YJ overheating?

[RideRED258]

I have an 89 YJ with a 4.2L. I ripped off the stock carb and replaced it with a TBI unit from Howell. Ever since it has been running a bit hot. I took out the stock 195 thermostat and replaced it with a 185. Its a new engine, with all new temp sensor, sending unit, water pump, ect. The problem is its not registering that hot on the gauge. It reads normal, but i checked the oil and noticed the paint bubbling off the valve cover. I checked the plugs which had a burnt white reside with blistered insulators. Im not sure if It is running lean, and if so, shouldnt the computer adjust the mixture accordingly(the Howell kit is computer controlled. Its off a 4.3L chevy)? Im not sure where to start, as the gauge reads normal, but bubbling paint and blistered plugs dont lie. Shes running hot! Any advice would be great.

 

[TerryMason]

I'd say it's running way lean. I'd get it fixed quick.

On my 914, I have a standard oil gauge, which read normal (this is after I added new carbs). I then bought what's called a cylinder head temp gauge, which had a temperature probe that you put under one of the spark plugs. That gauge would read waayyy hot. Just because the oil isn't too hot doesn't mean that your plugs and the areas around there aren't too hot.

I was able to tune that engine by buying a wide band O2 sensor however these guys are pretty expensive ($350). You can also tune by pulling the plugs alot.

I think your engine is running very lean, and I wouldn't drive it until you get it sorted out.

 

[RideRED258]

Thanks for the advice. What would be the best way of checking\adjusting the mixture. The only adjustment the manual states is the idle speed. To adjust the fuel\air mix i have to grind the throttle stop flat, drill into the $1200 TBI housing to allow a T20 torx bit to fit. It seems crazy to go through that if the computer is suppose to adjust the mixture already. Could the change in humidity and temp from winter to summer cause the computer to run lean? does the comp. do a self check everytime i start the engine? or only when first connecting the battery. I will disconnect it and see if that helps. I know it was running a bit on the rich side during the winter(black soot from the pipe), but that stopped when the weather warmed up. Im almost thinking its an electrical issue, tho im not sure. could it be too hot of a plug? Im running autolite platniums. Cant think of anything but a bad sensor, or gauge. Im pretty sure this TBI unit self adjusts the mixture. For now shes parked in the yard until i can get this fixed. thanks for the tip.

 

[TerryMason]

I don't have any experience with the TBI, so take this with a grain of salt.

I believe the mixture of these things is controlled by the computer, and if you want a leaner mixture you have to have a new chip burnt.

Maybe you have a bad O2 sensor, or an air leak? If the O2 sensor is cheap, you may try changing that.

Have you tried calling Howell?

 

[TerryMason]

I grabbed this from another bbs, it's instructions on testing the O2 heater - hopefully it will help

The 3 wire (heated) O2 sensor will have a ground wire, a wire to send voltage to the heating element, and a wire that sends the voltage of the rich / lean mixture to the ECM. I would first unplug the O2 sensor with the engine cooled down from sitting over night. I would connect the negative lead of the volt meter to the negative post of the battery. Then I would turn the ignition switch to the "ON" positon and test each wire of the plug going to the O2 sensor with the positive lead of the volt meter to see which wire had battery voltage (usually a fully charged battery will have about 12.6 Volt DC.) This would tell me that power to the O2 sensor was good. I would then turn off the ignition switch and plug the O2 sensor back together. I would then turn the ignition switch to the "ON" position and wait a minute or two to see if the O2 sensor is getting warm. The heated O2 sensor should be warm to the touch in about 3 minutes or so. To check the voltage of the O2 sensor lean / rich voltage wire, (with or without the engine running) I use the ECM wiring diagram to figure out which pin on the back of the ECM is the wire with the rich / lean voltage from the O2 sensor and plug the positive lead of the volt meter to that ECM pin, I like using the volt meter negative lead connected to the negative post of the battery when I'm checking voltage. Sometimes I find things wrong with the wiring when a voltage check fails with the negative lead of the volt meter connected to the negative post of the battery.
dave

 

[redrooster]

He may not have the Heated O2 with the Howell kit. Heated = 3 wire, standard =2 wire.

Either way, Terry is right, you cannot manually adjust the mixture. It has to be done in the fuel table programming in the computer. I doubt if that is the problem anyway, unless you are running a non-stock cam with a stock Howell program and didn't tell them.
It sounds like a sensor. Start with a phone call to Howell. Then maybe check the O2 and Map sensors. The Map sensor needs to be mounted correctly also.
Also, I don't know about Howell, but most TBI kits require you to set your timing at 0 with the Electronic Spark Control module unplugged. You Plug it back in after you get it set. Did you do that?

 

[RideRED258]

The howell kit came with a 1 wire O2. everything in the kit is off a 4.3l GM. The kit came with an dignostics port. you can ground out the ADLA wire and the check engine light will flash a code. Nothing. I put it in field service mode (driving down the road while grounded) and It flashed "open loop" which according to my manual is normal. So as far as the computer is concerned, it doing everything right. I will go pick up a new coolant temp sensor and sending unit, as well as new O2 sensor. Though If one were bad, the comp. should pick up on it? I also think i see a Hi-flow radiator and electric fan in the near future, as many people have told me the older jeeps cooling systems are hardly enough for the 4.2L. I just wish i would have paid the extra 30 bucks for a hi-flow water pump. Live and learn. thanks for all the help guys!