Posted this over on the combined forum but not reallying getting help.... Maybe someone here can offer some suggestions.

86 951 with Authority Stage 2 chips and (aledgedly) a Lindsey downpipe (haven't been in the engine deep enough to chk) 200k miles. Car will not pass emissions. It's running hi on HC and NOx.

Just did a Dyno pull the other day and (as you can see below) it's going WAAAY rich at about 3800 rpm, WOT/full boost and off the chart at 4000 rpm.


What should I be looking at/testing? One suggested the 02 sensor. How do you check the O2 sensor without replacing it with a new one?

Thx for the help.

 

O2 sensor isn't the issue - it is ignored at WOT. First question would be what FPR is on there, stock, or a 3 bar unit? That would make you go really rich at WOT, and turbos are usually calibrated to run richer than NA cars, so 10:1 isn't as far out as you may think. NExt question is if the AFM is good.

 

FPR is stock. To the best of my knowledge other than the mods listed everything is stock. Is the AFM good? Hell I don't know! The car is a daily driver (my only car) It runs strong, accelerates hard and other than the emissions thing (i.e. running rich) seems to fine.

 

You're going way rich right when you hit full boost. Sounds like a big boost leak to me.

 

Interesting.... Do you have a suggestion for how to find such? (other than the obvious of checking hoses, connections....)

 

Smoke test or pressure test on the whole intake system(after the turbo). I'd do a quick check on everything first, though. Just follow the path of the air from the turbo compressor discharge to TB and the connections on the intake manifold and put a screwdriver on every hose clamp. Then move on to smoke or pressure testing the intake.

 

Well I can do the screwdriver checking but how does one do a smoke or pressure test?

 

For the smoke test there is a smoke machine you use to fill the intake system with smoke. You see where the smoke is coming out from and you've found your leak.

Pressure test is the same idea. You pressurize your intake system to your desired boost pressure. If it does not hold pressure, see if you can hear where the pressure is leaking.

In each case you probably want to start after the turbo.

 

Thx