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Jeep Wrangler YJ
YJ General Discussion
Still overheating
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<blockquote data-quote="deadpool1" data-source="post: 439408" data-attributes="member: 21229"><p>update my 95yj, this PCM has 2 fast idle pins , pin 27 and 28</p><p>the FSM explains how it works.</p><p>in SHORT:</p><p>driver flips dash A.C knob to <strong>on.</strong></p><p>pcm sees that act on 28 , "select sense pin"</p><p>then RPM goes to PCM mapped, RPM for AC on, my guess 1000, (still wiring mine up now) << hard to reach wires on mine</p><p>then when programmed RPM is reached (ckp sensor RPM) the PCM then engages the clutch of the compressor</p><p>and regulates RPM agressively. IAC not gummed up that is.</p><p>and it also reads back on pin 27 that clutch did get power.12vdc. (13 to15v actual)</p><p></p><p>the clutch fan stock is super powerful. with the duct'ed shroud.</p><p>agreed!</p><p>fans on condenser, may be needed. the FSM states, these run, overheated or A/C is active. </p><p>I guess it is solved now?</p><p>Mine never overheats, even 110f outside but I am doing the PCM fast idle mode, to make mine just like factory A.C, when AC is on Fast idle is enabled. to PCM</p><p>not sure what PCM you run here, 87?</p><p></p><p>I will post the secret RPM my PCM does, not told an the 3 service, manuals I have SM, EFI and diagnostic, ,it does say it has Idle UP mode for AC but never discloses what.</p><p>i have a RPM digital optical hand meter that is dead accurate for RPM. (no DRB here to see RPM)</p><p></p><p>the IAC is a servo and all cars made run it in 3 modes{or more} (to avoid IAC RPM hunting) the rule is GAIN</p><p>at idle in neutral gain is low, so RPM regulation is slow and gentle, but Reliable.</p><p>then in DRIVE ( a/t box) it goes aggressive and high gain</p><p>the IAC+PCM servo goes to to aggressive mode.</p><p>if engine EFI is running great , in closed loop all is well but if not and running lean , the idle speeds fail.</p><p></p><p>this is why modern cars use TBW throttle by wire. (TB motor drive)</p><p>1000RPM is very common RPM on small engines,A/C on, I can name many.</p><p>when at that RPM the fan is way more effective say at red stop sign , 110F out and works perfectly</p><p></p><p>I am not prevy of all your driveline mods so my anwers can be dead wrong. Jeeps tend to be not stock this old, endless examples.</p></blockquote><p></p>
[QUOTE="deadpool1, post: 439408, member: 21229"] update my 95yj, this PCM has 2 fast idle pins , pin 27 and 28 the FSM explains how it works. in SHORT: driver flips dash A.C knob to [B]on.[/B] pcm sees that act on 28 , "select sense pin" then RPM goes to PCM mapped, RPM for AC on, my guess 1000, (still wiring mine up now) << hard to reach wires on mine then when programmed RPM is reached (ckp sensor RPM) the PCM then engages the clutch of the compressor and regulates RPM agressively. IAC not gummed up that is. and it also reads back on pin 27 that clutch did get power.12vdc. (13 to15v actual) the clutch fan stock is super powerful. with the duct'ed shroud. agreed! fans on condenser, may be needed. the FSM states, these run, overheated or A/C is active. I guess it is solved now? Mine never overheats, even 110f outside but I am doing the PCM fast idle mode, to make mine just like factory A.C, when AC is on Fast idle is enabled. to PCM not sure what PCM you run here, 87? I will post the secret RPM my PCM does, not told an the 3 service, manuals I have SM, EFI and diagnostic, ,it does say it has Idle UP mode for AC but never discloses what. i have a RPM digital optical hand meter that is dead accurate for RPM. (no DRB here to see RPM) the IAC is a servo and all cars made run it in 3 modes{or more} (to avoid IAC RPM hunting) the rule is GAIN at idle in neutral gain is low, so RPM regulation is slow and gentle, but Reliable. then in DRIVE ( a/t box) it goes aggressive and high gain the IAC+PCM servo goes to to aggressive mode. if engine EFI is running great , in closed loop all is well but if not and running lean , the idle speeds fail. this is why modern cars use TBW throttle by wire. (TB motor drive) 1000RPM is very common RPM on small engines,A/C on, I can name many. when at that RPM the fan is way more effective say at red stop sign , 110F out and works perfectly I am not prevy of all your driveline mods so my anwers can be dead wrong. Jeeps tend to be not stock this old, endless examples. [/QUOTE]
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Jeep Wrangler YJ
YJ General Discussion
Still overheating
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