I have a 90 YJ with a 4.2 in it. I installed a Howell fuel injection kit that uses the 4.3 Chevy throttle body and computer based in the year span of 1986-1991. Let me say that this is a great kit! I put it on over 17 years ago and aside from replacing the fuel pump (to be expected) a few years back, this is the first problem I've had with this system. As best I can tell it is running rich. Very rich! In the winter when it was still cold out it ran fine but would occasionally give a check engine light on a semi-warm day. Unfortunately it wasn't storing the code so I couldn't pull any codes from it. As it has gotten warmer out it has started to run a lot worse! It sputters when it starts and has hesitation issues on acceleration and is burning through a lot of gas. If it is real warm out then after the engine has warmed up then it wont restart like if I stop at a store or anywhere. It acts as if it is flooded and the only way to get it to restart is to unplug the injectors until it starts, let it run until it runs out of the "flooded" fuel and then reconnect the injectors and it will restart. The exhaust smells strong of gas and it tends to run better/smoother with a vacuum hose disconnected, sucking in more air. I have been able to pull codes as the check engine light is on nonstop now. I replaced the O2 sensor, the fouled spark plugs, wires and rotor and cap and got no improvement. The first code I pulled was 35 which is the idle air control valve. Howell technician recommended I replace that so I did with very little improvement. I test drove it and now I get 2 codes 34 (map sensor) and 45 (O2 sensor rich exhaust detected). Called Howell again and they recommended replacing the map sensor so I did. It seems to try to run a little better but it still is crap compared to how it should be. I just picked up an engine coolant sensor on my way home from work this A.M. because I've seen online where that can cause the ECM to signal the need for more fuel if the sensor is sending it incorrect signals. Still waiting on it to cool down enough to work on so in the mean time I figured I'd ask the great people of Jeep forum for some advice. Anyone out there have this kit, had similar issues or just have a better knowledge of these fuel injection systems than I do? Feel free to throw your ideas at me!
Check for vacuum leaks . Esp at the head and where the TB attaches.
I have had that system on several chevy engines, and the temp sensors do give them fits. There is more than one on the factory units, not sure how Howell set theirs up.
TPS could be giving trouble if you got water up near the connectors. Some contact cleaner and dielectric grease on reassembly usually helps.
Have you put a vacuum gauge on it at idle to se what it says?
Have you checked the fuel pressure yet? High pressure (bad regulator) causes rich condition
And check to see if your injectors are dripping, easy to do on a TB. They should be dry with the system pressurized and engine off.
An exhaust leak before the O2 sensor causes a rich condition also
Wow, 17 years! You are definitely an early adopter of the Howell system. You will find a lot of JF YJ and CJ owners have done this conversion. I just did mine and fired it up yesterday.
On top of what you've done and what Old4X has recommended, I would advise you to disconnect the battery and turn on the headlights for a minute. This will reset the ECM. These ECM constantly collect data and adjust to your engine conditions. With any bad sensors it has been learning bad data. Need to clear all that and let it learn from a clean image.
Other than that, after 17 years, could just need to rebuild the throttle body and injectors.
Old4X, FYI, the map sensor on this kit is hanging on the firewall and connected by a hose, which Howell specifies must not be more than 12" long, and must not be connected to anything else. Also must be above the level of the TB. Check that hose for obstructions/gunk.
Yeah, Howell is pretty strict and explicit in their instructions, so I guess they think it is critical to performance. Makes me wonder if they were so clear with the instructions 17 years ago.
Well I finally have an update and it is fixed and running great! Here is what I went through to get it working.
Took the plunge and replaced the ECM (computer) and got no improvement. Contacted Howell and the technician said that I had done everything and replaced everything on their system except 1 item, an electronic filter that filters the signal between the coil and the ECM. It is a small electronic circuit board mounted in the wiring harness next to the ECM connectors. It was $50 for that little part and it still didn't fix it! I had the ignition control module tested and it passed so now I was at a dead end. It was so bad that I could disconnect 1 injector and it ran perfect! I know my Jeep inside and out but I just could not figure it out. I left it sit for several days and while pulling some over time at work one night I decided to search online AGAIN for a probable cause. One possible solution I found I just had to try. Checking to see if the fuel return line was clogged causing too high of a fuel pressure. Some people claim their is something in the tank that can get clogged up. So I pull the return line off the back of the throttle body and attach a 7 foot section of new fuel line to it and put the other end in a gas can and it ran perfectly. Now I'm on to something! So then I try to blow air into it. When I did this the rubber line I had in my hand began to swell big time! I had a clog! I drop the tank and find the vacuum lines on top the tank had been smashed between the tank and body. Not the problem but not how it should be either. I then pulled the sending unit from the tank and found no problems there so my problem had to be inline somewhere. With the tank disconnected I try blowing air again and get the same "swelling hose" result. So I start tracing the return line down expecting to find a crimp in the metal line where a rock hit it or something but I don't. So I disconnect the 2 foot or so of rubber fuel line that connects between the tank and line and I cant pull them out!! Problem found! Not sure if this is a common problem for YJ's and I just hadn't heard of it yet or what but this is what I had. Tracing backwards from the tank to the metal fuel lines on the drivers side the hoses are encased in a rubberized foam block that pass between a cross member and the body. The cross member had began to rust and the more the rust expanded the less room their was for the fuel lines resulting in a crimped return and vacuum line! After removing the rust and using a pry bar to ensure enough clearance, I replaced the fuel and vacuum lines and put it all together and voila, runs like a new Jeep.
So, after spending roughly around $420+ in new electrical parts I fixed the real problem for the price of 7 foot of fuel hose, new clamps and vacuum hoses! Don't know whether to celebrate by getting drunk or drown my sorrows by getting drunk!:facepalm:
Tonka after you said it was running rich it should have been the fsecond place the tech took you after the O2 sensor. I wish I would have seen your post earlier. No reason to cry. $400 in 17 years, I call that a real good deal!
I appreciate you taking the time to come back and give us an update. Happy to hear it is fixed.
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