AAZ shaking at idle and hard to start

[SDTS]

Hi,

I have an AAZ engine from a Vento in my Golf Mk1. It has been running fine for the last two years, but the last few weeks cold starting has become a problem. I thought it could be a bad glow plug, so last week I changed all four, with no effect at all. Also suddenly the engine has started to shake at idle, this seems to get worse every day, you can feel the whole car shaking, like an engine running on three cilinders, so not the normal diesel vibrations. This goes away at about 1500 rpm, during driving there is nothing wrong, makes good power, and economy isn't bad either.

So now my question is where do I start looking for the problem? Could this have something to do with timing (timed at 0,95mm a year ago), or maybe a bad injector, or anything else?

Dennis

[burn_your_money]

Stop driving it until you verify the cam to crank timing.

[SDTS]

I was afraid of that, the aaz crank key problem. How can I best check this? Would it be enough to place the crank at tdc and check if the cam is still alligned? Or should I take the cam gear off and check the key, with the risk of it working loose in the future, I always thought if I don't mess with the bolt it will hold, since it has been holding for 350.000km.

[burn_your_money]

It is sufficient to just remove the valve cover and verify the cam to crank timing. If it is off then you need to remove the crank gear to see what is going on. Don't assume the last guy just did it wrong.

[SDTS]

Ok, thanks, I will check that tomorrow. I replaced the timing belt myself 50.000km ago, so I am sure it was exactly in time back then. Only the wear of the belt might be causing the cam to be off a little bit, but we'll see tomorrow what it looks like.

[burn_your_money]

I don't really notice these belts wearing, at least not stretching. But based on how bad you are describing it is running, it is probably off a good bit. You can even just check the pump timing and see if that has drifted from the crank timing. That way you don't have to remove the valve cover. You must use a dial indicator to do this and also must know exactly what it was set to initially.

[Mark(The Miser)UK]

Prioritize checking cam to crank positions. If they are not within half a flywheel tooth then something has moved. The cams do have some operational leaway, but unless you deliberately introduced it, something has moved.

If timing is fine, do not mess with the crank pulley.It doesn't last for 350000 km when faulty. But do check it...
 
I suspect an injector nozzle. Could be wear, or over tightening to suppress diesel leaks

Any difference between cold and fully warmed up?

[SDTS]

Maybe checking the timing is the easiest way, then I will do that first.

The shaking is only there at idle, up to about 1500 rpm. It seems like it gets worse when the engine is warm, but it is there both warm and cold. The whole car shakes, the engine can be seen shaking as well, but sounds normal, so i think it isn't running on three cylinders. Also the engine feels the same as it always did, enough power, not running rough or more smoke than usual.

Could a bad injector explain the hard starting? It only starts with the cold start lever in, throttle floored and glowing twice, and it isn't even below freezing here. Up until a few weeks ago it always started at the first try, with the cold start lever pulled out and not touching the throttle.

[Mark(The Miser)UK]

Always hard to put your finger on the problem, but you can often get near.

 If your cam/crank timing is good, then at least you can be pretty sure that you are fairly safe in driving carefully until problem sorted.
A car would start a lot easier with a bad injector removed, rather than it being in, but clearly you can't run like that.
Have you run any veggy oil?
Some vibration can develop from moved engine mountings, but it clearly doesn't make starting hard.
Compression can't drop over mere weeks from wear, but I guess worn rings could suddenly stick in.
When running rough what comes out of the exhaust?
I still think it's injector issue. Do you have a spare set?
An injector tester would be nice.
They are always resaleable when no-longer needed...

[SDTS]

I just made a timing tool and checked the timing, and it is exactly at 0,95mm so I think I'm lucky and the crankshaft gear is fine.

So now it looks like the problem is in the injectors. Would there be any way to verify this? I have a pop tester at work, but I don't know if this will work since the AAZ has two stage injectors.

I also have saved the injectors and fuel lines from the 1,6D CR that was previously in the car. Would these work in an AAZ? The engine runs on 0,7 bar boost (part time turbo) and has a modified LDA, for the rest it is completely stock.

[vanbcguy]

A pop tester will be able to show you spray pattern with 2-stage injectors, but it won't help you set the individual pressures.  You will be able to compare injectors to one another though; they should all behave identically even if you can't "set" them.

[Mark(The Miser)UK]

Indeed comparison between injectors is the easiest option with these experimental injectors...
 
Compare timed leak downs, general spray pattern, and low speed pop pressure.

There are more Urban Legends about these dual spring injectors than different story lines in Mr Stein's Goosebumps books...

[SDTS]

OK, thanks, I will try that.

Has anybody ever tried running 1,6D injectors in an AAZ? Looks like they are shorter, so with the 1,6 fuel lines they should fit. Only mayor difference I see is that the #2 injection line runs different, so it could interfere with the lda, but I'm not sure on this. Also maybe the different block height might be a problem?

If they fit I can temporarily run the 1,6 injectors and have the 1,9 injectors rebuilt, or rebuild the 1,6 injectors and just run them if there isn't much difference.

[Mark(The Miser)UK]

I think to get 1.6 lines and 1.6 injectors to fit you need the shorter 1.6 delivery valves. I think all 1.9 except 1.6 injectors might cope with the block height difference. If I remember correctly, standard nozzles can be substituted inside the AAZ bodies, but that doesn't help you send them off for testing. [Or were you going to test them your self at work?]
In about an hour you could take them out test them at work, reset the  shields using my well known technique, and reinstall them.
You would then know if one was faulty.
If it was, then you could then strip that injector down later... Take you 1.6 injectors to work and test them. They tend to get sticky when left unused. But if good may serve to use the nozzles in the AAZ ones. 350,000 may be close to having wear defects in the nozzles