east302
I'm Awesome
My 1998 (350, auto, 180k miles) has had this issue for a few years now but now has a new symptom.
1. Under hard acceleration when, for example, merging onto an interstate it will sometimes act like it is misfiring. Years ago it actually threw a misfire code, but I don't remember what cylinder it was. This is when accelerating with 3/4 throttle steadily from 10-mph or so to 60-mph. Once up to around 60, it will stumble and only stop when you let off the gas. It feels like you're hitting a really bad rumble strip. I had both catalytic converters replaced about a year ago (was told they were clogged and I could hear them rattling) and it solved the problem. But, what actually *caused* the converters to be damaged was not addressed so, of course, the problem is back.
2. Under steady cruising at 40-45 mph in 4th gear, it feels like the engine speed is too low for the gear and it seems to lug. It's in the 1100-rpm range I think. If it was a manual transmission, it would be like shifting up too soon. Getting out of that 40-45 range, dropping it into 3rd to bring the revs up or tapping the brake to disengage the torque converter fixes that. When I had the catalytic converters replaced, this problem went away.
3. Spark plugs and wires are ACDelco, with about 60,000 miles on them. The distributor is also a Delco unit and is about a year old.
4. No CEL right now.
5. I have had a gas smell at the exhaust pipes in the mornings. Now that it's cold, I've been warming it up in the mornings and now have black soot stains on the pavement under the exhaust exits.
6. I've had to run 91+ octane in it for years. It pings otherwise.
7. The O2 sensors are all original to the truck as far as I know.
8. All highway, I get about 13 mpg. Around town, 10-11.
9. Exhaust is a true dual setup.
So there we have it. Any thoughts on properly diagnosing this thing? I'm fairly sure that I've ruined or am about to ruin my new cats here, so it'd be good to fix this right this time around. Thanks.
1. Under hard acceleration when, for example, merging onto an interstate it will sometimes act like it is misfiring. Years ago it actually threw a misfire code, but I don't remember what cylinder it was. This is when accelerating with 3/4 throttle steadily from 10-mph or so to 60-mph. Once up to around 60, it will stumble and only stop when you let off the gas. It feels like you're hitting a really bad rumble strip. I had both catalytic converters replaced about a year ago (was told they were clogged and I could hear them rattling) and it solved the problem. But, what actually *caused* the converters to be damaged was not addressed so, of course, the problem is back.
2. Under steady cruising at 40-45 mph in 4th gear, it feels like the engine speed is too low for the gear and it seems to lug. It's in the 1100-rpm range I think. If it was a manual transmission, it would be like shifting up too soon. Getting out of that 40-45 range, dropping it into 3rd to bring the revs up or tapping the brake to disengage the torque converter fixes that. When I had the catalytic converters replaced, this problem went away.
3. Spark plugs and wires are ACDelco, with about 60,000 miles on them. The distributor is also a Delco unit and is about a year old.
4. No CEL right now.
5. I have had a gas smell at the exhaust pipes in the mornings. Now that it's cold, I've been warming it up in the mornings and now have black soot stains on the pavement under the exhaust exits.
6. I've had to run 91+ octane in it for years. It pings otherwise.
7. The O2 sensors are all original to the truck as far as I know.
8. All highway, I get about 13 mpg. Around town, 10-11.
9. Exhaust is a true dual setup.
So there we have it. Any thoughts on properly diagnosing this thing? I'm fairly sure that I've ruined or am about to ruin my new cats here, so it'd be good to fix this right this time around. Thanks.