7.4 87 2500 Sierra Classic SES

[Pagj17]

Howdy All,
Trying to figure out what's up with my car is like trying to read a Moron's Mind:P
I love her and all, but she's making life painful
Alright now, to the problem.

I often get a check engine Soon light at around 65-70, (although today that didn't happen). When It does activate, I can slow down some, and it deactivates after a little while, (usually with in 5-10 minutes). It also doesn't happen at lower speeds.
There are also times, when my friends are behind me, that they smell gas not being burned in the exhaust(and presumably it's noticeable enough to cause an issue) and of course, My mileage is down to around 8mpg.
Any help is beyond appreciated, thanks Folks
Also, I tried to check the codes, and found quite a bit of help, but all it does is flash "code 12" and then a few times it flashed three in a row, then 2.
Thanks

[CaliDude76]

http://freeautomechanic.com/diagnostictroblecodes5.html

Code 12 is a diagnostic sequence code.

I'd check your o2 sensor too though, if that isn't regulating the air/fuel mixture correctly, it'll set off the 'S.E.S' light. OBD 1 systems are very vague on pinpointing the exact problems. More than likely, it does have something to do with your emission system.

If your saying that it smells like raw fuel from behind, then your mixture is too "rich", and depending on the type of carb you have, something isn't allowing it to keep the proper air/fuel mixture. hence, the o2 sensor, or something sticking in your carb, you could try and run a can of "chemtool", or another type carb cleaner. The gas we get in California SUCKS... all the EPA regs and such. If your running 87 octane, you might wanna run a tank or two of the good stuff

[Pagj17]

Thanks it's running the tbi and yeah... the epa is a pain
I'll try a tank or few of the 89.
At least now I know how to access the codes.
Thanks again!
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