Hey folks. This group has been really helpful for me recently as I've been refreshing my YJ. I thought I'd outline some concerns I've got regarding my fueling/current carb tune, and see if anyone has any suggestions about how to proceed. First, a few bits of background. I've got an 88 with a 4.2. 165k mi. Back in 2015 I had an EMPI Weber Style carb installed and all the old emissions crap ripped out. Was installed by Collins Brothers Jeep here in the Dallas area. They're a reputable shop and are one of the go-to places locally for Jeeps from CJs to current.
When the carb was first installed it ran great from idle to driving in 5th gear on the freeway. Only slight complaint was a strong exhaust smell (maybe exhaust related, maybe running rich). I finally got that addressed by Collins Brothers at my most recent service which was just last month. Here's what's been done recently:
1. Catalytic converter was shot, so we replaced it. Also installed a downturn exhaust tip. This significantly improved the smell.
2. Basic tune up - oil, plugs, wires, cap and rotor. Air filter cleaned and re-oiled.
3. They said they tried to lean out the carb a bit in case part of the exhaust smell was due to running rich.
I've noticed a number of symptoms (most new) that have me concerned that my current state of tune isn't quite right. I'll outline my main observations.
1. Really sooty exhaust at start up. Sprays black crap all over my garage floor. Exhaust tip is brand new and already black. Exhaust smell once warmed up is much better than before, but still noticeable.
2. This is probably my biggest complaint and it's definitely a new symptom - when in fourth gear or especially in fifth the slightest bit of an incline in the road will cause the engine to lose revs and no amount of mashing the gas will give it enough fuel to regain revs. I never had trouble cruising at 65mph in the past, but now I'm downshifting to fourth gear to maintain revs. This can't be right.
3. In almost any gear, if I'm lower in revs, flooring the gas pedal will cause some sort of backfire/popping which sounds to be somewhere in the front to middle of the Jeep (maybe air filter or exhaust manifold? Not out the exhaust tip). I don't think I experienced this in the past.
4. Lastly, the idle is smooth in the sense that it will stay running at whatever rev amount it decides to run at. It doesn't bounce around. The problem seems to be that sometimes it wants to idle at 800 RPM and sometimes even after I've been driving around town and the engine is warm, I'll start it up and it'll struggle to stay running at 200-300 RPM until I rev the engine or drive it for a few minutes. Then it acts fine. This is pretty intermittent. The choke gives extra fuel at cold start up like it should, but this seems to be an issue after it's warm.
Sorry, that's a lot of info, but I wonder if there are some inter-related issues. Overall, the Jeep is still very driveable, but it's just not quite right compared to my previous experience. I'm probably due to take it back to Collins Brothers, but I like to have a decent level of knowledge about what's going on so I'm not just that guy that's like "I'm stupid. Fix my Jeep please.".
When the carb was first installed it ran great from idle to driving in 5th gear on the freeway. Only slight complaint was a strong exhaust smell (maybe exhaust related, maybe running rich). I finally got that addressed by Collins Brothers at my most recent service which was just last month. Here's what's been done recently:
1. Catalytic converter was shot, so we replaced it. Also installed a downturn exhaust tip. This significantly improved the smell.
2. Basic tune up - oil, plugs, wires, cap and rotor. Air filter cleaned and re-oiled.
3. They said they tried to lean out the carb a bit in case part of the exhaust smell was due to running rich.
I've noticed a number of symptoms (most new) that have me concerned that my current state of tune isn't quite right. I'll outline my main observations.
1. Really sooty exhaust at start up. Sprays black crap all over my garage floor. Exhaust tip is brand new and already black. Exhaust smell once warmed up is much better than before, but still noticeable.
2. This is probably my biggest complaint and it's definitely a new symptom - when in fourth gear or especially in fifth the slightest bit of an incline in the road will cause the engine to lose revs and no amount of mashing the gas will give it enough fuel to regain revs. I never had trouble cruising at 65mph in the past, but now I'm downshifting to fourth gear to maintain revs. This can't be right.
3. In almost any gear, if I'm lower in revs, flooring the gas pedal will cause some sort of backfire/popping which sounds to be somewhere in the front to middle of the Jeep (maybe air filter or exhaust manifold? Not out the exhaust tip). I don't think I experienced this in the past.
4. Lastly, the idle is smooth in the sense that it will stay running at whatever rev amount it decides to run at. It doesn't bounce around. The problem seems to be that sometimes it wants to idle at 800 RPM and sometimes even after I've been driving around town and the engine is warm, I'll start it up and it'll struggle to stay running at 200-300 RPM until I rev the engine or drive it for a few minutes. Then it acts fine. This is pretty intermittent. The choke gives extra fuel at cold start up like it should, but this seems to be an issue after it's warm.
Sorry, that's a lot of info, but I wonder if there are some inter-related issues. Overall, the Jeep is still very driveable, but it's just not quite right compared to my previous experience. I'm probably due to take it back to Collins Brothers, but I like to have a decent level of knowledge about what's going on so I'm not just that guy that's like "I'm stupid. Fix my Jeep please.".
