Cabletwitch]

Nope, pipe change did nothing much, still misfires and causes issues. However, I have been thinking of other causes, and I've only just thought it could be the injector itself. I'm going to consider a few other things first however, such as replacing all the pipes with new stuff to see if that has any effect (plus it's vastly cheaper). My other though was a leaking brake servo, but I haven't noticed the pedal getting harder, almost the opposite. Other than that, I've still got the option of taking the throttle body apart and finding this damnable leak (assuming the pipes aren't the culprit here).

I'm going gently mental trying to figure this out, but learning a LOT on the way to insanity...

[Robsey]

You could send your injector away for servicing.

A new one from genuine parts (GPS) is £107.
Ouch.

If the servo vacuum pipe was leaking, the pedal won't feel any different, but it will take a lot more effort to stop the car.

[cavalier1990]

Just a thought, the EGR valve perhaps? It's the UFO looking thing in the middle between carb and rocker cover with a vac pipe on it. Also see if you can get a video up of it running at tickover, and a wee rev up that would help a lot.

[Cabletwitch]

The EGR is a recurring thing on this car, so it could very well be part of the issue, but mostly that was down to a leaky gasket which has since been replaced. Tempted to get or make a blanking cap for the port anyway, to rule it out completely however. The brake servo however... I have noticed the brakes being a bit lacklustre recently. And given that's also a fairly big pipe to draw air through, and enough to make at least one cylinder lean enough on idle to misfire on idle...

At the risk of going cross-thread here, what other brake servo units will fit a Cav? I know MK3 and Vectra A units will, but will any of the other GM famil units drop in and work also? I just fancy putting the newest unit I can in there to ensure it's not going to be an issue in the future, mainly.

[cavalier1990]

Well, bugger me... I think I found the culprit. I removed the ICV to check it over, figured an inspection wouldn't go amiss on it before I did anything else... and found the plunger was seized rock solid. No movement, nothing. Given the Haynes Big Book of Lies said you may need to depress the plunger on a new unit if it sticks out too far, it's apparent that this one is NFG. After a gentle bit of persuasion on the kerb (no hammering, just a gentle push from the back of it) the plunger freed up by about 2-3mm, nothing more. The net result of that seems top be that the engine fires up at a higher RPM than before, but settles down to about where it should, at least within 2-3 seconds of start. I've yet to take it out on a trip to check if it's settled after a decent drive, but I suspect it'll still misfire due to an overly rich mixture, maybe a little less than before. So, going to order that one of Ebay, and see where that gets me!

Checked mine, it was seized solid, I got it to move - a bit - but was very stiff. Had to use a pair of pliers to pull it in and out, it seemed to free off a bit then seize up. Maybe dirt floating about in it. I freaked out at first because when I took the thing out I seen the little spring and thought ok well obviously this thing moves in and out and there is a tapered end on it like a big needle. So I pulled on it and it moved out but would not budge back in and with it being stuck out it wouldn't seat back in home. As I said I got it moving again but was very stiff.

After a bit of loose oil and copious plier related to and fro's I decide it really wasn't wanting to get much looser so refitted it and then moment of truth, started it and it cut out instantly. Tried again, cut out, tried again, cut out. So decided to hold the revs for a bit, let it go, cut out. thought oh flip done something to this. Tried again holding revs for a couple of mins, it then ticked over at 500 rpm. Eventually it seemed to clear itself, and honestly after doing my usual rounds to my maw and paws etc. it seemed a bit smoother and the idle a bit better.

I think though it would be worth changing it as I don't think it is working as intended. Still very stiff to move.

[Cabletwitch]

It's much cheaper to get a blanking plate and remove the EGR altogether, to be honest. It seems (from various sources I've looked at on t'internets) that doing so actually helps a lot with emissions and the like, so quite why they're actually6 a thing escapes me for the time being. I might even look into making one from a thick bit of alu and whatever tools we have in the workshop at work. But I do suspect it's something more than that, not even my catastrophe of an engine could run itself from its own exhaust fumes in lieu of an air supply... surely? XD

[cavalier1990]

The EGR is a recurring thing on this car, so it could very well be part of the issue, but mostly that was down to a leaky gasket which has since been replaced. Tempted to get or make a blanking cap for the port anyway, to rule it out completely however. The brake servo however... I have noticed the brakes being a bit lacklustre recently. And given that's also a fairly big pipe to draw air through, and enough to make at least one cylinder lean enough on idle to misfire on idle...

At the risk of going cross-thread here, what other brake servo units will fit a Cav? I know MK3 and Vectra A units will, but will any of the other GM famil units drop in and work also? I just fancy putting the newest unit I can in there to ensure it's not going to be an issue in the future, mainly.

I think cavalier servo fits calibra, and variants of the Astra. There are a lot of different ones for the cavalier alone and you'd need to cross check your own part number, if you can find it, with the ecat24.com site what other model it fits. You can easily test the servo by pumping the pedal up with the engine off then hold your brake pedal down and start the engine. You should feel the pedal sink slightly as servo assistance is applied from the engine vacuum. You can also test if it is leaking by popping the pipe at servo, block it tightly with some sort of tape or bung (it's a strong suction so make sure it is very secure) then run the engine see if it makes any difference. Remember if you drive it you will have no servo assistance and will need to apply a lot more force to stop.

With the EGR you can actually put your finger up under it and press up the diaphragm. If you do this you will hear the engine change tune, this is due to it being activated when not required. I'm not 100% sure when it activates but would imagine some sort of running condition sensed by ECU.

Maybe robsey knows a bit more about the operation of this on the cav?

[Cabletwitch]

Well, I managed to break my purge valve when trying to replace the hoses, two of the barbs have come off completely... If I connect the vac line from the servo pipe to the one going to the throttle body, will things will work for now, albeit with no canister purging for a while? And does anywhere still do them, can't seem to find any on Ebay. If anyone has any help here, it would be very much appreciated, or else I'm stuck taking the train for the next however long!

Edit: I find the engine improves some when I block that little line from the one-way valve on the servo line... maybe it was sucking too much via the canister? I can induced immediate misfires by leaving it open, and very smooth running when blocked. I'm guessing the purge line isn't required for normal running, but I need to be 100% certain before I block anything off and use the car.

As before, any help is good right now, sooner the better! Cheers!

Edit 2: I figure if I just attack the purge line to the line into the throttle body, that should be enough. It'll be open all the time, but better than just venting directly to the engine bay. And I'll block the vac line from the servo hose off, and see how that goes.

[cavalier1990]

I suppose the best thing to do is try and see how it goes. I've never switched pipes around like that but just remember the throttle body and engine create the vacuum so it might be better to just block off the canister feed just now. The purge valve you broke are you talking about the 3 way valve on the servo pipe? Pics might help in a case like this to explain what you are doing.