Sorry for the delayed reply guys, had vacation last week and a bit under the weather this week...
Thanks for all the input! I did the coolant temp sensor last week and it seemed to help. I left the battery disconnected while changing it to reset the ECM. It's pickup a bit more juice, still not where it should be, but not nearly as boggy to drive.
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Originally Posted by Dayton601
What is your current fuel mileage, most got around 16 to 18 mpg , i had a 91 did several thing to try to improve fuel mileage, I started at 15 and finished at 21 to 22
first I would check fuel pressure,
then spark plug gap and maybe go up a hotter setting, I did run the platinum plugs, not sure that did anything,
Also reading that you changed the the O2 sensor, did you go with factory. the aftermarket stuff is junk, I have heard people go through several autopart brands before finding a good one,
I would add throttle body spacer and fuel injector spacer, two different things, the spray pattern looks like a cone,
then I would add a hotter (super coil) coil, seems that's were I picked up my best fuel improvement I kept the stock coil mounted on the intake, hooked up my super coil, drove 300+ miles Houston to Dallas , then i would hook back up my factory coil, drive it back, did this several times to confirm, I say this because some will say coil will make no difference, each time there was at least a 4 to 6 mile difference, perhaps the octane grade might have an effect, nothing beat the coil, even running with windows down, A/C off and tailgate down,
Also was running 8.8 wires, better insulated, once i had just a cheap set of autozone wires, and I happened to open the hood when it was really dark, it looked like Christmas lights, after that I made sure i bought good wires,
that just my 2 1/2 cents worth
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My millage averages about 10-10.5MPG right now. When it boggs badly, usually 9.5.
O2 sensor was changed with an Acdelco replacement. I've been trying to replace everything with factory name brand hoping it will last longer. Hotter coil is a good idea. I remember changing that a couple years ago with a new one and the difference was incredible when the new coil went in. I could try to find a hotter one.
I'll check the wires too, that's a good idea at night. I think I'm running the heavier set that you can get through NAPA if I'm not mistaking.
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Originally Posted by Desert1957
Check the MAP Sensor, Is the tailpipe excessively sooty? Black smoke?
If so , locate the map sensor and pull the vacuum line from the sensor, engine should run fuel rich and have a noticeable change the way it sounds.
Make sure it has FULL vacuum at idle , check it with a gauge if needed. This is a CRITICAL sensor to the efficient way a TBI system runs.
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MAP sensor was done about 3 weeks ago. Definitely made a difference, replaced with ACDelco. That is one thing I have to do though is check the vacuum and see what it reads. Along with check all the lines for cracks again. Would a bad charcoal canister have anything to do with the way it runs? Do they ever go bad?
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Originally Posted by RUN GMC
I recently had the same problem on my 87 replaced everything except the spark plugs wires which in hind sight I should have done first but since they were not really old (14 months).....so I decided to replace the spark plug again and I saw only 3 spark plugs were fouled somewhat compared to the others (and I had laid them out in order to know what cylinders they came from)....after replacing plugs I started up the engine and noticed I had the same bog down and a slight miss....at this point I removed and replaced the 3 spark plug wires for cylinders that had the fouled plugs.....upon recranking it up I could tell it sounded better and it pulled better but I also read that it takes 40 cranks cycles to get the ecu to dial in the parameters to make it run really great again.....hope this gives you food for thought.........
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Thanks! That it does. I usually replace the plugs every year and the wires every 2. I keep a log on what gets done to the truck so maybe it's time to check that and replace again.