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Discussion Starter #21
While waiting for the PCM to arrive I went ahead and replaced the Hall Effect with no change, I am still having warm idle "hunting" issues. cold start idle is absolutely beautiful.
 

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Discussion Starter #22
I have received the new PCM, and it runs much better at a warm idle, I have also noticed that my fuel gauge now works. I will report back with any and all improvements.
 

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Discussion Starter #24
I have a question on the temperature sensor for the PCM, I bought a new replacement when I bought my new engine, is there a specific type of sensor (ohm range) that the PCM requires?
 

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Yes, it is a specific thermistor value range. Are you talking ambient (air) temperature sensor or coolant temperature sensor?
Many ambient temperature sensors are internal to the PCM, hence the reason that the intake air flows through it to the air cleaner.
 

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I think an 83 has a spark control computer (that is what Chrysler calls it). It probably has a vacuum line going to a vacuum transducer on that unit. I recall working on an 83 with erratic idle, and the problem ended up being a vacuum leak in the spark control vacuum transducer. The vehicle could not maintain the distributor timing to a steady level because of the vacuum diaphragm leak. I found the leak by using a hand operated vacuum pump and a junkyard SCC took care of the problem. Actually, the hand vacuum pump is very handy for troubleshooting these old early 80 EEKs since there are many vacuum operated valves and controls.

Other common problems that caused erratic idle were a leaking carb base gasket, EGR tube leak (intake manifold side), badly worn throttle butterfly shaft or egged out shaft bore in the carburetor, and a leak in the vacuum controlled air filter box flapper (stove pipe flapper).
 
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A bit OT for a second but--
Is this a switch as opposed to a sensor? I don't understand why you would need it to be a specific color if it's a sensor. I know the later cars with the SMEC have a thermistor-- a device that generates the changing resistance signal, like JAmmons mentioned. What I don't get is why you would need a bunch of different thermistors for different emissions packages and things like that. What I DO get is why you'd need a bunch of different switches for different emissions packages, just like you'd need different thermostats. So maybe the older computers just looked for a binary input-- the engine is warm or it isn't. Is this the case? I've never even seen an '83 PCM, so all this is speculation. If you've got your hands on a thermistor when you need a thermal switch, the PCM isn't going to know what to do with that input...
 

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A bit OT for a second but--
Is this a switch as opposed to a sensor? I don't understand why you would need it to be a specific color if it's a sensor. I know the later cars with the SMEC have a thermistor-- a device that generates the changing resistance signal, like JAmmons mentioned. What I don't get is why you would need a bunch of different thermistors for different emissions packages and things like that. What I DO get is why you'd need a bunch of different switches for different emissions packages, just like you'd need different thermostats. So maybe the older computers just looked for a binary input-- the engine is warm or it isn't. Is this the case? I've never even seen an '83 PCM, so all this is speculation. If you've got your hands on a thermistor when you need a thermal switch, the PCM isn't going to know what to do with that input...

I'm thinking it was just a switch back in 1983. That vehicle may or may not even have a feedback carb (probably not) and therefore probably not an oxygen sensor (the US car versions did). I also think the electric fan may have been turned on by a thermal switch in bottom of the radiator. There was an external voltage regulator (not in the computer). Actually the computer was pretty basic with the main purpose being to fire the coil and adjust the timing based on intake manifold vacuum and engine temperature (but possibly sensing only hot or cold). In this link is a minimal description and what they looked like.

www.omnilith.net/info/mopar_ecu/sccinst.pdf
 

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You guys are both correct. It appears to be a 125°F coolant switch.
The Rampage/Scamp were considered 'light trucks' emission-wise and didn't have to meet the tougher passenger car emissions of the Omni/Horizon/024/TC3 models.
California may have been a different story.
 

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So, to JAmmons--
If you're having problems with the CTS (like error codes), see if you have a thermistor or a switch installed. The parts look very similar; I don't think it would be too difficult for them to get swapped, inadvertantly or otherwise, at a parts store. I've been given a thermostat for the 3.8 V6 for my Spirit, and this was from an older guy who is usually excellent in terms of knowledge and service.
 

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Discussion Starter #34
The issue that I am still having is at cold start up my idle is perfect but at warm idle it hunts about 200 rpm swing (it used to be a 500 rpm swing but I have replaced many parts getting things better) I am looking into all possibilities. Right now I am looking at vacuum lines verifying everything.
 

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Is it a steady wavering in RPM, or more of a loping change in RPM? If it's a steady wavering, what's the frequency, and under what conditions (like idling in park/neutral versus drive, ambient temperature, etc.)? If it's a loping, rough change, you could be looking at a misfire. Remember that these cars have old-school, electromechanical distribution. Although there aren't breaker points, the terminals in the distributor are subject to rather heavy degradation due to the large gap inside. You could be looking at a damaged terminal, or a wire that may be broken in internally. It's unusual, but spark plugs can be bad "out of the box"-- I think this is unlikely here since the plug typically either works or it does not, but it's another possibility. I would pull the plugs and inspect the firing ends, paying attention to gaps, conditions of electrodes, and looking for excessive carbon deposits that may be indicative of misfiring.
 

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Discussion Starter #36
It's a steady wavering RPM at warm idle in park/neutral and when I hold the brake and put it in drive (100-200 RPM). Once I start driving I don't notice it. Everything is new, I have even replace the Hall effect electronic ignition, just for good measure. the spark plugs are good, gaped correctly and are clean.
 

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There's a slight chance your brake booster has a crack in the vacuum diaphragm. The best way to check is to totally plug the big vacuum line to the booster for a test. With the vacuum line sealed closed, start the engine and put it in gear. If it acts the same way, it's not likely a booster problem. If the idle is good, you found your problem. Of course, it usually goes without saying, but for that test, you won't have power brakes. :)
 

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Discussion Starter #39
The carburetor had better be rebuilt correctly I paid $300 for it, lol. Carb Cleaners and such have no affect. I am still looking at all the vacuum lines to verify there is not a leak.
 
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