outdoorfever

Why does my Runner idle rough when its in H4 but when I put it into Neutral it is so smooth. i am thinking its my spark plugs and wires, my MAF is clean along with my filter and throttle body. anything else it might be? any ideas? thanks, Kyle

williemon

It could be just the regular tune up items, clogged fuel injectors or as was my case, a bad valve. In my case though, the engine miss was felt up to about 2000 rpm, then you did not really notice it anymore.

Arnold

What engine? I know on 22RE's a VSV increases fuel press to richen the mixture whenever the t-case is shifted into 4wd. The VSV routes engine vacuum to the fuel pressure regulator which increases the fuel press. I'd assume 3.0's are the same so I'd check the vacuum lines going to the VSV and regulator.

mtnfreak

Need to know what engine, tranny and driveline to say for sure, but if you've got ADD up front, then it's probably a vacuum issue.

outdoorfever

its a 3.0 4wheel drive, need anything else?

mtnfreak

Auto or 5-spd tranny? Manual or auto-locking front hubs? Any change if you go to 4L?

outdoorfever

hey, its a 4speed auto and auto locking hubs as well, and no it doesnt change any going into 4l or 4h, and on the original message i meant Drive not 4h, sorry, but in any case, none of them make a difference, only when put into park or neutral. thanks a bunch, Kyle

outdoorfever

any other ideas...c'mon guys, i have seen you reply before. bring it.

williemon

My problem was like that. At idle in park or neutral, it did seem fine, but put it into drive, and the miss was noticable. I could even ease off the brake just a bit and the 4 runner would lurch forward and stop insync with the rough idle. Before you start buying all sorts of tune up parts, run a compression check on it. I did that as a last resort when all else had failed. Thats when I found the weak cylinder. Try this, fire it up and let it get all warmed up, then chock the wheels, pull the e brake and put it into drive. Write down the idle rpm from the tach. Now, put it in park and shut it off. Pull off a spark plug wire. Fire it up again, and put it into drive and again write down the idle rpm on the tach. Do this for all the cylinders. You should notice a 50 to 100 rpm drop on all cylinders except maybe one. If one of the plug wires you pulled off does not cause a reduction of idle rpm, that will be the cylinder in question. Thats how I pin pointed a starting place for my compression check. I had already changed plugs, cap, rotor, wires and ran the BG injector cleaner through it and when it still had a problem, I did just what I described to you. The middle cylinder on the passenger side seemed to not make a difference in idle rpm weather it was hooked up or not. I pulled the plug, hooked up my compression tester, pulled the center coil wire off the dist. cap and grounded it (so no plugs fired and to protect the coil) mashed the gas pedal all the way to the floor and cranked the engine for about 6 revolutions. The guage showed 80 psi. Much lower than the 170 that the others showed. Hope this helps, and if you find that the compression is low in a cylinder, I can help you with what NOT to do.

mt_goat

So why was the compression lower in that one cylinder?

mt_goat

I am trying to solve a rough idle problem too. I just hope its not the head gasket again. The last time my head gasket blew that was the first sign that it was going. I have tried replacing the plug wires, distributor cap, rotor, plugs, fuel filter, and run a can of BG injector cleaner, plus a couple cans of injector cleaner from the dealer. My next step will be to replace O2 senser and clean the thottle body. If that doesn't work I will try a compression test. If it is the head gasket again I'm looking to do a engine swap to a Taco 3.4L motor.

outdoorfever

wow thanks williemon, but i am not a mechanic. i can clean my bike chain, and vaccum the floors, oh and wash it without doing to much damage. i am afraid that i might mess something up when taking off the plug wires. is there anything that could happen? thanks for the replys. ~KyLe

mt_goat

As far as williemon's procedure I have no exerience, but when removing plug wires you need to be careful to pull on the cap and not on the wire itself. Before putting the wire back onto the spark plug apply a little smear of dielectric grease into the top of the spark plug, this will make the wire easyer to remove next time and will also help water proof the connection. Dielectric grease is at your local auto parts store. I have seen it in little one time use pacs for $1. When was the last time your plugs were changed?

williemon

Theres not really anything that can happen except that it is possible to rear the boot off the wire. Thats why you need to twist the boot to break it loose and then pull on the boot, not the wire. I always do that when the engine is not running. I dont like to get shocked.

The one cylinder had a warped or a not fully seating valve. Exhaust valve is what it was. Another trick, while it is idleing, hold a dollar bill or piece of paper up to the exhaust pipe. The exhaust pulses should hold the paper away from the pipe. If there is a not fully seating exhaust valve, the paper will get sucked up to the tail pipe with a slap sound every now and again during the process. Thats what was happening to mine. Since the valve would not seat properly, the air fuel mixture was being forced out the exhaust during the compression stroke. The explosion in that cylinder did not have very much fuel, and some of the force eeked past the valve and heated it up more and made it warp even more. This caused it to run like a 5 or 5.5 cylinder. As it got worse, the explosion from the spark could not drive the piston very hard and thus it felt like a miss. Also, the raw fuel being pushed out the exhaust was seen by the o2 sensor as a rich condition, so the computer leaned the mixture as much as it could so the rest of the engine was running lean. So a miss at idle, as the rpms went up, the miss was harder to detect and the power was down sllightly from sluggish to slug.

Check that compression. Mine had 134000 on it.

BTW I forgot to mention. A friend told me that if the valve got warped, something caused it to get that way. Maybe a lean condition in that one cylinder. While all was being worked on, I sent the fuel injectors to get flow tested and cleaned. They found 1 injector that was not fireing when it was supposed to. Im not sure if that was the cause of the warped valve, but it sounded good. If you need any new injectors, Toyota is VERY PROUD of them. Better to buy some used ones or some reworked ones from DOA or LC Engeneering or some place like that.

TStango

This sounds like what I am experiencing with my Honda. I had the transmission swapped out about two months ago and it hasn't been the same ever since. I don't know if a vacuum line was disconnected and not hooked up properly or what. Between idle and 2000 RPM the engine vibrates the car. I thought maybe it was an inbalance in the fly wheel or something since I had the clutch replaced and flywheel resurfaced at the same time while the tranny was out. I did a tune up and that did nothing. I guess I should investigate further. THose are some good tips guys

outdoorfever

I have no earthy idea. good question, i need to look that up. whats usually the norm on life for plugs and or wires?

mt_goat

30,000 miles for plugs with our trucks. Wires more like 100,000 miles or more probably.