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Discussion Starter · #1 · (Edited)
Taking @Elle_Rav4 ’s advice, I’m starting a separate thread for this, apart from my rebuild thread here. Sorry for the lengthy post, but there’s a lot to cover.

My Rav started misfiring a while back, and it’s progressively getting worse. I call it misfiring, but it’s better described as bucking. Maybe that’s the diff between a V6 and an I4? It’ll jerk violently if I’m accelerating hard. Almost like someone turned the ignition off and then on within a second. Trying to run it at high RPM, it’ll either buck repeatedly, stuck at 4k-5k RPM, or buck a time or two and then continue on up to redline. Lately, it won’t idle for more than 10 seconds before it’ll stumble hard enough to die. Cruising along at moderate RPM, it runs well, with an occasional bump from a misfire.

It has new NGK plugs & wires from my initial resurrection, which was to do a timing belt job, valve stem seals, reshim the valve clearances, reseal the oil pump, & install a Denso O2 sensor. This was all before this bucking started, and it ran quite well. Shortly after, I also pulled and cleaned the throttle body, and removed the IAC and cleaned it.

Since the bucking started, I’ve replaced the fuel pump (Denso), IAT sensor (AC Delco), both ignition coils (WVE), & the fuel filter (AC Delco). I also pulled and tested the “circuit opening“ relay, which controls the fuel pump operation. The coil resistance was about 30 ohms, and testing it with a 9V battery, the contacts closed with less than a half ohm of resistance.

I’ve also watched several things on an OBD2 monitor on test drives, including IAT, ECT, MAP, LTFT & STFT. All of those seem normal. IAT reads about 5-10F hotter than ambient air temperature. ECT holds at 190F after warming up. MAP reads about 0.8 ATM with the engine off, which is about right for my altitude of 5k feet. When running, it‘s 0.18 at idle, and goes up to near 0.8 when floored. It responds as expected to small changes in throttle position. LTFT runs around -5 to -10%. STFT bounces around between -5 to +1%.

I’ve checked the crank position sensor resistance twice at the connector near the alternator, and it was about 1300 ohms (cold) both times. Have not checked the cam position sensor, as that requires pulling the battery.

Spark plugs are dry and look normal color. None of the plug tubes are leaking oil and drenching the plugs.

Throughout all of this, there haven’t been any OBD2 codes set or even pending. I wish it would. The CEL light does light up when the key is turned to ON, and my two OBD2 monitors both connect without issue.

At this point, I’m thinking I may have a bad injector, fuel pressure regulator, or a flaky ECU. I don’t think my Rav has an igniter, as their function is integrated into the coils?

Maybe the EGR valve is opening when it shouldn’t be?… which is at idle and WOT. It should only open after the engine is warmed up, and then only at mid-throttle settings. I’ll try defeating it and do a test run tomorrow.

Any other ideas?
 
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From a prior BMR thread, this a 1998 3 door, AWD soft top with manual transmission.
Trying to run it at high RPM, it’ll either buck repeatedly, stuck at 4k-5k RPM, or buck a time or two and then continue on up to redline.
What necessitates driving at 4k-5k RPM and close to redline? What sort of speed are you driving at? Are you driving at high speeds up a mountain?

Lately, it won’t idle for more than 10 seconds before it’ll stumble hard enough to die. Cruising along at moderate RPM, it runs well, with an occasional bump from a misfire.
I am homing in on the above.

From a cold start, does the Rav idle some 10 seconds and then stumble and die?

From a hot start, does the Rav idle some 10 seconds and then stumble and die?

Did you install the twin electrode NGK plugs that the owner's manual specifies?

It has new NGK plugs & wires from my initial resurrection, which was to do a timing belt job, valve stem seals, reshim the valve clearances, reseal the oil pump, & install a Denso O2 sensor. This was all before this bucking started, and it ran quite well. Shortly after, I also pulled and cleaned the throttle body, and removed the IAC and cleaned it.
Can you clarify when you removed the IAC valve? Was the Rav running fine before you touched the IAC valve, but then started having problems after you removed and cleaned the IAC valve?

I am also homing in on: Before Timing Belt job, all was running fine. After Timing Belt job, bucking started.

Is your Rav a California emissions Rav4, as indicated on a sticker under the hood or possibly on the driver's door pillar where the VIN is?

What is the part number for the Denso front O2 sensor you installed?

Have you tried installing the old O2 sensor to see if this improves things?

MAP reads about 0.8 ATM with the engine off, which is about right for my altitude of 5k feet. When running, [MAP is] 0.18 [ATM] at idle,
An absolute pressure of 0.18 Atm is about 5 inches Hg Abs. This seems low to me for idle. In other words, vacuum at idle is somewhat higher than I would expect. Reports of about 9 or 10 inches Hg Abs are what I am seeing for Rav4.1s (granted with only a whopping two data points). I wonder: Is the engine being starved for air, producing this high vacuum at idle, and causing the stalling at idle your Rav is now experiencing? I do not have that much experience with MAP. Still, given the symptoms here, something may be off with the air flow at idle.

I would do the tests on the IAC valve given in the attachment on pages SF-34 and SF-37.

While diagnosing, I would also consider blocking off the vacuum port connecting to the bottom of the IAC valve, sort of in between the two coolant lines. The Rav should idle fine with this port stoppered (blocked).

Consider going to a salvage yard and buying a whole throttle body and IAC valve assembly. Use throttle body cleaner (not carburetor cleaner) to clean it. Do not take apart the IAC valve but do get some throttle body cleaner through its passages and operate the valve some while cleaning the IAC valve. Install the assembly. Any improvement? I keep a spare salvage yard TB and IAC valve in my parts bin.

I don’t think my Rav has an igniter, as their function is integrated into the coils?
Correct. For the 1998-2000 Rav4 the two coil packs (pulsing power to the four spark plug cables) are a combined coil and igniter, or at least this is how I think of the coil packs.

Toyota engine computers rarely go bad. To destroy a Toyota engine computer takes a flood or someone, say, reverse jumping the battery.

I am not ruling out some damage to the camshaft position sensor and reluctor or crankshaft position sensor and reluctor. Nor am I ruling out a vacuum hose leak. I am wondering if there are two things not working right (one at idle, one at high RPM), with at least one tracing back to the maintenance you have done.
 

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Why drive around 5000rpm? Because that's where the 3sfe feels alive haha!

Joke apart, can you reproduce the same symptoms in neutral?
 

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Discussion Starter · #4 ·
From a prior BMR thread, this a 1998 3 door, AWD soft top with manual transmission.
What necessitates driving at 4k-5k RPM and close to redline? What sort of speed are you driving at? Are you driving at high speeds up a mountain?
Normally I don’t. I just experienced it running very poorly one time. So I’m kinda focused on that. I was on paved country roads running it up to redline in 1st & 2nd gears, keeping it under the 45mph limit.

I am homing in on the above. (the poor idling -BMR)

From a cold start, does the Rav idle some 10 seconds and then stumble and die?
No. The higher idle RPM of a cold start keeps it from dying. It’ll still stumble, but then it’ll catch before it dies.

From a hot start, does the Rav idle some 10 seconds and then stumble and die?
Yes.

Did you install the twin electrode NGK plugs that the owner's manual specifies?
Yes.

Can you clarify when you removed the IAC valve? Was the Rav running fine before you touched the IAC valve, but then started having problems after you removed and cleaned the IAC valve?
It was running fine before I cleaned them. I was working on the EVAP sytem, fixing the P0446. While I had the intake ductwork removed, I thought I’d be proactive and clean the throttle body. While I had the throttle body off, I thought I’d be proactive and clean the IAC. Dirty IACs are a chronic problem on the 3S/5S motors, causing idle problems.

I am also homing in on: Before Timing Belt job, all was running fine. After Timing Belt job, bucking started.
No. I bought it non-running for cheap, betting it had a snapped timing belt, which it did. When I got the TB job done about 5 months ago, it ran great up until a few weeks ago.

Is your Rav a California emissions Rav4, as indicated on a sticker under the hood or possibly on the driver's door pillar where the VIN is?
Its Fed.

What is the part number for the Denso front O2 sensor you installed?
234-4624

Have you tried installing the old O2 sensor to see if this improves things?
Nope.

An absolute pressure of 0.18 Atm is about 5 inches Hg Abs. This seems low to me for idle. In other words, vacuum at idle is somewhat higher than I would expect. Reports of about 9 or 10 inches Hg Abs are what I am seeing for Rav4.1s (granted with only a whopping two data points). I wonder: Is the engine being starved for air, producing this high vacuum at idle, and causing the stalling at idle your Rav is now experiencing? I do not have that much experience with MAP. Still, given the symptoms here, something may be off with the air flow at idle.
Don't forget my 5k feet altitude. This will skew my numbers lower.

I would do the tests on the IAC valve given in the attachment on pages SF-34 and SF-37.

While diagnosing, I would also consider blocking off the vacuum port connecting to the bottom of the IAC valve, sort of in between the two coolant lines. The Rav should idle fine with this port stoppered (blocked).
I’ll read into those.

Correct. For the 1998-2000 Rav4 the two coil packs (pulsing power to the four spark plug cables) are a combined coil and igniter, or at least this is how I think of the coil packs.
Thx for confirming that.

Toyota engine computers rarely go bad. To destroy a Toyota engine computer takes a flood or someone, say, reverse jumping the battery.
While I agree it’s rather rare, over on the Toyotanation Camry forum for ‘92-‘01 Camry, it’s been happening more & more. Still rare, and not the first thing to jump to, as there is no diag’ing them.

I am not ruling out some damage to the camshaft position sensor and reluctor or crankshaft position sensor and reluctor. Nor am I ruling out a vacuum hose leak. I am wondering if there are two things not working right (one at idle, one at high RPM), with at least one tracing back to the maintenance you have done.
I agree. Although in my observation, a failed cam or crank sensor always gives a no start condition.
Joke apart, can you reproduce the same symptoms in neutral?
Ya know, I hadn’t really tested running it to redline in neutral (not something I would EVER do, normally). So on my test drive tonight, I did floor it in neutral. It starts running crappy just before redline, at about 5750. Redline is 6250, so it’s about 500 RPM short. Is that normal?
 
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Discussion Starter · #5 ·
My test drive tonight was with the EGR vacuum line disconnected and plugged with a golf tee. It made no difference at all.

Following are a few videos. This first one shows it stumbling when cold idling. I touched the gas pedal to goose it a couple times at 0:21.

Here’s a full throttle acceleration in 2nd. I never let off the gas until the very end. Sometimes it does this at 4k RPM.

In this one, I tried to catch it stumbling at a warm idle, but it died before I got the vid started. But you can see how long it cranks before restarting. I was giving it a little throttle, thinking the IAC might be not opening. But it didn’t start until I let up on the gas. It stumbled once right after restarting, then settled down for the rest of it.
 
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Don't forget my 5k feet altitude. This will skew my [MAP] numbers lower.
Certainly at Key On, Engine Off, the MAP should (and does) reflect the altitude of your location. But with the engine running and at an altitude of 5k feet, right now I am not convinced the numbers (MAP readings) should skew lower. The normal pressure in the intake manifold is sub-atmospheric (a vacuum). It seems to me that, with the engine running, the position of the throttle valve and the driver's desired RPM are going to yield a MAP that is about the same regardless of one's altitude.

Lots seems to point to the IAC valve being the problem. I would do the IAC valve checks. I would consider swapping out the throttle body/IAC valve with another.
 
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Discussion Starter · #7 ·
Here are the spark plugs, 1-4, L-R. #2 is slightly darker.
169315
 
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Discussion Starter · #8 ·
The IAC valve resistances check out. I’d call these “warm“ numbers, as the engine is still fairly warm from my test run.

From RSC to +B terminal - 23.1 Ω
From +B to RSO terminal - 22.9 Ω
 
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Discussion Starter · #9 ·
My gut says this is all one problem. And I suspect it’s the ECU intermittently shutting off the fuel pump. I’m thinking of wiring up a test lamp to the Circuit Opening relay’s output so I can see the bulb, and doing a test drive.
 

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I'm gonna call it ECU. To say these ECU are not known to fail is far from true. They fail all the time. The capacitors inside end up popping just due to age. Constant heat and cool cycles do that to electronics, especially ones that were originally designed in the 80's like the 3sfe ECU was.

BMR, I don't remember what other vehicles you have. If you have a 5sfe powered vehicle it will socket right in and run just fine. You can run a 3sfe off of a 5sfe ECU and vice versa, kinda neat. Makes engine swaps easier, in general. This also means that any junk yards near you that have any Camry, Celica, Solara, or Rav's will have an ECU for you to test with.

You will have to stick with the same year though. I'd help but right now there is only 1 98+ Rav4 within 100 miles of me and it's been there for 2 months already. I could nab you one of the other ECU if you wanted but I'd rather get you the correct one and finding a manual 98+ ECU will be slim pickings by me.
 

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Discussion Starter · #11 ·
I don’t have another 3S/5S powered vehicle. Never have. I may have to make the trek to the nearest U-pull yard, which is a good hour to 1.5 hours away. See if I can nab a throttle body/IACV too.
 

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To say these ECU are not known to fail is far from true.
I posted that they "rarely go bad."

I do not rule the ECU out. But since the symptoms started after cleaning the throttle body and IAC valve and while fixing the Evap system for a P0446, I think these need more investigation.

Ecudoctors.com mentioned checking for spark when there is a no-start situation, like BMR's Rav is having when the engine is warmed up; then stopped; then only cranks until he does more. No spark in this situation may give more support for a failed ECU.
 

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C'mon Elle, that's semantics lol.

BMR, I don't know your skill level with circuitry. You could pull the ECU and open it to check for faults. Corrosion, popped fuses, stressed capacitors, or even heat damaged chips would cause any of these symptoms. If you have never worked on circuits before I would suggest leaving it alone as not know what you are doing could cause catastrophic failure.
 

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No, it's you not owning your misrepresentation of my thoughts. Until this problem is fixed, I have not, and will not rule out the ECU. But the ECU is not near the top of my list of possible causes. If you are wrong in insisting that the problem is the ECU, this is a lot of trouble to which you are going to put the OP. To help reinforce (not confirm) the suggestion that the ECU is the problem, I would check for spark the next time the warmed-up Rav cranks but won't catch and start.
 

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No, it's you not owning your misrepresentation of my thoughts. Until this problem is fixed, I have not, and will not rule out the ECU. But the ECU is not near the top of my list of possible causes. If you are wrong in insisting that the problem is the ECU, this is a lot of trouble to which you are going to put the OP. To help reinforce (not confirm) the suggestion that the ECU is the problem, I would check for spark the next time the warmed-up Rav cranks but won't catch and start.
I'm a generally nice guy until someone calls me out. Ok then.

My semantics comment was referring to how "Rarely" and "Not known to" are the exact same thing just different words. Not once did I state you were incorrect in any of your deductions. Understand that please.

On to "Not owning your misrepresentation of my thoughts", never said you were right or wrong. I will now. You refused to read through maybe 10 minutes worth of reading to help someone and asked them to make a brand new thread for your convenience. That is bad form.

Windshield badly cracked. When replaced there was rust which meant at some point the windshield was leaking into the cabin. Even ambient wet air can effect electronics. The rear soft top was in very poor condition. Post #113 is where indication that the ECU is beginning to be suspect. BMR experienced possible surging, refused to rev past 4k RPM, and sputtering. All of which would throw a code immediately in a healthy ECU. The vehicle had gone into a limp mode. Those are the issues. BMR replaced and cleaned almost everything that would have affected the engine enough to go into a limp mode except the ECU. You seem to be harping on the IAC even though the old one was cleaned and a new one installed, yet still issues. For whatever reason you fail to see that the ECU has thrown no codes, including pending codes throughout this entire ordeal and has read normal readings when clearly it is not.

All of this leads me to believe one or two of the capacitors has either blown or come close to blowing. It most likely has seen moisture at some point, either from outside elements or from a capacitor (Which are filled with a fluid).

Here are some supporting threads:




Notice how all 3 of these threads have similar issues as BMR?

Your comment of "If you are wrong in insisting that the problem is the ECU, this is a lot of trouble to which you are going to put the OP" shows you clearly did not read post #10 of this thread. It is clear that I am in no way throwing any problems his way and am trying to help him as much as possible. I have sourced parts in the past for BMR and will continue to do so if I find the parts he's after. It just so happens right now is a relative dry spell in terms on possible vehicles in the yards for me to pull from. An ECU at the junk yards by me is about $50 and shipping it would cost maybe $4 or so as I get a massive discount on shipping. Should it not work I'd just have him send it back using my discount again. So it would cost maybe $8 from him for shipping and a few hours of my time. That is minimal trouble.

Please note that I looked for a possible ECU to send to use as a tester as I do not know BMR's skill level with circuitry and would much rather him swap an ECU around to see if that repairs the issue as opposed to him opening it. I even stated that in the same comment as the semantics reference, however you seem to have only seen the first sentence.

You are a generally good person Elle and I wish no ill will toward you. Please do not take me recommending things different from you as an insult. We both have very different ways of diagnostics. Comments such as "I'm gonna call it ECU" is not stating you are incorrect in any way, it is me stating that I think it's the ECU. Do not take every comment literally. The only thing from me anyone should take seriously and literally is any helpful advice.
 

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the IAC even though the old one was cleaned and a new one installed, yet still issues.
I have seen no report by BMR that he replaced the IAC valve.
 
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Discussion Starter · #17 ·
I have seen no report by BMR that he replaced the IAC valve.
That is correct, I have not. But there’s a lot going on here, so I fault no one for getting confused about the details.

A symptom I neglected to mention; it’ll sometimes buck under normal moderate acceleration, at much lower RPM. Makes for a very unpleasant ride, as it is very violent. If someone had an open cup of coffee, they’d be wearing it. Go back and watch my second vid. I was holding my phone with one hand, with my palm braced on the steering wheel, yet it was impossible to keep it steady while it was bucking repeatedly.

Off to the garage to rig up a test light on the fuel pump power input. Blue wire with a black stripe.
 

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I apologize, BMR replaced the IAT, not IAC. I will point out that if that's all you gathered from that that I wish to not deal with you at all Elle and will be setting you to "ignore" on this forum. It's clear to me that we will butt heads frequently if I do not. Will wait until tomorrow morning so you may at least see this message.

BMR, those are very severe misfires. You should have gotten a flashing check engine light, catastrophic failure. If you had a light for P0300 and P030X where X is the cylinder then I would suggest looking at ignition system. However, no light means the ECU is seeing everything as "normal". Clearly there is a severe enough misfire to "rock the boat" so that is far from normal operation.

I apologize for not seeing those earlier, I have a tenancy to not watch videos.
 

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Discussion Starter · #19 ·
Well, that didn’t take long to rig up. I’ve got the light’s two wires connected at the fuel pump. One to the blue wire with black stripe (FP power), the other grounded via the rear seat mounting bolt. At the other end, I soldered the two wires directly to the bulb.

The fuel pump not running is def not the problem. This was a cold start, but you can see the temp gauge is halfway to normal. Throughout this vid, I did not touch the gas pedal. The FP power indicator bulb (on the right) stays lit the whole time. It stumbles several times before a bad one causes it to stall. The bulb stays lit for a couple seconds after it stalls. If you listen close, you can hear the fuel pump shutting off with the bulb.
 
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I am late to this one. Well done with the test light, it loads the circuit - can I clarify (I have probably missed it), are you checking the power to the fuel pump, or the actual running of the pump? Just to be totally sure - but this is just my thought.

If you are not getting crazy codes for misfires, then indeed, the ECU thinks everything is good.

I can see your combined FT's are still around 15% removing fuel.

Gut feeling, have you got a vacuum leak somewhere? Are all the sensors running true and reporting the correct values?

Again, just my thoughts
 
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