Hi guys, I'm Jeff, I'm new to YotaTech. I've visited the site several times to get answers about my 1985 4Runner. Everyone has been a huge help, but I've still got a couple issues that need to be addressed.

Let me start out by saying forgive me if something along these lines has already been posted. If so, I couldn't find it.

My truck sat for quite a while, over a year, without being ran (it was at my parents' house while I was going to school). Recently, I got it back so we could reunite and I could get some work done to it. I knew that I was going to have my hands full for at least the first week, so I got started with the basics. I changed the oil, oil filter, drained the bad gas, ran some fresh gas through it, replaced the fuel filter, replaced the spark plugs, did a compression test, replaced the battery, and checked for vacuum leaks. The compression was low in cylinders 2 and 3, but a little Power Tune brought it right up.

I can get the truck running but it still runs like crap. It's not very noticeable at idle, but when I drive it, it spits and sputters and tries to fall on its face, especially when accelerating. I also have a CHECK ENGINE light that won't go away. It's not present when I first start it up, but as soon as I start to drive it, it comes on and stays on.

Once again thanks for all your help so far and hopefully I've provided enough information for some diagnostic advice. Please feel free to provide any feedback you may have and don't hesitate to ask additional questions if you have them.

 

Sounds like how mine was running when I first got it. 2 of the hose clamps between the air filter and intake were loose, letting in air that the AFM didn't know about which made EFI mad. I hope yours is as simple.

Read those codes, that's another good place to start.

Tell me more about Power Tune, how does that work?

 

Awesome! Thanks, that's actually something I haven't thought to check. I'll let you know what I find out.

Power Tune is pretty much my best friend. When you have low compression in a cylinder, most of the time it's carbon buildup (at least it is in most marine applications). Power Tune is made to break up all that carbon and help blow it out the exhaust. Just spray it into your cylinder, put the spark plugs back in, and crank the motor (don't be alarmed by the excessive smoke billowing out of the exhaust, it's just the Power Tune doing its job) Let it run for a few minutes so that the carbon has a chance to escape, shut off the truck, and recheck your compression. It's always a good idea to replace your spark plugs afterward, but it's definitely worth it.

 

Clay, it was so simple why my truck was running rough! The plug on the air box came loose. I plugged it back in and now it screams like a raped ape! It's not the first time I've been bested by something so simple. My starter would't move because the plug to it was disconnected too. I still have that CHECK ENGINE light though, and it still only comes on when I start accelerating. At least now, I can drive it safely to a shop so that they can run some tests.

 

Great to hear it was something easy! None of that was my idea, BTW. The guy at 22reperformance suggested it when I was having my issues.

If your CEL is still coming on, keep in mind that you can check it yourself instead of taking it to a shop because our EFI is so old that you don't need an OBD scanner, just a paper clip. In case you haven't read your own codes before, 4Crawler's site has tons of info (in general) and a good write up on reading the code. SEE HERE FOR INFO

That's interesting about the Power Tune. I would be afraid of hydrolocking after spraying right into the cylinder like that, but I'm doing my homework trying to learn how to clean these old motors out to restore some power and efficiency so I'm adding this to the list

 

Wow! Checking for fault codes is super easy! It turns out, I have three different fault codes:

2) Open or shorted Air Flow Meter (AFM) circuit
8) Open or shorted Air Thermo Sensor Circuit
12) Knock control Sensor (KS) signal has not reached judgement level in succession

I'm not entirely sure how to fix the AFM plug. The site you pointed me to said that a loose connection could throw codes 2 and 8. The plug is loose, but I don't see a way to adjust it. I'll figure it out. I still need to FIND the KS, I bet it's just not plugged in.

As for the Power Tune, I had the same concern about hydro-locking the motor too, but I've used nearly half a can in EXTREME circumstances on some of the v-6 Suzuki outboards (not all at once) but it still fired right up every time and didn't do any damage. At first, just try a two-second burst in each cylinder.

Once again, you've saved the day! Thanks a lot! Let me know if you have any questions, concerns, or dirty jokes.

 

If it were mine, I would clear the codes (unhook battery for a while) and see if the knock sensor one comes back. It could be old or somehow related to your loose AFM connector. Or actual knock could be related to all that carbon build up you were getting rid of with the Power Tune.

If the AFM connector is loose, I hear that Toyota uses a lot of the same connectors on a lot of vehicles, so poke around for what you need at a salvage yard.