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I've been trying to chase this down for a while now with no luck. Originally it was misfiring on one bank, pulled all 8 plugs and checked them, the plug from the cylinder that was misfiring looked bad so I replaced it. Got everything back together and it now misfires on the opposite side. After some driving I noticed that the problem got worse starting below 2/3 of a tank of gas. I ran some fuel system cleaner through it (BG 44k) and for a while it got much better. Fast forward a 150 miles or so and I went to pass someone on a 2-lane and boom, starts misfiring again. Anyway, at this point it seems like it misfires the most under a light load, say cruising at a consistent speed, but clears up considerably if you get on it a bit. Also, any change in the fuel level seems to have an effect on how well it runs but its not always consistent in terms of whether a higher fuel level helps or hurts. Its currently got codes for the misfire, rich condition, and a secondary 02 sensor. Any help is appreciated.
Ill go get them read again tomorrow. Been a bit since I pulled them and I cant remember the specific numbers. It was a specific cylinder misfire, rich condition on one bank, and the secondary 02 sensor on one side last time I pulled them.
I have not, mostly because I don't experience any of the specific issues listed in that post. I'm questionable on the condition of the distributor at this point. Think that might be the next thing I check out once it stops raining.
Would this have any effect on fuel pressure? I can check that more easily than just pulling all the injectors.
Well that would be the first step with the fuel system, but the fuel injectors wouldnt necessarily make a difference with fuel pressure I don't think, or cause multiple cylinders to misfire.
I think your first step in general would be to get those IAT and MAF codes sorted out, then go from there.
After a few months of not driving the car I finally decided to try and figure this out. I replaced the plugs and wires and saw no difference. So, I decided it was time to check the ECU after going back over the symptoms of leaking capacitors. Sure enough, that's what I found. I'm going to go ahead and order the new capacitors and hopefully this fixes things.
After a few months of not driving the car I finally decided to try and figure this out. I replaced the plugs and wires and saw no difference. So, I decided it was time to check the ECU after going back over the symptoms of leaking capacitors. Sure enough, that's what I found. I'm going to go ahead and order the new capacitors and hopefully this fixes things.
Hope the leaked liquid QAS didn't damage the internal layer yet. It's very strong alkali and eats the copper trace quickly. A surface damage can be mostly fixed but the internal layer's damage can't be fixed.
Hope the leaked liquid QAS didn't damage the internal layer yet. It's very strong alkali and eats the copper trace quickly. A surface damage can be mostly fixed but the internal layer's damage can't be fixed.
Yea that one particular spot doesn't look great. By the way, thank you for your contribution to this repair. I would have ended up burning through all kinds of parts before I found this. I'll try to remember to update this thread on my progress with this.
I finally decided to try and figure this out. I replaced the plugs and wires and saw no difference. So, I decided it was time to check the ECU after going back over the symptoms of leaking capacitors. Sure enough, that's what I found.
I also didn't think the ECU could be the bulk of my problems. I would read everything and say to myself "well there's no way that's my problem" so I was changing every part I thought it could be. When I started having the same symptoms on my 2nd LS400 I thought "maybe there IS something to this ECU problem". So I jumped on the bandwagon and changed the ECU and, BAMM, it was fixed. Oh well, live and learn. Like Yamae says, that board might not be good. Ya might need to find a decent junkyard ECU and redo the caps on that one. Good luck.
I think the one symptom that really got me moving in the direction of the ECU was remembering we had to try 4 different scan tools before we got one to connect with the car. The simpler scan tool would connect and show some data but the more advanced ones (Snap-On/Matco) would not. The new capacitors are supposed to be here Saturday and I found a friend that has more experience with this kind of thing to help me with the repair. Really hoping the board is still good.
Question on a replacement ECU, do I need to look for the exact ECU my car came with or can I use one from a later 96? Mine is the 89661-50303.
12-20-19, 02:22 PM
1996 LS: Misfire/rich condition
