2000 4Runner start up problems... misfiring...
- Thread starter DanRC30
- Start date
It's been doing this for a few years now... I've just ignored it because I thought it was a coolant leaking slightly into one of the cylinders, and that was messing up the spark pug which caused the sputtering. That's why I had the gaskets done last year... plus it was losing coolant and occasionally smoking from the coolant. But the sputtering didn't go away after the head gasket. So, if it was a weak pump, it surely would've died by now. As far as a bad check valve, I guess I could check that in the morning by turning the key off an on to make sure the pump primed the line.
If there is something wrong with the TPS, how would I troubleshoot that? Where is it and what should do?
If there is something wrong with the TPS, how would I troubleshoot that? Where is it and what should do?
kball
New member
See the pic below for location. As far as testing it, the online FSM is for 2002 model year which has a totally different TPS and throttle body. Not sure what the resistance values should be for a 2000. Maybe if someone else has a manual for that year they could look it up.
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YAY!!! More codes!!! Last night my idle was abnormally high and today the truck ran rough and actually stalled on me. Engine was fully warmed up now when all of these issues occurred. I have 2 new codes... P0172 - System too rich (Bank 1), and P0120 - Throttle/Pedal position sensor/switch A circuit Malfunction.
Does this help?
Does this help?
kball
New member
Unless I'm reading it wrong the FSM is confused on what's lean and what's rich.
I would clean your MAF, check for vacuum leaks and then change your pre cat sensor. If that doesn't help then replace your TPS. Or just change it since you've got the code for it a few times now so it must be having some issues.
I would clean your MAF, check for vacuum leaks and then change your pre cat sensor. If that doesn't help then replace your TPS. Or just change it since you've got the code for it a few times now so it must be having some issues.
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I cleaned the sensor that's right behind the air filter... it was pretty dirty. I also saw that I need a new air filter. Will get one today. It seems to idle better now. I took it out for a drive around the block and noticed that it seemed to run better, except when I come to a stop and I stomp on the gas. It hesitates once and then takes off. I think it's been doing that too all along, but I can't say for sure. Does this hesitation tell you anything?
That TPS doesn't seem to be extremely easy to get out... I'll have to get one first and then swap it out. Should I get it from Toyota or is there aftermarket available?
That TPS doesn't seem to be extremely easy to get out... I'll have to get one first and then swap it out. Should I get it from Toyota or is there aftermarket available?
I pulled that sensor out of the side of the plastic intake which is right behind the air filter. It has that amber ball thing with a wire in it. It was black so I doused the whole thing with carb cleaner. I'm not sure what all of your acronyms are.
If you're available to speak this evening, I could call you if you PM me your number. Might help solve this faster.
If you're available to speak this evening, I could call you if you PM me your number. Might help solve this faster.
kball
New member
Here's some links. They should help you more than anything I could say over the phone but if you still want to talk....
IAC is the Idle Air Control valve
Re: 3.4L V6 Hard Start "hot" Cleaned IAC (Pics) - YotaTech Forums
The IAC controls how your truck idles so when it gets gunked up it will cause problems.
Pictures of where to clean the MAF here.
MAF Cleaned / Before and After Pics / 2000 4Runner - YotaTech Forums
It's not the amber bulb on the outside, it's the little wires on the inside that need cleaning. Don't touch them because you might break them. Don't use carb cleaner, use contact or MAF cleaner. Just spray it in really good then let it dry before you reinstall.
Here's a link about the TPS. I would think aftermarket would be okay but if OEM is not much more dollars I'd buy that.
P0120 Throttle Position Sensor/Switch A Circuit Malfunction - YotaTech Forums
Good luck!
IAC is the Idle Air Control valve
Re: 3.4L V6 Hard Start "hot" Cleaned IAC (Pics) - YotaTech Forums
The IAC controls how your truck idles so when it gets gunked up it will cause problems.
Pictures of where to clean the MAF here.
MAF Cleaned / Before and After Pics / 2000 4Runner - YotaTech Forums
It's not the amber bulb on the outside, it's the little wires on the inside that need cleaning. Don't touch them because you might break them. Don't use carb cleaner, use contact or MAF cleaner. Just spray it in really good then let it dry before you reinstall.
Here's a link about the TPS. I would think aftermarket would be okay but if OEM is not much more dollars I'd buy that.
P0120 Throttle Position Sensor/Switch A Circuit Malfunction - YotaTech Forums
Good luck!
Wow, I think that should just about do it!
Here's some good news... I changed my air filter and the truck drives perfectly again. The filter must've been worse than it looked! Still don't know if that will solve my morning sputtering problem, but it fixed my hesitation problem while driving as well as my rough idle problem. Cleaning that sensor and a new air filter made all the difference!
If I still have hesitation when starting in the am, I'll go through everything you suggested. Thanks again!!!
Here's some good news... I changed my air filter and the truck drives perfectly again. The filter must've been worse than it looked! Still don't know if that will solve my morning sputtering problem, but it fixed my hesitation problem while driving as well as my rough idle problem. Cleaning that sensor and a new air filter made all the difference!
If I still have hesitation when starting in the am, I'll go through everything you suggested. Thanks again!!!
3rdgen_4runner
New member
Loss of power and rough idling after maintenance
It seems to be taking more effort to start my truck each time. I know better not to just hold the key down. I just turn the key and tap the gas at the same time when it doesn't start immediately.
My thoughts of what maybe causing the hard start (hot or cold) is that it's either:
A) Fuel pump issue
B) Spark plugs and/or wires
C) Fuel pressure regulator
D) Burnt-out cylinder
But I don't know how to exactly to diagnose any fuel issues. So if anyone could assist me in the troubleshooting and possibly a low-cost solution to fix my hard start and potential misfiring.
It seems to be taking more effort to start my truck each time. I know better not to just hold the key down. I just turn the key and tap the gas at the same time when it doesn't start immediately.
My thoughts of what maybe causing the hard start (hot or cold) is that it's either:
A) Fuel pump issue
B) Spark plugs and/or wires
C) Fuel pressure regulator
D) Burnt-out cylinder
But I don't know how to exactly to diagnose any fuel issues. So if anyone could assist me in the troubleshooting and possibly a low-cost solution to fix my hard start and potential misfiring.
3rdgen_4runner
New member
Fuel Pressure Regulator check
Here's a link I found that may help a little. Apparently it's highly overlooked with a misfiring engine but I was able to narrow down my issues to 3 out of 5 symptoms
7 Symptoms of a Bad Fuel Pressure Regulator | DoItYourself.com
Here's a link I found that may help a little. Apparently it's highly overlooked with a misfiring engine but I was able to narrow down my issues to 3 out of 5 symptoms
7 Symptoms of a Bad Fuel Pressure Regulator | DoItYourself.com
