mikes19984x4

Hey guys, I haven't been on here in a few months, but I'm back with a big question I need your help with. The other night my 4runner gave me a big problem. I was going about 65mph coming up to a stop light. The light turned red, so I popped it in neutral and coasted to the light. After traffic cleared out, I started to go but got some major shuddering from the motor. I put it back in neutral, thinking I might have not had it in gear good, put it back in 2nd gear, tried to go again, and got the same major shaking/shuddering from the motor and had no power at all. I had to limp it up the hill to the nearest parking lot. Later that night, my dad, uncle and a friend were looking over things and while doing a compression and leakdown test found that the middle cylinder on the passenger side of the motor (not sure the correct piston # for it) would not hold compression at all. What are you guys thoughts on this issue? Sounds like some type of valvetrain failure to me. It's a 1998 4Runner with the 3.4 V6 that has right at 180k miles on it and has never had anything like this happen before. What's your input on this issue? Thank you all in advance for any and all help.

-Mike

tigertowncruiser

timing belt jumped and the valves off? has it been replaced before? have you had any smoking or anything recently?

mikes19984x4

The timing belt had been replaced once (sorry for saying nothing happened before) due to having the balancer coming loose and messing up the crank. But no smoking at all, and it ran just fine. I was actually on about a 3.5 hour long trip, and had drove about 150 miles and this happened to it. But I don't think it was the timing belt as the motor will start up just fine and when the timing was off before it had more power than it does now. Also, while listening to the exhaust now you can here more of a deep "gurgling" type sound...it sounds deeper than normal.

84truck

that could be it. But from the sounds of it, it is possible you could've burned the valves by lugging the engine when you start off in 2nd gear. (If you do it all the time) When i had my 84 truck, my dad loaned it to some guys and after 3 month's, i got it back and it ran like crap. it turned out that they had always started off in second and burned all the exhaust valves and i had to get my head completely rebuilt. But that was on a 22R so i'm not sure how a 3.4 would handle that kind of stuff.

tigertowncruiser

from the sounds of it happening all of a sudden , i believe the top end for sure. If it was the bottom , it probably would not have been all of a sudden losing compression. Check the timing and inspect the heads

mt_goat

I'm going to guess a burnt exhaust valve too.

mikes19984x4

no no no, i never lug the truck or start off in second gear, i always shift at 2100-2300 unless i'm really getting on it. i started off from the stop in first and it happened when i had already shifted to second and was trying to accelerate...so then i was already rolling and just put it back in second to try to accelerate. but of course then it started the shuddering and shaking really bad. do you guys have any suggestions as to where to buy 3.4 crate motors? my dad and i have decided to probably just drop in a fresh 3.4 motor instead of rebuilding the entire motor due or just the upper end due to the mileage on the truck.

mikes19984x4

mt_goat, that's something we've been thinking it is...any tips on price wise of getting it fixed? haven't been able to call anywhere to get estimates due to the holiday and now the weekend...

KrashDH

I had the loss of power problem too. My buddy and I ripped the top end off and sure enough there was a burnt valve...it was almost an oval shape. All of the other valves looked fine, but I figured while I was in there I would replace them all anyway, as well as the timing chain, guides, pump, etc.

I had a reputable engine shop here do all of the head work (valve installation and re-surfacing the head) and I did all the rest and buttoned her back up. If I remember correctly I think the parts/labor for the head resurfacing and valve job was around $350...probably would be a tad more for you because of the 3.4 Keep in mind I brought him the head and all of the valves were out already, so he re surfaced it and put in the new valve kit I ordered through him and gave it back to me.

My burnt valve was due to the previous owner neglecting a manifold crack. I think if you tear down the engine yourself it's worth it vs what you will spend on a new engine...those 3.4's don't come cheap unless you can find a gem. And having this done is essentially like having a completely new top end. The bottom will still have the miles but you can inspect that when everything is off and then make your decision from there. Mine was in excellent shape. So although the truck has about 165k on it now, 15k of that has been with a completely new top end (and timing, etc)

mikes19984x4

thanks krash, that's definitely another option i will keep in mind

mikes19984x4

Hi guys, found out yesterday what my problem was. Turns out to be a combo of a coil pack went out and some bad plug wires making me run on only 4 of 6 cylinders. Apparently when doing the compression test (they tried the best they could) the motor wasn't exactly at TDC allowing a compression leak. But all new coil packs, wires, plugs, and cleaning of the throttle body and intake are in order now. Thanks for the help guys.

brian2sun

Nice, a couple hundred doesn't sound too bad after thinking thousands huh?

vital22re

iTrader: (2)

I was gonna suggest coil pack.... too late.. damn..