Hi All,
can anyone give me any tips on how to remove the black cover on the airflow meter? I am tracking down an issue with the car dying during idle once the car has reached operating temperature. Should I just leave the AFM alone? Is there a way to test this without pulling it apart? This had been an ongoing problem. I have also got to set the correct gap for the throttle body flap as mine is currently set at fully closed. Is the gap adjusted by the screw and set nut below the accelerator linkage?
When the car is cold it starts easily and runs ok but I think it may be running richThanks in advance
Con

 

The black plastic top is glued on, but can be removed with some difficulty using a craft knife to cut through the glue, plus some gentle pressure to raise the top. However, I don't think this is your problem. Have you tried adjusting the idle speed via the allen-headed adjustment screw on the air distribution block ? ? You may still have the plug in place that covers it.
Also read this: -

http://www.jagweb.com/aj6eng/42efi/index.php

 

Thanks Fraser,
No I haven't adjust the idle speed yet. when cold the car idles at about 1300 RPM and as it warms it drops to around 600 then when it is fully warm it starts to get really lumpy and then dies. The adjustment is on the list of things to do but I want to set the throttle body gap properly first. Thanks for that link. I thought that I had read this before but it is different and easier reading than the one I had read. A lot of it I was aware of but there is some new info ( to me ) there.
Cheers
Con

 

Before you go so far to open the MAF, I’d adjust the throttle butterfly as you mentioned. Fully closed creates a lot of idle issues. I wouldn’t touch the idle setting either until you sort the butterfly and MAF (if it’s the problem). Opening the MAF and changing the mix setting may only mask the real issues. If you suspect it’s the MAF, they have rebuilt ones for les than $250 and are easy to change. The previous owner of my car opened it up and was never properly sealed when put back. I had the same issue as you did. In my case the MAF was defective, butterfly gap closed and I had a leaking cold start injector effectively flooding the engine. I’d suggest trying to get as many things to baseline before opening and adjusting too many things. Good luck!

 

Thanks Robbo,
I spent some time yesterday working on this issue. I set the butterfly to the specified Gap and gave the throttle body a good clean. Also discovered that the microswitch on the throttle body had a dodgy connection to the Spade terminal so cut that wire and put a new Spade terminal on it and reconnected it to the micro switch. Reassembled all and started the car. It idled really well but it was a bit high at around 1200RPM. It used to gradually slow down as the car warmed up but this time stayed the same. I didn't have time to take the car for a run to warm it up properly but as it came up close to running temperature it definately seemed to be running leaner. Usually the exhaust fumes were very strong but this time not so bad. I think setting the throttle Gap has definately made a difference and the wiring issue to the microswitch also helped although I don't know it that was caused by me on pulling stuff apart. Do you think that setting the idle speed now is the next best step?
Con

 

That’s great! Good baseline on the throttle body! With that adjustment, There should be a noticeable increase in idle speed as the engine is getting more air at warm idle. I’d still suggest holding off on the idle adjustment screw until you eliminate the potential issue with the MAF. Any time you adjust something like that, take note on number of turns in case you need to set back to prior or factory settings. On mine, I purchased a rebuilt one (parts geek $200) and swapped it. It’s a very easy swap. If it turns out it’s all ok, still a good part to have on the shelf, because they can go wonky, certainly the terminal connections. If it improves the running, you’ve solved a critical component and have improved your overall baseline. For air/fuel mix. I also think if you adjust the idle screw, your idle would increase at cold start too-relatively. So your cold idle will likely be higher and it seems right to begin with. One thing that would indicate a potential MAF issue is how it isles and runs under load. What is the warm idle speed when you put into gear? If it stumbles or wants to stall while you drive, I’d definitely try a rebuilt MAF. If it’s just slow, then double check the butterfly, timing and distributor to be sure advance and vacuum are good. Let me know how it operates in gear and on a short drive.

 

Will do Robbo, gonna be another week now before I can get the car out, will let you know how it goes once I get the chance.
Con

 

Which suggests that someone before you was trying to fix, or mask, some other problem

Good advice and results so far.

For more ideas on rich running, if you think you still have that problem, can be found here:

XJ6 Series - EFI Rich Mixture

Another thing to check on these cars, if faced with running issues, is the ducting between the Air Flow Meter and the throttle body. If leaking/split/loose, weird things can happen. But, since you've adjusted the throttle gap, you probably already took a look at the ducting.

Cheers
DD

 

Hi Doug, You are right. I have read lots of threads about the cloth covered ducting. As far as I can see there are no holes in mine. The condition of the cloth is fairly average but no obvious holes. I am going to replace it attached some point once I sort out this running problem.
Con