Bunsen

hey all, apologies if this is in the wrong place, its my first day...

here goes,

I was gifted a 94 runner that had sat for a couple of years, with only minimal use to move it from one side of the drive way to the other for snow plowing.

Starts up great but runs rough and is guzzling gas like crazy, power is lacking and i'm needing to use 2nd and 3rd gear on small hills. The car is showing no codes, but when i pull the spark plug wires 1 ata time from the distributor with the motor running, #3 and #6 cause no change in idle speed, assuming those were my problem cylinders, I checked the wires and they are sending a strong consistent spark.
however when i pulled the number 3 plug, it was white on the tip, whiter than im used to seeing in my hondas.


===update===
i checked the #6 plug and it looks brand new.... looking into accessing fuel rail now


just curious if you guys may have any ideas on where to go from here? it looks like a big project to get to the fuel rails :/

Trents3.slow

Hey! Here's what my plan of action would be. (Other more experienced Yota Techs will be here soon)

1) check firing order. 123456
2) check timing
3) ohm test MAF
4) search for vacuum leaks <<---important
5) inspect intake tube for dirty air leaks (unmetered air)
6) DONT THROW PARTS AT IT. Diagnose and repair

Check and advise buddy

Bunsen

Pulled the plenum and other stuff, got fuel rail off and was able to check resistance on all the injectors. #6 was wayyyy low . Reading in mohms 2.3ish
The other 5 were at 14 ohms. Tomorrow we replace injector, re assemble (-_-) and check it all out. I will also check the above mentioned items, any idea what resistances I'm looking for on the maf?

Trents3.slow

No I don't know any of the specs off hand. Most likely easily found on here or the Internet. It seems like you are on the right track. When was the last time it received some regular maintenance? (Plugs, wires , cap and rotor)

Some may not think so but these 3.0's are pretty darn simple engines. I'm confident you will figure out the issue. Keep us posted!

Bunsen

well thanks to all who offered their advice after replacing the faulty injector that was reading low resistance (and many forgotten vacuum lines). the runner is running and idling, the exhaust no longer smells like fresh gas and almost all is well, all except for cylinder 3, when i pull the plug wire at idle, i get no response, which I believe means i still have an issue at that cylinder.

i tried switching the #1 and #3 spark plugs and the fault did not move with the plug. so now ....? i really would like to avoid pulling the plenum again until I have exhausted all other options, but aside from throwing a set of new wires and cap at it, i'm not sure where else to turn ...

any ideas?

Trents3.slow

Compression test that bad boy. You can buy a half way decent one from a lot of places and you can rent them at auto parts stores (if you don't have one) make sure the engine is warm.

Again on the specs....not sure. I believe it should be around 120 or 130 psi. Don't quote me on that. Check and advise. ::beer::

Bunsen

Well I got the compression test done for cylinder #3 its at 60 psi... hoping for a burnt valve and not a loose piston ring. if anyone has advice on any particulars of the valve replacement, I could use any help i can get with this one

Charchee

You are probably on the right track. A lot of folks are going to tell you that you have a blown head gasket due to the compression reading but I feel like your exhaust valve is not closing completely. This would cause low compression and a miss on that cylinder at the same time. Would also give you a smell of unburnt fuel at the pipe. You may have already done this but I would like to see compression readings on all cylinders. Whatever you do, you are about to spend some money and time to get it fixed. You need to get a real good idea as to the overall health of the engine before you spend that money because to fix a valve almost always requires you to remove the head which is a PITA. If I were you, I would check compression on all cylinders, check timing, replace #3 plug, look for evidence of a HG leak like too much oil on the stick, loss of coolant or bubbles in the coolant and if you still think you want to dive in deep, go ahead and pull the valve cover and see what you can find in there. I've seen broken valve springs before that could cause your problem and they say you can change one of these without pulling the head.

If you can, post a pic of that spark plug. You said it was white? That's normally caused by excessive heat in the cylinder. I hope you don't have piston or cylinder bore damage. How is your oil pressure? If you get the camera out to take a picture of that plug, go ahead and take your oil cap off and take a picture of what it looks like on the bottom.

If you do end up pulling the head, do your research and get only the best quality gasket set. The design of these engines and the fact that you have an iron block and aluminum heads make the head gasket a major weak point in them. Take your head to a machine shop and have it checked and surfaced no matter what it looks like.

Trents3.slow

Yea! Listen to this guy^^^^

If you have low compression ,do a leak down test to see if it is a valve or ring issue.

Charchee

I'll second that leak down test. That will get you even closer to the source. Looking back over the thread I saw something I missed in my last post. One of the main reasons I said that I was curious about the compression readings on the other cylinders is because, like you, I kind of adopted an 89 4Runner with, what I was told were major engine issues. I knew the cost of rebuilding the heads or complete engine so I went ahead and did a compression test first thing. I had compression readings on all cylinders that were way low and I knew that the engine was in better shape than that. I ended up taking my new compression tester back to Advance and got them to warranty it. When I got home and ran the test again I got accurate readings that were in spec for the most part. At the very least, run the test on that cylinder again. the # 3 spark plug hole is hard to see due to the EGR and all that other garbage on that side of the engine. If you had some dirt around the oring on the tester or it hung up on a bad thread before it was all the way in and sealed you might not get an accurate reading. Remember, being able to replicate your findings is the most important step in the scientific method.

Another reason I was wondering about compression readings on all of them was to add data to a theory of mine that nobody seems to be able to confirm. When I finally got down to the root of the trouble with mine, it turned out to be the injectors on three cylinders. I replaced all of my injectors and it solved all of it's engine problems. The thing I found interesting was that my compression on each of the cylinders with bad injectors was too high. There has to be a correlation. I would really like to know if your compression on #6 was high. I'm not ready to write down high compression as a symptom of a faulty injector until I get some feedback from other folks that have seen the same thing.

Best of luck and post what you find. I'm really interested in how this one turns out.

Bunsen

thanks to all who offered helpful advice with this thread of issues. I have been slowly learning my way around this motor, i have pulled the radiator, the fan, the plenum and airintake, as well as the timing cover.

it appears as if whoever did the timng belt last, decidednot to use a tensioner... and the timing is currently at 5deg btdc.. everything i find tells me that this motor should be operating at 10 deg btdc... could this slight misadjustment be responsible for a the low compression (30lbs) at cylinder three? with the other five cylinders at or near spec. 140-150lbs.

millball

No, that's not why the compression in a single cylinder is low.

Check the valve lash in that cylinder, you will likely find your issue there.

Bunsen

got under the valve cover and found the exhaust valve at cylinder 3 squeezed tight against the camshaft, tried the lowest in spec. .009 to no avail. and for kicks, went down through my gauges to the thinnest and none would slide between this valve and the cam. I made sure each valve was on the base circle of the cam... looks like i get to tear the head off and replaced the busted valve.

Charchee

10-4. Just take every precaution when it comes to the R&I of that head. Buy the best head gasket set money can buy and have the head surfaced. Check in to doing your cam seals and plugs while you are at it. They are known to leak, especially on that side, if they are not leaking already. I don't want to have to say, I told you so, later. Best of luck to you.

Bunsen

thanks, takin it apart is easy.... luckily the only time constraint is i'd like to have this done by the time it snows.

does anyone have advice on removing the coolant sensor housing thingy that blocks the back two intake bolts back by the firewall? i found one nut and removed it but theres something else holding this sucker on.

Trents3.slow

There is two nuts that hold it on. Right next to each other. And probably a really nice gasket that won't let go.

cbr600rx7

You should have above 145 psi on all cylinders at a minimal unless you have somthing mechanically wrong (burnt valves, carbon build up, head gasket blown, worn piston rings, etc) elevation also plays a factor as does tempature but if your at sea level a healthy 3VZE should be 160+ across all cylinders.