1996 LX450 Transplant Engine Installed...misfire problem

[TheOsprey]

If harness stayed on new engine during removal from donor rig, transportation to you, and your installation, it may of been damaged in the typical EGR area. Harness is over 20 years old, and even though it ran OK on donor rig, it may of been damaged at that point, but not critical damage until all of this moving around happened. Try moving harness around by EGR while engine is running. If it affects the miss-fire then it is a damaged harness. I just watched Tools perform this test on Friday, and the results were obvious!! You could just replace it with your original one, if it is NOT damaged.

I'll give that a shot if the new valve cover gasket kit doesn't do the trick. I noticed a bit of a leak and really hard gaskets when I was installing the engine. So, I took it off to investigate. In the process I may have created a leak around the 3 and 6 spark plug tubes. We'll see. Thanks for the suggestion.

 

[TheOsprey]

Well...since my last post I've tackled a couple of routine maintenance items. I bought an adequate battery (Odyssey Extreme Performance, no less), replaced the valve cover gasket, spark plug tube gaskets and PCV grommet, repaired oil pan gasket situation and installed new NGK double platinum spark plugs.

Once all that was done and the battery was hooked up I fired it up again to see if anything changed.

The first few seconds it ran a bit rough but then it evened out and there is no evidence of a misfire...at all.

I noticed when I was replacing the spark plugs that the old ones were soaked in gas even after sitting a few days.

I'm not sure what that's all about but that is what I found.

Maybe new gas sitting in the injector bodies for a few days loosened them up or maybe the spark plugs and battery improvement helped.

I honestly don't know but there is no misfire now and no check engine lights.

Is it possible that a weak battery could have kept the injectors from firing properly?

If the spark plugs fixed the situation it would literally be the first time new spark plugs ever fixed any problem I've had with probably eighty vehicles that I've owned.

If anything else develops I'll update.

Thanks for the suggestions.

 

[TheOsprey]

I just took it for a test drive and the misfire and flashing CEL returned. I also had a few backfires.

I hooked up the O2 sensors but just behind them and the cats I cut out the muffler because it was just about rusted out.

Could any of this be caused by faulty O2 sensors? They seemed to be working with the old engine.

If I installed them in reverse order would it cause any of this?

I don't think I did but I have been wrong before.

Before when it was idling in the driveway it seemed to be running very rich but no apparent misfires or roughness to the idle.

The accelerator pedal also seems pretty stiff and maybe a little sticky.

Any other suggestions?

 

[Malleus]

What's the new code? Check the cable connections and routing.

 

[96LXtech]

I just took it for a test drive and the misfire and flashing CEL returned. I also had a few backfires.

I hooked up the O2 sensors but just behind them and the cats I cut out the muffler because it was just about rusted out.

Could any of this be caused by faulty O2 sensors? They seemed to be working with the old engine.

If I installed them in reverse order would it cause any of this?

I don't think I did but I have been wrong before.

Before when it was idling in the driveway it seemed to be running very rich but no apparent misfires or roughness to the idle.

The accelerator pedal also seems pretty stiff and maybe a little sticky.

Any other suggestions?

What did you find? This just started to happen to me...