Backfire/Studder under acceleration

A big question

I know that your probably getting tired of these updates but bear with me. So I took it to the shop and got no results. I had to tow it home which was exciting. I got home and removed the ECU, opened it up to see if I could see anything. Nothing, but thats not surprising. I called a toyota dealership just to see if they could test an ECU. They tell me that there is no definite way to test it. So that leaves me with this question, should I buy a used ECU on ebay or have the one I have sent in to be rebuilt?

I tried the recommended ECU test of banging on it and instructed in the repair manual. The only other this that may be causing these same symptoms would be the catalytic converter being clogged right? I'm dont how to tell if it is clogged or how to be sure if it is in fact the catalytic converter. I do know that they are expensive :ybrick: I dont know what to do...

I have to move forward or give up and sell it. I'm close to selling it having exhausted a lot of my resources at hand already trying to figure this thing out. I don't live near a dealership so taking it to one is not an option without paying a huge bill for towing on top of whatever the dealership would charge. I cannot think of anything else it could be. I'm out of ideas and down to the most expensive fix... the ECU or the catalytic converter. Options and Ideas would be appreciated.
 
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Ok, tomorrow I am going to go out and cut out my cat. Talk me out of it if it sounds like a bad idea cause that's what I'm down to.
 
Go for it. I can't imagine you have emissions testing out there, right?

I don't think it's your problem so don't get your hopes up. But worth a shot to see if it changes anything. How many miles on your 4Runner?
 
PitbullRescuer said:
Go for it. I can't imagine you have emissions testing out there, right?

I don't think it's your problem so don't get your hopes up. But worth a shot to see if it changes anything. How many miles on your 4Runner?
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No emissions testing out here. I have right around a 140,000 on it. I don't know the exact mileage.

I have learned not to get my hopes up on any "fix" for this problem after the first few months. If its not the cat its gotta be the ECU right? There is nothing else to check that I know of.

From I've read, when a cat gets clogged enough it can throw a misfire code and cause all the symptoms I've been having. It wont even stay running now so something has changed since I drove it to the shop to be looked at.
 
If your cat was clogged it would throw a code from the O2 sensor behind it. Doesn't sound promising. It would only frustrate you more when nothing changed after the fact.

ECU is possible from what I know (not much when it comes to the computer side).
 
spectre6000 said:
If your cat was clogged it would throw a code from the O2 sensor behind it. Doesn't sound promising. It would only frustrate you more when nothing changed after the fact.

ECU is possible from what I know (not much when it comes to the computer side).
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I just don't know what else to do though. If i spend $200+ on an ECU and that doesn't fix anything? Should I just go ahead and buy it and hope for the best or should I give this cat idea a shot? I just don't know what to do with this thing anymore...
 
T4RFool said:
Bought new NGK Platinum plugs today and went ahead and put them in hoping that this would fix this issue... it didn't. i took a couple of videos to show what it is that's going on. when i first started it up and go to revving it up it was fine, smooth all the way up but after letting it run for a minute or two it started to do this:

4runner Studder - YouTube
4runner Studder 2 - YouTube


so since its not the plugs im gonna guess that its probably not the wires since they are about a year old and doubt they went bad that quick. if its a coil, how can i tell which one it is without replacing them all. they are pricey. also, how likely would it be from the crank bolt not being tightened enough and causing this. i didn't do the timing belt so im not familiar with that area of the motor.
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I just went back and watched these videos and it reminds me of a cheap Bosch distributor I had on a VW once. It was brand new, but it was Brazilian or Chinese or something and was just made poorly. I want to say there was slop in the shaft, or there was crap in the weights or something, and it would time out fine at idle, but wandered all over the place at max advance. It started out, just like yours, only under load; then eventually evolved to where it wandered regardless of load.

EDIT: I just remembered the cause (not that it truly matters in anything save the effect)! It was the aftermarket electronic ignition. The crappy distributor was a different car at a different time.

Obviously, these don't have distributors so you don't have a sloppy distributor drive shaft or anything (edit: or crappy aftermarket electronic points/condensor). Timing in these is handled by the ECU. If you've truly got it boiled down to those two parts, that's where I'd go. I have said it before and I'll say it again, I don't know much about the computer side of modern cars. I have no idea how you'd test an ECU save plugging in a known working unit, but that's the next stop.

Don't sell it, you'll regret it when you find out from the buyer it was just one little insignificant thing... And it is. If it was something truly catastrophic, you'd know.
 
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T4RFool said:
I just don't know what else to do though. If i spend $200+ on an ECU and that doesn't fix anything? Should I just go ahead and buy it and hope for the best or should I give this cat idea a shot? I just don't know what to do with this thing anymore...
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Do you know any other 4Runner people around there that don't rely on their runners as DDs? I would try to borrow one as previously suggested. Will probably require a lot of beer in exchange, but it'll keep you from having to drop two bills on something that won't fix the problem.
 
I wish there were other 4runners around here. There aren't any other 4runner in the area. There is only one other member on here that I know of and he lives over 2 hours away and he uses it as a DD. The only time I see another 3rd gen is when they are passing by on the interstate. I wish I still lived in Colorado.
 
I was going to go out and remove the O2 sensor in front of the cat but the bracket holding it on was rust too bad to the point that the bolts were rounded off. I was hoping the see if there was pressure building up in front of the cat. Since I could remove that I figured I might as well remove the whole thing and if it turns out its not the cause just have it welded back on. I may wait until I get back from my trip though. I was hoping that the shop would have found something so that I wouldn't have to be thinking about while I was on my vacation but it looks like that's not going to happen.
 
When did this problem start? After a timing belt? I dont feel like going through the full thread, I saw the videos and am having a very similar problem.

I have three 3rd gen 4runners so test parts are easy plus i have another entire drivetrain. I have swapped every componet. monitored it with a scanner, got no where.

Then last night was messing around with it and had the timing belt cover off looking at the tone wheel and noticed a bent tooth on the wheel. We will see to night if that will fix it.
 
T4R, have you searched for part outs anywhere? You could probably grab an ECU for a lot less going that route. There were a few part outs in the Classifieds here. And there are usually some going on YotaTech too.
 
PitbullRescuer said:
T4R, have you searched for part outs anywhere? You could probably grab an ECU for a lot less going that route. There were a few part outs in the Classifieds here. And there are usually some going on YotaTech too.
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I found an exact match ECU on eBay, Same year, all the number matched up. I went ahead and snatched it up since it was the only one I was able to find. I searched craigslist and wasn't able to find anything. There aren't a lot of option out here for me short of buying it off the internet. Iowa blows! Anyway, It'll a few weeks before I'm able to put the new used ECU in and give it a try.
 
mark3406e said:
When did this problem start? After a timing belt? I dont feel like going through the full thread, I saw the videos and am having a very similar problem.
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It all started around 3 months after the timing belt. I had revved it up to about 5000rpm and was greeted with an obnoxious backfire. It drove fine for another month before the hesitation started happening at lower rpm's where its stayed (around 2500rpm). It's not the timing though. I took it back to the shop that did the service and told him to have at it and tell me what he thinks. I got it back a day and a half later with nothing found. I'm down to it being either the ECU or the catalytic converter. I've pretty much replaced, checked anything else it could be.
 
T4RFool said:
It all started around 3 months after the timing belt. I had revved it up to about 5000rpm and was greeted with an obnoxious backfire. It drove fine for another month before the hesitation started happening at lower rpm's where its stayed (around 2500rpm). It's not the timing though. I took it back to the shop that did the service and told him to have at it and tell me what he thinks. I got it back a day and a half later with nothing found. I'm down to it being either the ECU or the catalytic converter. I've pretty much replaced, checked anything else it could be.
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Have you tried unbolting the cat at the manifold and seeing if it makes a differance? Not to hard to do. Also if its plugged you can see them glow at night a lot of the time.
 
mark3406e said:
Have you tried unbolting the cat at the manifold and seeing if it makes a differance? Not to hard to do. Also if its plugged you can see them glow at night a lot of the time.
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I had considered that but the bolts are rusted round and would require cutting. I actually drilled a hole in front of the front cat to see if it would relieve any pressure and actually stay running. Its not actually running right now. It'll start but will not stay running for more than a minute. The whole didn't in anyway other than making more noise.
 
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