Inspection trouble in Texas - emissions

[Stringer]

90 Suburban, 350 TBI, can't pass low speed emissions. Tried 3 times at the same place - same result. It's the NOx category that's failing.

This thing sat for a while before I bought it. I've burned a tank of premium and a couple cans of Seafoam through it. It runs fine - does not have any codes stored.

Anybody know what to look into next? Any sure-fire fuel treatments? Possibly timing? (I could go to another station but I'm afraid another one wouldn't pass the windshield!)

Trying to upload the results sheet. Not sure if it'll post or not.

[BigBlocksRule]

Sure, come to Lubbock and have it inspected where we have no emissions to worry about. That damned daily 10mph - 50mph wind takes care of that for us.

[Jonboy]

Are you getting it warm before taking it in for inspection? Going for a drive to get it warmed up before getting it inspected helps.

[Stringer]

Thanks for the replies. Yeah, it's been well warmed up when I've gone. I'd sure get it done elsewhere but I think they're supposed to check your dl for county of residence.

Been studying online about it. Like chasing a ghost - especially for somebody like me. Most sites say it's caused by overly high temps in the cylinders but I think it's a process of elimination thing.

Sorta wish I'd bought a pre 87...wouldn't have to worry about emissions.

[nlines]

I had the same problem with my '92 350 Suburban. Turned out to be the EGR valve was bad. I disconnected the vacuum hose and sucked on it, the diaphram was leaking.

[TheApocalyptican]

Originally Posted by nlines

I had the same problem with my '92 350 Suburban. Turned out to be the EGR valve was bad. I disconnected the vacuum hose and sucked on it, the diaphram was leaking.

This^
Not saying for sure the egr valve is bad, but definitely should be checked as the egr's job is to lower NOx

[Stringer]

EGR is shot. Diaphragm is stuck. Got a new OEM coming to go on today. Not sure that's all there is to this problem, but we'll see.

[jjmorrse]

If egr does not fix it sometimes ensuring that you have a higher temp thermostat may help. Especially in texas people try to fix other cooling problems by a low temp thermostat.
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[Stringer]

Thanks. Yeah, I just put a new 195 in it. It was on the verge of over heating - wild swings in temp on the gauge, at least.

[Stringer]

Hate to bump this back to the top, but in case somebody's got the same problem later on, replacing the EGR took care of the issue. Truck passed inspection with flying colors. Thanks.

[SBTork]

Very cool, glad you got it fixed!