My First Time Experiencing "Limp Mode" and Have Problems & Questions...

[eddielasvegas]

Hello All,

Leaving a parking lot a few days ago and my T4R ('01 with 200k miles) surged ever so slightly and then would hardly move. I was dumbfounded, but then again I set the bar low.

Anyhoo, I was 1/2 mile from the house so "limped" home at maybe 1MPH.

Thankfully I was on surface streets and the traffic was not too bad even though it felt like an eternity to get home.

Did some Google mechanic-ing and discovered "limp mode" and that disconnecting the neg. battery term. for a few minutes might fix the issue. I think I found a thread here that said the knock control sensors (there are two) are often the problem and this will reset the sensors.

Well, it worked and I was able to drive normally for the most part. I did notice some accelerator lag or slight pausing, but it drove normally for a day or so.

Last night, I started my 4R and the engine rev'ed to 2,000-3,000 RPMs immediately at startup. I shut the car off promptly.

I disconnected the neg. batt. term again and it now runs normally, but I expect that to be short lived.

Anybody seen this or have any ideas on troubleshooting or a fix?

I have ordered the sensors and short harness for it and they will be replaced in a few days.

Happy to provide additional details and will post my resolution once this is sorted out.

Thanks,

Eddie

 

[T4R2014]

I wonder if unplugging the throttle body would have the same effect as pulling the battery terminal.

 

[eddielasvegas]

It can't hurt so I'll try it.

I cleaned the MAF sensor too. I thought that might contribute to high rev, but alas it did nothing. Only the neg. battery term disconnect resolved both problems.

Thanks,

Eddie

I wonder if unplugging the throttle body would have the same effect as pulling the battery terminal.

 

[T4R2014]

I can't really see how knock sensors would cause this just yet. I'd hold off ordering those and the harness. It's a big job and if there's no codes I'm not sold on this being the issue.

 

[2TH4IST]

I'm wondering, due to the age of these 4runners, if the capacitors are starting to die/pop on the ecm. I know the mk3 supra's w/a 1jz swap usually needed the caps to be replaced. Just a thought.

 

[96RedRunner]

Sounds very much like problem I had at 225k, Scanner with live data look at Calculated Load % will show if TPS is issue.
Engine at operating temp idle calc load %, 12-15%, cold start hi idle 20-25% varies while driving normal circumstances.
Graphing will catch dead spots and spikes.
When in limp mode at first, I could do a restart problem gone progressed to tapping TPS with screwdriver handle.
4 pin TPS can be had, I opted to get new TB to get all the other things that make TB function drive by wire.

 

[alumarine]

I'd hold off on replacing the knock sensors for the time being as well.
Have you checked for codes?

 

[T4R2014]

I would download an OBD app and get a wifi dongle. From there you'll want to get some screenshots of live data.

 

[eddielasvegas]

Thanks for your comments and suggestions everyone.

I have not pulled the code(s) yet, but plan to do so tomorrow. I know, I know....that is what I should have done first.

Thread update soon.

Thanks again all,


Eddie

 

[phattyduck]

I'm wondering, due to the age of these 4runners, if the capacitors are starting to die/pop on the ecm. I know the mk3 supra's w/a 1jz swap usually needed the caps to be replaced. Just a thought.

Capacitor issues are less likely to happen on 'daily driver' type vehicles - electrolytic caps go bad faster when they are not 'powered' Still a possibility though.

I'd bet its an 01/02 'drive-by-wire' issue - but getting OBD codes is the first step to diagnosis.

-Charlie

 

[T4R2014]

I'm wondering, due to the age of these 4runners, if the capacitors are starting to die/pop on the ecm. I know the mk3 supra's w/a 1jz swap usually needed the caps to be replaced. Just a thought.

As stated prior, it happens more often on sitting vehicles. RVs are a perfect example. I've seen on IH8Mud that the similar vintage Prado 90 JDM imports can have ECM capacitor issues. I would imagine a lot of those part numbers would be the same.

KZJ78 Tigris Writeup: ECU Rebuild/Upgrade with Pics | IH8MUD.com Forum | Toyota, Lexus & Off-Road Community Discussions

 

[I'mStock]

If there's no CEL I'd be reluctant to call this "limp mode"?

 

[eddielasvegas]

Zero doubt on the LM. Also, no codes present when I checked this afternoon.

I do have my OBD II reader so when it throws another code, I'll be able to capture it.

Here's another tidbit related to this problem:

Took my T4R in for an emission test today and learned of a "drive cycle."

In 50+ years of driving and never heard of such a thing, but it's real.

Google your make/model/year and "drive cycle" and it pops right up.

Disconnecting the battery reset the data stored for the vehicle so I need to drive it a bit before I can take the emission test.

Learn something new everyday.


Eddie

If there's no CEL I'd be reluctant to call this "limp mode"?

 

[eddielasvegas]

Something is up with the forum as I can't add this image to my post from a couple mins ago.


Eddie

 

[ch1966]

It sounds like TPS to me.
On a 2001 it means replacing the throttle body.

Pull the code already. That tells you more than googling and guessing or calling Miss Cleo's 1-900 number.

 

[phattyduck]

Here's another tidbit related to this problem:

Took my T4R in for an emission test today and learned of a "drive cycle."

In 50+ years of driving and never heard of such a thing, but it's real.

Google your make/model/year and "drive cycle" and it pops right up.

Disconnecting the battery reset the data stored for the vehicle so I need to drive it a bit before I can take the emission test.

Learn something new everyday.

Eddie

Drive cycles have only been around since 1996, you aren't very far behind the times, don't worry... :nod:

-Charlie

 

[eddielasvegas]

Whew and that's good news given I'm older than dirt.

I did figure a DC was related to OBD II.


Eddie

Drive cycles have only been around since 1996, you aren't very far behind the times, don't worry... :nod:

-Charlie

 

[eddielasvegas]

Since the neg. batt. term. pull, no codes displayed with my AD310 scanner.

I have the AD310 with me now so the next time it happens and the dash lights up like this, I can display the code.

Thanks,

Eddie

It sounds like TPS to me.
On a 2001 it means replacing the throttle body.

Pull the code already. That tells you more than googling and guessing or calling Miss Cleo's 1-900 number.

 

[eddielasvegas]

I think we're getting somewhere folks. Just went into LM on the way home from my Mom's ALF. Same as last time, which is crazy.

Anyhoo, it threw a code and here it is. I'm so durn excited to know what I'm dealing with now.

Updates ASAP.


Eddie

 

[ch1966]

I think we're getting somewhere folks. Just went into LM on the way home from my Mom's ALF. Same as last time, which is crazy.

Anyhoo, it threw a code and here it is. I'm so durn excited to know what I'm dealing with now.

Updates ASAP.


Eddie

Code P1120 indicates a fault in the Throttle Position Sensor (TPS) or Accelerator Pedal Position (APP) sensor circuit

I've been down this road twice.

Someone here may have the procedures to test both of those items.

If you need a new throttle body shop around and look for Toyota sales. They're not cheap. Goodluck!