Rough Idle with New Spark Plugs and Coil Packs

[AverySimmons]

Hey guys! New here and new owner to a 1999 cruiser. I bought her about 2 months ago with 115k miles and has been great so far but started to idle rough a few days ago. The CEL came on and would flash when driving so we replaced all 8 coil packs as well as sparks plugs. Once replaced, the CEL turned off and it is idling better but still not 100% as smooth as it used to be. Any suggestions?

 

[Trunk Monkey]

'99 the actual swap is easy, it's right behind the glove box, the PITA is the keys, they were coded to the ECU. It was a big enough deal that for quite awhile if you lost all your keys since it was impossible to program a new one to the ECU, Toyota would cover the cost of the ECU replacement parts, you just paid the labor.

 

[Moparsncruisers]

It is 1000% possible to still get codes with a bad ECU. A Bad ECU doesn't mean completely dead! A bad driver say for an injector will still throw misfire codes and possibly injector circuit codes(as an example)....

 

[AverySimmons]

Sounds to me like you got taken. How much money did they charge you? 100% they didn't just have a brand new ECU for your 99 that they threw in real quick, reprogrammed, and fixed everything in a jiffy. It's not too late to cause a fuss over this and get our money back.

I bought a refurbished OEM plug and play ECU for $320 and they put it in for $90. I purchased it from Flagship one and they took my VIN and programmed it.

 

[AverySimmons]

'99 the actual swap is easy, it's right behind the glove box, the PITA is the keys, they were coded to the ECU. It was a big enough deal that for quite awhile if you lost all your keys since it was impossible to program a new one to the ECU, Toyota would cover the cost of the ECU replacement parts, you just paid the labor.

I only have the valet key so this was a great opportunity for me to buy a new key and have it programmed to my new ECU as well.

 

[AverySimmons]

If the ECU had failed it technically couldn't send a code, but glad it seems to have worked out with the new one. Wonder what code they think it was.

Great question for me ask them. I am a complete novice

After reading everything I'm inclined to think that shop may have taken you for a ride.

1. I don't see how its possible that replacing all the coils and plugs made it noticeably better but it was still a faulty ECU. To me it would make sense if you replaced those parts and the result was still the same rough running motor.
2. They were able to find and replace the ECU really quick, like abnormally quick. Yes its easy to reinstall the ECU but finding one is a different story. Usually places don't have one on the back shelf because they so rarely fail.
3. I don't think a failing/failed ECU could throw a code. Its possible the code could have been for something else and putting the new parts in fixed it but it all just seems like too much of a coincidence.

After writing this I feel like I should have a tin foil hat on lol it just seems fishy to me

1. I will be completely honest with everyone on here and say that this is my car and my boyfriend thought he knew what the problem was without us taking it to the shop. With the misfire he assumed(did not get code ran) it was the spark plugs or ignition coils since they had not recently been replaced if ever replaced. We only have one car at the moment and wanted it fixed quickly so he went to AutoZone had them look up the correct parts and then he replaced both the ignition coils and spark plugs himself.( We should have done more research on the correct parts for this car but again wanted it fixed quickly and I also just purchased this car a little over 3 months ago so we are complete newbies in the LC work, which is why I joined this forum). After replacing he jumped in the car and turned it on and for a moment it did feel better but as soon as he threw it in drive the check engine began flashing and the rough idle came back.

2. After this did not work I gave up and took it to the shop we have been taking our other cars to for years and he diagnosed it with needing a new ECU. I am not sure what tests he did or what codes came back I personally just assumed he ran the CEL code( Newbie again and was probably wrong). He said they did not have any ECU’s for my car in stock and they were back ordered from his manufacturer so if I wanted it quicker I could order it myself. Which is what I did from Flagship one. Once it came in he replaced the ECU and charged me $90 for labor.

3. Ever since then it has been working great but after reading everyone’s comments I will be ordering new OEM spark plugs and putting my old OEM ignition coils back in since our mechanic thinks they still have a lot of life in them. (I do not know when the previous owner last replaced them) Once I recover financially I will also be doing new OEM ignition coils as well.

Thanks everyone for your help and kindness. I am new to this world and not super familiar with cars in general but am learning so I am very sorry if I have worded anything incorrectly and caused any confusion. Happy to TRY to answer any questions you guys might have regarding my experience with this issue.

 

[cruisin4bruisins]

Great question for me ask them. I am a complete novice

1. I will be completely honest with everyone on here and say that this is my car and my boyfriend thought he knew what the problem was without us taking it to the shop. With the misfire he assumed(did not get code ran) it was the spark plugs or ignition coils since they had not recently been replaced if ever replaced. We only have one car at the moment and wanted it fixed quickly so he went to AutoZone had them look up the correct parts and then he replaced both the ignition coils and spark plugs himself.( We should have done more research on the correct parts for this car but again wanted it fixed quickly and I also just purchased this car a little over 3 months ago so we are complete newbies in the LC work, which is why I joined this forum). After replacing he jumped in the car and turned it on and for a moment it did feel better but as soon as he threw it in drive the check engine began flashing and the rough idle came back.

2. After this did not work I gave up and took it to the shop we have been taking our other cars to for years and he diagnosed it with needing a new ECU. I am not sure what tests he did or what codes came back I personally just assumed he ran the CEL code( Newbie again and was probably wrong). He said they did not have any ECU’s for my car in stock and they were back ordered from his manufacturer so if I wanted it quicker I could order it myself. Which is what I did from Flagship one. Once it came in he replaced the ECU and charged me $90 for labor.

3. Ever since then it has been working great but after reading everyone’s comments I will be ordering new OEM spark plugs and putting my old OEM ignition coils back in since our mechanic thinks they still have a lot of life in them. (I do not know when the previous owner last replaced them) Once I recover financially I will also be doing new OEM ignition coils as well.

Thanks everyone for your help and kindness. I am new to this world and not super familiar with cars in general but am learning so I am very sorry if I have worded anything incorrectly and caused any confusion. Happy to TRY to answer any questions you guys might have regarding my experience with this issue.

Great explanation thanks for taking the time, after reading this i guess it really was your ecu!
I was under the impression that the shop sourced the ecu out.

OEM coils are expensive from toyota, I would just change out the ones that look really bad, its not worth replacing each one but dont be suprised if autozone coils fail in a year or two.

I would say in my opinion oil changes, timing belts, and spark plugs are the most important maintenance items for the 100 series land cruiser, doing all the other things like differential fluid changes are good but can wait for another day when youre board. Definitely throw some nice NGK iridium plugs in (I think they are like $9 each on amazon), oil every 5-7k and belts every 100k, it will run a really long time if you do these things.

Sorry you had to go through all this i bet it was stressful, i think you are definitely a rare case. Good luck in the future and welcome!

 

[nissanh]

I see older toyota ECU's having bad capacitors (Leakout). Ivan in Pine Hallow and Ahmad in care care channel has a few videos on how to replace those capacitors. Won't cost you much, they also say a shop that sells good capacitors.

 

[AverySimmons]

Great explanation thanks for taking the time, after reading this i guess it really was your ecu!
I was under the impression that the shop sourced the ecu out.

OEM coils are expensive from toyota, I would just change out the ones that look really bad, its not worth replacing each one but dont be suprised if autozone coils fail in a year or two.

I would say in my opinion oil changes, timing belts, and spark plugs are the most important maintenance items for the 100 series land cruiser, doing all the other things like differential fluid changes are good but can wait for another day when youre board. Definitely throw some nice NGK iridium plugs in (I think they are like $9 each on amazon), oil every 5-7k and belts every 100k, it will run a really long time if you do these things.

Sorry you had to go through all this i bet it was stressful, i think you are definitely a rare case. Good luck in the future and welcome!

It was not fun but I’m glad it’s over! I agree with you on the ignition coils. Going to get all the life I can out of the old Denso ones and replace them slowly as they fail me.

I hope she runs forever! Just ordered the NGK spark plugs and the timing belt was replaced right before I bought it in January at 112,000miles.

Thank you again for your help!!

 

[AverySimmons]

I see older toyota ECU's having bad capacitors (Leakout). Ivan in Pine Hallow and Ahmad in care care channel has a few videos on how to replace those capacitors. Won't cost you much, they also say a shop that sells good capacitors.

Thank you! I’ll look into this.

 

[imhighlander]

How would you diagnose on a vehicle with no OBDII link? (JDM)