Jeep with GM TBI swap

Hey Guys, I'm sure this isn't one you will come across often. I've put a Howell TBI kit onto my Jeep (AMC) 304 V8. It's got hedders, glass packs, and
an Edelbrock Performer intake. I have an adapter to mate the GM TBI to the intake. And it uses the GM ECM and a Howell-made wiring harness. Some of the wiring colors don't match up to GM wiring colors. But I have the kit installed and wired up, and the fuel pump and lines all on it, it runs, but it runs too rich at idle prior to closed-loop operation. Once it goes closed loop and runs fine. Gets a bit too much fuel when really goosing it, but I've backed off the fuel pressure regulator about as much as possible. I've cleaned out the TB, the IAC port, etc, and it still doesn't want to idle properly, it's trying to idle at 600 rpm, with some surging, to about 700 rpm. But as it continues to run rich at idle it will foul a plug and eventually stall the engine. I have adjusted the TPS setting so it is at 0.6V with the throttle plate fully closed as per the manual. When I first tried that it would start, but wouldn't stay idled, it would stall out. So I increased the setting on the TPS until it would actually idle. It's now set at 0.75V with the throttle plate closed. And it ran fine for a little while, but would eventually idle down from about 850-900 all the way down to approximately 400-550 with a good bit of surging as the IAC <I assume> was trying to regulate the idle. I have checked the IAC, it measures out fine as far as Ohming it out, the MAP sensor reads good as well. And the TPS works just fine as well. I don't have the ESC set up on mine, it's running with a stock Jeep distributor, ignition module and an Accel super coil. Does anyone have any ideas on what might be causing the trouble and how to fix it. Also, when it is idling, I think with my current exhaust set up and the location of the o2 sensor, it's not getting hot enough to stay closed loop at idle speeds. I have it mounted just past the collector on the hedders, but since there is no cat (it's a 1973 Jeep), I'm guessing it's not staying hot enough, should I look into a 3 wire o2 sensor, right now it's a regular one wire set up. The TBI system is the same as the 86-90 truck set ups. As far as I know, it's the TB system for a chevy 350. I'm at a loss, about ready to make a bypass for the o2 sensor for when it's at idle and force it to run closed loop even if the o2 sensor isn't hot enough, just substitute the voltage output it should be sending to the ECM. I've been trying for quite a while to get it going right, without much luck. Also, it's a manual transmission, I've seen there are two different version PROMs one for an auto and one for a manual, could this be causing problems as well, I'm not certain which one I have, didn't bother to open up the case and see what number is on it.
Gus
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| Hey Guys, | I'm sure this isn't one you will come across often. I've put a Howell | TBI kit onto my Jeep (AMC) 304 V8. It's got hedders, glass packs, and | an Edelbrock Performer intake. I have an adapter to mate the GM TBI to | the intake. And it uses the GM ECM and a Howell-made wiring harness. | Some of the wiring colors don't match up to GM wiring colors. But I | have the kit installed and wired up, and the fuel pump and lines all on | it, it runs, but it runs too rich at idle prior to closed-loop | operation. Once it goes closed loop and runs fine. Gets a bit too | much fuel when really goosing it, but I've backed off the fuel pressure | regulator about as much as possible. I've cleaned out the TB, the IAC | port, etc, and it still doesn't want to idle properly, it's trying to | idle at 600 rpm, with some surging, to about 700 rpm. But as it | continues to run rich at idle it will foul a plug and eventually stall | the engine. I have adjusted the TPS setting so it is at 0.6V with the | throttle plate fully closed as per the manual. When I first tried that | it would start, but wouldn't stay idled, it would stall out. So I | increased the setting on the TPS until it would actually idle. It's | now set at 0.75V with the throttle plate closed. And it ran fine for a | little while, but would eventually idle down from about 850-900 all the | way down to approximately 400-550 with a good bit of surging as the IAC | <I assume> was trying to regulate the idle. I have checked the IAC, it | measures out fine as far as Ohming it out, the MAP sensor reads good as | well. And the TPS works just fine as well. I don't have the ESC set | up on mine, it's running with a stock Jeep distributor, ignition module | and an Accel super coil. Does anyone have any ideas on what might be | causing the trouble and how to fix it. Also, when it is idling, I | think with my current exhaust set up and the location of the o2 sensor, | it's not getting hot enough to stay closed loop at idle speeds. I have | it mounted just past the collector on the hedders, but since there is | no cat (it's a 1973 Jeep), I'm guessing it's not staying hot enough, | should I look into a 3 wire o2 sensor, right now it's a regular one | wire set up. The TBI system is the same as the 86-90 truck set ups. | As far as I know, it's the TB system for a chevy 350. I'm at a loss, | about ready to make a bypass for the o2 sensor for when it's at idle | and force it to run closed loop even if the o2 sensor isn't hot enough, | just substitute the voltage output it should be sending to the ECM. | I've been trying for quite a while to get it going right, without much | luck. Also, it's a manual transmission, I've seen there are two | different version PROMs one for an auto and one for a manual, could | this be causing problems as well, I'm not certain which one I have, | didn't bother to open up the case and see what number is on it. | | Gus |
Do you think the TBI for the 4.3 V6 might make a difference? It is closer to the C.I. than the 350.
--
Jarhead




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Jarhead wrote:

I was actually looking, and according to what's on the Howell website and what it says on the tag that's attached to my TB, it's for a 4.3 set up, either way they are all 500 cfm for those style of TBI set ups. So, I don't think that would be the problem either way. But that was something I had wondered about. But I checked for codes and there aren't any trouble codes stored in it. So my search continues. Thanks for the replies.
Gus
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Well I went to the junkyard today and pulled a 3 wire o2 sensor from and 90 something buick Regal. Gonna try and wire that in, and hopefully with the heater built into it, it may work better. Will let you guys know, I'm headed out of town for the weekend so it won't be until Tuesday or Wednesday.
Gus
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So I installed and wired up the heated o2 sensor (3 wire), it was still running rich on start up, but once warmed up it stayed closed loop during idle, so I think this will be a better set up. Taking it out tomorrow for a test run, will post more.
Gus
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