Two issues on V-6; pinging under load with 91 octane and hesitating from idle (no load).

Yep.

I am going to verify the jiggle valve on my thermostat this Saturday. Way too many guys say the 6 oclock position drops their engine temp 7-10 degrees, so I am going to check it out. Many many threads dedicated to this topic on multiple forums.

My engine doesn't ping around 190 F but it sure does around 200 F. Most often my engine is 199.4 degrees F. Note that the increments are 1.8 degrees F so one tick down is 197.6 and one tick up is 201.2.

 

Hmm, how hard is this to do? So basically what you're going to try to do is make it so the engine runs cooler?

 

I don't know what position mine is in, but it might have been flipped when I had the timing belt done at 90K. That was before I had the Ultragauge and could accurately monitor the temp.

I am going to check it; if it is at anything but 6 o'clock I will move it to 6 o'clock.

Relevant thread:

https://www.tacomaworld.com/threads/thermostat-replacement-question.276678/

Convincing Yotatech thread:

http://www.yotatech.com/f2/5vz-fe-running-warm-after-timing-belt-pictures-pleasure-249481/

To answer your question regarding checking it, you have to drain some coolant and remove three nuts and the lower hose on the V-6. Plus put on a new gasket.

I will post my results with Ultragauge pictures showing the temp, unless it doesn't change or it already was at 6 o'clock.

 

Thanks a TON!!

 

If I hadn't done it myself, I wouldn't believe it.

My jiggle valve was at 2 o'clock. I reinstalled the thermostat with the jiggle valve at 6 o'clock. Plus a new gasket, of course.

My engine absolutely, positively runs cooler now. After idling in my driveway for 15 minutes with the a/c on high, the Ultragauge read 188.6. I took a test drive of about 3 to 5 miles, and the hottest I could get it with the air conditioning cranked and nailing it up a hill was 192.2.

Going down a steep hill in fifth gear with my foot off the throttle plunged the temperature into the low 180's. Never seen that before.

Monday will be my controlled test as I take my 15-mile commute to work. My guess is that it will be 10°F cooler. I will take a picture of my Ultragauge when I get there and post the photo here.

I'm a believer!

 

Wow, so no more ping?

 

Can't tell that the ping problem is cured until I've burned all of my premium gas out. Might take me a tank or two.

 

Cool, let me know. I'll have to check my t-stat when I get some free time

 

I didn't read the whole thread, is there a link to the scan tool your using?

 

No. Just search on Ultragauge. I don't think you can get them from Amazon. I think you have to get them directly from the manufacturer.

 

..

 

Nice. Really interesting to see what happens after you start running 87 octane again.

 

So I ended up doing the same and flipping my T-stat so the jiggle valve is at 6 o'clock and I'm still hearing the ping.
First thing I plan on doing is pulling the EFI fuse to reset the fuel maps and maybe it'll recalibrate to a proper level and quell the ping.

If not...

At this point I'm thinking of running higher octane fuel to see what happens. If the ping is reduced then I may open the gap on my plugs to try to force it to run a little richer. If that doesn't help then I'm thinking maybe it's the valves that need adjustment.

 

Running higher octane should work, but I found it to be a losing battle.

At first, 89 octane stopped the pinging. Then it would only occasionally ping. Then it started pinging a lot, so I switched to 91 octane (highest available here unless you pay for what's nearly racing fuel).

Same thing happened with 91. No, pinging, occasional pinging, then frequent pinging.

I don't think you can fool your engine into running richer too easily. There are multiple sensors that adjust the air / fuel mixture on the fly. Earlier in this thread you can see that even with a bad MAF sensor, the computer was adjusting the a/f mixture to get to the perfect level, as measured by the oxygen sensor. I wasn't 'running lean' or 'running rich' with the bad MAF sensor; I was set up to run too lean or too rich until the fuel trims offset the bad measurement from the MAF sensor. If I was truly running too lean or rich I'd have a loss of power and would likely fail emissions testing, which I never have.

I don't know how adjusting the valves would impact the pinging, but I'm certainly no mechanic. My understanding is that pinging can also result from a buildup of carbon in the combustion chambers, leading to higher compression and/or higher combustion chamber temperatures.

 

I was browsing the Internet and a guy with an older Toyota on Pirate4x4 had the same problems we described and eventually came back saying the problem went away after the valves were adjusted. So it's worth a shot as a last ditch effort. And yeah I know what you mean about the gas, the timing will eventually speed up to compensate for the difference in octane, but I'm hoping I'll notice it go away before it re-adjusts the fuel/air mixture so I can confirm that it is in fact pinging before I blame in on the valves.

Maybe when the dealership did my timing belt, they adjusted the timing improperly and set it too quick.

 

Good read and great info.
I also am experiencing what I think is detonation under load.
I'll have to examine some things and try some of the suggestions mentioned.

 

Came across this in the owners manual, maybe we are being too paranoid haha

 

Mine was definitely worse than occasional…

 

Same. Mine was doing it bad tonight, A/C was off.. Ambient temp was around 85F.

I guess that means the thermostat flip didn't help... But I'll pull the EFI fuse tonight and let the fuel maps reset anyways. After that, gonna increase the gap on my plugs... Then if it's not that, I'll have to wait a bit to get the valve cover gaskets done, injectors fully serviced and valves shimmed by the stealership. And maybe have them check the timing belt while they're there and see if the timing is off..

If none of that works, then I'm out of ideas