Broke out the Z today & took it to an emissions test center / shop. It was right around closing time so the guy was cool & let me hook up the Z to the emissions machine on monitor mode.

At idle... a beautiful 50ppm HC

High speed test... 100ppm for about 15 seconds, then jumps to 450-500.

Limit is 220ppm. During the high speed, there is an obvious miss... gives a nice "putt" about every 2-3 seconds. So I have 3 weeks to find the prob! All I can think of is vacuum leaks, maybe a not so perfectly spraying injector, er somethin...

 

What is your first idea as to the cause of the stumble...mine also does this stumbling thing but between 3,000-4,000 rpms. It pulls good below 3,000 and above 4,000, or should I say part throttle and full throttle, tis mind boggling. I am pretty sure mine is vacuum related.

 

Vacuum leak, faulty / corroded electrical connection, possibly a bad sparkplug wire...

 

little too rich on your afm, tighten it just a coupla teeth for the test, thatll cure it. also change your timing. just do it in your driveway, you can hear it, so tune by ear.

 

I would adjust my AFM if I had one... but I have a Z31 MAF. And should I adjust my timing if it's already well within the limit at idle?

 

you may have to get closer to the limit on idle to pass the fast test, its a tricky balance. and i forgot aboot the z31maf thingy. i cant keep everyones project memorized!!

 

Shady was incorrect... as usual

 

Uhhhhummmm umm how does it go?

oh yeah..


PWNED!!!!!!!

 

sometimes ya score, sometimes ya miss the basket. the principal is still the same.

 

Turns out Shady IS still right a lot. I spent a couple hours going through my engine bay... checked all vac hoses (got rid of some I no longer need due to the Z31T ecu ... they were just temp plugged), di-electric greased all efi connections, and still no change. Then I remembered my wonderful advice to SNOWY this week about checking timing... got out the timing gun ... uh... timing set to 30 degrees. WOOPS! Turned it down to the stock 20... better... down to 10... excelent. Gotta take it back Monday & see if she'll pass!

WOOT!!!

 

wow, so it ran better at retarded timing from stock?

Why in 1983 did they suggest 24 BTDC instead of 20? I upped mine to 25 just for fun. Seems a little more peppy but maybe that's just in my head.

 

Well, the miss is gone @ 2500rpm, but it doesn't have as much power.

 

the retarded timing was just for emmsions purposes. i run my n/a at 20 deg when its not emmisons testing time. i back it down to 8 or 6 for the test.

 

Welp... She passed! Woot Woot! Timing set @ 10 degrees & puts out like a new car!!!

 

WOW! That's even better than my turbo Z! great jorb

but... I passed at +23 BTDC

 

EGR fail huh..... lol im searchin me up a n42 intake, i need to eliminate all that poop on the intake mani that i dont use lol. congrats i guess, glad to know i never have to g for emissions as long as i dont get anything OBD2

 

Nice numbers man. My Z had about the same numbers when I got mine done. It actually ran cleaner on the Z31 setup than it did on the stock efi haha. I had timing set at 18* and had a slight miss, but the guy said it didn't matter as long as it burned clean.