funxman

Well, Im going on my third round for getting my biannual smog check here in ca. . When I bought the car, the PO handed me a smog cert with the pink slip so I didnt have to worry about it, but I could tell it wasnt running very good and every red light on the dash was lit up. Did lots of work on the car the first couple of years and no more idiot lights. Went to smog it after two years and it failed with high NO. At the time I had more money than I did time so I let a "friend" have it for a week and like the PO, he handed me a passed slip and a $550 bill of which absolutely no parts were purchased. So, im thinking two shotgun smogs. Anyway, to make a long story longer. I went in today and as I suspected it failed. And I thought it was running pretty good. I did a search and all I got was confused.

86.5 928 manual trans.
Results
15mph. RPM 1490.
HC Max 128... measured 192...fail.
CO% Max .80.. measured 1.37...fail
NO.. Max 1106 measured 182 OK

25mph RPM 1448
HC Max 103... Measured 146...fail
CO% Max .60... Measured 1.70... fail
NO Max 936... Measured 206...ok

%CO2 1450
%O2 1.3

Two questions
1 Any basic thoughts on what is wrong?
2. Is there a relatively inexpensive way to measure this stuff at home. I really dont want to pay some idiot $500 every two years to get it smogged and not fix the problem.

thanks much.... Robert

zoltan944

high HC means your running rich. id first check your temp2, you can search that how to.
also think your cats might be old and not working properly?

Mongo

Your O2 is over 1%???

Either you have a really bad exhaust and/or vacuum leak, or your cats are at the end of their life. O2 should be zero or as close to it as possible.

WICruiser

The O2 sensor in the exhaust is suppose to adjust fuel delivery +/- from basically zero oxygen. Either O2 sensor is bad and you are running a default rich fuel map, or the signal from the O2 sensor is not being properly processed. If you can not test it replace the O2 sensor and go from there.

Mike LaBranche

+1 on all of the above... tired cat, dead O2 sensor, poor mixture tune, tired/failing fuel pressure reg or dampers. My 84 is barely on the charts with a fresh cat and otherwise good bits. The brain should get you pretty darn close if all the other stuff is working right.

Mike
84 black
80 white

funxman

Ok, did a quick search on the Temp II and checked it.. .It read 550 green wire, and 520 brown wire, each to ground. It came up about ten on each as it ran. I lost my downloaded workshop manual to a crashed harddrive last year, so not sure where I stand in the realm of #'s. My search here showed 480-720...@~140*? The car has 155000 miles on it, so the cats may have possibly used up thier nine lives. Also, I did adjust the MAF. When the guy smogged it 2 years ago, it had a hunting idle, he said he adjusted the mix, I do believe leaned it out to the point it had no power... I mean it pulled like a ford Pinto running on 3 cylinders up hill.... So using a swamp cooler snake I made a tool that stays there so I could adjust it without taking anything apart until I got it to run good and idle ok.. (did this mostly to find a dyno and fine tune, but noone around here would put it on one????). That surfaced a dead injector. Compression all tested out good, 170 +/- so I put in a set of the ford blue injectors and the miss went away. The MAF is set to run best, but might be off. If I turn it clockwise, (richen I think) it has more power but hunting idle and frequent stalls when you push in the clutch to idle down, turn it much counterclockwise (lean??), idle gets better but its gutless... That being said, I checked for vacuum leaks long ago, and many times since...

Mike Frye

Hey Robert,

I think you're going to find that you have more than one problem and adjusting the MAF is masking the rest of them. You said you'd found a sweet spot where it runs best by adjusting the CO pot, but I think that's probably the cause of your failed emissions.

Here are a few things I'd try:

I know you said you've checked for vacuum leaks many times but you didn't say how or where. If you have pressurized the intake from the MAF in and it holds air (I think 3-4 psi for a minute or two is all you need) then you're good.

If you've tried any other method you could still be getting leaks in various places that could give unpredictable results. If you have bad O-rings on your dipstick or oil fill cap you will not build up crankcase pressure. If the O-rings in your throttle body housing (or tb-to lower air guide) are leaking it could cause idle issues. There are a million places for a small leak and if more than one is leaking it's a major PITA to find. I had a problem that would only show up when the car was warmed up and the rubber expanded enough to allow a leak, when the car was cool it was completely fine.

In addition, I've had problems with the O2 sensor as well as the O2 sensor plug where it comes up through the floor. The plug itself had apparently been pulled away from the wire inside the insulation (that was a fun one to find).

Once you know the O2 sensor is fine and you have no air leaks, get a 'blink'r' from Ken (liftbars.com, no affiliation) and use it to adjust your MAF calibration.

Finally, make sure you get the cats good and hot when you get it inspected, they work best when they're fully warmed up. If there's a line at the station, come back when it's shorter so you don't have to wait and let them cool down.

Mrmerlin

read through this thread i has some similar issues getting the emissions to pass and here is how i did it..

https://rennlist.com/forums/928-foru...lh-system.html

SteveG

On an '85, I was failing rich too. Finally found the cats had been gutted. I replaced it with "H" pipe and high flow cats from 928 Int'l. It was expensive, but the sound was best I've heard and it passed w/no problems.

funxman

Mr Frye, I have no doubt that adjusting the MAF was masking other problems and would lead to smog failure. the first question I asked the guy is can we do a dyno tune on it before we smog- He said we dont work on Porsches' I said you dont have to, just turn hook it up and I'll do the tuning..(the adjusting calbe I made is right there???. Nope... Two places said the same thing so I just let them go for it. Its those other problems that I have been working on. I read up on sealing the MAF and pressurize the engine, Next on my list of things to try. My other test were with a vacuum gage, visual, and spray very nilk and cranny while running looking for RPM changes..nothing..

I was just looking at new cats here in california, good grief, I didnt know they changed the laws to only certified (aka outragiously expensive writing on the ouside) cats.

I maded one of those home made flashy light thingies that I seen somewhere on here to hook into the connectors on front engine ports, crossed the ones I was suppose to and had all that going on when adjusting the maf after changing the injectors. Today I am checking to O2 sensor. Called the guy that smogged it last time and he did say he changed it.. So I will verify that, its function and then do the pressurized vacuum test. The more I read on here, the more I agree with too much unmetered air getting in there somewhere. Then going on to checking fuel pressure, and do the engine vacuum check for the cats from Wally.

Keep the ideas coming. I am an active listener and would not even have this car were it not for Rennlist.. Plus it is soooo fun to drive.
Thanks so much.. Robert