yotabiff

I did a total rebuild of my 3.0 on a 94 4-runner,after start up got it timed, it runs smooth ,no missing ,would start right up and idled fair,a little uneven. But under load,as in going up hill,not only steep hills but slight grades it just hits a dead spot like it is getting too lean of a mixture,I replaced wires,cap and rotor,ran a little better,than I found a vaccum leak and corrected it and it started running worse as in worse under load,soI started testing at the EGR it all tested good,so I went to the TPS it tested bad so I readjusted it and it tested good,now it starts up and idles slow untill you give it throttle than idles about1200 and doesnt come back down if you shut it off and start it up it doesnt want to idle untill you give it throttle than idles fast,it still has trouble under load like it isn't getting the right mixture,but is smooth,even better since I adjusted the TPS I also changed the fuel filter,when I put the jumper wire on it still doesnt seem to drop RPM's,could the o2 sensor be bad ? It did blow a head gasket-the reason I rebuilt-could the steamed anti-freeze have ruined it? I did replace it once for high idle and rotten egg smell and it worked. Sorry for the long story but wanted to get everything in would appreciate any help!

yotabiff

Any opinions on whether a blowen head gasket might have ruined the O2 sensor and is now causing my engine to burn lean under a load?

vital22re

iTrader: (2)

yep my headgasket took out my o2. Not terribly cheap but i went the route of a toyota oem sensor.

OutlawMike

It could have taken it out, or clogged it so that it does not read properly.

Is the computer throwing any codes?

yotabiff

Thanks for the replies,no I havnt got any codes,it only has a little over 200 mi. just seems to be running lean,checked the plugs and they are burning extra clean,today I think I will try the tests the FSM calls on the O2 sensor I think the FSM says its not to get in cotact with water or petrolium products,thats why I thought it might have went out Thanks again any more ideas are appreciated

yotabiff

Help - per FSM I have tested the AFM,TPS,EGR,o2..sensors,all test good,the TPS needed adjusting and now the idle is good and steady,but still no difference when jumper is plugged into diagnostic ports,I know this could mean the TPS isnt good, could this affect wide open throttle? The motor runs good most of the time through the gears, but when I get into 4th gear,about 3000rpm and going about 60mph with WOT it's like there is a governor,it wont climb any higher,but if you let off the throttle a bit you could feel it want to go,TPS,AFM,o2 sensor? need some HELP!

TNRabbit

Off a tooth or two on your timing belt? You'd get similar issues.

yotabiff

TNRabbit--I wouldnt think it would idle good,run half way decent,start good and be able to time -10degrees BTDC-if the timing belt were off a tooth or two--would it? It has crossed my mind but didnt think it was possible -thanks

TNRabbit

Yep, off a tooth will become more apparent as you get up in rpms, getting worse to terrible as you go higher. I had this exact problem with a Nissan truck several years ago. That's where my money is, either that or a distributor issue.

yotabiff

Thanks TNRabbit,heck I would have thoght it would be popping or backfireing if it was off,I will get that cover off and check that out Thanks

yotabiff

well,at the advise of TNRabbit I took the timing cover off for a look,first thing I saw was the timing belt was loose between the cam sprokets where it loops under the top idler,you could turn the idler very easy,so the first thing I thought was the tensioner,but then I thought maybe it needed to be tightened up one tooth between the cam sprokets,so I turned it to line up the marks,everything lined up perfect and was tight,turned it somemore found the loose spot again,must be tensioner,so I lined it up again,took the tensioner off and tested it again per FSM,it failed two of the tests,leaking and protrution was out of specs,so I guess that would cause timing problems,will order a toyota replacment and try that

srozell

I'm curious to know how it goes.

I experienced the same problems you're talking about after a rebuild. I went through anything and everything I figured that could be contributing to the problem. I even replaced the O2 sensor with no apparent gains. It's like you say, everything is fine until I get out on the freeway and want to do more than 90kms or climb a mediocre hill.

yotabiff

Ya I have tested just about everything and I aint found anything bad except the tensioner now and I wouldnt have opened it up to check the belt cause it has been running pretty good so farexcept under load in higher gears, like getting up to hiway speed or under load going uphill and at times seems like it wants to get going,so this looseness in the belt I found just might be the prob its just weird that the belt is really loose in one spot,but as you turn it it tightens up,I guess that explains the inconsistency,if this dosnt work

yotabiff

Well the problem is finally fixed,thanks to the direction of TNRabbit,it was the timing belt tensioner,runs good

TNRabbit

Congrats! I know this from personal experience....it's a pain in the @$$ to have to open up that front end again, but it would have eventually worn out your belt, not to mention your mileage would have been crappy & you'd have had no passing power (ha).

I've learned a TON on this & other forums; I try to give back whenever I can...glad you finally got it fixed!