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Current test results. With engine running for several minutes at idle, disconnecting the IAC motor connector has no effect, the Idle continues to cycle up and down the same as before.
I have replaced the following since I purchased it used 2 years ago. Oldest part I have replaced since acquiring it 2 years ago has maybe 8,000 miles on it max.
I replaced old worn out and suspect parts as follows: (Note that I installed a cooler thermostat early on, about 160 F, due to overheating problems which is still installed!) then all new parts in this order (roughly), *catalytic converter, *radiator, *fan clutch, *coolant overflow bottle, (*the CC was backing up exhaust, giving me an oil pressure over 80 PSIG, and it was overheating the engine, then the radiator was shot internally, fan clutch was bad....all causing the overheating) also replaced craked flywheel, starter, Speed or CPS sensor, fuel pressure regulator, Distributor, Cap, Rotor, plug wires, plugs, fuel injectors, TPS sensor, Ignition control module (ICM) and HV coil, ignition switch, Park / Neutral switch, head light switch, EGR valve, Idle speed adjust or idle air control or idle air stepper motor (pintle valve, has many names!!! same part), MAT sensor, O2 sensor, alternator, MAP sensor, .....high flow oil pump, new crank shaft bearings. All parts replacements made slight improvements in performance at the time they were replaced. Oil consumption is nearly zero.
This list does not include suspension parts, tires etc, steering gear box, that I have replaced, LOL. (after all it has 247,763 miles on it, it is Jeep Wagoneer Ltd. 4X4, almost fully restored)
Knock sensor not installed (damaged)! Wire not connected. I just discovered this part, what it does, where it goes,etc. It was not installed when I aquired the jeep.
I also just found the real coolant temp sensor (it was hiding...and the knock sensor thanks to help from a new friend with Renix manual who steered me to this list) and hooked it up 100 miles ago (tested it first, got 1000 ohms at about 120 F, slightly warm engine) to the correct but previously 1 of 2 mysterious open (unused) connectors on the wiring harness. It has not made any difference in operation!
Has excellent engine acceleration when the transmission is not in gear. Sounds and runs great. But when driving, transmission engaged in drive, the acceleration is like having 4 cyl, 60 hp engine in it. It takes 2 minutes to get up to 60 mph.
No vacuum leaks that I can find. Excellent fuel pressure, it is right on to spec, even flow tested it.
Today I disconnected the IAC motor connector and the TPS connector to the ECU, one at a time while it was idling and it made no difference, it continued to cycle between 900 rpm and 300 rpm (with out dying!!). When I pushed the accelerator it died when it tried to return to idle with the TPS sensor disconnected, but disconnecting the IAC had not effect after pushing the accelerator (with the Jeep parked). I found it quite interesting that I could disconnect the TPS and IAC motor connections while at idle and watch the idle speed continue to cycle from 300 rpm to 900 rpm and back to 300 rpm on a 20 second cycle with the jeep parked!!!!!
I have read the Renix manuals I just received (today & Wed), and everything else I could my hands on in the past and a good bit from this forum the last few days, and I think these results today are pertinent and new to the discussion of erratic idles on these Renix system XJ jeeps!
I have more test data (VOM readings on connectors, wiring harness, and grounds!!!!!) to post, which I will do ASAP. This is a good start to get the discussion going, I hope.
Lastly, the new O2 sensor was disconnected for about 3000 miles (wiring harness got fried on the exhaust manifold one day) and was only operated for about 100 miles before the harness connector was melted from its encounter with the exhaust manifold. So I never got a real good look at what the new O2 sensor did. Before the new O2 sensor, and after its abroupt disconnection, I always had unpredictable idle speed issues like most of those frequently reported here. The newest idle cycling symptom is brand new to me!!! It began after I fixed the wiring harness and reconnected the O2 sensor.
I have replaced the following since I purchased it used 2 years ago. Oldest part I have replaced since acquiring it 2 years ago has maybe 8,000 miles on it max.
I replaced old worn out and suspect parts as follows: (Note that I installed a cooler thermostat early on, about 160 F, due to overheating problems which is still installed!) then all new parts in this order (roughly), *catalytic converter, *radiator, *fan clutch, *coolant overflow bottle, (*the CC was backing up exhaust, giving me an oil pressure over 80 PSIG, and it was overheating the engine, then the radiator was shot internally, fan clutch was bad....all causing the overheating) also replaced craked flywheel, starter, Speed or CPS sensor, fuel pressure regulator, Distributor, Cap, Rotor, plug wires, plugs, fuel injectors, TPS sensor, Ignition control module (ICM) and HV coil, ignition switch, Park / Neutral switch, head light switch, EGR valve, Idle speed adjust or idle air control or idle air stepper motor (pintle valve, has many names!!! same part), MAT sensor, O2 sensor, alternator, MAP sensor, .....high flow oil pump, new crank shaft bearings. All parts replacements made slight improvements in performance at the time they were replaced. Oil consumption is nearly zero.
This list does not include suspension parts, tires etc, steering gear box, that I have replaced, LOL. (after all it has 247,763 miles on it, it is Jeep Wagoneer Ltd. 4X4, almost fully restored)
Knock sensor not installed (damaged)! Wire not connected. I just discovered this part, what it does, where it goes,etc. It was not installed when I aquired the jeep.
I also just found the real coolant temp sensor (it was hiding...and the knock sensor thanks to help from a new friend with Renix manual who steered me to this list) and hooked it up 100 miles ago (tested it first, got 1000 ohms at about 120 F, slightly warm engine) to the correct but previously 1 of 2 mysterious open (unused) connectors on the wiring harness. It has not made any difference in operation!
Has excellent engine acceleration when the transmission is not in gear. Sounds and runs great. But when driving, transmission engaged in drive, the acceleration is like having 4 cyl, 60 hp engine in it. It takes 2 minutes to get up to 60 mph.
No vacuum leaks that I can find. Excellent fuel pressure, it is right on to spec, even flow tested it.
Today I disconnected the IAC motor connector and the TPS connector to the ECU, one at a time while it was idling and it made no difference, it continued to cycle between 900 rpm and 300 rpm (with out dying!!). When I pushed the accelerator it died when it tried to return to idle with the TPS sensor disconnected, but disconnecting the IAC had not effect after pushing the accelerator (with the Jeep parked). I found it quite interesting that I could disconnect the TPS and IAC motor connections while at idle and watch the idle speed continue to cycle from 300 rpm to 900 rpm and back to 300 rpm on a 20 second cycle with the jeep parked!!!!!
I have read the Renix manuals I just received (today & Wed), and everything else I could my hands on in the past and a good bit from this forum the last few days, and I think these results today are pertinent and new to the discussion of erratic idles on these Renix system XJ jeeps!
I have more test data (VOM readings on connectors, wiring harness, and grounds!!!!!) to post, which I will do ASAP. This is a good start to get the discussion going, I hope.
Lastly, the new O2 sensor was disconnected for about 3000 miles (wiring harness got fried on the exhaust manifold one day) and was only operated for about 100 miles before the harness connector was melted from its encounter with the exhaust manifold. So I never got a real good look at what the new O2 sensor did. Before the new O2 sensor, and after its abroupt disconnection, I always had unpredictable idle speed issues like most of those frequently reported here. The newest idle cycling symptom is brand new to me!!! It began after I fixed the wiring harness and reconnected the O2 sensor.