[jkeving]

I have an '87 Milano with 67k original miles. The car sat for 2 years and I was told it had a bent valve. Re-did the head, new O2 sensor, plugs and now the car wont pass emissions. (need 0.66%CO get 1.3%, 200ppm HC get 220ppm, NOX great!). Does this now need a CAT?

Thanks

 

[Graham D]

Test the CAT before you invest more money. It's easily done using a laser thermometer; any good mechanic will have one. If the CAT is working, it will be hotter at the rear than at the front, usually by about 50 F. If not, replace it. Harbor Freight Tools (www.harborfreight.com) (NFI) has an adequate and inexpensive unit, 91778-4VGA for only $40.

 

[slyalfa]

yea most cars that are L-jet need a new cat to pass here on the dyno.
mine is due and I need to do a pretest to see if I need to change it again.
bets to know before you do a test that can go to the state.

 

[alfaspence]

ah! the only reason to enjoy living in the uk! mine never had a cat, nor will ever have to! i hate the damm things, apart from screwing emmissions, they can also fall apart causing a blockage worse than what a normal silencer ever will....

 

[jkeving]

87 milano emissions problem

Ok, I got a waiver for the 1.3% CO 6 months ago, did not change the cat, but now after 5k miles the CO is at 3.5%, and the plugs are the same black/brown color. Seems like I toasted another O2 sensor, but why is the mixture so rich? I have tried the adjustment at the air flow meter but that does nothing?

Thoughts?

Thanks again

kevin

 

[75evo]

How is the HC? Please post exact figures.

 

[75evo]

Just read the original figures, a new cat should give you a temporary fix. Otherwise I would check out the cold start sensor and exhaust valve clearance.

 

[alfaspence]

I have tried the adjustment at the air flow meter but that does nothing?

Thoughts?

Thanks again

kevin

i tried adjusting my original but with no success, i fitted a new (second hand) AFM, and it improved things but was allready too late, my engine gave up cylinder 2 and 3 after a further 600 miles later....
I tried everything from tappets to plug leads, cap, rotor, plugs etc before to improve things but with no avail... performance was big time down compared to before... (the car was sat idle in storage for a year and a half)

For note, my car passed its emissions but was sky high in hydro wotsits and had a very rich smelling exhaust (eye watering) but economy was not down.

I checked everything from air leaks to timing etc, replaced all "consumables" etc.
The only thing i didn't check was the injectors themselves
Now if the motor had of been a 4 pot, it would have seized up turns out the other 4 pots were dragging 2 & 3 (motor is now stripped to find out what happened) All cylinders (1,4,5,6) are perfect showing no real signs of wear (for a 116k motor anyway) honing still present in the bores...
Cylinders 2 & 3 are COOKED... piston skirts have equally picked up showing signs of gradual overheating (still been running but on a weak mixture) and the rings are seized in the grooves but not down to corrossion or carbon.
Engine never ran hot or overheated.
Your system maybe trying to compinsate for similar symptoms (lambda control)

 

[jkeving]

The Hc on both of the last 2 readings was 230ppm, upper limit is 200ppm.

Thanks
Kevin

 

[crankCase]

If NOX is good, cat probably is too. The problem of too rich can be very tricky, I'd start with the fuel pressure & regulator. There's an excellent book by Charles Probst "Bosch fuel injection & engine management" published by bentley that got me through the emissions
battle here in NJ, but I did have to replace the cat, the header pipe was crushed.

Regards,
John

 

[slyalfa]

a rich mix will melt the cat. the pot on the afm will do somthing. if not there is somthing way wrong. the way I used to do mine was to unplug the the O² wire the single wire but keep the power for the heater on and look at the voltage. I would adjust the pot untill the O² was just at the crossover point. (in open loop it will snap to one side or the other as the is a narrow band type) then when I plug it back on it should start to oscolate back and forth. you can hear it and if you have a scope you will see a nice sinewave on the single O² wire.
as you rev it the osolation will get faster but should be there un less the WOT swich is clicked then it will go pig rich.

 

[slyalfa]

just so show what it looks like with no cat vs a cat this is what I got. I failed the first time and when I took off the old cat the insides were all gone. I was just a big open box.

so at 15 MPH
%CO² =14.1 %O² =0.8 HC=157 %CO=0.60 NO=944 No CAT (Fail)
%CO² =14.2 %O² =1.2 HC=19 %CO=0.00 NO=64 With CAT (Pass)

at 25 MPH
%CO² =14.1 %O² =0.8 HC=145 %CO=0.63 NO=836 No CAT (Fail)
%CO² =14.1 %O² =1.3 HC=25 %CO=0.03 NO=85 With CAT (Pass)

the tests ran at 2253-2324RPM for both speeds

 

[jkeving]

I had put a new o2 sensor & plugs in and it went to 1.5% CO. By "pot" I assume you mean the air by-pass on the afm? If not, where is there a potentiometer (pot) to adjust? Under the black plastic cover? The air flow by pass adjustment did nothing and it then slowly worked its way up to 3.5% CO , aka pig rich. What do you mean "WOT switch"??

Thanks

Kevin

 

[slyalfa]

the air bypass is the 'O' ring that goes in to intake manifold.
the O needs to be replaced anytime the air flow is changed. after a few weeks it gets rock hard and no longer can change size. the pot is on the AFM there was a round cover at one point. but most have been removed, look for the round cut out next to the square plastic part.
this will change the mix. the air bypass on the intake will change the idle speed.
there is a switch that next to the buterfly it is a 3way switch. one pin is common. and it connects the common to one of the pins when the buterfly is all the way closed. and none in the middle and it connects to the other pin when it is open all the way. check the switch if it is not working you will have problems.