Sinisterwillys1940 Posted May 10, 2017 Share Posted May 10, 2017 I put a new 2.5l into the jeep and it only has 400 miles. It was running great till suddenly the issues popped up again. I hooked the scanner up and saw that the short term trim was ridiculously high. Its reference point at idle is 128 and its running at 180. The long term trim is at 109. the injector pulse is 2.0. The o2 sensor was reading no higher than 500mv. Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted May 14, 2017 Administrators Share Posted May 14, 2017 Did you resolve this yet? Is the O2 sensor the issue? Moses Quote Link to comment Share on other sites More sharing options...
Sinisterwillys1940 Posted May 16, 2017 Author Share Posted May 16, 2017 Not yet. I have a lab scope I could use. I do agree the o2 isn't metering correctly I'll have to see what the lab scope says Quote Link to comment Share on other sites More sharing options...
Sinisterwillys1940 Posted May 17, 2017 Author Share Posted May 17, 2017 well I need a new o2 sensor. I accidently shorted the heater circuit with the t pins and it roasted me lead and some of the insulation on the wires. Oops..... Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted May 17, 2017 Administrators Share Posted May 17, 2017 Sounds logical, Sinisterwillys1940! What you described sounded like something that could happen during an engine installation...Apparently, it was. Let us know if that's the cure. Consider an NGK/NTK or Bosch O2 sensor rather than a Brand-X, especially if you can get the NTK at a fair price. This would be Mopar equivalent. I've had poor results with aftermarket Brand-X O2 sensors, they typically have generic (i.e., made for multiple applications) parameters that can create an issue. Moses Quote Link to comment Share on other sites More sharing options...
Sinisterwillys1940 Posted May 18, 2017 Author Share Posted May 18, 2017 That does sound like the issue. I had a crown automotive o2s in there. It did the trick but it was metering lower than what it should've been. The o2 sensor currently in it didn't pass the quick test or the propane test, it actually didn't respond at all to the propane test. I did have good luck finding a NTK o2 sensor for $30 on rock auto. Quote Link to comment Share on other sites More sharing options...
Sinisterwillys1940 Posted May 18, 2017 Author Share Posted May 18, 2017 I Just go the o2 sensor in the mail today and the st trim has dropped to a average of 130-158, its still high but much better. The Lt trim has gone up to 119. Is the o2 sensor supposed to jump around from 0-700mv and anything in between? should it be showing a reading of 0 mv at all? Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted May 19, 2017 Administrators Share Posted May 19, 2017 Are you testing for these results with a hot sensor and fully warmed engine? The sensor can be off when it is cold or if there is a remnant of cold start and warm-up A/F ratio. I would only consider the findings with a hot O2 sensor and fully warmed engine. Moses Quote Link to comment Share on other sites More sharing options...
Sinisterwillys1940 Posted May 20, 2017 Author Share Posted May 20, 2017 It was at operating temp. It was in closed loop too. I've adjusted the isc and the tps and the readings are still the same. I have noticed How ever that it runs a lot better, lower idle and no hesitation or stumbling during acceleration when its humid! This past week went by with out issues till just a hour ago the issues arose again. So weather is making a impact on how it runs. Could this be some kind of ignition problem? Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted May 21, 2017 Administrators Share Posted May 21, 2017 If this is clearly a humidity related issue, it could be ignition related or maybe connections at the ECU or coil. Worth a check...You can test spark wire plug leads with your ohmmeter. I always consider the coil to cap lead first. With the 2.5L TBI coil and distributor cap, the secondary coil wire fires four times per rotor rotation. This wire is more susceptible to failure. Test it before the others... Quote Link to comment Share on other sites More sharing options...
Sinisterwillys1940 Posted May 22, 2017 Author Share Posted May 22, 2017 I tested all of the plug wires. All but one had 1 km. One wire had 2 km. perhaps the 2km wire belongs on the coil to cap? Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted May 22, 2017 Administrators Share Posted May 22, 2017 Resistance is low on these cables...Before replacing them, though, try a basic spark arc test: Using an insulated spark plug pliers, hold a test spark plug's ground strap against the engine block or head. Widen the test plug's gap and see what kind of arc you're getting across the gap. Test each spark plug wire. A quicker test is to use an induction timing light. If you can replicate the missing or stumbling, watch the timing light at each spark plug lead. Try to match the miss with a stumble of the light. This would be a clear indication of an ignition problem. If the distributor cap is old, check the tower contacts for corrosion and also check for carbon tracking inside the cap (between the contacts). Check the rotor tip for corrosion. If the problem occurs when the engine is warm or hot, test the ignition module and coil. Quote Link to comment Share on other sites More sharing options...
Sinisterwillys1940 Posted May 23, 2017 Author Share Posted May 23, 2017 I checked the cap and rotor. the cap is still pretty new, from the fall but it had some corrosion on the tower contacts. I gave them a quick clean, and I cleaned the rotor as well. Both are still pretty good shape. I certainly agree that the wires are causing problems. I'll have to do the spark arc test when I get the chance Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted May 23, 2017 Administrators Share Posted May 23, 2017 In the EFI era, we're quick to rely upon check lights, fault codes and sensor troubleshooting. Often overlooked are the old mainstay issues like worn or defective spark plug cables. Your comment about humidity suggested checking the spark cables. How old are these cables? A long arc spark test would be helpful, ideally when it's humid. Quote Link to comment Share on other sites More sharing options...
Sinisterwillys1940 Posted May 23, 2017 Author Share Posted May 23, 2017 Makes sense. I did the spark ark test. I used a screwdriver instead and I could see a tiny little orange ark. If I was to assume the ark should be a little brighter than what I had Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted May 23, 2017 Administrators Share Posted May 23, 2017 Orange sounds weak. Should be a sharp blue under no firing load like your test. An arc length adjustable tester would be more accurate, but your method should be reliable. Spark cables or the coil's output would be involved here. Check the coil ohms just to be sure it's not the coil. If the coil reads normal, install new plug wires. Considering your ohms-resistance readings on the wires, I would replace the plug wires and coil lead regardless. Quote Link to comment Share on other sites More sharing options...
Sinisterwillys1940 Posted May 24, 2017 Author Share Posted May 24, 2017 I'll have to check the coil when I get the chance. I've found some mopar replacement wires. Quote Link to comment Share on other sites More sharing options...
Sinisterwillys1940 Posted May 24, 2017 Author Share Posted May 24, 2017 I checked the coil resistance. the primary had .3 ohms and the secondary had 7.25 ohms. I could've mixed up which circuit is which. If I'm not mistaken the primary is supposed to be at least .4 or .5 ohms. right? I'm not sure what the readings are supposed to be Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted May 27, 2017 Administrators Share Posted May 27, 2017 Where did you find these figures, Sinisterwillys1940? The ICM (ignition control module) is the module/coil assembly. The firing signal is from the ECU terminal 27 via terminal B of Connector #2 (the middle, two-wire connector). What's significant here is the relationship between the spark trigger signal (ECU generated) and the ICM. Make sure the ICM plug connectors look good and are free of any corrosion. You can see why the ECU plug connectors are equally important. Quote Link to comment Share on other sites More sharing options...
Sinisterwillys1940 Posted May 29, 2017 Author Share Posted May 29, 2017 I got the figures from the Haynes manual. The weather has been sunny lately here and It was running way better, I had plenty of power and it idled lower and smoother. then it started raining and the idle changed and I had less power than before. I'm convinced the issue is the plug wires. Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted May 30, 2017 Administrators Share Posted May 30, 2017 Simple proof? Try the wires and let us know how that works...It's clearly a case of higher resistance from the humidity or moist weather. Find the source of that resistance, and you have the solution! Quote Link to comment Share on other sites More sharing options...
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