Hello guys - this is a carry over from a post I'd made on the DIY for spark plugs...but allow me to reset. 2000 RX300 130km which had a misfire on plugs 1-3-5 for a while...tune up delayed due to the intimidating nature of that job. Thanks to the DIY, I finished the job this weekend. Have had some issues since though.

Most notably are the very poor throttle response below about 1,500 rpm's and a red hot catalytic converter after driving more than a couple miles. Engine idle is rough but much better than it was pre-tune up and the check engine light doesn't come on immediately after the codes are cleared or battery is reset. Misfires appear to be rare during the short trips I've take so far but the CEL is constant. When the codes are run, I get the following; 0300, 0302, 0304, 0306, 0171 and 1155.

Problems are that I took the three plugs(which I knew worked) out of cyls 2-4-6 and placed them in 1-3-5(formerly the problem bank). Cyl's 2-4-6 have new(matching) Bosch Platinum +4's. The other thing that confuses me is that bank 1 is now too lean, which seems to conflict with the red hot cat-which I presume is burning fuel from a car running too rich.

The car has new AF Ratio sensors if that's of use to anyone.

Does this combo of issues lead anyone to think one thing or another?
Thanks guys!!

 

Adding on to what I said earlier.

Ignore the lean error code.

One thing that might help is switching one of the coils where the misfire is occurring and sticking it on a cylinder where it is functioning well. That would confirm a plug issue. I've been reading around the net and seen people sometimes reporting issues with these plugs.

 

^^ Well heres your first problem.
Bosch plugs don't go well with Toyota engines.

Swap them out with NGK's or Denso's.
Like you said earlier. The problem didn't exist prior to replacing the plugs.

 

Again, I agree with Nad. T/L uses some extremely good parts to build their cars with. One of the outstanding examples is the Denso Iridium spark plugs and A/F ratio sensors. I would not consider using anything else in a T/L. You can often even buy the Denso parts online cheaper than you can buy aftermarket at a parts store. That may not be your problem, but that is my advice to any T/L owner.

 

The thing that gets me is two part:
1. The car previously had no misfires on plugs 2-4-6, which at the time had bosch+4's. To isolate the problem, I took the worn but working plugs from bank 2 and moved them to bank 1. I also moved the coil from cyl 1 to cyl 2. Now I have the new plugs in 2-4-6. Fickle plugs makes good sense-I'll try the ngk's I bought and then pulled in 2-4-6.
2. I'd really like to understand the smoking cat before I cook it for good. I live in a state without emmision testing but it's gotta be a fire hazard-is the cat a problem that runs secondary to the misfire?

denso seems like a great product - my other car is an audi tt so my affinity for bosch is rooted there.

 

Lets see what happens when you switch the plugs.

On the cat problem, that's because with a misfire, not full combustion, and the fuel is getting dumped down the exhaust pipe and meets the precat and this is a choke point with high heat (since it's not a straight pipe) and thus it's going to go red. You really don't want that thing turning red at all. I wouldn't call it a fire hazard per se, but if that heat gets too hot it can crack and hurt things around it.

Bosch works well in some things but other things...it depends.

 

I highly go along with everyone else, the Bosch plugs have caused me a lot of problems over the years....I use Denso or NGK inthe Lexus and will use Champion, Autolite, in my other vehicles....My old mercedes Mechanic said the Bosch keeps his business going well with the high failure rate...

 

Tom- I won't ask why you use "Champion" in your other vehicles (other than your lawn mower) (because, although I wouldn't, I know why)

 

I feel bad for Bosch. One of my high school friends used to work for them helping make vehicle oxygen sensors.

 

You would think Bosch would be top notch parts. They do work well in some cars, others not well at all.

 

Correct and that goes with other brands, too. I really have nothing against Bosch they do make some great parts for other vehicles, but Japanese vehicles seem to be really pick on things like ECUs particularly Lexus/Toyota and A/F sensors come under that.

 

Sorry for the delayed response guys-work/newborn come first sometimes.

I swapped the plugs back to the NGK's and the coil from 2 to 4. Moving the coil seems to have solved the hesitation from start issue but there's still at least one misfire. Was going to take the RX to the local dealer for their scan but they're too busy replacing floor mats-appt was two weeks out and wouldn't have confirmed my new diagnosis.

Bad coil/coils.

Any suggestions on a good place to pick some up? I have 140k on the car and it seems like it might be about time for them to start going bad. Couldve contributed to my pevious misfire problem too...but check me on that.

 

Check engine light ON?
If you still feel it misfiring, there should be at least a Pending code stored in the ecu.
Have it check by PepBoys or Autozone which cyl it is. (free)

I'd clear out your codes first before you drive down there to rule out codes you had B4.
They should pop back up since you still feel it misfire.
Brother's RX(125k) coils crapped out on him on 2 occasions in 2 weeks time.
He had them check it and bought the coils right there. $70ea I believe he paid.

Also don't rule out a bad injector.

 

Yes its is on my Ford F150 with the three valve 5.4 engine...The Ford plugs are big time loosers for that engine....The ground shield breaks off because of the design...Champion had a one piece plug that doesnt have that problem.

 

We also have a 99 expedition with the 5.4 and have similar problems/misfires but luckily I can get coils for it for under $30 a piece here.