mjensen

I took my 84 928S in for the WI state emission test, and I FAILED! I did not feel/realize that the car was running rough/hesitation/starting issues,etc. According to my print out, HC and CO fail, NOx passed. relative air/fuel is around 30% rich. The only thing I feel might be off is my idle is around 1000RPM. Is there a way I can trouble shoot or does anyone have any suggestions...

FlyingDog

Lowering idle on an 84 is easy. There is a slotted screw about 1/2" diameter on the throttlebody. Screw in to lower idle, screw out to raise. Make sure you adjust it after the engine is warmed up.

Check for vacuum leaks, especially near the fuel dampers and regulator. Make sure your smog pump is working. Try swapping for a known good O2 sensor. Other than that, I have no suggestions.

Mark

Move to a state that doesn't have emmission testing!

Seriously, tho - post the numbers, and some of the more knowledgeable on the boards can probably help you out.

Fastest928

look for a vacuum leak .... make usre your plugs and wires are good with no corrosion around the cap/rotor. Check your cat temp ...should be around 350 400 Deg C with a 50 c difference betwee in and out.

Imo000

When my brothers '83 928 went in for it's last e-test (20 years old) had only a test pipe and we installed a generic catalytic from NAPA($80). The air pump was not connected (belt was on but the hose were not connected) and it passed with flying colours. I just came across the test printout Monday during a routine clean up of the garage. I'm pretty sure the air pump is an over kill for emissions and newer cats don't really need it.

Sounds like the car is running in "cold" mode or the AFM is not working right. High hydrocarbons are unburnt fuel = rich condition.

mjensen

How do I test for a "cold" mode. Now thinking about cold startup my car would run @1000 momentarily and then drop to around 800+/-. My emission numbers are: HC-4.2775 grams/mile(limit 2.0), CO-136.8886 grams/mile(30.0 limit), NOx- 0.5670 grams/mile(limit 3.0). HC and CO failed, NOx passed.

Rich9928p

After making sure everything is in tune and your plug wires are in good shape, have the base CO checked (most shops have the equipment). On 928s up to 1987, the base CO is adjustable. For L-Jet cars, you must remove a plug on the airflow meter. The LH-Jet 928s (Euro 1984 - 1986) and US (1985 - 1986), the MAF has a plugged hole with a pot. There is no base CO adjustment on LHs from 1987 and newer 928s. On L-jet and LHs up to '89 (?), the base CO is sniffed at the tubes that come up from the exhaust to the side of the air filter box. Newer cars require sniffing from plugs down on the exhaust system.

mjensen

Thanks guys, I just ordered my tune up parts, hope to get the work done and emission tested by the end of next week. I am also waiting for a new alternator(high/excessive voltage)...

Imo000

My bother's '83 had a high voltage problem years ago too. The problem was the regulator in the alternator has failed. To my suprise it's a standard Bosch part and the local alternator rebuiling shop was able ot fix it for $25. I was told by the shops owner that it was an off the shelf item. You don't hear this every day about the parts for the 928.

mjensen

Just keeping you guys up-to-date... I have all the tune-up stuff except waiting for the wires. While I was inspecting hoses/vac lines,etc. I noticed that one of the 1/2" i.d. hoses that go through the right fender to the charcoal canister was severly bent and pinched off. Could this be one of the problems for the test?

Schocki

I think your car comes from the factory with an air pump...

Disconnect the vacuum line to air pump valve for emissions testing. This is necessary to pass emissions with your car and is mentioned in the Porsche factory manual. If you have more questions talk to ROG 100.

Look at his post and especially at his latest one when he tested after a year again.
https://rennlist.com/forums/showthre...iled+emissions

mjensen

Yes, it has an air pump. I was going to pull the filter out and inspect it. Wisconsin does not visually inspect so if that is true should I just remove the pump/bracket/belt and plug/cap the vacuum line off. Also, after the car passes should I remove the cat, run without it? Does it change how it sounds? I would prefer for the car not to get too loud!

Schocki

Don't remove anything! Much more simple!
Take a look at this webpage at the last picture http://members.rennlist.com/v1uhoh/underthe.htm

#12 is the air pump changeover valve and #22 is the vacuum line. Just pull #22 and cap it and try to pass emissions again.

Why do you want to run without cats? A test pipe should change the sound but I don't know for sure, my GTS is bone stcok and drives beautifully!!!

mjensen

Keeping you guys up-to-date, part 2. While I was installing plugs/wires,etc., I removed the airbox to gain some working room and I realized that the afm to intake o-ring needs to be replaced. The afm was extremely loose, and if I was a gambli' man I know I could have tested for an intake leak by spraying some cleaner at the sealing area. Once again I will be waiting for more parts and let you guys know..

Randy V

As Schocki has demonstrated, the 'search' function is also your friend.

Let us know how it turns out.