Ongoing problem seems like ignition, but I dunno

[KelOfTheRockies]

Truck: 2000 4Runner Ltd 3.4L V6 250,000 miles. Located Rocky Mtns (6000 ft ASL)

It's been fine, but a couple of months ago, I started getting some engine hesitation getting off the line.
Acceleration at cruise speed (of any range) is great. From a still, like stop sign or red light, the engine stutters getting going, and smooths out somewhere between 1500 and 2000 RPM. Doesn't matter if I'm gentle on the pedal, WOT, or anywhere in between it acts the same.

I replaced the ignition coils and the problem went away...for about a day. Then I replaced the ignition wires, and the problem went away...for about half a day.

This last weekend, I cleaned the MAF and connector, no change. I pulled the throttle body and it looked like the third ring of hell, so I figured I may have found it. I cleaned out all the gummy crap until it was spotless. I removed the IAC and did the same - it was solid with black goo inside.

Truck ran great for the 5 mile test drive through the neighborhood stop signs and signal lights.
In the morning, it started up immediately and idled smooth as glass. Acceleration was also smooth as glass throughout my 50 mile round-trip commute. Not a hint of trouble.
The second morning, on startup the idle was way bumpy and the acceleration off the line was back to the same shakey shuddering until 1700 or so RPM.

Earlier, I had no OBD codes, but today the CEL was on and I found P0300 about misc misfires and P0171 about lean condition.

I sprayed starter fluid all around the intake stuff while it was idling in my driveway and got nothing.

I'm going through the hoses and the TB again today to make sure all is sealed.

Other suggestions are appreciated. (please. I'm not at the end of my rope, but I can see it from here)

—K

 

[spartacus]

Truck: 2000 4Runner Ltd 3.4L V6 250,000 miles. Located Rocky Mtns (6000 ft ASL)

It's been fine, but a couple of months ago, I started getting some engine hesitation getting off the line.
Acceleration at cruise speed (of any range) is great. From a still, like stop sign or red light, the engine stutters getting going, and smooths out somewhere between 1500 and 2000 RPM. Doesn't matter if I'm gentle on the pedal, WOT, or anywhere in between it acts the same.

I replaced the ignition coils and the problem went away...for about a day. Then I replaced the ignition wires, and the problem went away...for about half a day.

This last weekend, I cleaned the MAF and connector, no change. I pulled the throttle body and it looked like the third ring of hell, so I figured I may have found it. I cleaned out all the gummy crap until it was spotless. I removed the IAC and did the same - it was solid with black goo inside.

Truck ran great for the 5 mile test drive through the neighborhood stop signs and signal lights.
In the morning, it started up immediately and idled smooth as glass. Acceleration was also smooth as glass throughout my 50 mile round-trip commute. Not a hint of trouble.
The second morning, on startup the idle was way bumpy and the acceleration off the line was back to the same shakey shuddering until 1700 or so RPM.

Earlier, I had no OBD codes, but today the CEL was on and I found P0300 about misc misfires and P0171 about lean condition.

I sprayed starter fluid all around the intake stuff while it was idling in my driveway and got nothing.

I'm going through the hoses and the TB again today to make sure all is sealed.

Other suggestions are appreciated. (please. I'm not at the end of my rope, but I can see it from here)

—K

Did you replace the plugs? Did you replace the iac gasket? Is your truck high idling?
When was the pcv valve last replaced? Replacing the pcv valve might help. Replacing the gasket on the fuel filler cap or new cap on these old trucks always good. Check the ends of hoses for cracks and check the intake air tube's for cracks from air filter to the throttle body. If you have an obd and torque app. Look at the maf readings within spec . Also the oxygen sensors are functioning with in the limits. Fuel Filter and finally injectors.
Helpful link.
Help!!! P0171!!!

 

[brillo_76]

What kind of parts did you use? If the wires and coils come from amazon or ebay its possible that you got counterfeit parts. Would explain instant failure or near failure.

 

[2TH4IST]

As brillo said, stick to actual store or dealer or rockauto for parts.

One other thing to look as is failing injectors. They are old and known to fail with high milage.

 

[KelOfTheRockies]

What kind of parts did you use? If the wires and coils come from amazon or ebay its possible that you got counterfeit parts. Would explain instant failure or near failure.

Thanks, Brillo. I got the coils from a relatively low-mileage 2000 4runner at a salvage yard. Wires are ACDelco I got from Rock Auto.

I have another set of wires from the salvage trip, and a couple of extra coils. I suppose I could try those, except the codes I'm getting now are P0171 which would point to MAF or air leak.

I tried a MAF from a working rig and got no difference.

 

[KelOfTheRockies]

Did you replace the plugs? Did you replace the iac gasket? Is your truck high idling?
When was the pcv valve last replaced? Replacing the pcv valve might help. Replacing the gasket on the fuel filler cap or new cap on these old trucks always good. Check the ends of hoses for cracks and check the intake air tube's for cracks from air filter to the throttle body. If you have an obd and torque app. Look at the maf readings within spec . Also the oxygen sensors are functioning with in the limits. Fuel Filter and finally injectors.
Helpful link.
Help!!! P0171!!!

Thanks for the reply, Spartacus.

Plugs are new about 8,000 miles ago, and I haven't looked at them.

I did not replace the gasket on the IAC, although it did seem a bit thin. Idle varies from solid at 650rpm to bumpy at 500 +a-tiny-bit.

Don't know about the PCV status - I did find that the hose which goes from the intake pipe that is between the resonator and throttle body to a metal pipe on the intake plenum, wasn't connected at the far end and I had a hard time figuring out where it goes. One salvage yard trip led to discovery that it connects to fitting coming out of the rear of the port-side valve cover, so I glean it's part of PCV system. It is reconnected now.

I'll have a look at the gas cap, never thought about that.

There were some hoses with cracks, and they have been replaced. Also, the intake pipe, mentioned earlier - from resonator to throttle body - has been replaced due to tiny cracks that were of concern. Rubber intake hose from MAF to resonator is solid.

I have a Foxwell OBD reader, but have so-far just read codes and cleared them (still learning how to use it).

I have a new WIX fuel filter to install, it's next up on my list.

A bit later today, I will plug in the Foxwell and clear today's codes. While there I will take a look at the MAF readings and see what it says about the O2 sensors.

Thanks for your input!!

—K

 

[KelOfTheRockies]

Thanks everyone for replying. I truly appreciate your suggestions and council.

I read the linked discussions in full and came away with useful knowledge.

Here's the finale of the story, and the things I did in the best order I can recollect...presented for the next person with perplexing problems.

I replaced the IAC with a moderately expensive model, but not Toyota platinum-plating-priced unit.
I immediately noticed a change in startup. Previously, it always started fine, and would rev to about 1700 rpm, hang there for a bit, then slowly quiet down to around 1000. After driving around it would settle at around 800 pretty solid.
After replacing the IAC, the startup bursts firmly up to 1100 for a fraction of a second, then quickly back down to 650 and sits there like a rock. Every time, when cold, warm, fully hot, or sitting overnight.

It ran pretty good...again for a day, then the stutter on accel was back.

I got no codes now, but I put the straw on the starter fluid can with my Foxwell set on RPM. I went very carefully around the intake from MAF to the block with tiny squirts and watch the meter. There was a very slight rise around union of the Throttle Body and the Intake Plenum. I had re-used the metal gasket after I cleaned out the TB, so figuring it was poorly sealed, I bought a new one.

New gasket fixed it for about 20 miles, then problem was back. At the salvage yard, I got a good look at some of the hoses and their connections and discovered where the hose which goes from the rubber pipe just in front of the TB around between the IP and the firewall connects. Earlier I had found it just hanging open on the port-side, and could not find where it went, so I plugged it. At the yard, I could see there is a port on the back of the port-side valve cover, and I installed mine properly

That did not change anything, much to my disappointment.

Next, I started pulling spark plugs. You may recall that they were replaced around 8,000 miles ago and were not suspect.

Still not suspect after pulling them, because all six looked just fine. Clean white insulators, no cracks, no build-up, near new looking, as expected after only 8k miles.

Getting really frustrated, I said F---k IT! Already spent plenty chasing ghosts around this engine, what's another 70 bucks. I did some reading and concluded which plugs were recommended and got them from Autozone.

Engine ran pretty good after that. But, I'd seen that so many times. This time, however, I could feel better acceleration and throttle response even though that never seemed bad to me before.

Epilog: I've driven about 1800 miles - 50 mile daily commute - and truck still runs great. Startup is crisp and solid. Acceleration is smooth. Pull is much better - even find myself going way too fast on occasion without realizing it.

I don't feel duped by all the crap I did, because the TB did most certainly need cleaning - don't think it was done anytime in the previous quarter-million miles.

IAC replacement absolutely improved startup and idle. I know the MAF is good, all the hoses are sound, and the spark system should be good for some time.

So, Next up...suspension.

Thanks, again everyone!!!

—KotR

 

[Malcolm99]

I gotta ask what plugs did you put in originally and the supplier, there is usually a sticker on the T-belt cover advising a dual ground plug I assume for good reason. You really only have 2 choices of brand Denso or NGK, and the OE Sumitimo wires are the best fitting and have a date on them which is handy.

 

[spartacus]

Thanks everyone for replying. I truly appreciate your suggestions and council.

I read the linked discussions in full and came away with useful knowledge.

Here's the finale of the story, and the things I did in the best order I can recollect...presented for the next person with perplexing problems.

I replaced the IAC with a moderately expensive model, but not Toyota platinum-plating-priced unit.
I immediately noticed a change in startup. Previously, it always started fine, and would rev to about 1700 rpm, hang there for a bit, then slowly quiet down to around 1000. After driving around it would settle at around 800 pretty solid.
After replacing the IAC, the startup bursts firmly up to 1100 for a fraction of a second, then quickly back down to 650 and sits there like a rock. Every time, when cold, warm, fully hot, or sitting overnight.

It ran pretty good...again for a day, then the stutter on accel was back.

I got no codes now, but I put the straw on the starter fluid can with my Foxwell set on RPM. I went very carefully around the intake from MAF to the block with tiny squirts and watch the meter. There was a very slight rise around union of the Throttle Body and the Intake Plenum. I had re-used the metal gasket after I cleaned out the TB, so figuring it was poorly sealed, I bought a new one.

New gasket fixed it for about 20 miles, then problem was back. At the salvage yard, I got a good look at some of the hoses and their connections and discovered where the hose which goes from the rubber pipe just in front of the TB around between the IP and the firewall connects. Earlier I had found it just hanging open on the port-side, and could not find where it went, so I plugged it. At the yard, I could see there is a port on the back of the port-side valve cover, and I installed mine properly

That did not change anything, much to my disappointment.

Next, I started pulling spark plugs. You may recall that they were replaced around 8,000 miles ago and were not suspect.

Still not suspect after pulling them, because all six looked just fine. Clean white insulators, no cracks, no build-up, near new looking, as expected after only 8k miles.

Getting really frustrated, I said F---k IT! Already spent plenty chasing ghosts around this engine, what's another 70 bucks. I did some reading and concluded which plugs were recommended and got them from Autozone.

Engine ran pretty good after that. But, I'd seen that so many times. This time, however, I could feel better acceleration and throttle response even though that never seemed bad to me before.

Epilog: I've driven about 1800 miles - 50 mile daily commute - and truck still runs great. Startup is crisp and solid. Acceleration is smooth. Pull is much better - even find myself going way too fast on occasion without realizing it.

I don't feel duped by all the crap I did, because the TB did most certainly need cleaning - don't think it was done anytime in the previous quarter-million miles.

IAC replacement absolutely improved startup and idle. I know the MAF is good, all the hoses are sound, and the spark system should be good for some time.

So, Next up...suspension.

Thanks, again everyone!!!

—KotR

Thanks for posting the results.

 

[KelOfTheRockies]

Well F&%K!!!!

The problem has returned. Every bit as bad, maybe worse.

What I thought, and explained above, fixed the problem was removing NGK BKR5EGP and replacing with new NGK BKR6E-11

Started a week ago Friday with a slight bump while idling at a stop light. Over the next week or so, it got worse and worse until now it is running just as bad as when I started on this stupid problem.

I think I'm still under 2000 miles on these plugs and now I get very bumpy idle in the morning. Terrible shudder/stutter on acceleration from full stop, i.e. stop light stop sign.
Acceleration at cruise seems worse now, but that could be perception after having it run so well when I replaced the plugs.
I have noticed that at highway speed with cruise control on, it pulls the transmission kick-down often to keep the speed, even if it's just a gentle incline.

Haven't done gas mileage since this crap came back, but I am, thoroughly disgusted and aggravated.

Considering parking it on the street with the title pinned to the seat and key in the ignition.

—K

 

[pluton]

I know the feeling when one is tempted to abandon the problem vehicle. I'd look to see if there are any service techs in your area that are familiar with these vehicles. The ones that used to work in Toyota dealer service departments when these vehicles were current have the best knowledge.

 

[KelOfTheRockies]

I know the feeling when one is tempted to abandon the problem vehicle. I'd look to see if there are any service techs in your area that are familiar with these vehicles. The ones that used to work in Toyota dealer service departments when these vehicles were current have the best knowledge.

Yeah, that's probably the best next step. I met a guy years ago at Advance Auto who was a Toyota guy before. I kept in touch usually bug him when I need to buy tires - he finds great deals as a sideline.

Worth a call, I'm sure.

—k

 

[KelOfTheRockies]

I think next, until I hear from Mr. Toyota, I'm going to pull the spark plugs Saturday morning and check the gap, and check for damage

The fix was so dramatic and complete when I put these damn things in, I can't help but think they're involved in the backsliding somehow.

Update will follow

—k

 

[spartacus]

Any codes?

 

[spartacus]

Check the resistance of the injectors 13.4 to 14.2 Ohms at room temperature.

 

[KelOfTheRockies]

So, it's fixed....

again....

For now....

No codes, Sparticus. That was curious too, since the stumble/bumping was so dramatic

Anyway, I did some research and learned (as likely many of you know) the single-ground plug, i.e. BKR6E-11, aren't correct for this v6 and can prematurely fail. Failure was described as rough idle, stumbling on gentle acceleration, which is just what it was doing.

Recommended in my reading was the BKR5EKB-11, so I had two problems. One, of course, is just total wrong design/type - single vs double ground electrode. The other is the colder-than-recommended heat range.

Now, even though the "wrong ones" are less than 2000 miles old, I bought the recommended ones and parked the truck in the drive to cool.

A couple of hours later, I pulled the BKR6E-11s out and they still look just fine. There is a small bit of carbon around the edge which I guess is to be expected from running a too-cool plug.

Anyway, it idled a bit high on startup with the BKR5EKB-11s at 850, but it kicked right off and idles smooth as new. A drive around the block had no hint of my trouble.

So. Fifty dollar lesson/class on spark plugs for the 3.4L Toyota v6.

Thanks for all the input so far, everyone. I will update this thread periodically as I complete my 250 mi/wk commutes to work.

—K