LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

Need help diagnosing misfire 91 ucf10

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Old 05-07-12 | 10:14 PM
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Replaced the fuel filter today, it was not in terrible shape but still needed to be changed. Did not solve my problem though,

Last edited by Luxurexus; 05-08-12 at 02:46 PM.
Old 05-08-12 | 08:30 AM
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[quote. It will also seem to bog or misfire when I punch it as the car is downshifting. The car is bogging really heavily when I punch it, it will feel like its only running on a few cylinders but if I ease on the gas it works just fine[/quote]

I think it's important to distinguish between these terms, because they could be two different causes; bogging is almost always related to air/fuel delivery, or in rare cases, exhaust backpressure. Misfiring is almost always an ignition issue, but can be caused by valvetrain issues as well, or even clogged injectors. Bogging is distinct from misfiring, in that the engine simply does not deliver expected power. Misfiring produces very noticeable pulsations and vibration, often producing backfiring. Which of these symptoms do you have?
You've changed the fuel filter, good. How much fuel pressure do you have?
Old 05-08-12 | 11:11 PM
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I have both. In Park/Neutral/Reverse it will misfire, generally between 1-4 times giving the impression that it is coil packs. While in drive if I punch it to the floor all at once it will bog heavily for a few moments then take off but if I ease on the gas it will accelerate like normal. I think this may also be the coil packs or a fuel pump. I plan to buy the packs this weekend and will go from there.
Old 05-08-12 | 11:23 PM
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Definitely an ignition problem. Weak primary ignition or high resistance on the secondary side will cause these situations.
Old 05-09-12 | 02:49 PM
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where are the coils located? Anyone maybe post a pic? I've scoured this forum for any type of engine compartment diagram, but unable to locate... I'm having a very similar problem with my '93 SC400, and will also attempt repair by replacing the original coils...
Old 05-10-12 | 01:13 PM
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I am going to replace the coils this weekend, I hope that solves my problem.
Old 05-10-12 | 02:21 PM
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I'm having similar isshues, been having em since I got the car. never tried fixing it yet.
Old 05-11-12 | 05:57 PM
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as bott63 says there is no information on where the coils are located and how to properly change them out on this website or even on lexls.com does anyone have a diagram or anything?
Old 05-11-12 | 07:54 PM
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Originally Posted by Luxurexus
as bott63 says there is no information on where the coils are located and how to properly change them out on this website or even on lexls.com does anyone have a diagram or anything?
Umm.. wow! I can't belive I just heard you say that. Honestly I don't have the ancer, but I have the simplest of all ancers for ya.
Step 1) pop your hood
Step 2) remove the plastic cover on the valve cover.
Step 3) fallow the sparkplug wires.
Step 4) what you are now looking at is the coil pack or distributer.
If it is the distributer, the coilpack may be an internal one. If so, remove the cover and wahla! If not there will be a wire just like the spark plug wires leading straight to the coil pack.

I didn't mean to sound rude, its just an obvious ancer to you question if your actualy going to be working on your car your self.
Old 05-11-12 | 08:12 PM
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Originally Posted by Luxurexus
as bott63 says there is no information on where the coils are located and how to properly change them out on this website or even on lexls.com does anyone have a diagram or anything?
Not to hard to find.

http://www.lexls.com/tutorials/ignition/sparkplugs.html
Old 05-11-12 | 09:41 PM
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actually yes there is. several times over. with pictures.

https://www.clublexus.com/forums/search.php
is your friend.
Old 05-12-12 | 07:11 PM
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As johnny says it was not very hard and I did not need any directions. The driver side coil was a little bit of a pain but nothing I couldn't handle. It cleared up my bogging problem but I still have a misfire in park/reverse/and neutral. I have a valve cover leak, could that be the culprit? I plan to replace the gasket and grommets in a few weeks regardless.
Old 05-12-12 | 07:20 PM
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Originally Posted by ocr
Umm.. wow! I can't belive I just heard you say that. Honestly I don't have the ancer, but I have the simplest of all ancers for ya.
Step 1) pop your hood
Step 2) remove the plastic cover on the valve cover.
Step 3) fallow the sparkplug wires.
Step 4) what you are now looking at is the coil pack or distributer.
If it is the distributer, the coilpack may be an internal one. If so, remove the cover and wahla! If not there will be a wire just like the spark plug wires leading straight to the coil pack.

I didn't mean to sound rude, its just an obvious ancer to you question if your actualy going to be working on your car your self.
Whats really surprising is that you made that many spelling errors when there is an automatic spell check...and while it was not the most difficult of tasks if you dont know what your looking at it can be confusing. I never claimed to be a mechanic of any sorts but I like to do my own work because its cheaper and I put pride and care into my work.
Old 05-12-12 | 07:31 PM
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Originally Posted by Luxurexus
Whats really surprising is that you made that many spelling errors when there is an automatic spell check.
The spell check isn't available when using the phone. And why are you griping about my spelling if you could still read it perfictaly fine. I know my spelling sucks, and I don't care cuz you can still understand me just fine.
Old 05-12-12 | 07:35 PM
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Originally Posted by ocr
The spell check isn't available when using the phone. And why are you griping about my spelling if you could still read it perfictaly fine. I know my spelling sucks, and I don't care cuz you can still understand me just fine.
Why are you griping about my automotive repair abilities? I know I am not a master tech but acquiring information is what the forum is for. My point is no one knows everything so get off my nuts.



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