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!986 4runner 22re Random Misfire Short E2/FC/FP

Old 06-13-2019, 05:39 PM
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!986 4runner 22re Random Misfire Short E2/FC/FP

So I've been having this random misfire from hell on my fresh rebuilt 22re with 5k miles on it for a while now. At 1500-3100 RPM this misfire shows up but it's not missing on any specific cylinder. If I retard the timing it calms down but is still there and only seems to surface once the engine warms up and the idle drops. I've gone through a lot of diagnostics on this, I basically rebuilt the fuel and ignition systems, and injector wiring and over the weekend I installed a second EFI harness but when I fired up the truck it started throwing AFM codes like crazy and was acting like it was starved of fuel and dying. all the color code and pinout on the new harness seemed to match my old harness so I started testing the wires between the ECU and the AFM for resistance, what I found is E2 has a complete circuit between each end but it also has a complete circuit between E2 and FC. For ˟˟˟˟s and giggles I tested E2 to FP and also get a complete circuit between those two circuits. It also seems that E2 is shorting to several other sensor wires via testing from where the cowl harness and the EFI harness mate above the ECU. I understand E2 is the sensor ground so circuit wise all these sensors should be using this same ground but on a resistance test it's my understanding that shouldn't be getting a complete circuit between two separate wires unless there is a short. Just wondering if there is something I'm not understanding about this or if I really have diagnosed a short. I laid out and connected the second EFI and cowl harness I have and ran resistance tests on the same wires and did not get any resistance across any wire that I wasn't connected to directly between point A and B so I assume this backup harness is normal but would appreciate if someone could chime in and tell me if I'm going down the wrong path here? I'm learning wiring as I go so I could use outside opinions.

Thanks in advance!

Last edited by outdoorjunky; 06-13-2019 at 05:42 PM.
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Old 06-13-2019, 08:43 PM
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If I read this correctly, you check the harness resistance with it completely unplugged and found no shorts? 99% of the time this is going to mean it's good with a slight chance that the short is due to the positioning and some vibration. I'd say it's probably not a harness short.

The resistance you see between FP and E2 is the fuel pump, it's always connected to ground it's one of the switched power circuits, not a switched ground.

A resistance measurement between FC and FP is the coil windings in the COR with the relay closed, contamination of the dielectric compound in the diagnostics connector or maybe something I'm over looking like an ECU fault. Try that test again with the COR disconnected to rule the COR out. I don't recall in detail if unplugging the ECU disconnects E1 from E2, I kind of think offhand they are each half of that split ground terminal on the intake.
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Old 06-13-2019, 08:45 PM
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You can see here the few paths to ground from FC
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Old 06-13-2019, 09:04 PM
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Originally Posted by Co_94_PU View Post

You can see here the few paths to ground from FC

yeah basically I did tests of one harness that was in the truck connected to the ECU and back probed the pin for E2 and then connected the other probe to E2 on the AFM connector side of the wire ... for a second I was hunting for E2 because the connector was turned upside down at the AFM side and thats when I noticed I had resistance on FC and E2, then I noticed about 4 or 5 wires on the cowl connector had resistance from E2 as well. I wasn't sure if since they are in the engine bay connected to the sensors and the harness is grounded if thats why I was seeing resistance or not. that makes sense about the split ground on the intake .... ok so about testing with the COR removed, that is to see if it isolates E2 right? with the COR disconnected it should simulate the same result as when I tested the second EFI and Cowl harness on the bench which showed only resistance on E2 and not the other circuits right? for clarity there were two tests done, one of the harnesses installed in the engine bay and dash and the second a bench test of a totally different EFI/body cowl harness.
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Old 06-13-2019, 09:54 PM
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if it's not something related to wiring I'm really getting stumped on what the actual cause is. I have literally gone through everything in the EGR system, the Ignition system, and the fuel system... I found so many "bad" out of spec parts and just replaced everything as I went. I rewired the injectors due to the classic corrosion of the splices and tested my work and it's solid, the injectors just came back from witch hunter and are flowing at 98-99% spec across the board, the cold start injector also got serviced (that actually resolved my bleeding off fuel pressure faster than spec when the motor was turned off that I had asked about a few months ago). I was hopeful I might have found the source of the mis when the data from witch hunter showed injector number 2 was only at 48% of capacity before they cleaned it but that just smoothed out the idle didn't help with the ongoing misfire. I tested idle vacuum at the plenum and I'm getting right between 19 and 20 inches of vacuum and it's steady.

These are the things I haven't touched yet:
the resistor solenoid for the injectors ohmed out slightly over spec at about 3.3 ohm but thats not so much as to cause some intermittent problems is it?
the TVV for the EGR system
did not test the Knock Sensor as I don't have the capacity to do that but the ECU is not throwing any codes at all.
the COR (have a spare to swap in now)
the EFI main relay (also have a spare of this I can try)

the TVV seems to be closed when cold and open when the coolant is warm. I also blocked off the EGR at the plenum with a aluminum can strip and that didn't really help the misfire.

If I pull the TPS connector off while the truck is running it throws its self into a misfire frenzy at idle ... the misfire doesn't come on until about 1500 rpm with the TPS plugged in. If I pull the 02 sensor connector the misfire stops completely, I replaced the o2 early on with a new Denso. if the ECU sits with the battery disconnected and it resets sometimes the misfire won't come on right away and then it surfaces mid test drive. I'm on my second ECU with the same behavior as well. I'm just at a loss for what else could be causing this except for some jenky wiring somewhere. I did read a tech bulletin about some early 22re ECU's causing this random misfire and than retarding the timing to 2-3 degrees actually fixed it, it almost fixes it with both ECU's but not all the way. I supposed it's possible I got two ECU's with that fault but seems unlikely.

Last edited by outdoorjunky; 06-13-2019 at 10:10 PM.
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Old 06-14-2019, 05:24 AM
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the ecu TSB issue with the circa-'87 trucks was that under some circumstances, the ecu would advance the timing extremely high, iirc above 25 to 30 degrees advanced. not sure whether it was ever solved/resolved by toyota, ie, issuing new ecus.
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Old 06-14-2019, 06:23 AM
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Originally Posted by wallytoo View Post
the ecu TSB issue with the circa-'87 trucks was that under some circumstances, the ecu would advance the timing extremely high, iirc above 25 to 30 degrees advanced. not sure whether it was ever solved/resolved by toyota, ie, issuing new ecus.
My truck advances to 37 degrees at 3000 RPM confirmed using my advance timing light . A symptom of whatever is going on is that under load, like up a long grade on the Highway, I get a spike in coolant temps (confirmed not the Custer or sender as I did an SR5 cluster swap and tried two different sending units with the same results)... the needle stays put in the middle on the gauge the entire time driving except on hauls up hills where the engine is working harder or in some cases after I've been on a long term freeway drive. As soon as the load is off the engine the cooling system cools it right back down. It's not actually overheating, never reaches the red line it just spikes from the middle mark to about the 75% mark on the white. I've searched for what the correct amount of advance is and haven't found a definitive answer but I have read where several people that said about 37 degrees advance is normal at 3000 rpm. Engine has 5k on it and I rebuilt it with a Toyota OEM overhaul seal kit I bought from Toyota so the head gasket isn't some cheapo gasket. I'm also not losing any coolant or seeing any sign that fluids are mixing. The water pump is a new Aisin pump, radiator is a new dual core CSF all metal, hoses are new, using a OEM Toyota two stage thermostat, and running Toyota red coolant and it's been properly burped of excess air. I've been pretty meticulous about updating things.
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Old 06-14-2019, 06:32 AM
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Not sure you have a wiring problem or not, so I am going to throw this out there.

Have you tested the distributor? They do wear out.

Pull the cap off, and remove the rotor. Grab the shaft, and see if it has any play. Test the signal generator pickup coil. You can also check the air gap.

If the shaft does have play, the wobbling shaft messes up the air gap which in turn causes misfire.
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Old 06-14-2019, 06:42 AM
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Originally Posted by snippits View Post
Not sure you have a wiring problem or not, so I am going to throw this out there.

Have you tested the distributor? They do wear out.

Pull the cap off, and remove the rotor. Grab the shaft, and see if it has any play. Test the signal generator pickup coil. You can also check the air gap.

If the shaft does have play, the wobbling shaft messes up the air gap which in turn causes misfire.
I tested the air gap on the original distributor and resistance tested it and it was showing high resistance I replaced it with a remanufactured unit. the first remanufactured unit had the drive gear pressed on wrong and it was impossible to advance timing any further than 5 degrees BTDC (it was hitting the bolt at 5 degrees)... got a warranty replacement and it stabs correctly. the cap, rotor, distributor, coil are brand new, the plug wires are tested and in spec, tried a ngk wire set for comparison no change, also tried a second igniter with no change, and a second ECU. I tried getting a Toyota OEM replacement but Toyota discontinued the distributor and the pickup coil several years ago. only thing I haven't touched in that chain is the ignition switch. Plugs are gapped to .31 and are NGK of which I have installed two sets to make sure.

Last edited by outdoorjunky; 06-14-2019 at 06:54 AM.
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Old 06-14-2019, 07:01 AM
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Definitely test the ignition switch. It's in the spark test flow chart. Get somebody to wiggle the switch with the key switched to on, and see if you get random no voltage at the coil positive terminal. Then you can do a wire wiggle test under the hood to see if it loses voltage at the coil.

Other than that, I don't know what's going on with it. The last thing in the spark test flow chart is to try another igniter, and you have already done that.

Last edited by snippits; 06-14-2019 at 07:06 AM.
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Old 06-14-2019, 07:20 AM
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Originally Posted by snippits View Post
Definitely test the ignition switch. It's in the spark test flow chart. Get somebody to wiggle the switch with the key switched to on, and see if you get random no voltage at the coil positive terminal. Then you can do a wire wiggle test under the hood to see if it loses voltage at the coil.

Other than that, I don't know what's going on with it. The last thing in the spark test flow chart is to try another igniter, and you have already done that.
ok will do. Thanks for the suggestion I must have missed the part about testing the switch in my FSM.
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Old 06-14-2019, 10:56 AM
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Originally Posted by outdoorjunky View Post
ok will do. Thanks for the suggestion I must have missed the part about testing the switch in my FSM.

And I figured out how I missed the test procedure for the ignition signal ... I was troubleshooting using a tree from the EFI section (rough idle or misfire) where it goes through the same test procedure but starts at the coil not the ignition switch so I ended up testing everything after the ignition but not actually testing the ignition. The Ignition section in the FSM has the exact procedure you describe. I'll get on that this evening.
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