Poor running on a DX engine - help.

It was pinking horribly when it was on TDC, regardless of the fuel I tried, so this seems better. I'm quite happy to keep filling it with premium!

rubjonny said

But it might be a bit coked up, as you run it now its setup better the carbon gradually burning it off hence the pinking getting better. a way to speed up the process is get the engine to suck in a little water, steam cleans the bores. its tricky to do on a kjet though, for a carb you would just trickle water in the choke flap

one way is pop a vacuum hose to the throttle body off and submerge it in water, give it some revs and it'll gradually drink it all up pull the hose out if the engien starts to bog, hold the revs till it clears then put it back in the water. half a litre should be more than enough!

So I let it slurp up about pint or so of water this evening then took it for a quick drive. It does seem to be getting better. I think having the timing put to 6 BTDC and giving it a shot of the Redex cleaner has sorted it. Very pleased about that.

But, as always, with one problem sorted another one crops up: the clutch cable has ripped the bulkhead!!

ah that old chestnut, i think the patch panels are still available

I've ordered a patch. Does it just stick on, or is anything else required? I was shocked that it'd torn the bulkhead!

The clutch was adjusted recently as it was really stiff. I wonder if it might be worth replacing it and the cable at the same time.

they just stick on, some have bought 2 and stuck both sides of the bulkhead for extra strength

rubjonny said

they just stick on, some have bought 2 and stuck both sides of the bulkhead for extra strength

Yes, I ordered one and figured it out. Thank you. I got it sorted last week – the clutch was worn, so the adjustment to the cable must've increased the pressure on the bulkhead. Very annoying, really, as the guy in the garage has worked on VWs for 40 years so knew the cables pulled through the bulkhead before he fiddled with it. So, now I have a new cable, clutch, and patch. And a new friendly old school mechanic.

Anyway, now I just need to stop it pinking.

Deandubya said

TeeTee said

rubjonny said

they just stick on, some have bought 2 and stuck both sides of the bulkhead for extra strength

Yes, I ordered one and figured it out. Thank you. I got it sorted last week â€" the clutch was worn, so the adjustment to the cable must've increased the pressure on the bulkhead. Very annoying, really, as the guy in the garage has worked on VWs for 40 years so knew the cables pulled through the bulkhead before he fiddled with it. So, now I have a new cable, clutch, and patch. And a new friendly old school mechanic.

Anyway, now I just need to stop it pinking.

From “Poor running on a DX engine - help.”

hi mate, glad things are moving forward, have you checked your fuel pressure or thought about having a tune? 2 issues I had done, after various other stuff & it now runs sweet… 

No, haven't checked the fuel pressure. It takes a while to come through when first starting, so maybe it's lower than it ought to be?

At the moment I'm focussing on giving it an Italian tune-up to see if that does it any good. I plan to give it blast from London up to Yorkshire in the next couple of weeks. After that, yeah, I've found a place that I could take it for a proper tune. I imagine it'd benefit from it. As far as I know, the car has spent the last 26 years pootling about on local journeys.

Right, I thought I should update this…

To recap:
The timing is now set to 6 BTDC
The old distributor cap, arm, leads, and plugs have all been replaced with Bosch or NGK items
I have run a bottle of Redex Advanced Fuel System Cleaner through the system, and on another tank a bottle of Wynn's Xtreme Petrol System Clean (snake oil…?)
I have done the water trick on three separate occasions
I have been using Shell V-Power Nitro Plus and on the latest tank BP Ultimate petrol.


I have been trying to drive the car hard, but as I live in the middle of London that isn't easy - there are 20mph limits pretty much everywhere. I've had a couple of seaside jaunts where I've tried to give it a bit of a blast. But, over the weekend I drove 600 miles - 250 miles in one journey, 100 in another, and 250 in the last one. A lot of that was at high speed on motorways, some of it was B road blasting. I tried as best I could to redline it and use the full rev range, although I drew the line at holding it at 70mph in 3rd on the motorway. I was watching the oil temp on the MFA, trying to get it up.


And…

The car is much livelier than when I got it. The acceleration seems keener and it just seems more willing to go. The hesitation it had when I got it has pretty much disappeared. But, the engine still makes a rattly thrum on acceleration. It's almost like the noise you'd get when you stuck a card in your spokes on your bike to make it sound like a motorbike when you were younger. It does seem to be getting a bit better, but it's definitely still there. I'm beginning to wonder if it will ever stop.

The car had one owner before me, a middle aged lady who had it from new. She used it as a local runabout. I met her and she didn't seem like the sort of person who'd have thrashed a car, ever. Her husband picked me up in the car when I collected it, and on the drive from the station to their house seemed to have it in 4th or 5th at 30-40mph. My guess is that it's had 26 years of being driven like that. Also, when I got it the car did not have a thermostat fitted. I assume that as a result of all this the engine will be coked up.

So, I guess my question is: how long til the engine stops pinking (if that is what's happening)? Cabby Info (Engine) suggests running it on premium fuel for 6 months. I've had the car for just over 2. Is it possible that serious damage has been caused by all the gentle driving?

Any further suggestions? Or should I just carry on doing what I've been doing?

Thanks for your help.

  

maybe take out all the plugs, and turn the engine over slowly while you shine a torch down each cylinder to see if the pistons are very badly coked up still.

The noise you describe doesn't quite sound like pinking to me, possibly now you just have a mechanical rattle which needs hunting out, perhaps a worn timing belt tensioner or bad bearings in waterpump/alternator. Take off the wateprump belt and rotate/wiggle the alt and waterpump pulleys, see if either feel dry, rough or have excessive play. take the timing belt cover off and look at it for signs aof rubbing from either belt, look at the tensioner see if it looks old and corroded, check the lower plastic cover and inner metal part bolted to the side of the waterpump closely as well

OK - I'll investigate.

The timing belt and tensioner were replaced with INA items at the end of May, so it shouldn't be them.

There is a constant high pitched scream/whine when the engine's running though - it's a lot noisier than the PB in my mk2. I thought that maybe that was the alternator. It get worse the greater the load on the engine, so at high revs it's very loud. That's in addition to the rapid rat-a-tat I get when I accelerate.

Update:

I took it to an old school garage (the owner says he once had a mk1 GTI) to take a look. They observed that it was pinking badly at 6 BTDC so they set the timing using a timing gun (for the first time in 10 years, he reckoned) at 5.5 BTDC. That stopped the pinking. Any more than that and he said it'd sap the power.

I took it for a drive to Southend and back yesterday. Very hot weather, a mix of fast motorway, in town, and sitting in traffic. All in all, five hours in the driving seat, 100 miles covered. On the journey there the car behaved nicely - no pinking, decent acceleration. By the time I set off for home, by which time I'd covered about 60 miles, it gradually started pinking again. By the time I got home it was as bad as it was before it went to the garage.

I've just been and asked the garage for advice. He suggested a lead substitute fuel additive. I will try this.

But, I'm beginning to despair. Does this mean the engine is knackered?

you shouldn't need lead substitute, as all the mk1 engines are designed for use with unleaded (vw started doing this in the 70s)

get a compression test done, and get the fuel system double checked. pull the plugs out, see if they all look ok or if some/all are all sooted up perhaps

did they check the CO? 1.5-1.8% works well on a kjet

That's what I thought. My PB-engined mk2 has always run happily on unleaded. And presumably the PB and DX engines are basically the same.

I'll ask them to do a compression test and check the fuel system - that needs doing anyway as it started reeking of petrol yesterday. The CO will have been checked for the MOT recently, but no idea what it came out as. I'll ask for that to be looked at too.

The thing is, these old boy mechanics really don't like it when their diagnoses are challenged, especially when it's by a geeky looking non-mechanic like me.  I'm out of my depth with this. I just want someone to fix it for me!
 

well I wouldn't say challenge, but mention the reeking of petrol and see if they can check the co is around 1.5%

it may be the mixture is very lean, if you go too fasr you get a load of unburnt hydrocarbons out the back making it smell rich, when its the opposite. this is what my digifant was like when the co was around 0.2%…

Ha! Good thinking.

The petrol smell was most noticeable when it was sitting in traffic, I guess because when it was moving it wafted away. I had a look under the bonnet and underneath but couldn't see anything obvious. It was very strong though, much more than I'd expect.  

Here's another thought: could a vacuum leak make it pink?

I've not yet checked the seals on the injectors, so I guess it's possible that it could be sucking air in that way, which I guess would make it run leaner… right?

yeah any air leak will lean out the mixture, easy test just spray carb cleaner or similar around various points in the engien if the idle changes you have found an air leak

Update:

The CO has been checked… and is at 0.5%. The adjuster screw was stuck though, so it's been soaking in penetrating fluid. Hopefully we'll have the level up to 1.5-1.8% by the end of today.

The guy at the garage had already checked the injector seals with the spray test and thought they were OK, so hopefully that's that ruled out.

Right, time for an update on this.

We eventually decided the "dug-a-dug-a-dug-a" noise on acceleration must be coming from a cracked exhaust manifold or a dodgy gasket either between the manifold and the engine or between the manifold and the downpipe. According to the maintenance history paperwork, the manifold had warped and been skimmed at some point in the past. So, for good measure, we replaced the manifold and all the gaskets (all like-for-like, no upgrades), which seems to have solved it – the car doesn't sound quite so tractor-y now.

We've also reset the mixture and adjusted the timing to 6 BTDC with a timing light gun. We also replaced the fuel filter. With that done, and the engine warmed up, the flat spot in the pick-up seems to have gone. Correct timing and premium petrol seems to have stopped the pinking.

Hooray!


But… we've a strong suspicion the fuel pump is on the way out. When we moved it out of the garage last night the car was running fine and then, all of a sudden, just died. The pump was wheezing away, but the engine just wouldn't start – like it wasn't getting any fuel. We left it overnight and for whatever reason it started fine in the morning. I took it for a quick drive and it didn't cut out but the pump is very noisy – a wheezy whine the whole time. So that's due to be replaced with a new Bosch one next week.

check the lift pump in the tank first, if that dies it makes the main pump struggle