98 4Runner Constant Downshifting to Maintain Highway Speeds

[19963.4lsr5]

I did notice a very small pin hole leak in the muffler the other day. But that being quite a ways behind all the 02 sensors would that cause an issue? I was just planning on throwing some weld over it.

Reversion will suck fresh air in the exhaust stream. Screwing up the O2 sensor readings.

Put the MAF PID and the LTFT for bank 1 sensor 1 in your ScanGauge.

When it dogs down what is your percent load?

If you turn on your ignition and watch your TPS position without starting it does the position increment smoothly when you slowly depress the throttle to the floor?

How much tension is on the TV cable going down to the transmission? Too much is not good. At idle position you should have a slight amount of slack.

I think I found the real time Air Fuel Ratio for the 96-98 automatic ECU but need some to test and verify it. I feel it’s real time and behaves as I’d expect it to. You could try that too and watch what it’s at when you loose power.

First thing I’d look at is the TPS. If you got 300k miles on it......at highway speeds it could be reporting a lower or higher position than actual causing the ECU to chose the incorrect fuel map and spark table.


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[19963.4lsr5]

At 50mph I had 19% throttle and around 48% load on as flat of a road as I could find. 55mph was not much different. Say 19 to 21 for TPS and 48 to 51 for load.


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[BoomerBob]

At 300k miles on this trans and 5 years since a drain and fill; I would definitely drop the pan, change the filter, then do a complete fluid change (flush). Timmy has a good video on it using a pump. I found a $17 Walmart pump to work just fine.
YouTube

I do the trans flush on every used vehicle I buy. Hardly anyone changes the brake, power steering, diff, or trans fluids like they should.

 

[BostonJon]

How much tension is on the TV cable going down to the transmission? Too much is not good. At idle position you should have a slight amount of slack.

I was going to suggest checking the transmission kick down cable as well.

 

[brillo_76]

I was going to suggest checking the transmission kick down cable as well.

Dont those occasionally bind and cause issues too.

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[brillo_76]

Any idea how to check the torque converter?

The Factory Service Manual [FSM] has a testing procedure in it.

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[Greenmachine86]

Did you say your running mud tires? 33s? Have you switched tires? Maybe heavier wheels and tire combo??

 

[Gho5t5niper]

Did you say your running mud tires? 33s? Have you switched tires? Maybe heavier wheels and tire combo??

Yes I’m on 33s but it did this when I was on 31s as well. Has been an issue for awhile now


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[Gho5t5niper]

At 50mph I had 19% throttle and around 48% load on as flat of a road as I could find. 55mph was not much different. Say 19 to 21 for TPS and 48 to 51 for load.


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Sorry just getting back. Been changing out knock sensors and wiring harness to fix a po330 code I’ve been having. (Ended up being a short in the harness). Also did valve cover gaskets and all the seals while I had it apart. Changed out pcv valve as well. Got it all back together now so I tried tour test with my scan gauge.

I’m reading the same as you are at 50mph and 55mph. 19-21 TPS and the LOD varies between 42-50.

I tried a test at 70 as well. TPS @ 30 and LOD at 64ish. Other than an initial spike when my torque converter unlocked (RPMS jump from 2200 to 2600) I got the about the same readings when at 2200 (locker torque converter) and at 2600RPM (unlocked torque converter) once it leveled out.


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[Gho5t5niper]

With ignition on and engine off my THrottle position sensor is at 12 without my foot on the gas (idle), goes up smoothly from there as I slowly depress the throttle and maxes out at 75 TPS at full throttle. Is that normal?


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[19963.4lsr5]

With ignition on and engine off my THrottle position sensor is at 12 without my foot on the gas (idle), goes up smoothly from there as I slowly depress the throttle and maxes out at 75 TPS at full throttle. Is that normal?


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Yes it’s normal.

Did you check your cable slack going to the transmission? I don’t know about Toyota but other brands that tells the trans to kick down. It does control line pressure. And the trans may have a way of kicking down a gear with an increase in line pressure. Also make sure the lever on the trans isn’t rusty and sticking.


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[Gho5t5niper]

So I think I found my problem...

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[Dieselchessy]

So I think I found my problem...

It looks like your cam timing is 10+ degrees retarded.

You said earlier you put in a JDM engine 4 or 5 years back. Did you do the timing belt then?
Did you replace the tensioner, idlers, ect....?
Have you had this issue since the JDM install?

I guess you found something to fix, that’s good.

Also, there is a lot of oil on that engine. Did you not replace the cam seals, valve cover gaskets, oil pan seal, ect... when you installed the JDM?

 

[19963.4lsr5]

the only true way to verify your cam timing it to remove the harmonic balancer and look at the lower belt sprocket and make sure its on its mark.

 

[Gho5t5niper]

So I think I found my problem...

It looks like your cam timing is 10+ degrees retarded.

You said earlier you put in a JDM engine 4 or 5 years back. Did you do the timing belt then?
Did you replace the tensioner, idlers, ect....?
Have you had this issue since the JDM install?

I guess you found something to fix, that’s good.

Also, there is a lot of oil on that engine. Did you not replace the cam seals, valve cover gaskets, oil pan seal, ect... when you installed the JDM?

I just did the valve cover gaskets and all the seals a couple weeks ago. But yeah I did the timing belt, water pump, and all those goodies when I installed the jdm engine. So it looks like I royally screwed that up and have been rolling around like this for the last 5 years lol... I chalked the no torque problem up as normal until I drove my dads and saw how much better his felt. Then I started looking at mine.


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[Gho5t5niper]

the only true way to verify your cam timing it to remove the harmonic balancer and look at the lower belt sprocket and make sure its on its mark.

The balancer slides on a keyway on the sprocket so there is only one way it can go on if I remember right. So I believe the timing has to be Truly off this much right?


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[02SE]

I've seen woodruff keys that were worn away, and slots in the harmonic balancer which were worn away, or a combination of the two. That happens due to installation error.

Hopefully the T-belt was just installed improperly, and the woodruff key and all keyway slots are still fine. The only way to know is to disassemble and check everything.

I'd put on a new T-belt while you are at it, along with a new crank bolt, which should be torqued to 217 lb-ft.

Maybe just do all the components while you're at it. Water pump, tensioner, idler and tensioner pulleys.

 

[nevada]

The balancer slides on a keyway on the sprocket so there is only one way it can go on if I remember right. So I believe the timing has to be Truly off this much right?


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based on the issues you're having, and the timing mark being off...that is probably correct.

however balancers can shift, throwing the marks out of wack. as said, the only way to truly know, is to verify with the crank sprocket.

 

[Gho5t5niper]

based on the issues you're having, and the timing mark being off...that is probably correct.



however balancers can shift, throwing the marks out of wack. as said, the only way to truly know, is to verify with the crank sprocket.

Well started disassembly this morning. I’m to the sprocket now. Sure as shit looks like timing is off by 1 or 2 teeth

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[nevada]

yep, looks like you found your problem.