Random Misfire - 1998 SR5 3.4V6

Mopar_Mike

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Hello! I hope to be around this community for a while, so I'll introduce myself. I'm Mike, 20 years old from Missouri. I'm a full time college student studying Criminal Justice and I work part time.

I recently purchased a 1998 Toyota 4Runner SR5 4WD 3.4L. when I bought it, it was in pretty poor shape. Filthy on the inside, not much better on the outside (at least the rain helped wash it a little on the outside). Tires had great tread, but dry rotted. However, it started right up, 4WD worked amazing, and smooth, shifts great, but it was misfiring. This thing was clean underneath, and had no rust, and was pretty cheap, so I bought it, hoping it would be a simple fix.

It has 230,500 miles on it. Going through the vehicle, I found a previous registration paper, and in 2011, it had 225,000 miles, so this thing has been sitting around for a while. The lady I bought it from said she had been driving it until the Check Engine light started flashing one day, she said she opened the hood and found that the battery had shifted, and fell onto the belts. She claims ever since then, the light has been on, and won't go off. It was misfiring really bad, even at idle, and had absolutely no power. I replaced all 6 spark plugs, which were in horrible shape, and long overdue, and then replaced the wires as well which had cracks. It runs 10x better, but still misfires. It doesn't misfire at idle, the engine light even stays off until I rev it, then it flashes again. I removed the EFI fuse, as well as unhooked the battery to reset the computer, and it did nothing. I had a friend use a scan tool on it, and he says it came back saying misfire on all cylinders. That's all his tool would tell him. The next thing I'm going to try is the coil packs, I'm pretty sure they're the original ones still. Anything else I should look for or do? It also has a really bad exhaust leak, like it sounds like there is no muffler at all, but there still is.

I bought this because they supposedly run forever, and Toyota 4Runners, and Tacomas in my area are worth their weight in gold it seems like, even 15-20 years old. I've had to replace the brakes and rotors all the way around, and get new tires as well. I'm running out of money on this thing. I plan on changing the Coil packs, and if that fixes it, great, if not, I'm just going to resell it as it sits. I can easily get back what I have in it, probably a little more actually, I just can't afford to keep throwing parts at it. Is there any thing else I should check before I do? This is my first Toyota, heck this is only my second vehicle. I've had my first, a 1999 Dodge Ram for 5 years, and I've never had a single problem out of it, so this trouble shooting thing is new to me. Any help is greatly appreciated!
 
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Damn dude that sucks. Check the timing. It may have jumped a tooth or something. Maybe the cam or crank sensors? Good luck man!
 
Get a better scan tool and recheck it. It could be a P0300 random misfire or it could actually be on all 6 cylinders. I highly doubt all the coil packs went bad so hold into your money for now.
Pull the MAF sensor and clean the sh*t out if it with MAF cleaner. Same for the throttle body. I'd also recommend you put new air & fuel filters in it for good measure.
But definitely get it rescanned and report back with the actual code or codes. We could probably help a lot more once you have the specific codes available to us.
 
It is indeed the P0300 Random misfire code. Cleaned the MAF today, did nothing, vacuum lines look good. Air filter does need replaced, but an air filter alone isn't going to make it run this bad, I can smell unburnt fuel.
 
It is indeed the P0300 Random misfire code. Cleaned the MAF today, did nothing, vacuum lines look good. Air filter does need replaced, but an air filter alone isn't going to make it run this bad, I can smell unburnt fuel.

I know that this is all in pretty technical terms, but it gives you ideas of the possible locations of your problems. If you read through it, there is a flow chart that shows the factory diagnostic steps. Obviously not all the steps can be performed because you don't have a Toyota testing computer, but it gives you good ideas of what to look at. Hope it helps.
View attachment P0300.pdf
 

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