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2.1 DJ engine timing

PostPosted: 25 Feb 2020, 10:29
by scotttie
Hi all,

Firstly, apologies, I know this topic has been covered a lot and is in the wiki.... But I wanted to get some advise before I potentially damage my engine.

So I'm off on a trip around Europe in 2 weeks and I wanted to make sure my engine was timed to 5 degrees instead of 10 because 95 unleaded is more common across the pond. I followed the process described on the wiki by letting the engine get up to temp, turning it off, unplugging the two connections to the idle stabiliser and connecting together, disconnecting the yellow connection (green wires) in front of the idle stabiliser and removing/plugging the 2 vacuum hoses to the distributor.

When starting the engine back up, the rpm is quite high (around 1600 rpm). Obviously I can't check/change the timing at this rpm, so question is do I adjust the screw on the AFM to bring the rpm down to do the timing? My concern with doing this is that by turning this screw am I also changing the fuel/air mixture? Alternatively, if the rpm is this high, should I be looking for other potential causes before masking the problem with the AFM screw?

I maybe being overly cautious but best to be safe than sorry!


Re: 2.1 DJ engine timing

PostPosted: 26 Feb 2020, 19:03
by Mr Bean
Well I put off responding to this post hoping that other would come up with something better but reading it again I believe your concern about the fuel air mixture being affected is groundless. I believe you will find that the AFM will automatically compensate for the additional air admitted. If I am wrong then someone please put me right.
In the meantime however and bearing in mind that the adjuster is simply no more than a tubby flat ended threaded screw with "O" ring seal, and providing that you mark and record it's present position ideally by counting the number of turns and final position when screwed in until it stops, I see no reason why you should't set it to achieve your RPM and return it to it's original position if in doubt.

Re: 2.1 DJ engine timing

PostPosted: 27 Feb 2020, 10:17
by scotttie
Thanks for the reply.

My understanding is that the adjustment screw on the AFM allows for unmetered air to pass as it controls the amount of air bypassing the AFM flap. Therefore allowing more air through will lean the mixture and vice vera. Good idea on marking the position of the screw. Then atleast I can get it back to how it was if it all goes pear-shaped!

So after a bit more investigative work, I have discovered the following:

With engine set up for timing adjustment (dissy vacuums plugged + Idle stabilser bypassed + yellow connection disconnected), if I disconnect the idle control value or squeeze the hose going to the idle control valve the revs drop. So the idle control valve is still having some influence over idle speed. I tried a spare idle control valve and idle control unit (behind offside light cluster) and experienced the same symptoms. If I check the timing with the idle control valve disconnected (revs around 900), the timing is too advanced. Same goes for when the idle control valve is connected (revs around 1500) but slightly more advanced due to increased revs (I guess this is the mechanical advance in the distributor having more influence when rpm is higher). I also checked my throttle body switch which is working correctly. It appears my best option is to leave the AFM screw where it is, and bring down the idle with the throttle body idle adjustment, which will then allow me to adjust timing.

The one thing I don't fully understand is why the idle control valve is having an influence over idle speed for timing set up. I thought by disconnecting the yellow connection, this takes the idle control valve out of the equation. But this does not appear to be the case.

The only other thing worth mentioning is that with everything connected on the engine for normal running. The timing at around 900 rpm idle is around 6.5-7 degrees which seems to be about right with the vacuum advance of the distributor advancing the timing slightly.

Re: 2.1 DJ engine timing

PostPosted: 01 Mar 2020, 07:26
by scotttie
So another thought: for setting up timing, following the procedure described in haynes where it comes to "disconnect vacuum hose(s)", if i don't disconnect the vacuum retard hose then everything is pretty much spot on for idle speed and timing....

I was speaking to a garage about our daily driver (someone stole the catalytic converter...) and I asked them to check what timing procedure they have on their system for the 2.1 DJ. They checked a database (can't remember what he said it was called) which said to only disconnect the vacuum hose the advance side.

So I am wondering, does the retard vacuum hose need to be disconnected?

Silver lining of this process is I'm gaining some knowledge on how this digijet system works!