so you can watch the tps dip? did you try to disassemble it and clean it out with contact cleaner?
sounds like you've focused in on the problem. might be time for a jy pull?
tony

 

Yeah I'm leaning toward that after my recent test drive. So I set it to graph the TPS, and I didn't catch it red-handed but it dipped, which changed the lower limit of the graph scale from 10.1 to 9.7. No press on the pedal or anything.

Also noticed that when under load, standing still on uphill grades, it will stumble on takeoff.

If I get a chance to hit the JY this weekend (doubtful), I'll nab one. Otherwise, I'm checking the plugs tomorrow so might order a Beck/Arnley or maybe an Airtex with new plugs, wires, and maybe coils.

 

Air conditioning on or off?

If you shift to neutral from drive does it recover?

Have you tried readjusting the TPS?

 

Greetings Insight,

Have -all- primary battery cables, connectors to ground, and primary fuse box / Main (100A) fuse been voltage checked / verified? What's the voltage @ the cigarette lighter plug (aka: accessory port) in the passenger cabin look like when the issue happens?

* I would also be suspect of the TPS if reading dipped 'on it's own', but low voltage /poor ground can (will) cause the same behavior .. Just saying.

I wouldn't make a career out of it, but given the past voltage/sensor issues it may be worth some time to verify good stable voltage, and sensor connectors, e.g. ECT/AIT/MAF/VSS as well. And if the RAV4 uses a NSS like the Camry does, well .. That might be worth a look also.

Alright, got some stuff to update.

1. Haven't adjusted the TPS. After this morning's test drive I'm going to put this on the back burner (read on).

2. I've been driving it a bit harder than I normally would (or the owner does) to try and "stress" the problem into rearing its ugly head. Yesterday, it didn't do the stumble in Reverse, but today it does. It also stumbles on takeoff sometimes. The big thing: I was merging onto highway 87 on a ramp with a steep (10-15%) grade, and it started stumbling under WoT. Soon as it leveled out, I mashed the pedal to get up to speed and it started misfiring bad enough to flash the CEL. Threw a P0300. Since none of this happens until it's warm, I'm thinking it's a problem with the coils.

3. I was thinking NSS yesterday because it wasn't stumbling in Reverse, but I reconsidered that. Might still do a cleaning, since nobody probably ever has.

 

Greetings Insight,

Have -all- primary battery cables, connectors to ground, and primary fuse box / Main (100A) fuse been voltage checked / verified? What's the voltage @ the cigarette lighter plug (aka: accessory port) in the passenger cabin look like when the issue happens?

* I would also be suspect of the TPS if reading dipped 'on it's own', but low voltage /poor ground can (will) cause the same behavior .. Just saying.

I wouldn't make a career out of it, but given the past voltage/sensor issues it may be worth some time to verify good stable voltage, and sensor connectors, e.g. ECT/AIT/MAF/VSS as well. And if the RAV4 uses a NSS like the Camry does, well .. That might be worth a look also.

 

Just to throw a wrench, EGR can do that too if it's not fully closing all the time or opening a little when it shouldn't. You can see if it's EGR by watching the O2 for a sudden lean when it stumbles or by just disabling the EGR totally as a temporary test.

 

Well, upstream sensor voltage hovers around 3.3, and does the same thing when it (a) stumbles and (b) I rev it: voltage jumps up a tiny bit, then bounces up and down back to 3.3 as the ECU corrects. Car never stalls or anything, what do you think? I'm thinking that's normal behavior for closed loop and the EGR is probably fine. No codes so far other than P0300.

See if it's a crack on the coil:

kent55's, crack across the coil near the bottom of the pic:

Yeah, I'll pull the coils soon(TM). They need the car back so they can go to work, but I have the Denso coils on order. This is my prime suspect

 

See if it's a crack on the coil:

kent55's, crack across the coil near the bottom of the pic:

 

Could be a spark problem but there is no distributor instead 2 coils, waste spark style like the 5S-FE.

 

I'm going to move from the coils to the wires and check the plug gaps (also for cracks)

 

3.3? Volts? Shouldn't that be a narrow band sensor between 0 and 1 volt?

 

Nope, AFR upstream

Right, if it's the ignition system then bad wires or large gaps in the plugs can also stress the coil (the coil really heats up and try to expand). Usually intermittent rough idle/misses primarily when warm would get me to look at the coils, especially the newer pencil coil-on-plug types. In most cases the roughness is at idle but tends to smooth out at higher rpms though.

Also check the dizzy rotor too, the tip might be worn. I guess we'll find out.

No distributor, waste-spark two-coil system

 

Right, if it's the ignition system then bad wires or large gaps in the plugs can also stress the coil (the coil really heats up and try to expand). Usually intermittent rough idle/misses primarily when warm would get me to look at the coils, especially the newer pencil coil-on-plug types. In most cases the roughness is at idle but tends to smooth out at higher rpms though.

Also check the dizzy rotor too, the tip might be worn. I guess we'll find out.

 

Oh didn't know they were using AFR that early on.

 

Well, maybe it has to do with being CA-spec

 

OK, I pulled both coils and swapped them for new Densos. After a short test drive to warm it up, I didn't notice any stumbling in gear while it idled. HOWEVER

...now that stumble/misfire when I press on the gas quickly seems to happen every time. I forgot to check the plugs, but will do that tomorrow. In the meanwhile, I've got a Schrader valve on order to check the fuel pressure.

EDIT: I'm going to see if my scanner (Actron CP9580A) can pull up a misfire counter for this car. I seem to remember there being one for my '01 DeVille, but dunno. Also have to dig up my ELM327 reader.

 

I don't think that Toyota has a misfire counts like GM does, I do love that on GM stuff! Check the plugs, maybe they're Bosch platinums!

 

Yep, CA emissions 5S-FE's got A/F's in '97, and 1MZ's got 'em in '98; see p/n's in red in the chart below. So it kinda figures the 3S-FE would have 'em in 2000.

 

Good stuff. You guys rock and are worth your weight in burritos

 

Alright guys, progress. Past couple days it threw a P0304, so I'll focus on that.

I did install the Schrader valve and test fuel pressure, which was in spec. 49 PSI at idle, doesn't move under throttle all the way to WOT, and held at 47 PSI for 5 minutes after shut-off.

So next up is plugs and wires.

 

Hopefully you are not getting bit by bad capacitors in the ECU. I've read quite a few stories where there were random codes and seemingly explainable problems that turned out to be leaking caps. Have you tried watching the engine run when it's dark out to look for spark leak? Especially if you wet down the engine.

 

Ooh, good idea. Is the spark leak related to the ECU?

 

Well, it's throwing a P0304 which is pretty specific. Going to swap in an NGK wireset and OEM plugs, let's see what happens before I touch an injector

 

OK guys, problem solved I think. I pulled the plugs: they weren't the OEM NGK 3452 double-plats, rather they were NGK iridiums. NBD, they all looked great and were within spec (0.045 in, max gap 0.051). I pulled #4 first, and it had a carbon track:

Matching carbon track in the boot:

...so it seems the crappy (seems like Duralast) plug wire is what failed. I replaced them with some sweet NGK blues:

Then I drove around for a good long while. No misfires, so I went back and swapped the plugs for the 3452's. Little dab of aluminum antiseize, 13 ft-lbs, 3M silicone grease in the boot, and buttoned her up! Good to go, thanks all for the help.

If I come across other gen1 RAV4's, I'll collect more data because this isn't enough to say that it's the only cause of the stumbling issues on these CUVs. Now to tackle the other problems (fuel gauge not reading correctly, rear drum brakes squealing, trans drain-and-refill, oil change + Fumoto valve).

 

Ah yea, carbon tracking. Hard to find if you're not looking for it!

 

isb those plug insulators look filthy. how long have those plugs been in there? how long for the wires/boots?
it didn't occur to me to ask when the last major tuneup was done in your case, as i usually do to others in this situation.
good you got it fixed.
tony

 

Well, the owner said maybe three years ago. It's worth mentioning that he came to me because his previous mechanic repeatedly ripped him off...the last of which was claiming to replace the rear brakes and not actually doing it (guess what I'm doing when RockAuto delivers).

The plug wires' insulation was cracking and peeling all over. It's just rubber, not silicone like the NGKs. Lol, some of the filth on the plug ceramic might be from my gloves, I'm trying to fix about five cars at once here :wink:

 

roger that. thanks for closing the loop for future searchers isb.
tony

 

With 267K on the injectors, it's time to pull them and get them professionally cleaned OFF the engine, regardless of whether it fixes the issue or not. The shop I use in Tucson charges $35 per injector. They are sonically cleaned, forward flushed and back flushed until a good spray pattern is achieved. The injector coils are load checked, new inlet screens and tip protectors are installed, all for $35. Hard to beat.