NotSoNew92

Hey guys, first post here after some frustrating months trying to rehab this 4Runner. I've searched here and all over the google, but it's time now for my own thread. I'm currently fighting an intermittent misfire, but lets start with some background...

I bought this 92 4x4 4Runner with an auto trans and the 3.0 with 180k miles for $500. Great deal right? And it ran when I bought it. It needed a power steering pump, valve cover gaskets and some front end work, but I'm a big fan of preventative maintenance and didn't leave it there. I had the time and spare cash for parts, and this poor thing looked like it hadn't been cared for in a long time. It just got worse and worse the further I got into it. Here's a list of what I replaced:

Power steering pump
High and low pressure power steering lines
All 3 accessory belts
Alternator
PCV valve
Harmonic balancer
All vacuum lines except the two that run down to the front axle
Black/orange vacuum valve on passenger side vacuum mess
Water pump and thermostat
Timing belt, tensioner, and top idler with the coolant line running through it
Top intake mani gasket
Bottom intake mani gaskets
Throttle body gasket
Vacuum switching valve on passenger side of the coolant block at the back of engine
Reman'ed Injectors
Air filter
Oil and filter
Spark plugs and wires
Cap & Rotor
Ignition Coil
Ignitor
Knock sensor, knock sensor rewire with separate cable, & ECU (SOLVED MY CODE 52 THOUGH!!)
TPS
Cleaned decades of carbon off EGR, throttle body, and out of both upper and lower intake mani
Used VAFM (after trying to pull apart the connector to clean it... DON'T PULL THE CONNECTOR APART!!!)
Yanked all the cracked and brittle stock airbox stuff and replaced with a malleable hose from VAFM to TB, connected all open lines to this hose too
Cleaned every engine ground I could find and added two more: one from the passenger side engine hook to the battery negative and one from the passenger side block ground to the battery negative

There may be more, but you get the idea. I've been busy. The problem is, I now have a misfire that I'm fighting. It seems to only happen at idle/low RPMs and bounces from cylinder 6 to 3, but is usually on 6. I've pulled the plug wires with the truck idling and heard the spark arcing from cap to plug wire (and got shocked pretty good a few times too) and the arcing is consistent on 1, 2, 4, and 5. When revving it up and holding the #6 wire a small distance from the cap, it starts arcing.

I warrantied my new plug wires (import direct) and got a second new set of NGK copper core plugs that I gapped at .032", and didn't fix it. I warrantied my cap and rotor (import direct) and didn't fix it. I tested the distributor pickup coil resistances and found they were all in spec. I measured the air gap on the NE coil and it was within spec. I still need to measure the other two air gaps, but so far the distributor looks alright.

Ignition coil resistance is within spec per FSM, and I get about 12V on the coil output with the key turned to the on posiiton.

I found my old TPS was bad, bought a new one, painstakingly adjusted it per FSM, fixed the idle, but still getting misfire.

I bought a new EFI relay and igniter. Still misfiring.

I haven't been able to get the timing at 10°BTDC; it's either 15 or 5 at best. I thought maybe the timing belt had skipped a tooth. Pulled the top cover and got both cam tick marks pointing straight up with the crank at TDC. Verified again with one full cam revolution by turning the crank, and once more with another full cam revolution. Perfect.

My next move is the remove and clean the igniter/coil bracket and mount surfaces to get better grounding there, then test the remaining two coil air gaps on the distributor. I'm leaning towards the distributor since it is the only ignition component I haven't replaced, but I'm hesitant because the coil resistances were well within FSM specs.

Please tell me there's something easy I'm overlooking. I'm really tired of throwing parts at this in hopes of getting it running. I wanted a reliable adventure rig, not a money pit.

TIA

stefanc

Hi there!

Have you checked your compression?

I'm in a similar predicament, a nice misfire at idle resulting in a lot of shaking. I also checked that I was getting spark everywhere, and I got a stethoscope to most of my injectors and they seemed to be working (was trying to identify the cause of a Code 26 running rich).

I ended up checking my compression and wouldn't you guess, I have low compression on 3 cylinders. Now I just have to identify what is wrong. Bought a Leak Down Tester so when I get a chance I'll be doing that...

millball

Didya spend all this money and time without doing compression testing and valve adjustment??

millball

JINX!! we got on at the same time!!

NotSoNew92

I haven't checked compression yet because I can't see that cutting spark, but it is on my list of things to do next.

I realize now I should have adjusted the valves too, but I jumped into this without doing enough research. Found out after that these are prone to head gasket failures. Live and learn.

I'll report back any findings I get. I won't leave this another dead end thread. I plan to solve this.

NotSoNew92

So I have two votes for a compression check to see what state the cylinders are in. Any other suggestions?

I get that it's a good idea to do a compression test, but bad compression and bad ignition are different problems with different solutions...

millball

Your assumption that all misfires are spark, or fuel related is misplaced.

There can easily be compression misfires at lower RPM that aparently disappear at higher speeds.

NotSoNew92

Nah, I know there are other problems that cause misfire, I just know for certain I have a spark problem. I figured I'd get that resolved before moving on to anything else.

I'm doing the compression check regardless. I should have done it a while ago. Just looking for any other ignition ideas that I overlooked, that's all.

Thanks though.

stefanc

Keep us posted on how it goes

Co_94_PU

iTrader: (-1)

If you can get the timing to 15 and 5 you can get it to 10. Try again, make sure you are following the directions and the test port signal is reaching the ECU. Don't forget timing and idle speed screw are connected you'll probably need to do a little back and forth if they are way off.

NotSoNew92

I may not have explained my ignition timing problem correctly... I currently have it set at 15°BTDC with the distributor all the way over at one side of the adjustment slot. In order to get it to 5° I need to remove the distributor, rotate the gear a tooth, then reinstall and put the distributor at the OTHER end of the adjustment slot. It's like this thing is a half tooth off or something.

I can see how what I wrote sounds like I just haven't finely adjusted the timing, but that's not the case. This is part of the reason I checked my timing belt over the weekend. I wanted to make sure my belt hadn't skipped a tooth on the DS cam sprocket. Maybe this is yet another sign that I may need to just replace the distributor.

Anyhow, after work today I'll be cleaning the igniter/coil bracket to get a better ground connection, check the air gap on the other two distributor coils, pull the plugs on 3 and 6 to inspect them, then firing it up again.

Just a thought, but is there any chance this is all off because of the new ECU I put in to fix my code 52? Could something be wrong with that unit that would prevent me from setting my timing correctly and maybe causing intermittent spark problems?

One more thing. Co_94_PU: how are the idle speed screw and timing connected? Are you saying I can adjust the timing also by playing with the idle speed screw? The FSM only says to adjust that screw when idle speed is off. Am I missing something?

Thanks for the responses. Much appreciated.

millball

The ecu will not enter base timing mode if the idle speed is too high. About 800-850 is low enough..
The ecu will not enter base timing if the tps does not tell it that the throttle is closed.
Both these things need to be satisfied, even when the timing jumper is in place or else indicated base timing will be improper.

helidriver

OMG, just posted my own thread on this, having the exact problem with mine, it's a 22RE, at the dealership stumping the tech after all day there......

Have you tested vacuum on the top end? Unmetered air in not through the AFM can cause computer to compensate for lean situation by dumping rich.....

NotSoNew92

Ok, I wasn't able to work at all yesterday but I'm jumping straight into this when I get home.

I spent some time looking for a tach to measure RPMs while adjusting the throttle speed screw, and found a way to do that with a standard multimeter that reads Hz! Jam a wire into the Hz port, wrap the other end around a plug wire, and the spark induces a Hz signal that can be read by the meter. Then just multiply that by 60 to go from Hz to RPM. Pretty cool.

I plan to test vacuum on this over the weekend, maybe today if I can get to it. I'm planning on doing this to check valves though. I don't think I have any unmetered air coming into the system; I just redid all of the little vacuum lines and sealed up any cracks in the larger ones with many wraps of gorilla tape (love that stuff!). If I need to look for vacuum leaks, I'll spray carb cleaner on the areas I think might be leaking. If RPMs go up, the carb clearner got into the system and burned. Easy trick.

Anyhow, I'll make sure the idle RPMs are good today, then go from there. It'd be great if this was really that simple of a fix!

I'll post back later with results.

NotSoNew92

I pulled the cap and rotor to check the G1 and G2 coil air gaps, but my thickness gauges are both too wide to fit behind the signal wheel that the rotor fastens to. I assumed they were find and moved on.

Thinking I may have put my distributor a tooth off while trying to correct my timing issues, I removed it and reinstalled it per FSM, lining up all the little marks. The rotor landed where it's supposed to, so I thought I was fine.

I jumpered TE1 and E1, fired it up, and let it idle til warm. The idle bounced around by maybe 200-300 RPM while warming up. Timing was maybe 30°BTDC. Rotated the distributor down as far as it would go and got it to 15°. I figured I'd use my test light inductance coil to check spark on all of my wires. Everything except #3 was firing. I pulled the #3 plug wire and managed to sever the wire while doing so. I pulled the old wires, got 13.5 K ohm on one, plugged it in and fired it up. Had spark on 3 again. This time, #6 was the only one not sparking. This is maddening.

While doing all of this, I had my homemade tach set up and it was giving me readings that didn't make sense. I moved it around and didn't get better results. I scrapped that idea. YMMV.

So,I was unable to set the idle to where it needs to be because it was bouncing around too much and my tach didn't work. I'll try that again in the morning I guess. Maybe if I get that settled the ECU will set the timing correctly and I'll be out of the woods on that issue. FSM says timing needs to be set before adjusting the idle RPMs though, so I'm still not sure what to make of this.

One thing I noticed today is I'm missing the filter and cap on the dashpot on my TB. How much of a difference does that make? I get that it should be there, but I can't see how that would affect spark related misfires.

I'm leaning more and more towards just getting another distributor and trying that out. Any other suggestions?

I'll report back in the morning Wrapping it up for the night.

NotSoNew92

Oh and FWIW, it seemed to run a little smoother at 30°BTDC.

millball

About 30' advanced is where the timing sits at idle when the ecu is not seeing throttle closed signal from the tps.

NotSoNew92

I'll pull the TB and adjust the TPS again today then. Thanks for the tip.

You know, even though my timing light indicated no spark on 3 and 6 at different times, it was running pretty smoothly. I'm going to go back to pulling wires at the distributor to check for spark. I just wonder how consistent my cheap harbor freight timing light is...

NotSoNew92

OK. Pullled the TB and tried the old TPS just for kicks. Reading through the FSM again, I noticed this time that I need to apply vacuum to it to adjust the TPS. That makes a bit of a difference. The old TPS that I thought was bad actually checked out fine, so I'll be taking the new one back today. I just put it all back together.

Firing it up in a minute.

NotSoNew92

Forgot to connect the TPS harness, fired right up, killed it and pulled the negative battery cable to clear the code. Plugged the harness back in and three times it fired up and died within a couple seconds. Looks like the TB is coming back out and that new TPS is going back on.

I'm just glad I have the day off to do all of this. Hopefully I get this resolved and it's actually a good Friday...