Hi all,

I have an 86 s10, 2.8L. I just got it with low miles considering the age. Only 94k. Anyway, it runs well, But when i tried to smog it for title transfer it failed.

The report shows failed fuel cap, failed ignition timing, and high HC at low and high rpm. I was told to go to a "test only" shop. So the guy just said it failed. No reasons. So I took it to a local smog shop and the guy there showed me that the timing is dead on. It seems the first guy didnt unplug the wire under the dash before checking it.

So that should fix the functional ignition timing failure. But i still have high HC. I also had the plugs checked and replaced for the hell of it, but they all looked good. Old maybe, but not caked with carbon.

I really don't have the money to shotgun it by replacing one part at a time. I'm really hoping someone here can help me out. There is no stink or rttle from the CAT, so I don't suspect that. Ignition seems to be in good shape. I assume that if the rotor, distributor or wires were bad, then it would show with carbon on the plugs.

The previous owner was the only owner, and took very good care of this truck, so im hoping its just some small part somewhere that I can fix for cheap.

Any ideas are appreciated. Thanks

 

Does it have a carb or is it fuel injected?

Heres a couple things to check:
Vacuum leaks could be a problem.
What temperature does it run at? If it's running too cold the computer will run it rich, if its got TBI of course.
Is the check engine/service engine soon light on?
It might seem silly but a dirty air filter can cause HC failure.
Also its possible to have a bad 02 sensor even if theres no check engine light. O2 sensors are like $15 but they can be a little hard to replace

 

Yeah, I dont think it was hot. I went from work and the smog place was only about three blocks away. I didn't notice the temp at the time. It normally runs right about 210 deg. It's a TBI. I didn't even think about the air filter. In fact the last time i looked at it, the air filter cover had a bit of ioly substance on it. As if the fuel was splashing back up on it.

I guess it wouldn't hurt to chnge out the filter and the O2 sensor. Thanks for the tip.

 

High HC is HydroCarbons - or fossil fuel containing carbon

So try burning something that is not a hydrocarbon - like alcohol - and you wont have to fix anything.

Run your tank down low, and dump in a gallon or two of methyl hydrate, go ace your test, then top up the gas to dilute it. I did this with mine and my emissions were crazy low on my second try around when I passed. It also feels alot more powerful and is noisier with the alcohol in the tank, which is probably not good, so get it back to gas after real quick. I bet it cleans out the fuel system real well too as well and being the number one emissions cheat. If they Dyno your truck, make sure your tires are up to like 50 psi for the testing, less rolling resistance = less fuel burned. And replace that gascap.

 

Yea and after you replace the alcohol with gas-then you can replace the fuel pump when the tank is full.

Stay away from the alcohol. Do the other stuff listed above. Air up the tires for the dyno is also a good idea.

Good luck.

 

That could be it right there, being hot isn't an issue. If the coolant doesn't have enough heat in it, the computer will have it run rich. Make sure the engine is up to operating temperature when it gets to the testing.

Don't put alcohol in your fuel system...it is very hard on rubber. It's bad enough fuel today has 10% ethanol

 

Thanks for all the tips. I'll give that a shot.