I have a 92 RS 305 tbi auto w/201,000 miles(everything is stock), but winaldl shows that it's running rich (BLM stays around 117 & the integrator stays between 126-128) in closed loop. The car runs great otherwise, but CO, HC & NOX all failed on the emissions test (on idle & cruise).

There are no drivability problems at all, & all sensors (except the knock sensor) have been replaced, new fuel pump, fuel filter, tune up, egr is functioning, timing at 0 degrees, no ecm codes & it still has the same rich issue.

There are no vacum leaks & the fuel pressure is a steady 11psi. I removed & cleaned the TBI, the injector has always sprayed a steady cone with no drips.

The one thing is that if i use 87 octane gas it pings under load (when hot), but when i use 93 octane gas it doesn't ping at all.

The exhaust smells absolutely horrible, but again the car runs great, & doesn't smoke at all.

FYI:

When i bought the car it had 99,000 miles on it & the engine looked as if it were new, but the exhaust smelled the same back then as it does now, but back then i lived in a non emissions county so i never had to deal with it.

I appreciate any assistance with this issue.

 

What will cause rich?

coolant temp sensor.... reporting the coolant temp as fridged.

 

I agree with Ronny. But I also think you have a bad catalytic converter. But if the engine is running rich you gotta fix that first because a rich engine will burn out a catalytic converter

 

test coolant sensor. I recall placing mine in freezer and then watched ohms change as it came to room temp and then in hot water kettle.

 

The coolant temperature sensor has been replaced already & the winaldl datalogging showed that the old one & the new one started out cold & climbed normally as the engine warmed up.

 

Find the connector to the ecm, figure out which terminals are for the grounds & do a continuity test. The ecm ground wires are usually at the back of the engine or near the t-stat. GMs run funny w/ bad grounds.
Ok, you checked the timing, but does it advance when you rev? This would impact the engines ability to make vacuum for the map sensor. What is the engine vacuum? Should be 18" or higher at hot idle. Put the test tee at the map sensor hose connection.
Does this year have an air temp. sensor? Test it like a CTS.

 

Thanks for the responses so far, but again the car runs great, the timing has been checked & checked & it does advance when i rev it, no trouble codes, but the hc, co & nox emissions are extremely high & will not pass inspection, & the exhaust smells horrible.

I can drive this car from here to the moon in total confidence.

I have attached 3 datalogs so that u guys can have a better understanding of what's going on.

 

What was the vacuum reading top the map? Use a gauge tee'd into the map sensor line.
Maybe at some point someone swapped 5.7L injectors in it.
Do a continuity test on the ecm grounds at the ecm connector.

 

I forgot to mention that the injectors are the correct part number for the stock 305 tbi, i checked the injector numbers with the ones on the internet, & i also bought another complete tbi unit from a salvage yard & the injectors are the same part number as well.

I will check the ecm grounds & the vacum reading & post the results.

Has anyone taken a look at my data logs yet?