Post Nutter Bypass Power Issues

kwrsmith2000

New Member
Joined
Nov 22, 2020
Messages
3
Location
Raleigh, NC
87 Wrangler 4.2, just completed a nutter bypass and totally replaced the old carb with a reman carter carb without the stepper motor......fired it up and saw immediate results with strong stable idle and engine sound generally....



However, seem to be having a consistent problem with power when the engine gets warm.....during the first ten min of a drive, runs great, nice acceleration, etc......however, once engine is warm......seems like I really struggle in 3rd and 4th gear to sustain any power.......in particular if there is any grade at all in the road......at times when engine is sluggish, seem to get vibration in the steering wheel and feels like it is just going to die a slow death..........



Trying to figure out where I should start looking to understand? I have already replaced wires, plugs, cap, rotor......as mentioned new carb, nutter bypass.....the timing when checked was at 9 otc....



so.....

EGR Valve?

Cat?



Can some smarter people give me some ideas where I should start.......i got so damn excited post nutter bypass, but can only enjoy the beast for ten min before I start to slowly, sadly drag my no power, light vibrating sweety home....
 
I’ve been working on my 90 4.2l and have had issues. Here’s what I found. First let me say that you should check your compression to determine if you engine is tired. I nuttered mine an rebuilt my carter carb. Although the engine ran better something just wasn’t right. Here’s what I found. The distributor needed to be recurved. My distributor had full advance at 1800 rpm. This is because when you’re connected to the computer, the computer retards the distributor advance depending on information it receives from the sensors. After nuttered , the computer does not control the distributor and the timing is too advanced. I recurved my distributor to have 32 degrees of advance at 3000 rpm. Initial timing is 9 degrees @ 500 rpm.
Next. Check your CTO coolant temperature switch. On my 90 YJ the coolant temp switch controls ported vacuum to the vapor canister and the EGR valve. This can create a vacuum leak when the timed ported vacuum kicks in at about 1500 rpm. The old vapor canister diaphragm is probably creating a vacuum leak. My vacuum canister has 4 hoses. One from the gas tank, and one from the carb float bowl to collect vapors. Leve these 2 hoses connected. The third hose goes to the carburetor and ties in with the pcv valve hose. This hose allows the vapor to be sucked into the carb. Leave this hose connected. The last hose is the purge valve. Remove this hose from the vapor canister. Cap the opening at the vapor canister.
At the carb the ported vacuum port is facing the valve cover. Disconnect the vacuum hoses going to the CTO switch. If you want to run an EGR valve you can run a vacuum hose directly to the EGR. These changes fixed the problems I had on my 90 4.2l
 
Thanks for the update, that is awesome...I will give it a go....I changed the fuel pump, filter and ignition coil...but have yet to fire it up due to the cold and no time.....

Much appreciated!!