High CO & Fuel Trim Troubleshooting

[ElvisRockVinyl]

Hi guys, although I'm new here I'm not new to the world of MR2's currently in 9 years of ownership of a rev 2 3sge import,
Anyway introductions aside my rev is having a hard job getting through co emissions test on fast idle then again it always has but now it's failed, the limits are 0.300% and mine is 0.387% no matter how hot the cat and engine is, yet CO at idle is 0.001% so it passes it easy, hc is at 22ppm and lamda is at 9.99

I've been looking into my fuel trim tonight with a volt meter across E1 and VF1 with the engine spanking hot my engine is super lean at idle its on 5.00v which means the ecu is having to really richen up the mixture on idle but when i take her up to 2500rpm the voltage drops back to 2.88 volts which is still a slightly lean condition so ecu is again banging in more fuel, I know my 2 is running lean because it pinks and the plug are to clean and white on the electrode tip, she does misfire a bit when I raise the rpm

anyone know what could cause me to go so lean on idle and slightly lean with rpm.

this is what I've done so far

1. fuel pressure at idle and high rpm is correct
2. taken injectors out pressure tested them and cleaned them
3. tested tps voltages which are correct no spiking or open circuits
4. Map sensor tested and working
5. Engine and air temperature sensors working
6. pcv tested and working
7. Engine vacuum at idle is a good 21 hg and is rock steady and slightly rises with rpm
8. Lambda sensor is working though a little slow to respond and correct when i create a rich or lean condition even though it new
9. new plugs, leads & dizzy cap
10. check ign timing...spot on 10 btdc
11. Done a dry compression test and I have 210 psi a cyl on all 4

so kinda scratching my head now as to what is causing this.

[Peter Gidden]

Sounds like your cat is old and due for replacement.

[ElvisRockVinyl]

Sounds like your cat is old and due for replacement.

Yea but if i'm running a bit rich because of a lean condition a new cat wouldn't do a lot to the figures as excessive co is due to to much fuel, I need to pull back the fuel trim to 2.50v which is where it should be, if it still fails co after thats corrected then yea the cat is knackered

[Peter Gidden]

OK

[vtecpower]

Not being funny mate but peter probably the best mr2 specialist. If he saying it's a new cat time it's new cat time..

However since your car is a rev2 tubby it doesn't need to go threw a cat test you can decat the tubby and put it threw a non-cat test and pass.

Even better you could leave the cat on go threw a non cat test then decat her after the mot

[ElvisRockVinyl]

rev 2 n/a buddy

Also had a new cat last year as i thought that was the problem but reaading pretty much stayed the same, I usually run a decat all year round cat only goes on for mot

[vtecpower]

arhh my bad though it said 3sgte .. but still being a import and pre 95 means it goes threw a non cat test ?

[ElvisRockVinyl]

arhh my bad though it said 3sgte .. but still being a import and pre 95 means it goes threw a non cat test ?

Right I managed to get the fuel time sitting at 2.5v at idle and 2500 rpm, 2.5 is where it should be indicating a now good running engine so I should lol touch wood pass emissions now

Vtecpower, yea I tried to tell them that but because there is a UK 3SGE MR2 in the book they go by that, the turbo isnt listed in the book so they have to go by non cat limits.

I have got mine though many of time on non cat test because the old guy that always did my car new about old cars and always put it through as non cat test but he's now retired and the young ones aren't quite so helpful they seem to want to go by the book all the time if mine was a K reg 92 then a non cat test could be done.

[RST]

Gonna ask a silly question but: if you've meddled with anything have you done an ECU re-set afterwards? When was the last time the fuel was cleaned out also.

I'm only saying because:

a) I did some work on a Toyota before, failed emissions TERRIBLY, I forgot to re-set the ECU, passed more than perfect afterwards
b) I know some say it's snake oil but for ME I know in the past running a good shot of injector cleaner (red-ex) has transformed a horrible fail into a pass before. I swear by it now every 6 months.

Your lambda reading should be in the +/- 1.0 reading, what did you get on the test (9.9> doesn't sound right).


...you can argue all you want re test specs, all you have to do is look up in the book.