Basszilla

Hello,
New to the site and looking for some advise. Thanks to anybody willing to help.

I have an 1988 S10 Blazer. Lower miles and "was" running great. Here is what its doing. Starts and runs great. Driving in town, no problems. Seems when I get on highway, after a few miles, my Check Engine light comes on and then engine starts to run like crap, causing horrible gas mileage. When SES light isn't on, runs great. As soon as light comes on, it seems to bog badly and I can smell gasoline. To maintain same speed, I am forced to depress gas pedal down a lot further. Still seems to be running on all cylinders. No shaking or vibrations. Its like something is causing throttle body to dump too much fuel into engine.

I have just changed the O2 sensor, MAP sensor, and coolant temp sensor. Did nothing. My Blazer is the V6 TBI 4x4 model if that helps any. I also checked the trouble codes and it keeps flashing the code 12. No other codes will flash.

Last, the only other thing is my oil pressure sensor is out of whack. Gauge reads as if I have no oil pressure (or very little when engine revs) when I know there is sufficient pressure. Absolutely no valvetrain noise and sensor has been like this for years. If no oil pressure, engine would of seized by now.

Any ideas on what problem could be? Any advice would be greatly appreciated.

Sincerely,
Errol (Basszilla)

bountyh

Sounds like the gas filter needs replaced

Basszilla

I don't see how a clogged fuel filter could throw a Check Engine light and cause me to use twice as much fuel. And the smell of gas?

Wouldn't a clogged fuel filter "starve" the engine of fuel?

Whatever it is, it has something to do with the Check Engine light. Runs excellent until that light comes on then instantly a bogging, fuel guzzling turd. Like night and day noticeable.

steverap

Sounds like an egr problem or soleniod. Is it eletronic, if so it would throw a code. Quick test is to cap the vacume line to it and run it on the highway.
Oil pressure is probably the oil pressure sender or connector for it. Ifit is the obd system code 12 is the hand shake code. Lets you know that the computer can comunicate. Possible computer problem.

Does it do it in neutral? Only at exactly the same speed?

Basszilla

Hey thanks steverap,

I will try that. I failed to mention before, the EGR was new also.

Never tried to get Check Engine light to come on while in neutral. Drive around town all day with no problems. Once I get out on highway, after 5 - 10 miles of running great at 65 - 70mph, BOOM, Check Engine light goes on and engine instantly starts to run like crap.

I commute about 45 minutes one way to work everyday. Before this started, I could almost make it a full week on one tank of gas. Now since its doing this crap, it swallows a half tank for one way! No joke. It's killing me to say the least.

I've been told there is lots of black smoke coming from my exhaust pipe when it's running like that on the highway. Maybe this will help.

Tomorrow after work I will re-check the codes, just to make sure its still throwing 12.

Thanks again.

steverap

www.gmtuners.com/OBD1_DTC.htm - 12k

here is the site on the obd 1 codes
I was wrong for your year truck on the codes. If you look it says no distributer pulse. I wouldn't go any farther with fuel.
Your'e probably running on back up timeing. check all conectors for open. have the module tested. if thats not it I would investigate pick up coil in the distributer.
Dont rule out computer either.
Keep me informed on whats going on

jlglift

mine is doingbthis exact same thing, engine runs great otherwise, until check engine light comes on - then it gets like 8mpg w

tech2

read out the flash codes. goggle how to read obd I codes by grounding the diagnostic link connector pins. the car will flash out the fault code by blinking the check engine light