Backfire/Studder under acceleration

Update:

I'm not sure if anyone is following this thread or not anymore but i'm updating it in case anyone has a similar problem in the future. I replaced my fuel pump the other day and it did nothing to fix the problem i'm having. it is currently not starting. its was running while i was out working in the garage and it just sputtered off and died and now it wont start. also, NOW i have a code. The code is p1300.

So i tested all my wires with a multimeter. Wires are good. Tested the coil packs and they all tested the same so it seems its not a coil pack. I haven't had any luck on finding how to test the ignition igniter so i ordered another one from eBay and it should be here on Saturday, it was only $40. If this does not fix it, i'm not sure where to go from here.
 
Yes I am following this thread. I haven't provided any theories because I don't have any experience with Toyota engine maint. / problems.

I'm certainly rooting for you to get this behind you soon without it becoming a money pit. I share your pain as I also lived about 100 miles from civilization before. Good luck!
:thumb3:
 
Update:

alright, here is another update. i replaced the igniter.... nothing. nothing fixed, nothing changed. i replaced the plug wires to cover my bases with some ngk's.... nothing. so i set up an appointment to have the shop that did my timing belt kit back in december double check the timing. if its not the timing im really not sure what to do... let it sit? sell it? its not doing me any good if i cant use it so idk what im going to do.
 
Chk your fuses. See if your fuel pump is working. Check you relays. I bought a fuel pump one time (new) and it was DOA.


See if you are getting fuel.
 
Singtoe is right, sounds like your fuel pump isn't getting power. Could be a fuse. Could also mean your problem is as simple as a bad ground.

However, a flashing CEL is also an indicator of a misfire. Assuming it has compression and you already addressed the spark issues, it's fuel.

I just had the same thing on mine, was idling fine, ran like hell under load. Changed the plugs and wires, no good. Wound up being an injector. I replaced all 6 simply because I had 6 rebuilt ones from WitchHunter. Runs like a champ now, no issues at all.
 
sorry, i forgot to post that it runs and has no CEL but still has the original problem. i believe i may have caused that code on my own when i was messing around with the EFI relay. i currently cannot go past 2500rpms without it studdering really bad. if it isnt the timing do think that it is most likely an injector? how would i know which injector? would it be worth it to have the injectors cleaned at a shop?
 
Very odd that you don't have any CEL. Sounds like a misfire to me but that should trip a CEL. Are you sure it's not a driveline vibration you're feeling?
 
i actually drove it around town today and it drove perfectly fine as long as i kept the rpms below 2500ish. no CEL, it drove really smooth and normal knowing that i couldnt take it over 2500.
 
Bad Grounds

I have a Mazda Miata that exhibited the very same symptoms you mention. After many, many hours of research and checking, I found an article the told of the 'ground' gremlins. Seems sometimes engine grounds can get corroded and be intermittent. The solution for me was to fabricate several ground wires and attach them from different parts of the engine to a good ground point on the body. Violla, never a problem again. It might not work for you but you have nothing to lose and it's cheap to try.
Good luck.
 
sounds like your 4runner is in a limp mode. Check you transmission neutral safety switch.

It might be telling the ECM that it is not in drive.
 
My 2000 was having this exact issue when I had inspected and test drove before the purchase. Sputtered up to about 3500 RPM, then had lots of fun little surprises if I had accelerated quickly at speed, also a noticeable decrease in power. Told the dealer it had to be fixed before I bought it, inspector theorized it was restricted exhaust or CAT. No CEL. Took it to a local Toyota dealership to have their service department run a diagnostic work up. Not the CAT. Not the restricted exhaust (tech said it wouldn't really have revved at all if that were the case). They recommended cleaning the injectors and replacing the MAF. Selling dealership addressed those two things, runs like new now.

Possibly helpful: I was out of town when the pre-purchase inspection took place, so the inspector sent me this video to help illustrate what he attempted to describe in the inspection report. http://youtu.be/YGG0z6pb_As
 
Last edited:
here is a video of mine doing its thing:4runner Studder 2 - YouTube

its started out at higher rpms but has since began doing it around 2500 now, it hasn't done it any lower than 2500 though. everyone is saying its injectors but wouldn't that throw a code?
 
When my inspector ran for codes none came up. Never triggered the CEL, and the Toyota tech didn't mention anything. So, not necessarily?
 
moneypit said:
I have a Mazda Miata that exhibited the very same symptoms you mention. After many, many hours of research and checking, I found an article the told of the 'ground' gremlins. Seems sometimes engine grounds can get corroded and be intermittent. The solution for me was to fabricate several ground wires and attach them from different parts of the engine to a good ground point on the body. Violla, never a problem again. It might not work for you but you have nothing to lose and it's cheap to try.
Good luck.
Click to expand...

like you said, i have nothing to lose and its a cheap check so i went out and double checked all my grounds. i couldnt find any corrosion on any of the ground wires. i ran an extra ground wire just to be sure but it didnt change anything :(
 
I've experienced some hesitation under load at high RPM, but does not occur on demand or consistently.

I'm following this thread, and thanks for updates. Good luck!
 
did you figure it out yet. If you didn't, i would unplug all the plugs on the transmission and transfer case. Take it for a test drive. If the problem goes away then your neutral safety switch is bad.

Unplugging everything will throw some CEL codes but disconnecting the battery will reset them.
 
My 4Runner did this same thing when I first got it. Turned out the ORGINAL plugs were still in it @ 150k. New wires and plugs fixed this problem for me.

Since you already did this, I would say check yout TPS(throttle position sensor). I had a '99 Taco that did this same thing, back fired like a mother, studdered. If I drove it in Low, and shifted up, It would run great, But in drive, it ran like sh*t. Also, had a misfire code and a Bad 02 sensor code because of the ratio being bad. changed the TPS and it ran fine. Just throwing that one out there....

I also had my neutral safety switch go out on the same truck, and it wouldn't even start. I had to get under the hood, pull the top off the starter relay, and jump the relay with a piece of wire. So, if your truck is cranking over and running, I highly doubt it's the NSS. Definately check the TPS.
 
ok so i have taken it out for a drive the past couple days because i havent had a any CEL and the hesitation only happens at 2500ish so i have been able to take it out for a quick trips to the store and what not. runs just fine as long as i stay light on the skinny pedal. i took it out to the store this morning, started right up, got back, parked it and turned it off and went inside. came back out a little later to go somewhere and now it wont start. it cranks over just fine but will not start, and now it has a code. probably code p1300 because that is the only code that keeps popping up. that code will cuts off fuel delivery to the engine i believe.

so, its not spark plugs, its not wires, its not fuel filter, its not fuel pump, its not the igniter(was replaced), i ohm tested the coil packs and they were within spec.

what are the symptoms of the neutral safety switch? it cranks over just fine, it just wont start now.
 
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