Emissions

[Paul in the Port]

Evening gents (and ladies)

Just been having a read through the forum regarding emissions after my MOT at the weekend. I initially failed on the CO being too high (4.2%) with the HC being what looks fine to me a 370ppm.

I changed the air filter, plugs, leads and dizzy cap as there was a slight misfire but this only brought the CO down to 3.8%. Didnt get a chance to do this pre MOT due to the mad dash to fit my home refurbished brakes (was bleeding them 12 hrs before the MOT!!). A tweek on a screw on the TVIS by the MOT guy got the CO down to 3.31% so i passed but feel there's something not right still as it seems pretty high - not enough air at idle surely.

So what would be the first port of call? Clean out the throttle body / TVIS? Order the manual choke conversion kit from a certain Mr Woods in case it the waxstat??

Cheers
Paul

[blueninja66]

mine was timing mate, checked that recently?

[Paul in the Port]

To be honest nope - not checked it since i picked the car up last summer. I'll have to sort out a timing light - would be useful i'm sure.

[jimi]

Check for an air leak on the vacuum piping, mine failed on emissions last year (boy was I surprised) It turned out to be a very slight leak on the idle-up vsv piping, also discovered while the car was on the machine that raising the idle to around 950/1000 improved the emissions and lowering it to around 800 made it quite a bit worse

[Paul in the Port]

Check for an air leak on the vacuum piping, mine failed on emissions last year (boy was I surprised) It turned out to be a very slight leak on the idle-up vsv piping, also discovered while the car was on the machine that raising the idle to around 950/1000 improved the emissions and lowering it to around 800 made it quite a bit worse

To be honest Jimi - i think thats the screw that the MOT man tweeked to lower the CO to 3.31% to get me through!! Now you mention it - i'm convinced the idle is now at about 1000 - 1150 rather than the 850 as previously. Its the one under a plastic cover at the air filter end of the TVIS - right by the engine lid catch that he tweeked.

Where's the best place to get a workshop manual??

So thats timing and vacuum leaks to check so far

Cheers guys

[jimi]

That screw is for the idle speed not the mixture, sounds like he's just done what I described, raised the idle. The mixture screw is on a bracket next to the MAP sensor, it's on the bulkhead behind the intake manifold
Here's the adjustment (courtesy of Jeremy Ross)



Give me 20 mins or so and I'll PM you a link to where you can download a PDF copy of the 1989 MK1 BGB (the Toyota workshop manual)

[Paul in the Port]

Thanks Jimi - the link would be great. I've been meaning to sort a manual out for ages as i generally do all my own servicing.

I've just ordered a timing light as my old one died last year so will go right through all the possible checks including checking the waxstat first. I'm sure new vacuum hoses wouldnt go amiss anyway - its a 21 year old car after all!!

[jimi]

The vacuum hose that was leaking on mine looked and felt tight, but I could hear a slight hiss where it went onto the fitting on top of the throttle body, changed the hose and it passed no problem, the MOT guy was spot on, put the car back on the machine while I played with the idle so I could see what was happening, nice guy

[Kateg28]

Mine is idling about 600 (and it passed the MOT easily) but I keep thinking it is going to stall. How can I raise it slightly?

[jimi]

You can see the idle speed adjustment screw in this picture, on the throttle body just beside the TPS, it's usually got a round black plastic cover on it