KidV's 1985 4Runner

[KidVermicious]

Yesterday I replaced the plugs and wires, and cleaned the air filter. Didn't do anything else. This morning I grabbed the now-dry air filter and oiled it up per instructions. Put it in and fired the truck up. It's stumbling and making a funky popping sound at the exhaust. I start pulling wires, and it doesn't get worse when I pull the wire on cylinder 2. I grab one of the old wires that I pulled off and put it in place, no change. I verified I've got spark from the plug to the block. I frogged the plugs between 2 and 3, no change. I put them back and I frogged the wires between 2 and 3. No change. I try two of the plugs that I pulled out yesterday. No change. I look at the plugs themselves - the one that was originally in 2 is still pristine. The one next to it in three is already browning and discolored from the 10 or 15 minutes of idling it's done since I changed them. The cylinder is definitely not firing.

So it's got to be fuel, right? Bad injector? But it didn't have this stumble before I changed the plugs, and all four old plugs were evenly sooty and slightly wet with gas.

I'm stumped, and could use some ideas. It's not a bad plug, and it's not a bad wire, but how on earth could it be fuel? What am I missing?

eta - nevermind. It seems to even out for a second when I shoot carb cleaner in the intake. It's got to be fuel. What the hell.

eta2 - please don't be poor compression. Please please don't be poor compression, I do not want to pull that head right now.

 

[SV_Dude]

At this point you need to verify that you have fuel and spark. Pull the spark plug and put it next to something metal. Have someone crank the engine while you look at the spark plug and visually verify that you have spark. Then to test for fuel, rent a noid light set from your local auto parts store and check to see that the injector is getting signal to open. If you have spark, and the noid light says you're getting fuel then odds are your fuel injector isn't opening up and it may be all gummed up.

Did you run anything through your fuel tank that would suddenly cause this?

 

[KidVermicious]

At this point you need to verify that you have fuel and spark. Pull the spark plug and put it next to something metal. Have someone crank the engine while you look at the spark plug and visually verify that you have spark. Then to test for fuel, rent a noid light set from your local auto parts store and check to see that the injector is getting signal to open. If you have spark, and the noid light says you're getting fuel then odds are your fuel injector isn't opening up and it may be all gummed up.

Did you run anything through your fuel tank that would suddenly cause this?

Oh, there's spark, I shocked the **** out of myself . I still need to ohm out the wire and change out the rotor and cap just to cover all my bases, but I'm confident there's good spark, it makes a nice strong arc to the block.

I'm going to pick up a compression tester in the morning, I'll ask if they have an injector tester too.

All I've run through it is seafoam. But I don't know the condition of the fuel filter or how long the gas it's got has been sitting in there. It could easily be an icky or leaky injector, it just threw me off that the trouble wasn't apparent before I changed the plugs and wires. Maybe it was running so crappy on the Botch Platinums that I didn't notice it.

 

[BucknutBob]

If the thing's been sitting for a long time, that gas could've turned to varnish inside--I remember that from my motorcycle years, having to pull the carbs and have them cleaned every now and then after long winters. Wouldn't be surprised if your injectors are gummed up.

 

[Mudcat47537]

You can feel the injector and tell if it is getting a pulse and clicking. If you feel a pulse and have good compression it probably is a piece of crap in the injector.

 

[KidVermicious]

No compression on cylinder 2.

 

[KidVermicious]

I'm trying to come up with any sort of scenario where this not a complete PIMA, and failing. I made sure the compression tester was working by sticking it on another cylinder, and it is. I put it back in 2 to see if maybe I didn't seat it right, still no compression. Needle didn't even move.

So I'm googling around for reasons I could be lacking compression. Short of a hole in the block, I'm seeing a hole in the piston head or a stuck/burnt intake or exhaust valve. Bad rings would cause low compression, but surely not zero, right? What else is there? I had to prop my phone up to get video while I turned the crank, but the rockers on cylinder 2 appear to move when I turn it, does that tell me it's not a stuck valve? Or is poor quality video not sufficient to diagnose that? If the valve was burnt, would the rocker still move?

Do I need to pull the head? Is that where I'm at? I'm burnt out, frustrated, on unfamiliar ground and over my head (again), any help or advice here would be welcome.

 

[SV_Dude]

Your rockers will pretty much always move. As long as your t-chain is connected to your crank and cam, your rockers will move accordingly with your cam shaft.

Zero compression on a cylinder could be a busted valve, hole in the piston or no piston rings. I would think that if you had a worn piston ring or even a sticking valve that you would have SOME compression.

Try and stick a light over the spark plug hole and see if you can see any damage to the top of the piston. You may need to pull the head and get some good visuals on the bottom of the head and the top of the piston.

Did you put any oil into the cylinder when you did the compression test?

 

[KidVermicious]

Did you put any oil into the cylinder when you did the compression test?

I didn't bother. I didn't see any way a couple drops of oil was going to magically turn 0 psi into 170.

I don't see any way around taking this head off, so that's what I'll be doing tomorrow. I've already got the plenum half off, so it shouldn't be too bad. I've got the perfectly good head from my '86 that I'll take to a shop for a just-in-case checkup, and this will be a good time to put my hotter cam in.

Besides, my wife is going to her parents for dinner and I was looking for an excuse not to go. Cloud, silver lining, etc...

 

[mikebontoft]

damn. sorry bout that. do you have an air compressor or something like that, or access to shop air? what I've done in the past is pull the schrader valve from the compression tester and hook up the other end to an air hose to use a a leakdown tester. as long as you put that piston at tdc and make sure it doesnt push the piston down some when the air is added, you'll know right quick what the problem is.

don't forget you said that it ran fine while spraying Carb cleaner.

my friend bought about 4 different compression testers before getting one that worked. I've also had my fair share of "oh wtf no compression" in a single cylinder but after switching a few times the stupid thing read.

Not entirely convinced its a compression problem just yet.

 

[KidVermicious]

damn. sorry bout that. do you have an air compressor or something like that, or access to shop air? what I've done in the past is pull the schrader valve from the compression tester and hook up the other end to an air hose to use a a leakdown tester. as long as you put that piston at tdc and make sure it doesnt push the piston down some when the air is added, you'll know right quick what the problem is.

don't forget you said that it ran fine while spraying Carb cleaner.

my friend bought about 4 different compression testers before getting one that worked. I've also had my fair share of "oh wtf no compression" in a single cylinder but after switching a few times the stupid thing read.

Not entirely convinced its a compression problem just yet.

Well, it didn't run "fine", it just seemed like it evened out a little. The gas itself is definitely bad, smells sickly sweet, so I would loooooooooove for this to still be a fuel injector issue. I have a small compressor, and can probably rig it to the compression tester hose - how do I know when cylinder 2 is at TDC? And if I blow air in there and get nothing out the intake, exhaust, or dipstick, is that confirmation that I do have compression? Or just confirmation that the head and piston are good, and it could still be a bad gasket?

 

[SV_Dude]

The idea of putting a little bit of oil in the cylinder is to see if you get any higher reading. If you get a higher reading then it leads towards a piston ring issue. If you don't get any higher reading then it leads towards a head/valve issue.

If you're going to do as mike suggested, take out the #2 spark plug and look for the #2 piston to come to TDC. You can also verify that the piston is at TDC by turning the crank till it's at TDC and look at the rocker arms. If the #2 piston is at TDC then both of the #2 rocker arms will be loose.

 

[GonOvr]

If you had a hole in the piston you would be compressing the crankcase. Your pcv and breather and possibly intake would be overly saturated with oil. You would probably notice a bluish white smoke out the exhaust. The fact you hear popping noise in the exhaust tells me you have a bad exhaust valve. More than likely it and or the seat is burnt.

Did you sea foam it. It could have excessive carbon buildup at the head of the valve not letting it sit all the way in the seat.

 

[GonOvr]

Also did when you pulled the plug out did you smell it. If it smells like varnish due to your awesome gas that tells you the injector is firing. No smell no fuel.

 

[KidVermicious]

Appreciate the insights, Nate. I did Seafoam it once, 1/3rd each in the tank, in the brake booster, and in the crankcase. It sat for a couple weeks after that though, and I didn't start it again until after I changed the plugs and wires. I didn't notice it popping before though. The old plugs were all 4 wet with fuel, I didn't ever notice any fuel at all on the new one. From what you're saying, I'm wondering if the Seafoam broke something loose to clog the injector and the valve?

 

[KidVermicious]

I dropped a small glug of oil in the cylinder, and tried the compression test again - still zero, the needle doesn't budge. I fired up the compresser and stuck it on there - I can't detect any air coming out of the lower plenum (the upper is removed) or the exhaust, and the PSI on my tank doesn't drop. I think this compression gauge is flaky.

But there was the popping sound at the exhaust - bad valves, or just weak little backfires from unburnt fuel making it into the exhaust? And it did seem to even out a little and stopped the popping when I squirted fluid into the the intake.

Knowing all that, and KNOWING that there's bad fuel, and time being of the essence (I need this truck running next week, and would really rather not have to wait on a machine shop to check out my other head), would you pull the head anyway? Or would you just drain the gas, change the filter, swap the injectors with your spares from the '86, and button it up and hope?

 

[GonOvr]

First change the gas and filters, it needs to be done regardless.

Now just answer the questions.

Is the injector plug pulsing voltage at the plug?

Is the spark plug gettin wet with fuel?

If the compression gauge works for the other cylinders its gonna work for that one.

At tdc compression you do a leak down test. If you don't have compression that air has to go somewhere. Did you pull the dipstick, pcv or beather and listen?

Narrow down the problem and tear off the head as a last resort.

 

[mikebontoft]

likewise, if there's a hole in the piston or the rings are dead, you should have fuel in your oil soon enough.

 

[KidVermicious]

Fuel filter changed (and relocated to the fender, no way was I going to try and maneuver the new one back onto the side of the block with my giant numb hands) and injectors pulled. Taking them in for a rebuild and balance tomorrow - I thought about sticking my spares from the '86 in there, but decided not to cut corners.

First change the gas and filters, it needs to be done regardless.

Now just answer the questions.

Is the injector plug pulsing voltage at the plug?

Is the spark plug gettin wet with fuel?

If the compression gauge works for the other cylinders its gonna work for that one.

At tdc compression you do a leak down test. If you don't have compression that air has to go somewhere. Did you pull the dipstick, pcv or beather and listen?

Narrow down the problem and tear off the head as a last resort.

Dunno about the voltage - I rented a noid tester and it told me I didn't have voltage at ANY of the injectors, which I know isn't true. Dunno if they were pulsing. I don't think the plug was wet with fuel, no.

I rotated the motor to TDC and verified that by seeing the piston at the top and checking that the rotor was pointed at #2. I plugged my air into the cylinder and it didn't go anywhere. The upper plenum and valve cover were off and the radiator drained at this point, but I listened/felt at the lower plenum, dipstick, and exhaust - I didn't feel or hear any movement of air. I marked the exact location of the needle on the compressor gauge and watched it for over a minute, it didn't budge. I don't see any way that there could be a breach so bad as to cause ZERO compression on that cylinder that wouldn't empty my little 3 gallon air tank in a matter of seconds. I have to assume a faulty/flaky compression tester or user error.

I'm proceeding on the assumption that the bad fuel clogged the injector, because the fuel system needed overhauled anyway. If I'm right, woohoo! If I'm wrong and that cylinder still won't fire, at least I'll have the motor put back together and I can redo your tests with an intact motor and maybe get better data.

Please don't think I'm blowing you off, I absolutely appreciate the help and insight! But I had to pick a direction and get moving on this. Hopefully I picked right.

 

[GonOvr]

Alright man, I'll keep checking the thread for progress. I hope it's as simple as swapping an injector out. Next time I bet you drain the fuel out first.