Emissions corrected with MAF and Dizzy adjust but very lean now

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ashbash2403

ashbash2403

New Member
Posts
79
Location
Walsall area West Midlands
Hi,

Recently had the 3.9 EFI RR fail MOT due to HC and CO emissisons. Took it to a guy who specialises in tuning and he adjusted the Dizzy and MAF in tandem with each other while on the emissions machine... Got it to about 1/2 the limit to pass MOT which was good all in about 30mins.

It now seems to be running very lean i.e. kick plate is more of a gentle toe poke plate... which I expected as the Dizzy was out at 36deg and he brought it back in to 20deg...
I understood these are normally set to 4-5 deg and so there must be some issue with the setup for them to have tweaked it in the first place.

The plan is to take the dizzy out and get it checked etc... or try another one in there.

Would this seem about right ?? need to get my Oomph back !
 
If you remove the dizzy ,BE VERY CAREFUL to align and mark everything before you start !!!they are right beggers to refit without marking first . If the MAF and dizzy needed adjustment , it must have run like a pig before .
 
Just read the post again , I'd get a second opinion from another garage , never mind specialist , some thing isnt right with the way it's been set up . My opinoin , I only worked on them for way too long . From what you say the timing is and was 15 odd degrees out and Maf was out , either he's wrong or there's an under lying fault as well .
 
ashbash2403 said:
Dizzy was out at 36deg and he brought it back in to 20deg...
I understood these are normally set to 4-5 deg and so there must be some issue with the setup for them to have tweaked it in the first place.

The plan is to take the dizzy out and get it checked etc... or try another one in there.
Click to expand...

Timing should be 5 deg +/- 1 deg for catalyst engine. If LPG fitted it would be slightly different, but I would suggest get it right on petrol first then go from there.

I would check that the vac advance is working. Next check/set pick up air gap and check that the centrifugal advance is working - gently try to turn the rotor arm back and fore, you should be able to feel if the weights are moving or if the thing is seized up.

The V8 is surprisingly tolerant on ignition timing but you will really feel a difference when it is right.

Once the ignition is set you need to go back and check the air flow meter - you can do this with a multi meter; check CO trim and air flow signal.

Once you have got it where it needs to be it might be worthwhile removing the plenum and giving it and the ram housing a good clean then check/set the throttle disc.

When you've done all that you should then set your base idle.

That little lot should hopefully result in a sweet running V8.

If you are going to swap the dizzy pay attention to the numbers on the existing unit, whilst any DLM8 will fit, there are different advance curves for different set ups - not hugely significant but worth bearing in mind. Good luck.
 
classic kev said:
Timing should be 5 deg +/- 1 deg for catalyst engine. If LPG fitted it would be slightly different, but I would suggest get it right on petrol first then go from there.

I would check that the vac advance is working. Next check/set pick up air gap and check that the centrifugal advance is working - gently try to turn the rotor arm back and fore, you should be able to feel if the weights are moving or if the thing is seized up.

The V8 is surprisingly tolerant on ignition timing but you will really feel a difference when it is right.

Once the ignition is set you need to go back and check the air flow meter - you can do this with a multi meter; check CO trim and air flow signal.

Once you have got it where it needs to be it might be worthwhile removing the plenum and giving it and the ram housing a good clean then check/set the throttle disc.

When you've done all that you should then set your base idle.

That little lot should hopefully result in a sweet running V8.

If you are going to swap the dizzy pay attention to the numbers on the existing unit, whilst any DLM8 will fit, there are different advance curves for different set ups - not hugely significant but worth bearing in mind. Good luck.
Click to expand...

Thanks for the advice Kev a nice simple basic how to get the V8 setup.
He did mention about the Vac advance may not be working.... It ran rich before running at down about 9-11 MPG and HC emissions was horrific on MOT. I think if the guy had more time he would get it setup quite sweet. He even silicone sealed the MAF adjusted so no one would just tinker with it while we sort it out properly....
 
Dizzy will only be handled by my friend Lincoln who knows what he is doing and rebuilds them for fun (the proper parts for the proper car) as he calls it and its planned to have the heavyweight Rear Trailing arms done and fully poly bush before we give it the final waxoyl in the summer.....
 
Last edited:
ClassicKev ... You sound quite knowledgeable, and quite local. Do you take on instructional work? I visit Llandernog quite often and can easily bring the vehiicle to you.

I've been waiting for Elsie to give it a tweak since before Xmas.

I have PM'd you details, but as they never show up in my 'Sent' file, I'm not confident these PMs get through.

Johnny.
 
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