2000 4Runner start up problems... misfiring...

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DanRC30

New member
This problem has been going on for a while and it's really beginning to annoy me. It seems to not run on all cylinders when I start it in the morning and it gets worse the colder it is outside. Code reads P0300. Any ideas from the pros in this forum?
 
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P0300 is multi cylinder misfire. How long since it was tuned up? Plugs/wires, clean the MAF and throttle body etc...
 
kball said:
P0300 is multi cylinder misfire. How long since it was tuned up? Plugs/wires, clean the MAF and throttle body etc...
Click to expand...

That was all done within a year when I had the head gaskets done. It's all new. It was doing it before the head gasket job and still does it. I thought the head gasket leak is what was causing it, but obviously not... it read another error at one time but I can't find my notes on it.... :/
 
This makes it a bit harder to trouble shoot the coil packs...

Is it possible to check the coil packs with a multimeter?
 
With direction from someone I can. But here's the thing... the truck runs fine after I stomp on the gas and clear it out. Then as long as it's warm, all is good. It's only at startup. Another thing is I remember the code said something about a sensor. I took a pic of the code and I'm still looking for it... haven't found it yet. If/when I do I'll let you know.
 
Multi misfire would mean more than one coilpack had gone bad and that's unlikely. I'm thinking your code was a P0171 which could be the pre cat O2 sensor but in this case I'd bet on a vacuum hose leak that seals up when the rubber warms up.
 
If I start the truck up cold, and I stomp on the gas, it will stop within 30 seconds. So it's really not even war at that point. It's almost like a cylinder gets flooded and it clears the plug by revving it.
 
Yes, but more light greyish puff, but then goes away when running fine. And it doesn't smell like oil or anti-freeze...
 
FOUND IT!!! P0120 - Throttle/pedal position sensor/switch A circuit malfunction

That's what the code read. Does that help? :)
 
I don't see how a TPS could cause misfires. Since your plugs and wires were done with the head gaskets by a shop?? I'm thinking they didn't use good dual ground plugs. After a year single ground plugs could already be toast. You might want to pull one and see what it is.
 
It began doing it right after I got it back and has been getting worse slowly... it would happen more if the truck sat for longer but now it happens every morning. He used all Toyota parts because he's a Toyota mechanic and works for the dealer...
 
That's the problem... he worked there, but he did it as a side job. And he doesn't work there anymore either... lol! Plus it was a problem that existed before the head gasket job was done. I originally thought that the head gasket leak was causing it, but it wasn't...

Does that other code I cited help in any way?
 
Most of the time the P0120 or TPS just throws a light and doesn't cause an issue. Sometimes it will make the truck act strange like going from full to no throttle but I don't think it will cause a misfire. Your P0300 might have just been a random thing and may never come back. Maybe what you are feeling is the TPS acting up. It's a fairly cheap sensor to buy so you could try it and see what happens.
 
If I don't rev the engine when it's misfiring, it'll keep the sputtering going, which usually triggers the engine light. Maybe tomorrow morning I'll do that and see what happens... I need to figure this out because it just doesn't seem like it's a good thing.
 
I let it sort itself out this morning and only took about 10-15 seconds before it ran perfectly. No smoke either. It only seems to put out a puff if I stomp on the gas. Any ideas?
 
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