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Unread 12-01-2012, 02:47 PM   #1
fastener
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CJ7 w/Howell Running rich and rough

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.


Last edited by fastener; 12-01-2012 at 08:57 PM..
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Unread 12-01-2012, 09:02 PM   #2
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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???
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Unread 12-02-2012, 12:13 PM   #3
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Where is your vacuum hose to the MAP hooked up?
Manifold? Is it clear? No kinks or low spots? It must "cascade" down from the MAP to the intake manifold. No P traps in it.
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Unread 12-02-2012, 05:25 PM   #4
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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.
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Unread 12-02-2012, 05:36 PM   #5
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My concern is that if it's above the throttle plate there will be low vacuum. Below the throttle plate is manifold vacuum. Might be worth a look-see.
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Unread 12-02-2012, 05:56 PM   #6
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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!!
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Unread 12-02-2012, 06:08 PM   #7
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Hook your vacuum gauge to a manifold vacuum source and get a reading.
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Unread 12-03-2012, 07:40 PM   #8
fastener
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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?
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Unread 12-03-2012, 07:45 PM   #9
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17 to 21 inches of vacuum at sea level. Does your distributor have a vacuum advance?
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Unread 12-03-2012, 07:56 PM   #10
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Quote:
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17 to 21 inches of vacuum at sea level. Does your distributor have a vacuum advance?
yes it does
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Unread 12-03-2012, 08:00 PM   #11
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Where is the vacuum advance line hooked up to? Did you set the timing with that line connected or disconnected?
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Unread 12-03-2012, 08:09 PM   #12
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Quote:
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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.
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Unread 12-03-2012, 08:11 PM   #13
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Try setting the timing to about 12* with no vacuum connected. And then, find a PORTED vacuum source for your vacuum advance. That's one ABOVE the throttle plate.
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If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

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My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 12-03-2012, 08:46 PM   #14
fastener
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Quote:
Originally Posted by cruiser54 View Post
Try setting the timing to about 12* with no vacuum connected. And then, find a PORTED vacuum source for your vacuum advance. That's one ABOVE the throttle plate.
Did the above and it runs a little better and now I have 13" vacuum. Still really rich and rough though.
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Unread 12-03-2012, 08:55 PM   #15
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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?
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Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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