"Intermittent electrical issue causing misfire"
10-07-16, 02:19 PM
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"Intermittent electrical issue causing misfire"
What's up guys, this is my first post to a forum and pardon me if this is in the wrong section, but I'm picking up a 93 Sc300 5speed this weekend and the guy mentioned it had an "intermittent electrical issue that caused a misfire." I haven't been able to take it for a test drive to verify it, however I'm not to concerned about it, for it'll have to sit a little while anyways before I get to doing things to it. I just wanted to see what kind of ideas you guys might have as to what could cause this issue. He said he had replaced the spark plugs and the wires for them, then the problem came up. The car does have 230K miles on it, but its a steal in my eyes. I'm thinking it could be the distributor assembly as a whole for he said he hasn't messed with it at all, and given it's miles, its probably due a change out anyways. So yeah, let me know any suggestions as to what you may think it could be and ill take a look at it and let you know, Thanks in advance!!
Also I haven't been able to check to see if it has any codes, ill get to that later today and update this post tomorrow morning when I get to work.
Also I haven't been able to check to see if it has any codes, ill get to that later today and update this post tomorrow morning when I get to work.
10-08-16, 03:47 AM
#2
Funny your seller should mention this. I feel like I've had the same problem for a year now with my 242k mile SC300 5-speed. However in my case I've replaced so many components recently (had an emissions test and registration renewal deadline to meet a few months ago) I have my fuel pump and fuel ECU as last resorts to try replacing.
In your case I really think you need more information to go on than just what the seller said. However with no baseline and no testing done to your car it could be many, many things:
-ECU (not a bad idea to have your ECU capacitors replaced due to age. We recommend Tanin Auto Electronix for this service)
-plugs
-plug wires
-distributor cap & rotor
-distributor (possible but given the cost don't jump to replace this until you have strong reason to believe it is going bad)
-GE ignitor (generally not a culprit)
-fuel injectors
-TPS sensor
-Engine Coolant Temp sensor for the ECU (located on the cylinder head)
-bad MAF (DO NOT CLEAN YOUR MAF!!!!! CLEANING WILL DAMAGE IT. It's either good or bad. Buy the same part on Rockauto, eBay or from Aliga if it needs replacing)
-Fuel ECU issue (you can replace it IF you can confirm it has gone bad... or you can do the common +12V bypass mod w/shutoff relay. But you should confirm a failure first)
-Fuel pump... but again, better to narrow it down to a bad pump component before spending money and time to replace it.
Without knowing more I would suggest you get into a basic tuneup first (plugs <get quality plugs like Iridiums>, wires, cap, rotor) and also get your ECU rebuilt if the problem persists after that.
Actually with the ECU's a rebuild service is also considered preventative maintenance: you want to replace possibly leaking capacitors sooner rather than later because the longer you wait while ECU performance worsens the greater the chance the capacitors can leak onto the logic board and damage it. Now having said that... don't let that advice excite you. The majority of the time people have some ECU issues will send theirs in for capacitor service and get it back good as new with no issues-- good for another 20-25 years.
Basic tuneup as a baseline and getting your ECU serviced would be my first two orders of business since you know nothing else.
These cars are good, even with 230k on them. You will encounter some things that will need repair but the chassis and drivetrain is very solid. Make sure the timing belt and water pump have been done or were done less than 60k miles ago. If not... those are due. Getting service records from the previous owner would be ideal. Second to that, sign up (for free) on Lexus.com and enter the car's VIN under your account to see what service history has been entered. You can also use that service to enter your own records manually (with some limitations but you can be creative within those descriptive limitations Lexus.com gives you).
Good luck!
In your case I really think you need more information to go on than just what the seller said. However with no baseline and no testing done to your car it could be many, many things:
-ECU (not a bad idea to have your ECU capacitors replaced due to age. We recommend Tanin Auto Electronix for this service)
-plugs
-plug wires
-distributor cap & rotor
-distributor (possible but given the cost don't jump to replace this until you have strong reason to believe it is going bad)
-GE ignitor (generally not a culprit)
-fuel injectors
-TPS sensor
-Engine Coolant Temp sensor for the ECU (located on the cylinder head)
-bad MAF (DO NOT CLEAN YOUR MAF!!!!! CLEANING WILL DAMAGE IT. It's either good or bad. Buy the same part on Rockauto, eBay or from Aliga if it needs replacing)
-Fuel ECU issue (you can replace it IF you can confirm it has gone bad... or you can do the common +12V bypass mod w/shutoff relay. But you should confirm a failure first)
-Fuel pump... but again, better to narrow it down to a bad pump component before spending money and time to replace it.
Without knowing more I would suggest you get into a basic tuneup first (plugs <get quality plugs like Iridiums>, wires, cap, rotor) and also get your ECU rebuilt if the problem persists after that.
Actually with the ECU's a rebuild service is also considered preventative maintenance: you want to replace possibly leaking capacitors sooner rather than later because the longer you wait while ECU performance worsens the greater the chance the capacitors can leak onto the logic board and damage it. Now having said that... don't let that advice excite you. The majority of the time people have some ECU issues will send theirs in for capacitor service and get it back good as new with no issues-- good for another 20-25 years.
Basic tuneup as a baseline and getting your ECU serviced would be my first two orders of business since you know nothing else.
These cars are good, even with 230k on them. You will encounter some things that will need repair but the chassis and drivetrain is very solid. Make sure the timing belt and water pump have been done or were done less than 60k miles ago. If not... those are due. Getting service records from the previous owner would be ideal. Second to that, sign up (for free) on Lexus.com and enter the car's VIN under your account to see what service history has been entered. You can also use that service to enter your own records manually (with some limitations but you can be creative within those descriptive limitations Lexus.com gives you).
Good luck!
10-09-16, 06:26 AM
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Totally agree with checking out the ECU. My 93 had bad caps causing an over fuel issue, sent to Tanin for the repair. They did and good job, car running much better. So the ECU could possibly be the issue or ignition. I would lean more toward those two items.
Good luck with the new to you SC.
Good luck with the new to you SC.
10-09-16, 07:47 AM
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Funny your seller should mention this. I feel like I've had the same problem for a year now with my 242k mile SC300 5-speed. However in my case I've replaced so many components recently (had an emissions test and registration renewal deadline to meet a few months ago) I have my fuel pump and fuel ECU as last resorts to try replacing.
In your case I really think you need more information to go on than just what the seller said. However with no baseline and no testing done to your car it could be many, many things:
-ECU (not a bad idea to have your ECU capacitors replaced due to age. We recommend Tanin Auto Electronix for this service)
-plugs
-plug wires
-distributor cap & rotor
-distributor (possible but given the cost don't jump to replace this until you have strong reason to believe it is going bad)
-GE ignitor (generally not a culprit)
-fuel injectors
-TPS sensor
-Engine Coolant Temp sensor for the ECU (located on the cylinder head)
-bad MAF (DO NOT CLEAN YOUR MAF!!!!! CLEANING WILL DAMAGE IT. It's either good or bad. Buy the same part on Rockauto, eBay or from Aliga if it needs replacing)
-Fuel ECU issue (you can replace it IF you can confirm it has gone bad... or you can do the common +12V bypass mod w/shutoff relay. But you should confirm a failure first)
-Fuel pump... but again, better to narrow it down to a bad pump component before spending money and time to replace it.
Without knowing more I would suggest you get into a basic tuneup first (plugs <get quality plugs like Iridiums>, wires, cap, rotor) and also get your ECU rebuilt if the problem persists after that.
Actually with the ECU's a rebuild service is also considered preventative maintenance: you want to replace possibly leaking capacitors sooner rather than later because the longer you wait while ECU performance worsens the greater the chance the capacitors can leak onto the logic board and damage it. Now having said that... don't let that advice excite you. The majority of the time people have some ECU issues will send theirs in for capacitor service and get it back good as new with no issues-- good for another 20-25 years.
Basic tuneup as a baseline and getting your ECU serviced would be my first two orders of business since you know nothing else.
These cars are good, even with 230k on them. You will encounter some things that will need repair but the chassis and drivetrain is very solid. Make sure the timing belt and water pump have been done or were done less than 60k miles ago. If not... those are due. Getting service records from the previous owner would be ideal. Second to that, sign up (for free) on Lexus.com and enter the car's VIN under your account to see what service history has been entered. You can also use that service to enter your own records manually (with some limitations but you can be creative within those descriptive limitations Lexus.com gives you).
Good luck!
In your case I really think you need more information to go on than just what the seller said. However with no baseline and no testing done to your car it could be many, many things:
-ECU (not a bad idea to have your ECU capacitors replaced due to age. We recommend Tanin Auto Electronix for this service)
-plugs
-plug wires
-distributor cap & rotor
-distributor (possible but given the cost don't jump to replace this until you have strong reason to believe it is going bad)
-GE ignitor (generally not a culprit)
-fuel injectors
-TPS sensor
-Engine Coolant Temp sensor for the ECU (located on the cylinder head)
-bad MAF (DO NOT CLEAN YOUR MAF!!!!! CLEANING WILL DAMAGE IT. It's either good or bad. Buy the same part on Rockauto, eBay or from Aliga if it needs replacing)
-Fuel ECU issue (you can replace it IF you can confirm it has gone bad... or you can do the common +12V bypass mod w/shutoff relay. But you should confirm a failure first)
-Fuel pump... but again, better to narrow it down to a bad pump component before spending money and time to replace it.
Without knowing more I would suggest you get into a basic tuneup first (plugs <get quality plugs like Iridiums>, wires, cap, rotor) and also get your ECU rebuilt if the problem persists after that.
Actually with the ECU's a rebuild service is also considered preventative maintenance: you want to replace possibly leaking capacitors sooner rather than later because the longer you wait while ECU performance worsens the greater the chance the capacitors can leak onto the logic board and damage it. Now having said that... don't let that advice excite you. The majority of the time people have some ECU issues will send theirs in for capacitor service and get it back good as new with no issues-- good for another 20-25 years.
Basic tuneup as a baseline and getting your ECU serviced would be my first two orders of business since you know nothing else.
These cars are good, even with 230k on them. You will encounter some things that will need repair but the chassis and drivetrain is very solid. Make sure the timing belt and water pump have been done or were done less than 60k miles ago. If not... those are due. Getting service records from the previous owner would be ideal. Second to that, sign up (for free) on Lexus.com and enter the car's VIN under your account to see what service history has been entered. You can also use that service to enter your own records manually (with some limitations but you can be creative within those descriptive limitations Lexus.com gives you).
Good luck!
10-21-16, 07:24 PM
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Alright guys, I picked up the SC300 5speed today, and I finally felt what the guy meant. So I had to let him drive it first because I have minimal experience with manuals and the battery was dead so he took it for a quick TD. While he was driving, he tended to use the parking break to slow down instead of the brakes, and would down shift from 5-4-3-2-1 to come to a stop. While he was doing all of that the check engine light would start flashing erratically and it would hesitate and bog down real bad, I knew what I was getting into so I bought it anyways. While I was driving home, I would put it into neutral when coming to stops rather than downshifting and it ran FINE! No problems what so ever. I did down shift from 4th-2nd because it was red and then turned green while I was slowing down and it started the same symptoms for me for about a mile at most, it would hesitate and try to stall out, and my buddy said it was sitting out a lot of black smoke from both tailpipes while it was acting like this, but after that mile or so it stopped and straightened up the rest of the time I was driving. I let my buddy drive it a bit and he was saying the wining noise was the alternator, which eventually stopped making noise, lights dimmed out, and he stalled it and the alternator was in fact finished. So we got it back to the house safely and now I'm not sure as to what to look at first.
P.S. the wining noise I didn't mention at first because the owner said it was the "6 pluck clutch" which I doubt is in it because of how easy it is to shift.
I found an ECU that was rebuilt for $50 i'm going to pick up tomorrow and a new alternator and we'll see if the helps the situation. A coworker said the compression/oil rings could be allowing blow by so ill check that tomorrow as well. Ill check this again tomorrow around 3-4PM let me know what you guys think, I can get a refund for both if they don't help.
P.S. the wining noise I didn't mention at first because the owner said it was the "6 pluck clutch" which I doubt is in it because of how easy it is to shift.
I found an ECU that was rebuilt for $50 i'm going to pick up tomorrow and a new alternator and we'll see if the helps the situation. A coworker said the compression/oil rings could be allowing blow by so ill check that tomorrow as well. Ill check this again tomorrow around 3-4PM let me know what you guys think, I can get a refund for both if they don't help.
10-22-16, 11:41 PM
#7
OneSC, forgive me if this was a no-brainer for you but I hope you double-checked the 5-speed ECU P/N and got an identical one. There are several different ones for different years between Federal and CA Spec.
https://www.clublexus.com/forums/per...s-by-year.html
I'm not sure what to make of the previous owner's constant need to downshift. The stock brakes on 92-97 SC300's are horrible and that might have something to do with it. An 1995-2000 LS400 caliper upgrade is the popular solution for that.
If that car really does have a 6-puck clutch there really is no need for it with a stock NA engine. The OEM full-face clutch kit will do fine and it's also exactly the same factory clutch kit used with 1993.5-1997 MKIV Supra NA 5-speeds.
Doing a full compression or leakdown test is good peace of mind if you have concerns about the piston rings.
https://www.clublexus.com/forums/per...s-by-year.html
I'm not sure what to make of the previous owner's constant need to downshift. The stock brakes on 92-97 SC300's are horrible and that might have something to do with it. An 1995-2000 LS400 caliper upgrade is the popular solution for that.
If that car really does have a 6-puck clutch there really is no need for it with a stock NA engine. The OEM full-face clutch kit will do fine and it's also exactly the same factory clutch kit used with 1993.5-1997 MKIV Supra NA 5-speeds.
Doing a full compression or leakdown test is good peace of mind if you have concerns about the piston rings.
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10-24-16, 07:32 AM
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OneSC, forgive me if this was a no-brainer for you but I hope you double-checked the 5-speed ECU P/N and got an identical one. There are several different ones for different years between Federal and CA Spec.
https://www.clublexus.com/forums/per...s-by-year.html
I'm not sure what to make of the previous owner's constant need to downshift. The stock brakes on 92-97 SC300's are horrible and that might have something to do with it. An 1995-2000 LS400 caliper upgrade is the popular solution for that.
If that car really does have a 6-puck clutch there really is no need for it with a stock NA engine. The OEM full-face clutch kit will do fine and it's also exactly the same factory clutch kit used with 1993.5-1997 MKIV Supra NA 5-speeds.
Doing a full compression or leakdown test is good peace of mind if you have concerns about the piston rings.
https://www.clublexus.com/forums/per...s-by-year.html
I'm not sure what to make of the previous owner's constant need to downshift. The stock brakes on 92-97 SC300's are horrible and that might have something to do with it. An 1995-2000 LS400 caliper upgrade is the popular solution for that.
If that car really does have a 6-puck clutch there really is no need for it with a stock NA engine. The OEM full-face clutch kit will do fine and it's also exactly the same factory clutch kit used with 1993.5-1997 MKIV Supra NA 5-speeds.
Doing a full compression or leakdown test is good peace of mind if you have concerns about the piston rings.
Sorry for the late post, very busy weekend and no computer at the house.
10-29-16, 11:23 AM
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OneSC, forgive me if this was a no-brainer for you but I hope you double-checked the 5-speed ECU P/N and got an identical one. There are several different ones for different years between Federal and CA Spec.
https://www.clublexus.com/forums/per...s-by-year.html
I'm not sure what to make of the previous owner's constant need to downshift. The stock brakes on 92-97 SC300's are horrible and that might have something to do with it. An 1995-2000 LS400 caliper upgrade is the popular solution for that.
If that car really does have a 6-puck clutch there really is no need for it with a stock NA engine. The OEM full-face clutch kit will do fine and it's also exactly the same factory clutch kit used with 1993.5-1997 MKIV Supra NA 5-speeds.
Doing a full compression or leakdown test is good peace of mind if you have concerns about the piston rings.
https://www.clublexus.com/forums/per...s-by-year.html
I'm not sure what to make of the previous owner's constant need to downshift. The stock brakes on 92-97 SC300's are horrible and that might have something to do with it. An 1995-2000 LS400 caliper upgrade is the popular solution for that.
If that car really does have a 6-puck clutch there really is no need for it with a stock NA engine. The OEM full-face clutch kit will do fine and it's also exactly the same factory clutch kit used with 1993.5-1997 MKIV Supra NA 5-speeds.
Doing a full compression or leakdown test is good peace of mind if you have concerns about the piston rings.
So now ill either be sending them both, or the "tuned" ECU's to a remanufacturing shop, Or just buy a brand new one and be done with it.
Thanks again for you guys help!!
P.S. he said the IAC motor could be faulty causing the rough idle with the "tuned" ECU in it. However it doesn't explain the way it runs while driving.
10-30-16, 06:27 PM
#10
I think you're looking in the right direction with the ECU. They are notorious for causing intermittent issues with these cars. Years back my ECU was causing the injectors to stick wide open, which I confirmed with a noid light. I replaced the ECU and it ran great.
Funny you mention the alternator whine as well. The alternator went bad in my Sc and had been whining, so I just replaced it today. You might as well change the drive belt while you're at it, and check the idler pulleys for any noise.
Funny you mention the alternator whine as well. The alternator went bad in my Sc and had been whining, so I just replaced it today. You might as well change the drive belt while you're at it, and check the idler pulleys for any noise.
10-31-16, 04:10 AM
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I think you're looking in the right direction with the ECU. They are notorious for causing intermittent issues with these cars. Years back my ECU was causing the injectors to stick wide open, which I confirmed with a noid light. I replaced the ECU and it ran great.
Funny you mention the alternator whine as well. The alternator went bad in my Sc and had been whining, so I just replaced it today. You might as well change the drive belt while you're at it, and check the idler pulleys for any noise.
Funny you mention the alternator whine as well. The alternator went bad in my Sc and had been whining, so I just replaced it today. You might as well change the drive belt while you're at it, and check the idler pulleys for any noise.
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