This is a mess, but here we go..

2002 Rx300, 175000. Initially it started running rough and throwing codes. Along with knock sensor, multi misfire, #1 #2 #6 misfire.

I replaced plugs with OEM, upgraded coils with Accels, OEM knock sensor (#2, yuck). This cleared it up for a couple thousand miles. Then it went back to stumbling, misfire the same, loss of power. It actually was getting harder to even make speed after stopping. Codes ran, multi misfire.

Plugs replaced again, along with new injectors completely, new fuel pump and filters.

Now engine cranks, no codes. I am assuming that since compression is in tolerances, that timing belt is due to be changed, since I owned it at 150000. I just got the new belts, idlers, tensioner, gaskets, water pump.

Any advice if I am going in the right direction, or do I need to look elsewhere?

Thank ya!

 

I would have suggested OEM coils.

I also do not like doing too many things as it muddies the debug as there are too many changes. So hold off the t-belt change [Please use your judgment, as the recommended interval for timing belt is 90k for the first gen RX].

OCV can be a source of problem. You may like bench test them.

If the engine cranks but does not catch, you should test if you are getting the spark. Just lay the plug with the coil on the block and in a dark environment you should see the spark. If no spark, it could be the immobilizer.

Salim

 

I did get new OCVs, both banks and installed them. No change.

i checked the immobilizer, the security light blinks when the key is removed, and turns off when the key is put in the ignition.

i do have fuel, and i do have spark. Spark was strong enough that i could just lay the coil on the cover and watch it arc.

Engine turns freely and fast, just no bang!

 

If spark is there [imobilizer is out of the picture], you need fuel air and timing.

Was timing tinkered with by t-belt replacement and the problem happened afterwards.

You can confirm by checking spark at 0tdc on plug #1. Plug one is firewall side towards closest to the from passenger.

Salim

 

Sadly, timing has never been messed with in the time i have owned it. I got it at 160000 or so, and at the 175000 now.

I do not believe timing was done by previous owner. Only because i have discovered a lot of factory parts that should have been replaced long ago.

As of this moment, i am checking into the IACther build up.

I have had minor oil consumption since owning it. I did upgrade many maintenance items, including royal purple full synthetic 10w30. So, i like to make sure its tip top since i have owned it!

Thank you for the assist!

 

iAC, can be bypassed by holding the gas pedal down a bit. But the engine must catch and with IAC problem it will stumble and die.

I am leaning on fuel+air and timing.

RX engine meters the air and inject fuel based on that. If you have the intake open, you can try starter-fluid (with care). You just want to see if the engine catches.

Salim

 

Absolutely with ya there!

It was thanks to you folks that i did a cram course on this thing, lol! After nailing every part along the way, this seems to be narrowed down to timing, or electric gremlin. I doubt the gremlin as there has been to signs of chopping or mismanagement of wiring.

On its last trip home, weather was extremely hot, AC had to be run, so there was a fair amount of load (running scan @ 37% / 65mph, 1° grade.) It was already running poor, with the common CEL giving me #1,2,6 misfire, with the 300 random misfire. I did catch a 1349 once, but it didnt come back. Timing has remained a constant 5° advance on idle or turn over. But this is by toyotas sensor standard.

During the drive, got the whole OD limp out, stumble on stop in gear, super sluggish take off. As i pulled onto my road, at WOT it couldnt make it up a 5° grade at 5mph. I gave a good backfire (new exhaust parts been trickling in) and broke the down pipe mesh.

Old school training tells me that belt slipped or gave, but i wont know till i get those timing covers off!

I appreciate all the help!