LouisUGA

Hello All,

I have enjoyed reading posts on this forum but this is my first time posting a message. I am writing because I have a 1999 Lexus RX300 that has been having some issues lately. I am nut sure which symptoms are related to the current problem, so I will give a brief history since I have owned it.

Bought it in 2010 with 169,000 miles
Ran great the first 18 months.

About a year and a half ago, a check engine light came on. A local mechanic ran the code and said that it indicated that a catalytic converter was bad. Because I live in Routt county, Colorado where there are no emissions requirements, he suggested that I do not worry about fixing it because it will not affect the performance of the vehicle.


One year ago, the engine was idling very rough as in an engine misfire. Ran the code (dont remember it now) and figured out that it was one of the easily accessible engine coils. During the misfiring, I had to drive the vehicle over a mountain pass to get to an auto parts store. At the top of the pass, I hopped out of the vehicle to see what the cat looked like. As expected, It was bright red hot. So the already damaged cat was definitely toast. When I got to the auto parts shop, I Replaced the ignition coil and the car ran great again. About 6 months later, I got the same symptoms, the same code, and replaced the same ignition coil. Again, the car ran great.

Six months after that, the car began bucking during acceleration in a lurching motion. As soon as this happened, the check engine light would begin flashing. My local mechanic believed this to be related to the aforementioned rear catalytic converter. He removed it and replaced it with a straight pipe. He test drove it and it seemed to work. I gave him a hundred bucks and picked it up. The next day, the same problem started intermittently occurring again. I called my mechanic again to let him know and he did not have many ideas as to how to proceed. He suggested that I get a tune up (not sure when the last one was performed) and that he would check the other two cats while he was in there. Because the plugs are hard to get to, the labor is estimated at 2.6 hours for the tune up plus whatever it takes to get the other cats off. So it would cost around 500 and may not fix the problem.

So I am asking you folks for advice. I know I have not been able to provide all of the necessary information (error codes, etc.), but do any of you have a guess as to what is going on? Could the problem lie in the O2 sensors? Is the tune up worth it?

Any advice is greatly appreciated,

Thanks,

Louis

lexus114

If your check engine light was flashing, more than likely it is another misfire going on. Stop wasting money on the after market auto parts crap and get a coil from either Sewell Lexus online, or a Toyota dealer. (not scolding you,just giving advice) Also, you may need spark plugs.

Baetke

Welcome to CL. You have come to the right place.
Quite a good history you gave in your post. There are several issues to discuss.

1) When you first got the code indicating a bad Cat, it could have been due to a couple of things. A bad Cat error code is set when the ECU reads data from the A/F sensor in front of the Cat and the O2 sensor behind the cat and determines that the Cat isn't doing its job. This could be due to a bad Cat, but more likely due to a bad sensor. A bad sensor will usually throw a different error code but not always. A bad Cat will not make the car run rough or effect fuel efficiency so it was reasonable to keep driving it if you didn't have to pass an inspection.

2) When you had your misfire error code due to a bad coil I would bet that the check engine light was flashing, not steady. This is critical. A flashing CEL tells you that the problem is severe enough that you WILL damage the car if you keep driving it. A flashing CEL means pull over and call the tow truck. A steady CEL means you have time to troubleshoot and fix the problem. As you described, you burned up your cat because you were dumping unburned fuel into the exhaust system when the coil stopped firing. Very predictable failure.

3) Your last symptom requires more info but if the engine starts bucking intermittently and you have a hard brake pedal, you most likely have an OCV problem. This is a relatively simple DIY.

If at all possible, provide error codes and we can be more specific. I'm a little bit concerned that your mechanic recommended a "tune up" since this is kind of an archaic concept with modern vehicles. If you have definite symptoms, a competent mechanic should be able to diagnose the specific problem, not make a general recommendation such as "get a tune up".

Baetke

salimshah

I would start by getting the codes read. Without the codes you will get generic advice.

I second the advice about sticking with OEM when it gets to run based electronics.

If you have not replaced the spark plugs, they should be replaced at 110k miles.

Salim

engine89

Bad plugs can cause the problems as described. Un burned fuel mixture can enter the cats, burn inside them and cause them to glow red. I saw this on a car with a fried alternator causing weak spark as the car struggled to run off the remaining battery power . Cat was glowing red when the car pulled in.

JAB

Spend $30 and get a cheap code reader. Won't answer all your questions, but at least when the CEL comes on it will give you some information about what the problem MIGHT be.

LouisUGA

Thank you all for all of the advice. I will clarify any questions that you have.

Most recently, when the car would lurch while accelerating, the CEL was flashing. It would buck 3 times fairly quickly, then I would release the accelerator and the car would stop bucking. Usually, the CEL will flash for about 1 minute, then would just go back to steady on. This has happened 4 or 5 times, usually once per 3 miles and usually on an uphill. I know that a flashing CEL means pull over and have it towed, but I have limped it home and am no longer driving it.

Both of the times that ignition coil went out, the resulting engine shake was much different than these lurches. Those times, the engine would just idle poorly until the ignition coil was replaced. This time, the engine sounds like it is running fine, but will jerk on the uphills.

A friend of mine riding in it said that he believed that the jerks were indicative of a transmission issue and sent me a link to this thread regarding loose ground wire connections on the plenum: https://www.clublexus.com/forums/rx-...mission-2.html
I reached back in there and nothing appeared to be loose, but I am not confident that I was in the correct spot. Is this a reasonable problem?

I am not sure if the plugs have ever been changed. Should I go ahead and have them do that? Which plugs should I use? Could bad plugs be causing heavy jerking?

I will get a code reader, but since I live in Steamboat, I am prefer to buy stuff like this online and not pay mountain prices. Can any of you send a good link to an inexpensive but good quality one?

I will post the codes as soon as I get them.

Thanks again!
Louis

salimshah

We have had discussions on plugs and coil-packs. Please use search and as stated before, stick with OEM.

Based on what you have stated here, your RX problems relate to combustion (or lack of combustion). Plugs, coilpacks, crank-shaft, cam-shaft sensors come to mind .. but you need to give us the exact error codes.

There has been discussion on the code reader too... please search or read the mega-thread sticky.

Your friend can be right (although unlikely in this case) about transmission but lets get the obvious fixed and not start chasing a ghost.

It is important to know what else has been tinkered with after every thing was working. Things like loose ground etc can then be traced by examining the work area/surroundings.

Nothing wrong with net shopping. Stay with reputable sellers and here in Club Lexus we always would recommend sponsors.

Salim

LouisUGA

Thanks for all of your help. I borrowed a friend's code reader and it read 6 codes:

P1300
P1310
P1315
P1320
P1325
P0300

The P0300 is a random multiple misfires code.

What do you guys think is the best course of action? Because I am not sure that the plugs have ever been changed, I am planning on having that done on monday.

Thanks again,
Louis

Baetke

Correct me if I'm wrong but I bet you also had a P1305 code too and just forgot to list it.
With these codes you can forget about spark plug or coil problems. They're fine. These codes are misfires on each individual cylinder. Since you have misfires on all 6 cylinders the problem lies with something common to all 6. Most likely you have an intermittent open or short on the IGF signal going from the ignitors to the ECU. This is the wire that provides spark confirmation from the ignitors to the ECU. Finding and fixing this requires experience with diagnosing electrical circuits and the proper tools and documentation. If you aren't capable of doing this yourself, shop around for a mechanic that is really good with electrical troubleshooting.

LouisUGA

I do believe that that error code was also displayed. I will do some research on our local mechanics and see who would be the best to take it to. Do you think that it is a loose connection somewhere? Hopefully it will be an inexpensive fix. Thank you guys for helping me out.

Louis

Baetke

Yes, As I stated in my previous post, the IGF wire from the ECU to the ignitors is the most likely culprit. You need to find someone who has the schematics for your car and can locate and verify the proper operation of this wire.

LouisUGA

Thanks, I will find a competent mechanic and take it in on Monday. I found a wiring diagram on this thread and plan to print it out and bring it along:

https://www.clublexus.com/forums/rx-...rx300-ecu.html


Ill let you know how it goes.

Thanks,
Louis

Baetke

Great, you found the right schematic. The information he is looking for is on pages 1 and 2. (pages 1 and 3 of the pdf file).

LouisUGA

Hi guys,

I wanted to update you as to what happened with the vehicle and seek some advice about a new problem.

I rechecked the error codes and got error codes for only 5 of the 6 cylinders. This seemed bizarre for 5 of the 6 to mess up all at once. Because I was frustrated and busy at the time, I took the RX300 to a mechanic to have it checked out. They used their fancy code reader and got the same thing, determined that it was 5 faulty coil packs, and convinced me to replace them. I agreed (foolishly) and paid something like $1300 for 6 new coil packs (5 for the faulty ones and one because that one was likely to fail soon as well.) + Installation.

After receiving the car and the huge bill, It ran well, but only for a couple of weeks. I returned to the same place, not because I was impressed with their service, but because I felt that since I had already used them for a problem that was not fully resolved, they may cut me a break and would also be somewhat more knowledgeable about my car/problem. At this point, they reccommended changing the spark plugs as they had not been changed as long as I have owned the car (25000 miles) and I was unsure if they had ever been changed. I agreed, and $360 later, the car seemed to run well again.

This time, it ran well for 2 weeks until it began misfiring again. Usually the car starts and runs fine for the first 10 minutes or so until it begins misfiring. I recognized the feeling from the previous events, but only this morning (2 weeks after the problem), did the car finally throw a code (P0302).

I am very frustrated with the car and myself for wasting money on a mechanic that has not fixed the problem.

For a recap:
The Vehicle is a 99 RX300 V6 AWD

In the past 1,000 miles, we have replaced all six ignition coils and all six spark plugs.
In the past 2500 miles, the catalytic converter under the center console was removed and replaced with straight pipe. (no emissions testing in my county).

The current error code is a P0302.

Any ideas would be greatly appreciated!
Thanks,
Louis