I changed the timing belt after 128,000 miles.It ran great before I changed the belt.I also installed Iridium BKR5EIX-11 spark plugs and new Toyota plug wires.The engine fired right up and idled fine.But when you rev it up,there's a pause before it revs.When you drive it,the same thing happens.Sometimes it feels like it's going to kill,but never does.Runs great all the other time.I put the old plugs back in,does the same thing.I rechecked the timing marks on the cams and the top dead center on the crank,there right on.Any one have any ideas what might be wrong? 2000 4Runner.

 

Check engine light? Have you looked at all of your vacuum hoses? MAF unplugged?

 

vacuum leak is my guess also.

good to know it went 128K, thats where im at now.
how did the belt look?

 

I was going to say, a tooth off on one of the belts. But it sounds like you checked that. Right?

 

not to second guess you but are you 100% positive the belt aligned with everymark? if so i would check everything that you removed or touched to do this job.

 

No warning lights of any kind are light.MAFis plug in(didn't need to unplug it to change belt).I can't see or hear a vacuum leak anywhere.I sprayed starting fluid around the air tube leading to the throttle body.no change in engine speed.My Haynes manual shows the 3.4 having a EGR valve,I don't think the 2000 has one,I sure can't find it.

 

The check engine light came on yesterday,read the code PO172 rich fuel mixture.Could that be caused from timing being off a notch?

 

Did you mark the old belt first before you pulled it...then count and mark the teeth for the new one ...routine ?

 

It really sounds like a timing issue at this point. Did you get an oem belt that had the markings already on it? You could also go rent (or buy) a timing gun and check things out.

I have no expierence with the iridium plugs but if you did not toss your old ones I would put them back in. This way you can eliminate them as being part of the problem.

 

Try the old plugs in the engine first and then double check the timing marks on the cam pulleys and crank. If your timing belt had any lines on it, I hope you disregarded them and just used the timing marks on the engine block itself and cam/crank pulleys or the timing may be off too. Double check everything you touched because it's not impossible that something else happened but more often than not, it's something you just worked on.

 

I tried the old plugs,still had the same pause when you started out. Gas milage drop 5 to 6 mpg also.When I rechecked the timing I lined up the tdc mark on both cams with the tdc mark on the timing scale by the crank.Shoudn't that be correct.
I have a timing light,does anyone know what the timing should be on a 2000 3.4 ?I threw the old belt away ,Thanks.