Weston

These are the results of my Colorado I/M 240 emissions test on my '83 944 ('84 motor)...

HC: 6.5, limit 4.0
CO: 114.6, limit 30
CO2: 318.8 (info only; there's no limit on this)
NOx: 0.96, limit 8.0

All numbers are GPM (Grams Per Mile). The limits are pretty generous for cars this old, but the CO reading was still nearly 4 times the limit. For comparison, I once got a turbocharged Acura Integra with valve damage and an incomplete tune through this same test with only 1.1 HC and 12 CO, and I felt that was running a bit rich, since I've seen it as low as 5 CO on the same car 2 years earlier; a normal fuel injected car is around 2-3 CO.

Obviously, my 944 is running super rich. Given the low NOx numbers, I'm thinking the catalytic converter is possibly still good. Everything I've read so far seems to point to the O2 sensor and/or the AFM adjustment, but I'm wondering how many people agree with that, and if there might be other ideas or theories. I just don't get how my numbers can be this insanely high, and I didn't think that the O2 sensor made that much difference. I already picked up a new Bosch 1-wire O2 sensor, but I want to do everything that I reasonably can before I test the car again (I only get one free re-test).

I bought the car a few months ago, after it had been sitting outside for about a year. It had some running issues, but I got it's maintenance up to date and fixed things, so now it runs pretty good, without any noticable driveability issues. It also has 160 psi compression on all 4 cylinders (at my 5300ft elevation). Here is what I have done so far, before even taking it to be emissions tested...

- 2 new Bosch reference sensors
- New timing & balance belts and rollers
- New Bosch fuel pressure regulator
- Replaced vacuum lines
- Ran SeaFoam through a tank of gas
- New Mahle fuel filter
- Replaced vaccum lines
- Replaced breather hoses
- Replaces oil/air separator seals
- Rebuilt the throttle body with new seals
- Replaced intake manifold gaskets
- Replaced fuel injector seals
- None of the injectors leaked when I had the fuel rail pressurized and pulled out of the intake manifold
- Cleaned air filter (K&N)
- Oil change with Castrol 10W40 and a new filter
- New spark plugs
- Re-tracked the AFM and tested it's output with a multimeter
- Adjusted the TPS and tested it's output
- Tested DME temperature sensor
- Tested altitude sensor
- Inspected distributor cap and rotor
- Replaced DME relay with a 993 relay


Thanks for any info/advice/ideas/etc...

barelyrunshalfthetime

Could be that you need a new Catalytic Converter... or an O2 sensor.

marky522

O2 sensor... I just found out that on the older cars, O2 sensors were supposed to be replaced every few Services (30k.. not sure) Anyway, Your cat doesnt effect NOx, newer Cats do, but not the older ones.

Mark

barelyrunshalfthetime

Hes not failing the NOx... Either one would be a good thing to replace, the old cats get clogged after so long and the backpressure in the exhaust system increases until it sometimes clogs completely.

BTW, I know all about failing NOx, as I did it quite a few times before I successfully passed the last emmissions test that I will ever need. I finally passed by one ppm lol. I have the all the info from this incident in another thread on here I believe.

marky522

I never implied he failed NOx.... He said he thought his cat was good because his NOx was low... I was simply stating that Cat had nothing to do with NOx.. And actually, not sure if it actually would happen but if the cat was plugged, his NOx could be high, because NOx is formed when combustion temps exceed 2500 Degrees F.

Mark

barelyrunshalfthetime

my bad, I guess I misread a little.

marky522

Not a problem, I dont think it would be a cat though, cause those numbers are really high, but if he keeps running that rich or it has been running like that for a while he will need to replace it, that much fuel in the CAT and it will start to melt down.

Mark

jsaindc

Do you have an after market chip? My 87 came with an autothority chip. Ran great but failed emissons with similar readings. I messed around with all kinds of things and could not get the numbers to come even close. After several attempts I replaced the chip with the OEM and it passed with flying colors. What about the 993 DME relay you put in? Could that have changed the maping at all?

76 911s

Last year my car failed the B.C. AirCare inspection due to a bad catalytic converter. I suspect that your car failed for the same reason.

My failing readings for the idling test were:

HC(ppm): 634, max allowable: 390
CO(%): 12.63, max allowable: 4.43

After installing an aftermarket cat:

HC(ppm): 15, max allowable: 390
CO(%) .03, max allowable: 4.43

Obviously my high readings were also due to a very high mileage (293K MILES!!) engine, but a new cat lowered the readings substantially. I didn't expect that dramatic a change in the readings.

If you buy an aftermarket cat advertised for the car, be careful to make sure that the diameter of the tubing matches. I initially bought one from Parts Heaven, but found that the tubing was about 1/4" smaller than the exhaust. I eventually returned it and found a universal one at a local parts store.

ibkevin

If you don't have records of the O2 being changed, they are ~$20, so just change it. Without the narrow band the DME reads lean so it adds more fuel.

My '83's lasted 23 years and then bugged on me last year to give me the coveted "gross polluter" prize.

Weston

Thanks for the help, guys. As far as I know, the DME is stock... it still had red paint on some of the screws, so it didn't look like it had been opened before. The O2 sensor has been replaced before, but then again, it's a 24 year old car, so that doesn't mean much. I picked up a new Bosch O2 sensor from AutoZone for $18 yesterday, and will install it soon. I'm going to borrow a wideband from a friend tonight so that I can see just how rich it is, and how much that new O2 sensor changes things...

Weston

Just a quick update in case anyone is interested... I put the wideband in my tailpipe and it's showing 11:1 to 12:1 A/F at light throttle when warmed up, so it's definitely running pretty rich (this is what my turbo car runs at WOT!). The wideband is just in a temporary mount I made for the tailpipe, which is far from ideal, but it should be reading too much air (ie lean) if anything, and it's still showing pretty rich, so I think it's safe to say that I have a mixture problem. I'm going to install the new O2 sensor tomorrow and see what the wideband says about it... I really hope I'll start seeing A/F's in the 14's under light throttle...

SoCal Driver

Your See-Foam killed the CAT. Use it on old Fords only.

Weston

Another update... I replaced the O2 sensor and made sure the wiring was good (the previous one was spliced and pretty questionable). The wideband now shows it doing a real good job of staying around 14.7:1 at light throttle (13's at WOT), and it drives noticably smoother. This is a big improvement from constant the 11's and 12's I was seeing last night. So, the O2 sensor can, in fact, make a big difference. I have a few things I need to do, then I'll get the car back to emissions in a day or two. Hopefully this will be the last time I have to go there... they failed my gas cap too, which is brand new.

Weston

Just got back from the emissions place and it passed, well inside of the limits...

HC: 2.17, limit 4.0, previously 6.5
CO: 13.76, limit 30, previously 114.6
CO2: 354.67, previously 318.8 (info only; there's no limit on this)
NOx: 1.66, limit 8.0, previously 0.96


To solve the gas cap issue, I just took the seal off of my new aftermarket (Stant) gas cap and put it on the stock one, which passed perfectly. Both hold pressure fine, but the Stant cap was some advanced venting one, so I suspect that they didn't take the key out, causing it to be in vent mode, and that's why it failed their stupid test. In any case, I'm all done with emissions for at least 2 years now, and I'll also be eligible for collectors plates next year, which means no more emissions at all!