4runner weirdness - Catalytic converter issue?

[rileyb76]

Hey guys,
I have a 99 4wd limited with 220k miles on her. Lately, when I first crank her she will idle perfectly but then when I put in drive and press the gas she will run really rough. After about 500 yards of this sputtering (where I really can't get up past 25mph) it will kick in and everything will be back to normal.

That is until the other day... I was driving up a mountain where the speed limit is 55mph and I couldn't get her about 2500rpm. I put the pedal to the metal and still nothing. Tried to press the overdrive and also nothing.

Another thing is that if I'm on a straight and level road and stomp it, it stutters really badly. It reminds me of when you crank a chainsaw with the choke On and it just bogs down when you give it gas. If I gradually accelerate she drives great.

The strange thing is started a couple of weeks ago around the time I got my timing belt changed. It was a tune-up where they replaced plugs, plug wires, flushed the coolant, new fuel filter, oil change. I have known my mechanic for a while and is a friend so I don't believe its anything fishy.

He is saying that has checked the fuel pressure and it is okay. Actually everything he has checked is okay. He says he is going to try to clean the catalytic converters (which I have no clue about). Does anyone have any ideas as to what this sounds like?

I should mention that my check engine light (code says o2 sensor) has been on since about 100k miles

Thanks for reading this novel if you made it this far!

 

[brian2sun]

I should mention that my check engine light (code says o2 sensor) has been on since about 100k miles

So why haven't you changed the O2? A bad O2 can cause all the symptoms you decsribed and they only operate optimally for about 85K miles or so - you have 220K on yours right? And now your mechanic is going to clean the cats, but leave the sensor that's been throwing a code for 120K miles alone? ...mkay.

 

[RUNNINIT]

Try cleaning The MAF sensor. Mine did the same thing I cleaned the MAF that fixed the problem completly

 

[kball]

So why haven't you changed the O2? A bad O2 can cause all the symptoms you decsribed and they only operate optimally for about 85K miles or so - you have 220K on yours right? And now your mechanic is going to clean the cats, but leave the sensor that's been throwing a code for 120K miles alone? ...mkay.

haha half the time I read this forum for comedy...

Dude! change the o2 sensor!

 

[Terrapin]

haha half the time I read this forum for comedy...

Dude! change the o2 sensor!

lol!

 

[rileyb76]

Try cleaning The MAF sensor. Mine did the same thing I cleaned the MAF that fixed the problem completly

Thanks for the reply. When you turned left or right, would yours sometimes stutter?

 

[rileyb76]

So why haven't you changed the O2? A bad O2 can cause all the symptoms you decsribed and they only operate optimally for about 85K miles or so - you have 220K on yours right? And now your mechanic is going to clean the cats, but leave the sensor that's been throwing a code for 120K miles alone? ...mkay.

Maybe because its run five years and 120k miles with no issues before this. Why would I spend the money if its running perfectly and getting great gas mileage for a 4runner (20-21mpg) up until now? Now, if we find out that is exactly what the issue is I will buy an o2 sensor off ebay with no qualms.

 

[rileyb76]

haha half the time I read this forum for comedy...

Dude! change the o2 sensor!

Thanks for the insight. I definitely will if thats whats causing this issue.

 

[kball]

Thanks for the insight. I definitely will if thats whats causing this issue.

Really? You mean if it's not causing "this" issue you won't change it? Are you going for the highest mileage on a bad o2 record? Funny your mechanic thinks your cats need cleaning (which I don't even think is possible). Guess what driving for 100K with a bad o2 does? It can clog the cats and it doesn't take anywhere near 100K to do it. You need a new mechanic.

 

[brian2sun]

Maybe because its run five years and 120k miles with no issues before this. Why would I spend the money if its running perfectly and getting great gas mileage for a 4runner (20-21mpg) up until now? Now, if we find out that is exactly what the issue is I will buy an o2 sensor off ebay with no qualms.

Or it could be that your O2 sensor fell below it's optimal threshold years ago and now it's deteriorated to the point where it's seriously affecting your air/fuel mixture by sending the ECU misinformation. The way I see it is, something is wrong with your O2 because your engine threw a code to tell you that. The O2 also has a big effect on the fuel mixture and overall performance of the engine including mpgs.

Here's a scenario: Say you've been running lean for the last 120K because your O2 sensor has not been operating properly, but that's why your gas mileage is still good. And then that lean condition gets worse the more that sensor deteriorates and then cylinders start missing because the ECU isn't giving them enough fuel and then your truck studders. You probably wouldn't know if you've been throwing other codes (like for missing cylinders) since you have let your CEL glow for 120K miles like you said in the 1st post.

Why have you gone that long with a known problem and a CEL? It's very possible from missing (because what it sounds like the studdering is) that your cats are screwed up too, but I would (obviously) start with the way less expensive sensor 1st. It's not good to ignore that kind of stuff, one thing goes bad, which causes another to go bad.. it can be a domino effect.

And BTW, "cleaning the cats" means shoving a broomhandle up there (Jeffrey Dahmer style if you know what I mean) :frisky:

 

[TheDurk]

Well said, Brian. Also, I wonder if the OP (or his mechanic) has checked codes lately. He could be throwing P0300's (or other codes) and not even know it. Rileyp??

 

[rileyb76]

Or it could be that your O2 sensor fell below it's optimal threshold years ago and now it's deteriorated to the point where it's seriously affecting your air/fuel mixture by sending the ECU misinformation. The way I see it is, something is wrong with your O2 because your engine threw a code to tell you that. The O2 also has a big effect on the fuel mixture and overall performance of the engine including mpgs.

Here's a scenario: Say you've been running lean for the last 120K because your O2 sensor has not been operating properly, but that's why your gas mileage is still good. And then that lean condition gets worse the more that sensor deteriorates and then cylinders start missing because the ECU isn't giving them enough fuel and then your truck studders. You probably wouldn't know if you've been throwing other codes (like for missing cylinders) since you have let your CEL glow for 120K miles like you said in the 1st post.

Why have you gone that long with a known problem and a CEL? It's very possible from missing (because what it sounds like the studdering is) that your cats are screwed up too, but I would (obviously) start with the way less expensive sensor 1st. It's not good to ignore that kind of stuff, one thing goes bad, which causes another to go bad.. it can be a domino effect.

And BTW, "cleaning the cats" means shoving a broomhandle up there (Jeffrey Dahmer style if you know what I mean) :frisky:

Thanks. I believe at the time when the check engine light came on I took it to the Toyota dealer and they quoted me (I believe) $500 to fix the o2 sensor. The guy said I could still drive it but my gas mileage might decrease. Since money was really tight at the time and I kept getting nice gas mileage I guess I thought everything was kosher and continued to drive. Going to talk to him again today and see if we can get it fixed since apparently I'm an idiot:wink2:

 

[rileyb76]

Well said, Brian. Also, I wonder if the OP (or his mechanic) has checked codes lately. He could be throwing P0300's (or other codes) and not even know it. Rileyp??

Thanks. I will try to get the codes and report back.

 

[Deep_palancar]

I'd bet a sixpack of dr. thunder that your camshaft timing is off as a result of an incorrect alignment when the timing belt was installed. If you don't have the slack of the belt on the tensioner side when it's released, the cams will roll off the mark. It should only take decent shade tree mechanic 10 mins. to check this.
If the cam timing is late when the ignition timing advances quickly on acceleration the engine will spit, sputter and stumble. If it's just a small amount off the engine will idle and increase rpm slowly, but not rapidly.
A bad O2 sensor should not cause these symptoms. A bad #1 (pre-cat) sensor will send the ECU into dumb mode and the engine will run throughout the entire power range just less efficient. The #2 sensor does not influence engine operation, it's only purpose if to report on a bad cat.
A plugged cat will restrict the engine regardless of how fast you accelerate.

If your mechanic speaks of 'cleaning' the cat., I'd think that increases the likelihood of a screwed up timing belt install.

 

[brian2sun]

A bad O2 sensor can't cause these symptoms.

My old O2 sensor would have to argue with you about that. Not that the mechanic couldn't have screwed up the timing belt install too, that's entirely possible, but an O2 sensor can in fact cause the engine to sputter/miss, it's happened to me.

 

[Deep_palancar]

My old O2 sensor would have to argue with you about that. Not that the mechanic couldn't have screwed up the timing belt install too, that's entirely possible, but an O2 sensor can in fact cause the engine to sputter/miss, it's happened to me.

No argument here. When dealing with anything that has electronics nothing is absolute. I should have said 'shouldn't instead of 'can't' .

Won't be the first time that i've been wrong. Won't be the last.

 

[rileyb76]

Try cleaning The MAF sensor. Mine did the same thing I cleaned the MAF that fixed the problem completly

Just to follow up on this... My mechanic replaced my MAF sensor (was beyond cleanable), and now she runs like a dream! Acceleration is great and no sputtering. Got out of there for $211. Thanks!