I have failed emissions test (high HC) three times on my 91 Pickup after I repaired the head gasket. First time HC was only high at idle, the last 2 times it was high on both ends. Truck runs good.

No codes are being sent out and rotor, plugs, cap, etc are good. I did break a bolt off where the EGR connects to the Upper Intake. The other bolt is tight. Do you think that can cause me to have high HC?

Thinking about replacing oxygen sensor and cat converter. I think they are still original.

Any other ideas? HC reading is around 280 and limit is 180.

I tried the denatured alc and 2 bottle of heet trick but no luck. Engine has been good and hot before test as well.

Thanks for any input!

High Speed RPM 2324
HC Reading 221 Limit 180 FAIL
CO Reading 0.68 Limit 1.20
CO2 Reading 13.9
O2 Reading 1.08

Low Speed RPM 2324 FAIL
HC Reading 284 Limit 800
CO Reading 0.49 Limit 1.20
CO2 Reading 14.1
O2 Reading 1.01

 

If your O2 Sensor, cat & EGR are all original, I would check them over to make sure they are in working order. Is your truck is running rich? if so, that will also fail emissions tests. Symptoms could be EGR valve, bad or leaky fuel injector(s), old/bad cat. I would start looking at your EGR valve and go from there.

Also, heet trick is more to get moisture out of fuel vs clean the system. For fuel treatment, go with Chevron w/Techron, B-12 or SeaFoam to name a few.

 

Thanks!
I found a place that will diagnose the problem for $60 to $80. At this point I think it is worth it to have someone figure it out and I can do the rest.

I will write back what the problem is.

 

Good luck man!


We have no emissions/smog check here in Hawaii but the tree huggers are calling for it. The city council squashed it the last 2 years. In your folk's locations, I thought smog checks were grandfathered for vehicles older that a certain year?

 

Who you callin' old?

In CA, vehicles before 1975 are exempt, and the year has not changed. There were no standards for vehicles THAT old, but there were for later. So they used those stds in 1980 and still use them in 2016.

This isn't social security; there's no social benefit to keeping old beaters on the road just because the owner won't keep them up.

 

So the place I took it to told me they tweaked the timing and adjusted the idle screw and it passed except for a little blue smoke coming out of tail pipe when you stomp on the gas. They then took it to "their" guy and he passed it so I am good for two years.

Don't think I will worry about the smoke because it is not bad at all. Might worry about it in two years if they truck is still running then.

I also have a exhaust leak under the hook I have to look into. Thought I tightened all bolts but it seems to come and go. Also there when cold and when very warm but not in between. Will check all bolts and hopefully that will be behind me.