Backfire/Studder under acceleration

I was talking to one of my business partners yesterday or the day before about cars. He's looking for a hobby car and we were talking about new versus old and computers and I used your car as an example of how ****ed up things can get with computers. My explanation over the phone to him was that it was like something had a bad connection or something because it seemed to be dependent on vibration or heat with the higher RPM, and that because of the infrequent and variable condition it was nearly impossible to figure out what the hell was going on. I'm not saying I had any better clue what was going on, but in retrospect (hindsight is 20/20) it makes perfect sense all the way through. I really don't have much of a grasp of the computer side of these things (I'm getting tired of saying that) and really need to get schooled up before I get caught in one of these spirals.

I'm still glad you got it figured out, and I've learned quite a bit from this exercise and I'm pretty sure that shop needs to pay you back for all the parts you shoveled out for to fix their stupid mistake.
 
spectre6000 said:
I'm still glad you got it figured out, and I've learned quite a bit from this exercise and I'm pretty sure that shop needs to pay you back for all the parts you shoveled out for to fix their stupid mistake.
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I agree but at this point I'm just gonna wipe my hands clean and walk away. I'm gonna try to sell my ECU and keep everything else and be glad that nothing was seriously damaged.
 
Finally taking it for a drive

I got the exhaust put back together and got it all cleaned up. The exhaust needs new gaskets but is driveable until I get new ones in the mail. When I got it all put back together, I took it out and just drove around for like an hour just because I can. I was really hesitant to take it past 2500rpm for a while, traumatized I guess lol. It all runs good now and its back to being my get around vehicle again. :party:
 
spectre6000 said:
Don't drive without a functional head gasket! That's how you burn out valves and crack heads. Asking for trouble now!
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No, of course not. Its the little metal O rings gasket between the front and rear cat that I need. It was rusted pretty bad when I took it all apart and wouldn't properly seat when I put it all back together creating small gaps that leaked a little exhaust. No worries :thumb3:
 
My mind immediately went to the gaskets between the heads and the exhaust. Given the trouble this truck has given, it seemed in line. Gaskets further down stream are nowhere near as bad, but still worth addressing ASAP.
 
BFEATHER2008 said:
I am a toyota mechanic and id say get ride of those crappy plugs i stick with oem plugs and wires. I had aftermarket plugs and wires in it when i bought the teuck and it misfired and studdered on acceleration. I replaced plugs and wires and bam its fixed. Then it stated misfireing again later down the rode and had to replace a coil. Id would say start with new plugs oem preferred but if not get only denso or ngk plugs due to the fact they are what comes from factory from toyota. And with the CEL flashing then going off is overheating the convertor. If you drive it drive it easy cause you can melt your CAT and if you do that OEM CAT is 1600 bucks. So just beware and drive with ease. Like i said start with new plugs first if its still there replace wires if its still there which i doubt it will be it would be coils. I really doubt it has anything to do with fuel injectors. I have never replaced any fuel injectors. My dad is also a toyota mechanic of 32 years and he has barely if ever replaced an injector. They are one of those parts that seems to never fail on toyotas. Good luck on the truck hope you get it fixed. And try to stay away from plugs that arent ngk or denso. Every car that comes in with a misfire code at work we always check the plugs and they seem to always be aftermarket plugs and we put OEM in and it fixes them.
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I agree with it being a coil since this just recently happened. Pulled code and cylinder 4 was a misfire. Replaced coil (about 15 minutes) and then OEM plugs and wires shortly after and she purrs like a kitten with 218k miles under her belt.
 
'96 5Speed said:
I agree with it being a coil since this just recently happened. Pulled code and cylinder 4 was a misfire. Replaced coil (about 15 minutes) and then OEM plugs and wires shortly after and she purrs like a kitten with 218k miles under her belt.
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I wish it had been that easy. I tested the coils a while back, several times actually. Fortunately I did figure it all out and it runs great again.

T4RFool said:
I FIGURED IT OUT!!! After all this time it was in fact a sensor, not a bad sensor though. It turns out that the crank position sensor can cause all of these problems. I never tested the senor though, keep that in mind. Apparently when I took it to the shop to get the timing belt done, they disconnected the sensor but never connected it PROPERLY! They half a**ed plugged it in, it looked plugged in but it wasn't. I got to fiddling around with stuff today, just double checking things. I went and touched, just touched, the plug and it feel right off.... I plugged it back in properly and started it up and boom, revved it right up past 2500, no problems. I couldn't believe it! I reset the ECU, cleared out any codes and just sat there and revved it in disbelief.

I never considered the crank position sensor because I thought that it would effect idle, there should have been a CEL right? It's almost like it was plugged in enough to work sometimes. I don't know what to think now cause I am relieved that I figured it out and don't have to buy anymore stuff but at the same time super pissed that the shop missed that TWICE!!! I have enough spare/replaced parts to keep it running for a long time now but at the same time, I cant go out and drive it because my exhaust it still disconnected. I feel stupid because it was something so trivial, so simple.
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I was searching and found this old thread.

I found out that I pinched my cam sensor wire. I ran the wire in the wrong place and it got under the idler bracket. Hopefully that is my only problem. I'm amazed it runs at all. Runs fine sitting still but starts really bad cold. Under load though, it pops and backfires really bad.

The funny thing is there are no codes, no CEL. Which seems impossible because it sounds so bad when it runs.

Anyway, thanks to those who have gone before.
 
I found this while looking to diagnose my own problem with my 99 4wd. The symptoms were exactly the same. Even down to the stuttering moving from near 4k rpms down to around 2500 rpms. I checked the plug for the crank sensor but it seems to be fine.

I'm guessing if that sensor goes bad it would have the same results as being unplugged right? My problem at the moment is getting my fat hands in that little space without taking everything apart.

I was really glad to find this thread since I had already replaced the MAF and was discussing which of the many things listed here to try next with my regular Toyota guru. Hopefully this will save me replacing all the things you've replaced.

Thanks for the effort and I will hopefully have a resolution soon as well.
 
I'm pretty certain that if the sensor is on its way out it would act the same as what i had going on. Unfortunately getting to it does require removing a few things to get to the sensor.
 
Sorry it took me a bit to get back but it's been really cold here and I haven't had the inclination to try to work in single digit temps. Whining aside here's where I'm at:

I bought a new crank position sensor yesterday. Got it out of the box at home. Broke.

Home from work today with another one. I replaced it and the truck won't even start. I put the old one back in and it starts and cuts out, stuttering, at 2500 rpm just like always.

I did, however, notice that the new sensor has a rubber gasket attached that the old one doesn't have.

Is it possible that this gasket (or grommet or whatever) is keeping the sensor far enough away from the teeth of the gear it is supposed to be sensing?

I will attach a picture in a few.
 
The little brown rubber ring isn't on the one that's on my truck right now.

<a href="http://s569.photobucket.com/albums/ss135/Daemoro/?action=view&current=918fc64b6d31d367075389d5c82a3c25.jpg" target="_blank"><img src="http://i569.photobucket.com/albums/ss135/Daemoro/918fc64b6d31d367075389d5c82a3c25.jpg" border="0" alt="Photobucket Pictures, Images and Photos" /></a>
 
Its possible but unlikely that the rubber gasket would create a big enough gap to cause the sensor to not work. Does it feel like its not seating right? what brand did you go with?
 
OK so I went back to the parts store and told them that the sensor wasn't working and they "tested" it and said... Oh that's because it's evidently defective, here's another one. (I gotta hand it to them they have been really helpful and understanding of broken parts). They "tested" this one the same way and assured me it would work.

So I get the 3rd one home, install it and.... truck won't start with the new sensor. Put the old one back in the truck starts and same problem as always, stuttering at 2500rpm.

I'm considering on my next day off loosening the bolt a bit and wedging a toothpick under the edge of it just to move the sensor "out" a little. Since the sensor that is in the truck doesn't have the rubber gasket I'm wondering if it's "too close" to the gear and that's why at higher rpms it starts to miss.
 
i find it odd that the one on the truck now wouldnt have a rubber gasket. i doubt its a tight enough fit to protect from all water.
 
VICTORY! :reddance:

Well I was right about being suspicious of that little rubber grommet. It was preventing me from seating the sensor far enough for it to pick up a reading from the gear.

The grommet doesn't actually prevent anything from getting into the hole where the sensor goes in. There is a gap (about 3/8") between the flange that the sensor bolts into and the hole that the sensor end sticks into.... wish I would have taken a picture now.You could even see the metal barrel of the sensor clearly through that gap. Try as I might I could NOT get the sensor to seat into the flange with the bolt hole. Not even using excessive force via improvised prybar. The grommet was just too damn big..... so I took it off.

Truck started right up and revs to 5k rpms purring like a kitten again.

I have to thank you for posting your misadventure here. Without it I would have likely spent WAY too much money trying to run down such a simple problem.

So if you are even in the Nashville Tennessee area you need to send me a message and let me know... the least I can do is buy you dinner and a beer. :beer:
 
That's awesome!!! I'm glad I could help out in some small way. I did learn a lot of diagnostics when I made this thread which has made me understand my 4runner a lot more. It's good to know this thread has helped at least one person.
 
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