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03-28-2024
Fourjeepin

Newbie - here to learn more

Hi - I have a 1979 CJ7 with a Howell EFI on an AMC360. I added the Howell about 15 years ago and it has been great. Well, it ran open loop for at least a year before I figured out that it needed better grounding. I’m not the best with electronics but I go to extremes to avoid taking my junk to be repaired by someone else.

I joined last night because it is running like garbage since the fall. Rough idle, stalls if I don’t give it gas, and runs waaaay rich. Unsure what I did to cause this, but it started after I made a bunch of changes last summer/fall building some tube fenders. I accidentally clipped the tach feed wire and after about a couple of weeks of troubleshooting, found the wire issue but now it is undrivable due to mystery issue.

Last weekend I replaced the MAP sensor. No difference. I also connected to TunerPro. I don’t yet understand how to use it well, but it showed some interesting issues:
- it showed much higher rpms than my tach. About 50% higher. Tach believed to be accurate.
- volts showed at about 10 vs. voltmeter gauge and multimeter both read just over 12
- runs closed loop but crazy rich

To anyone that made it through all of that, thanks and please send suggestions on next steps. Until then, I am going to absorb what I can on troubleshooting this system.
03-28-2024
MO LS Noobie

Quote:

Originally Posted by Fourjeepin

Last weekend I replaced the MAP sensor. No difference. I also connected to TunerPro. I don’t yet understand how to use it well, but it showed some interesting issues:
- it showed much higher rpms than my tach. About 50% higher. Tach believed to be accurate.
- volts showed at about 10 vs. voltmeter gauge and multimeter both read just over 12
- runs closed loop but crazy rich

First of all, since your troubles began when you were welding on your truck, it is very possible that you damaged something inside the PCM. Did you disconnect the battery prior to welding? The wire that you shorted out going to the tachometer might have done something, but not likely. I would go through your ground wires again, even using battery size cable to ground the battery to the frame, battery to the engine, and engine frame. Make sure the ground wires for your computer are sound.

Tuner Pro requires that you have the proper BIN and .XDF file or it will give you erroneous information. There is a lot of information on this site for TunerPro help. If it is in closed-loop it should not be rich, fuel trims would be really negative but it should self adjust. The oxygen sensor could be bad, or the ground for the oxygen sensor could have a bad connection. Is this a one wire oxygen sensor or three/four wire?

Howell EFI is a good system using the older GM technology. I hope this helps, Jeff
03-29-2024
ralmo94

Like he said said, you need the proper definition files for tuner pro, otherwise it's like trying to decipher Greek with a Spanish English dictionary.
You need to know what mask your ECU is using, then you can get the correct definition for the data stream.

Do you have a functional check engine light? If so do you know how to check for codes at the aldl port with a jumper wire, or paper clip? What codes if any are present?
03-29-2024
Fourjeepin

Quote:

Originally Posted by MO LS Noobie

First of all, since your troubles began when you were welding on your truck, it is very possible that you damaged something inside the PCM. Did you disconnect the battery prior to welding? The wire that you shorted out going to the tachometer might have done something, but not likely. I would go through your ground wires again, even using battery size cable to ground the battery to the frame, battery to the engine, and engine frame. Make sure the ground wires for your computer are sound.

Tuner Pro requires that you have the proper BIN and .XDF file or it will give you erroneous information. There is a lot of information on this site for TunerPro help. If it is in closed-loop it should not be rich, fuel trims would be really negative but it should self adjust. The oxygen sensor could be bad, or the ground for the oxygen sensor could have a bad connection. Is this a one wire oxygen sensor or three/four wire?

Howell EFI is a good system using the older GM technology. I hope this helps, Jeff

Thanks Jeff! I've been real happy with the Howell system. It is very possible that I didn't disconnect the battery ground before welding so I ordered a replacement (or spare) ECU. I will check the grounds thoroughly this weekend and also reconnect TunerPro after double checking my files. My O2 sensor is a one wire. I thought it was showing a good signal in TunerPro, but need to double check all of my sensor data to make sure all are good.
03-29-2024
Fourjeepin

Quote:

Originally Posted by ralmo94

Like he said said, you need the proper definition files for tuner pro, otherwise it's like trying to decipher Greek with a Spanish English dictionary.
You need to know what mask your ECU is using, then you can get the correct definition for the data stream.

Do you have a functional check engine light? If so do you know how to check for codes at the aldl port with a jumper wire, or paper clip? What codes if any are present?

It is possible I was using the incorrect files; I will double check them and try again. Thanks for the advise. I do have a check engine light and keep a paperclip handy. I will check for any codes when I fire it up next. I was so discouraged last weekend that I didn't think to check codes.