khalloudy

Hi all,

Failed emissions and i am at a loss... this is becoming black magic to me. I have a new MAF, New LH, plugs are 6k old, wires, coils, caps and rotors are all new, Cat is a good used one from 928Intl which made a good change killing all the nasty smell my car was making . I still failed with a NOx above acceptable.

HC 0.23 (1.6 allowable)
CO 2.97 (15.00 allowable)
NOx 2.94 (2.50 allowable)

I tried to disconnect the air pump vacuum line as suggested by some posts and my readings went ballistic

HC 0.41 (1.6 allowable)
CO 8.57 (15.00 allowable)
NOx 5.15 (2.50 allowable)

This is starting to get really annoying dealing with this POS ungrateful car. What can be wrong with it????

P.S. I have ran diagnostics and the WOT is not working, but the switch seems to be working other than that... i have no idea how to test the vaccum, but seems to be working fine. And yes, I have run multiple bottles of injector cleaner in the system over the past 2 weeks.

Sincerely,
Khaled

OrionKhan

Dude, you got bad luck. Time for you to pay homage at the 928 Shrine.

ViribusUnits

Proformance chips?

Maybe it needs out of the car injector cleaning?

That is all I can think of.

khalloudy

Wade,

i have to admit, i have **** luck with this car

Viribusunits,

I added injector cleaner (used both BG and Techron). I have regular LH and EZK - no performance chips anywhere

dr bob

Khaled--

I convinced the test driver to do the rolling test in second gear, and that was enough load to get the cats to light off. I passed easily when I did that. The test was a marginal pass/fail without that step.

Since then, I changed back to Bosch copper plugs from the plat +4's I'd installed early in my ownership. NOx came down noticeably with the plug change.

Yours is so close that the second-gear option may be just enough to get you through. If that doesn't cut it for you, try the plug change. Plugs are cheap...

khalloudy

Bob,

thanks for the feedback. I will go ahead and change the plugs. I managed to get them to run in 2nd gear (but stupid me disconnected the air pump as suggested by some posts which made things really bad... you can see the results above). Should i worry about my injectors or replace them? could they be causing a lean condition? how about the fuel pump? vaccumm system?

Sincerely,
Khaled

Randy V

High NOX is pretty much always associated with too-high combustion temperatures often from a lean condition.

khalloudy

what could be causing the lean runnign condition?

mjensen

I had trouble passing my 84 928s this summer, I replaced the water sensor for the dme and the O2 sensor, all good...

khalloudy

I did run the Hammer on the car and it did not report any malfunctioning sensors except the wide open throttle sensor

Bill51sdr

Believe it or not, your readings are actually showing the car running a bit on the rich side, especially as evidenced by the CO reading. Have you replaced the cats? If not, you may want to look into that. A healthy cat should reduce the NOX substantially.

EDIT, just read your 1st post again... I would still suspect the cats. Neither you or 928 Int'l has any way of knowing how those used cats were functioning on the other engine. If you burned out your other cats, did you address the problem that caused that, or was that the reason for the LH and AFM? I would also check the function of the O2 sensor.

khalloudy

Bill,

thanks for the follow up. My old cats have been dead since i bought the car and were pretty foul smelling. The 928Intl used cats actually feel pretty good. I put my nose up to the exhaust and it smelled like water and air. The bad smell is all gone. The last time i tested my car with the bad cats it passed (donno how). I think i will be doing the following:

- replace plugs
- check o2 sensor

Does anyone know how i should check or what part of the vacuum system should be checked? My mechanic does not have a smoke machine... so it is hard to pinpoint the fault area unless someone has another way. I will also be considering changing the injectors. I think my car is running lean though as sometimes it does ping. I checked the knock count and it came back at 188 if that means anything i donno how to fix it though as no sensors were returned as faulty.

P.S. new cats are on my list to buy, but at almost 3k, i am taking my time I will only buy factory cats btw.

Sincerely,

John Speake

Hi Khaled,
When you disconnected the airpump line, did you seal the end of the pipe that goes to the heads ?

This is essential...

khalloudy

John,

what i did is disconnect the vacuum line that controls the airpump vacuum actuator. My airpump feeds the cats since it is a cat equiped car

Sincerely,
Khaled

Randy V

Actually, cats do very little to reduce NOX emissions. They primarily reduce CO and HC output.

In your case, I'll bet that replacing the O2 sensor will get you right. Often times an O2 sensor will test OK, but is actually failing.