Post queries regarding your Mk3 Cavalier's mechanical components (engine, transmission, turbochargers etc.) here
#161938 by Cabletwitch
Mon Mar 27, 2017 12:41 pm
I'm currently in Devon at the moment, sans Cav, but I'll check it out when I get home. I need to look up and learn about a number of parts on the 2.0 that don't exist on the 1.8, and try not to break anything in the meantime.
#162486 by Cabletwitch
Sat May 13, 2017 8:04 pm
AAAAARRRRRRRGH!

So, I got me a nice 2.0i as noted before, and wouldn't you bloody believe it? The damned thing has the same sodding issue, low idle RPM with what sounds like misfires (thudding noise from the exhaust every so often). I've changed the plugs, no dice. Cleaned out the ICV, nada. Today was spent changing all but the manifold and the downpipe on the exhaust (I did the gaskets though), and still nothing. The 1.8 has this issue, even with a new O2 sensor, so I'm almost reluctant to change it.

The one thought that springs to mind is that of injectors. I don't know if either is overfuelling, but at the price that most injectors go for, I'm again reluctant to swap those out. It's just the idle, fer chrissakes... drops almost as low as 500 on the 2.0i, and it's really doing my head in now...

Also, I don;t rate EuroFlo exhausts... I can put my hand over the end of the pipe now and watch it blow condensation though the seams of the middle and back boxes...
#162526 by cavalier1990
Tue May 16, 2017 9:39 am
Cabletwitch wrote:AAAAARRRRRRRGH!

So, I got me a nice 2.0i as noted before, and wouldn't you bloody believe it? The damned thing has the same sodding issue, low idle RPM with what sounds like misfires (thudding noise from the exhaust every so often). I've changed the plugs, no dice. Cleaned out the ICV, nada. Today was spent changing all but the manifold and the downpipe on the exhaust (I did the gaskets though), and still nothing. The 1.8 has this issue, even with a new O2 sensor, so I'm almost reluctant to change it.

The one thought that springs to mind is that of injectors. I don't know if either is overfuelling, but at the price that most injectors go for, I'm again reluctant to swap those out. It's just the idle, fer chrissakes... drops almost as low as 500 on the 2.0i, and it's really doing my head in now...

Also, I don;t rate EuroFlo exhausts... I can put my hand over the end of the pipe now and watch it blow condensation though the seams of the middle and back boxes...


Did you swap anything over from the 1.8 to the 2.0, like ignition parts? Can't believe you still got the same problem. What's the 2.0 out of? is it later or earlier model cav?
#162627 by Cabletwitch
Tue May 23, 2017 7:44 pm
No, the two cars are completely separate, it's just the problem is present on them both. The 2.0 is from a MK3 L reg, so post-facelift.

I'm just hoping what eventually fixes one fixes them both...
#162862 by Cabletwitch
Sat Jun 10, 2017 5:34 pm
Well, apart from the exhaust sounding like it's about to shake itself to bits (never cheap out!), nothing has gotten any worse. However, I DID score a nice brand new set of injectors on the Fleabay for 160 notes, MUCH cheaper than retail (yet still from MPD... strange...). I'll be fitting those the weekend after they arrive, and see if that solves anything.

Wish me luck!
#164539 by Cabletwitch
Mon Nov 13, 2017 9:21 am
Right, just a quick one, back in the right thread (maybe, I seem to be in several systems at any one given time). I've tried all sorts... new FPR, new injectors, plugs, CTS, leaning ground straps, etc.

BUT... I recently saw a few videos on how to overhaul and fix the Bosch AFMs that seem to be fitted to just about every car from that era, and one of the symptoms is... yes, you guessed it, crap running at low RPM etc. So this coming weekend, I'm going to open 'er up and have a cleanup to see if that helps. If it does, happy days! If not... well, shouldn't be any worse, right? Just running out of things to mess with now without admitting to myself it's a mechanical issue at the core of the engine, and that would make me very sad...

Also, a new picture to more accurately reflect my ongoing saga with these bastard things...
#164540 by Robsey
Mon Nov 13, 2017 8:44 pm
Have you tried running the car with the AFM disconnected?

The car ECU will use default values to allow the engine to run.
The ECU light will illuminate, but the car should run.

Just as with the ICV, if running with the sensor disconnected appears to be an improvement over with the sensor connected, then it may hint that the disconnected sensor is not working properly.
But don't treat this as a definitive answer - just as an indication.

There are no guarantees with anything Vauxhall related.
#164546 by Cabletwitch
Tue Nov 14, 2017 8:33 am
While I haven't tried it again recently, pulling the AFM out of the loop when running kills the engine, haven't tried running without it disconnected from the start. I'll give that a go and see what happens after work.
#164550 by Cabletwitch
Tue Nov 14, 2017 7:23 pm
I'm wary saying this, but I think we've bloody got it! After a short trip home from work today, just long enough to get the engine warmed and doing the low RPM thing, I parked up, switched off and unplugged the AFM. First restart conked out, but the second ran smoothly, and because I know my base idle RPM has been adjusted upward in the past to try and compensate for this issue, it peaked at 1500 RPM at idle. I shut down and restarted, same thing happened.

SO... I think we're now at the fault, and as such, I'll be removing and cleaning/unsticking/sorting the ARM over the weekend. I've seen a few videos on how to do this, so I'll report back anything I find, and anything I do. If this cures the issue, I'll be so damn happy.

However... this doesn't explain the issue on the 1.8, because it has a MAP sensor instead of the AFM, and I know it's a good one because I replaced it, same issue. I'll have to do more work on that, but as long as the 2.0 works fine, I'm probably going to take parts of the 1.8 and send it to it's final resting place eventually.

We might be done in this bloody saga yet!
#164559 by Robsey
Wed Nov 15, 2017 2:39 am
On the 1.8, the map issues can be just as easily a cracked or leaky vacuum hose.

The 2 litre air flow meter just looks more complicated than it is.
A variable resistor controlled by a moving vane, that can suffer a dirty or worn rub-track.
The hard bit is removing the top cover without injuring yourself or breaking something.
#164596 by Cabletwitch
Sat Nov 18, 2017 11:18 pm
So, I managed to kinda sort the issue somewhat... I got the AFM out of the car and opened up eventually... a lot of cutting silicone seal and trying not to slice up fingers in the process. Eventually though I had it open, and thus the innards were exposed for all to see...

Image


After checking the vane was free moving and fine, and the airways were all clear, I set about going over the internals. The carbon track was somewhat worn, but not too much considering the age of the part. I cleaned up the track and the contacts as best I could (a sheet of paper apparently has enough abrasion to clean them without damage), and pondered how to reseat the contacts onto an unused are of the strip. As it turned out, undoing the three screws holding the PCB to the frame allowd the board to shift ever so slightly, resulting in the needed adjustment. After ensuring the contacts weren't drifting off the track, I did em up, and all seemed well.

Image

I checked the air temp sensor in there too (and stupidly forgot to take a picture, but it's in there) by blowing and huffing on it, and checking the resistance changed properly. All seemed good, so reassembly and testing proved all worked fine. It seems to have given me smoother running of the engine overall, with less misfires, but ultimately they still persist with the low RPM issue, so I can honestly say the AFM isn't the cause. I did remember I hadn't checked the TPS on this car, so a new on is on order and I'm probably going to kick myself hard if that turns out to the cause. Failing that, I've still got the new O2 sensor to fit because lazy and it's been raining, so maybe somewhere in all this mess the cure lies.

We shall see...
#164597 by Cavalier342
Sat Nov 18, 2017 11:34 pm
That looks very technical. Credit to you for digging around, I wouldn't have a clue how to do any of that.
#164598 by Robsey
Sun Nov 19, 2017 2:44 am
Thankfully there are lots of videos on YouTube for stripping and cleaning Bosch air flow meters.
Fitted to lots of cars and camper-vans with Motronic and Jetronic fuel injection systems.

I have done many of the jobs that you have done, or plan to do.
I too still have the low idle when warm.
In my particular situation, I have changed the idle control valve, throttle position sensor, oxygen sensor, octane plug and I have cleaned the ICV twice.
I haven't done the pcb in my air flow meter, but I did clean all the parts exposed to the air flow.

This potentially leaves two further checks.
1 - Engine ECU for having clean contacts and no signs of water damage.
2 - Air leak in the gasket between the throttle body and inlet manifold, and the inlet manifold gasket.

(I have already checked all the ground wires in the injector loom).

Hopefully you are not far from sussing the final culpret in this saga.

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