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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.

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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

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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.

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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

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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?

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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...

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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.

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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

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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.

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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. 

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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.

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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.

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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!

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