340 1.4 rough ans slow idling

[Two340'sman]

Originally Posted by Laird Scooby

Gap is about right (from what i remember of them) but the important bit is what brand plugs are you using?

Also if the insulators have brown rings on, there is "blow-by" past the insulator. Sooner or later this will cause tracking on the outside of the plug and when the pugs get warm, a slight leak so will help to cause a misfire.

I'm thinking if one or two plugs are just slightly misfiring, this will cause the black smoke as it will be unburned fuel in the exhaust that burns once the others fire normally. It will also make the others run slightly richer so again, extra fuel going in.

I would use NGK, Denso or Bosch in that order of preference. Also bear in mind that new plugs are generally (certainly NGK) are set by default to 0.9mm or 0.036" so will need closing up slightly before use.

The plugs that were in were NGK, looked black (rich) when I took them out just now. The insulators were fine, no evidence of blow past.

I just fitted a set of new NGK ZGR5B plugs, initially good tickover, then the trouble started again.

This is a terrible video, but may show something. The squeak is the fan belt.

https://youtu.be/6Fsk70QQZr4

Turning off the engine and restarting can sometimes clear the bad idle.

[Laird Scooby]

Listening to that it sounds like it's not the fan belt, more the alternator bearings are going. Does the increased squeal accompany the rough running?

[Two340'sman]

Well!

About 5 years ago I set up my carburettor idle CO using my Gunsons gas tester. Each year before the MOT I checked it and it was always fine.

Last year I could not test the CO before the MOT as I damaged my meter by stupidly connecting it up backwards. The car passed fine.

So this year before the MOT I was reluctant to touch the mixture control.

However, seeing the plugs that came out today being black after bad idling, I thought I'd screw the mixture control in and out a bit. I then adjusted it to get the fastest smooth idle. Then set the idle screw to give about 900 RPM.

The car seemed to idle quite nicely.

I then decided to refit the original Renix unit and test car again. All seems OK at the moment. But I need a good run to check it properly.

Perhaps I dislodged some grot when moving the mixture screw?

Anyway, it seems that the 360 Renix unit will work on a 1,4 and 1,7 340!

Next few days I'll test the car out further, then I need to look into repairing a Gunson gas tester so that I can set the CO more accurately.

[Two340'sman]

Originally Posted by Laird Scooby

Listening to that it sounds like it's not the fan belt, more the alternator bearings are going. Does the increased squeal accompany the rough running?

The recording makes stuff sound different, it's the belt, when I put water or a bit of silicone on it, it stops. I have a new one. I have a spare new alternator too. Squeak nothing to do with rough running.

The electric fan cut on during the video, this sounds completely different to live!

Next time I'll put my listening stick on the alternator, just to be sure!

[Laird Scooby]

Originally Posted by Two340'sman

The recording makes stuff sound different, it's the belt, when I put water or a bit of silicone on it, it stops. I have a new one. I have a spare new alternator too. Squeak nothing to do with rough running.

Next time I'll put my listening stick on the alternator, just to be sure!

If the bearings are beginning to bind in the alternator then it could put extra load on the engine which would cause rough running. Also alternator belts usually go quiet by themselves once the battery has recovered from starting, it's rare the squeal is more or less permanent unless there's an underlying problem.

I have a rumbly bearing on the A/C compressor clutch on my other beast, most of the time it's just noisy but occasionally it sticks a bit and makes the engine grunt a fair bit, knocking a big hole in the performance. Sometimes on idle it can almost stall it if the compressor kicks in.

I have a bearing but crawling under with the front wheels on ramps, dropping the compressor and then pulling the pulley off to replace the bearing doesn't sound very appealing at the moment, especially with how wet it's been! Daresay it'll keep going a while longer!

[Two340'sman]

Very light rain only for a few min today, nice and sunny. London.

Possibly I'll do another recording, saying that it will probably rain!

Never owned a car with air con!

[Laird Scooby]

Originally Posted by Two340'sman

Very light rain only for a few min today, nice and sunny. London.

Possibly I'll do another recording, saying that it will probably rain!

Never owned a car with air con!

Aside from the 3-week "heatwave" recently and a few sparsely scattered warm dry days, it's been 10 months solid of cold and/or wet weather here.

Even on most of those dry days, it was threatening rain all day so very little has been done this past couple of years or more.

[Two340'sman]

I love work, I can watch it for hours.

[Two340'sman]

So far, fiddling with the idle mixture screw seems to have done the trick. I need to test on a good run tomorrow, but I'm very hopeful.

Another vid of the engine ticking over, in real life it's much quieter than this, not so tappety. I checked the alternator and water pump bearings for noise and they are OK.

Found my analogue Gunsons gas tester, took it apart, say no obvious faults, cleaned the zero adjust pot with Servisol, connected up power and nedle goes full scale, no adjustment possible. Tomorrow, my friend is bringing his faulty one, I'll look at that too.

https://youtu.be/mtl2ETfI07g

Once again, many thanks to all that have contributed ideas. This is a fantastic site.

[Laird Scooby]

Originally Posted by Two340'sman

Found my analogue Gunsons gas tester, took it apart, say no obvious faults, cleaned the zero adjust pot with Servisol, connected up power and nedle goes full scale, no adjustment possible. Tomorrow, my friend is bringing his faulty one, I'll look at that too.

You didn't have the switch in the "Test" position did you? That makes the meter go FSD with no adjustment. On mine, there is a spot on one end of the switch, if this end of the switch is down, it's in Test mode. Try moving the switch a few times and see what happens.