AZSPEED

This nightmare never ends, replaced knock sensor and all gaskets that needed to get to it, replaced timing belt and pulley and tensioner pulley. put it all back together and wouldn't run for crap, was missing and backfiring. pulled the cat as it was fully clogged, still wouldn't run right, checked the compression and found the 3 cylinders on the passenger side showing 30 psi on each cyl and drivers side all 3are 150 psi. I thought maybe the timing belt was off on the passenger side so I pulled it all back apart and the marks are all lined up.... Any ideas why I would have no compression on one whole side of engine? It's a 90 4runner 3.0 manual trans 4x4. This thing is driving me crazy half tempted to put a rag in the gas tank and blow it up.

ThatGuy1295

Crazy.. And it did in fact run better before you did all this?

AZSPEED

yes, my wife was driving it and she said when she was going through an intersection the engine just stopped and she couldn't get it to start again. when i pulled it apart i found the timing belt was bad and had skipped a few teeth. After putting a new belt on and getting it back together, when I started it I couldn't get it to time properly then I noticed the cel was a 52 knock sensor, pulled it all apart again and replaced the wire to the sensor that was broken.
Now here I am having done all this I checked the compression and found the cylinders on the passenger side are all showing 30 psi while the drivers side is 150 psi. So I pulled it all down again thinking my timing belt was off a tooth or more on the passenger side and found everything was lined up properly. The engine ran when I started it up but was missing and wouldn't rev up.

James Woods

iTrader: (1)

Are you sure you don't have the famous 3.0 head gasket problem? Maybe check with a leak down to see where all the compression is going. It really does sound like possibly the head gasket blew with low compression on one side.

AZSPEED

Yeah I was thinking that but all 3 cyl with 30 PSI? seemed like the cam was out of time more then anything else I could think of.

rworegon

Are you sure you got the cam on the side set at TDC when doing the timing belt? I've read here where some have confused the marks on the cam and have incorrectly set it.

AZSPEED

Yes there is only one mark on the cam, and it ran fine up until the timing belt going.

rworegon

Yes, there should only be one mark and often it has a little paint on it. There was a thread some time back that had a second mark that was probably a manufacturing blemish that certainly did look like the mark.

The 3.0 is a non-interference engine. However, if someone had shaved a bunch off that head before the timing belt went maybe it did some valve damage?

wii_tarded

What are the odds of all three exhaust valves (or intake) being bent from when it jumped timing? It may not even be all of one type, just one of the two valves per cylinder bent just enough to not seat properly. Could the cam be trashed? Just tossing out ideas that might help.

ThatGuy1295

Is it still apart? Access to the timing belt I mean?

AZSPEED

yeah i'm thinking the valves might have got hit the previous owner said he had the heads done if they machined them flat they might have removed enough material to make it an interference motor thats the only logical thing i can come up with. with 3 cyl at 30 psi i am surprised it even started. i'm going to pull the head off and check the damage.

ZeroHour

Makes me wish we all readily had those little bitty cameras available to inspect without having to pull the head. One day I'll have one of these! Anyway, it doesn't seem logical that you'd have 30 psi across the entire head. I would feel that it jumped a tooth when reassembling or starting the first time. I take it you DID recheck the timing again? Even if it were off though I wouldn't think you'd have the even compression across all 3 but just my 2 cents (which is actually worth .5 cents )

AZSPEED

it's aggravating for sure...........

ThatGuy1295

Liken this...

ThatGuy1295

Even compression in those 3 cyl?

Lets say for fun the heads where shaved down so much as to make it an interference motor and bend all 3 cylinders valves. If the motor wasn't timed wrong,,, then it wouldn't matter. Or bend any valves right?

ZeroHour

I'm trying to figure out how it's physically possible to bend 3 valves causing evenly poor compression across an entire side. Did she try to restarted it repeatedly? Did she mention it would come to some halt when trying to start or anything?

James Woods

iTrader: (1)

Did you happen to pull the EFI fuse before doing the compression test, or somehow disable the fuel injectors?

ThatGuy1295

It would only need to be turned over a few times, after it jumped time, and only if the heads were shaved down a whole bunch if thats even possible to shave the heads so much that the valves could touch.

But ya in that case all three valves would bend exactly the same amount.

But thats not what I think happened here either.

ZeroHour

Not to venture off topic much but curious, if that WERE the case how would one avoid such in the future with dramatically shaved heads? You would stand to lose slight valve clearance then correct?

James Woods

iTrader: (1)

I don't know if it is possible to shave the heads that much without a ton of drivability problems, you would dramatically increase the compression ratio and with running regular octane fuel you would have detonation, pinging and engine run on or dieseling. I just can't see how you would even be able to start an engine that has bent valves on 3 cylinders, I can't see that happening.