I have a 1985 CJ7 258 4.2L that I installed a Howell fuel injection California model on. I also installed a Borla header. When I start the jeep it runs rough and will barely idle. It is running very rich (the plugs are black). Howell is closed on the weekends so I can't call them. Check engine light shows code 33.
Here is what I have checked so far: Fuel pressure is 13 to 13.5 psi. O2 sensor checked with volt meter readings were .9V DC when heat applied and dropped to .1V DC when heat removed. Map sensor checked and reads 4.85 volts and drops 1 volt for every 5 inch Hg added with a vacuum pump. Replaced cap, rotor, plugs, wires and checked timing which was about 5* BTDC. All vacuum lines have been replaced with new lines. Anyway, I don't know what else to check and would appreciate any help or feedback anyone might have.
I did some further checking and I have found the problem. I only have 8 inch Hg of vacuum, (map sensor should have around 20 to operate correctly) but have no idea why my vacuum is so low. Compression on all 6 cylinders are 142, 148, 148, 150, 152, 151. I performed a smoke test on the motor and no leaks anywhere. EGR valve is new. Any ideas???
The vacuum goes from the MAP to the back of the Howell fuel injection. I think you would call it the throttle body. This is where Howells instructions say to attach it. And it is only about 12" long and has a nice cascade to it.
In the Howell instructions it states that "the MAP sensor has its own vacuum tap at the right rear of TBI and nothing should be tee'd into this line". I double checked and this is where I have the MAP vacuum connected. FRUSTRATED!!
Okay, so I read where the timing should be 8* with the Howell install not the factory 5*. I set the timing to 8* BTDC and now the vacuum to the MAP is 10 (increased by 2). I also checked the manifold and it's at 10 at idle as well. If I connect my vacuum gauge to the MAP sensor and pump it up to 15 and keep pumping it a little to keep it there, the engine smooths out some and definitely runs better. My other question is....shouldn't the manifold vacuum be around 20?
Where is the vacuum advance line hooked up to? Did you set the timing with that line connected or disconnected?
It's connected to a splitter coming out of the manifold. I set the timing with the advance line disconnected and plugged. When I checked the manifold pressure earlier, I checked the dedicated line going to the brake booster.
Vacuum is too low and is indicative of retarded ignition timing. The MAP is probably telling the ECU that the engine is under a load when it's not, so the ECU adds fuel. Are there any adjustments on the Howell?
Any vacuum leaks? Have you tried spraying throttle body cleaner arond the intake manifold to head to see if there's a leak there?
Originally Posted by chris87xj
If you own a Renix Jeep, you'll want to check this out. >
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