Ran the obd scanner today, no fault codes and this..





Engine idling in the garage and up to temp - fan kicking in.

Thoughts?

I will check readings my Plus 8 in the next few days.

According to the MOT emissions report there was a pass of CO at idle, the failure with CO was at fast idle, did you have a snapshot of a fast idle

R2967 is the standard tune (PROM)

One item that came up some years ago was an issue if the Mass Flowmeter body was not electrically isolated, maybe a heater hose or a grounded item touching it, haven't experienced the problem myself

Checking the tests on my Plus 8 in the last two years it tends to scrape through CO on idle, but sails through on fast idle

Rovergauge screens from my +8 as follows, the fuel map is very slightly different to standard

first is fast idle at a bit over 3,000 rpm

second is idle at 750

Main difference is that the MAF reading goes up from 3% to 11%, throttle from 6% to 20%, injector duty from 3% to 13% between idle and fast idle

One other check, are you getting any non-metered air entering via a split in the hose from MAF to plenum

Teknome, thanks again for your posts.

Happy to report that we managed to scrape though the emissions today. Replaced the MAF with the cheap Chinese jobby and although it runs less smoothly it did scrape though. Old MAF will be put back on the car!

Yours also runs a bit warmer than mine - I have a sifab aluminium radiator fitted

I’m going to go though all the pipes etc over the coming lock down. Might have a look at the idle valve too.

Thanks all

Gary

That is good news. I do have a Mulfab radiator, normally run at 80 on the open road, fan keeps it around 90 when stationary. I am temperature gauge watching at the moment as I have just replaced the distributor and don't know if the advance curves are correct, in the process of creating a test fixture as I don't have the money, or a fork lift, to get a SUN distributor tester.

Years ago I had a hesitant running issue with the +8 on checking the airflow meter I found that it was not electrically isolated and the heater hose was causing a grounding resulting in faulty readings. Wrapped the hoses checked the meter for grounding all clear and never had the hesitating again.

So pleased mine was 40 years old back in March. So no MOT needed

Sorry forgot to reply, there’s no electrical connection between the MAF and the chassis

It got through with a. Combination of the cheap Chinese MAF, cleaning the idle stepper motor and some tweeks but drove awfully. I replaced the MAF with the original one and it drives much better.

Couldn’t resist opening the MAF electronics and having a look at the screw pot. Very interesting. It’s a multi turn pot, six turns takes it from 0 to 100 ohms (checked on the Chinese one) and it would continue Turing if tempted

After lockdown I’m going to take it back to my tester chap and tell him to try multiple turn on the original MAF screw to see if he can get the emissions low enough yet still drivable. Oh and I’ll fit a new stepper motor, plugs and leads too as I’ve nothing better to do but decorate the house for two weeks now!