Power Loss/Hesitation/Miss Firing on Steep Grades
 

Hi guys,

I have a 1997 Chevy Blazer LT, 4.3 liter engine. I have almost 188,000 miles on it. In the last two months I've experienced issues when going up a long steep slope hills with this vehicle. First sympton about halfway up the hill I'll notice a loss power (rpm drop), then I start to get this hesitation and miss fire thing going on, then the "Check Engine Light" goes on. Both times I've tried to give it more gas when it starts doing this, but it seems to make the miss firing worse like it doesn't want to take the gas. Both times I've been able to make it to the top of the hill, barely, and once I get to the top it'll stop carrying on and the "Check Engine Light" will stay on for about a day or two, then it goes out. I've tried to put the engine to a test on a flat open road and give it a lot of gas like you would to pass another vehicle on the roadway. The old Blazer has the kick up and go and does not start acting up at all like it does when it takes on a steep hill.

Any ideas what this may be?

I do need to replace the following preventive maintenance items:
- Spark Plugs
- Spark Plug Wires
- Rotor
- Distributor Cap

Could this be an O2 Sensor issue? (not even sure this old suv even has O2 sensors?)

Something else?

Any opinions or help would be great.

PS - I did replace the "Fuel Pump" 2 years ago with a GM Replacement pump.

You can take out one of the pre cat o2 sensors and run it up the hill. If it does not happen you need a new cat.

Check fuel pressure and leakdown first. Most auto parts stores loan the tester for free, and sell them for ~$40. Takes less than 15 minutes to check it. Let us know when you have a tester and we can guide you through the procedure.

Plugs, cap & rotor should be AC Delco, wires need to be a name brand quality set, not some el cheapo store brand. Fuel filter should at least be checked for restriction. Your 97 has 4 oxygen sensors, but they usually don't cause what you're experiencing.

What codes does it have when you scan it?

I agree with Captain Hook. I would check my fuel filter first... I had similar issues a couple years ago and it turned out the filter was clogged.

I have seen something similar happen to a box van with a 5.3l v8, turned out it was the cat converter. Everything inside the cat had broken up, and when going up hill it would clog the exhaust and no power and almost die, replaced the cat, and it ran great, no more issues.