zclubhouse

Hello everyone,
I purchased a 87 4runner 22re 6 months ago and now have an unique set of surging symptoms that I can't seem to track down a cause for. I have read upwards of 40 pages of "surging 22re" posts but I cant seem to find a link or solution to my problems. Ive done my research but now I'm grasping at straws and do not want to just start throwing money at the truck. Any other advice would be appreciated.

Heres a history/diagnosis addressing the common causes I have looked over:
Truck started to bog down and run rough a few days ago. I thought it might be missing so I pulled each plug wire and grounded them out but they all had spark. Truck seemed to recover from its mid range bogging (1.5-3k) and I drove it another 15 miles. Now the truck has progressed to constant bogging or violent surging (no power-full power alternating every 1/2 second) and cannot really be driven. Idle doesn't wander around, the truck either seems to run fine at 900 or bogs/rough at 500. Sometimes the truck will start strong and seem to run great through 1st gear and then 5 seconds later its lurching around and surging. If I can flatfoot through the surging, the truck generally runs fine in the upper rpm range ~4000 and up. The truck doesnt have any trouble starting and even when running rough around 500rpm, it will not stall on its own.

TPS
I bought a brand new TPS and installed it. Didnt have a ohm meter available (fixing the truck in a parking lot at school 300 miles from home and my toolbox,) so I set the TPS at the same position as the old one. Unplugged the battery to reset the ECM and truck still ran poorly. Adjusted the TPS to both extremes with no result. Brought the TPS adjustment close to center and bridged the E1 TE1 diagnosis terminals and the idle did drop. However, the idle only drops when the truck is idling normally at 900. When the truck bogs to ~400rpm idle, bridging the terminals does not affect idle. Unplugging the TPS just makes the truck fall on its face and hardly run. How sensitive is the TPS adjustment? Does it have to be spot on perfect (tested with an ohm meter,) or is close enough good enough?

Ignition
Had some problems with the truck a few months ago and fixed it by replacing the Ignition control pack and the coil. Distributor cap is clean and rotor does not have any serious wear. Plugs were a bit fouled and worn down, so I bought new NGK's, gapped them to 0.032 and installed with a new set of wires just to be sure. Timing set was replaced by saitotiktmdog (yotatech board member, future brother-in-law, previous owner of the truck and on call mechanic for my 4runner problems) right before I bought the truck, so skipping a timing tooth is out of the question. Like I said earlier, spark is good on all cylinders. No backfiring when I get on the throttle past 4k and let off at idle.

Vacuum System
EGR is blocked off/removed from the truck. I do not hear any vacuum leaks and pressing the brake doesn't affect the idle at all. I do not know why low vacuum and high vacuum conditions do not affect the truck while intermediate conditions cause the truck to stumble. I do not think its vacuum related. PCV valve is operating normally.

AFM
I have tried two different AFMs on the truck. No difference. Got ahold of a ohm meter and tested the resistance across the various pin terminals and in reaction to opening/closing the door. Pretty convinced I have a good AFM. Also put in a new air filter just to make sure I have optimum air flow. The motor runs somewhat rich when it bogs, but its not in full on fuel dump compensation mode (no black smoke or fuel out of the exhaust.)

general engine
My 22re has a fair amount of valve train noise but still has good oil pressure and doesnt use any oil. Headgasket was replaced 15k ago when I bought the truck so I am pretty sure I have good compression although I have not tested it to be certain. No antifreeze/oil combination happening anywhere. Truck has overheated since I bought it due to a broken thermostat, but that have been replaced and the truck ran fine afterwards. I did remove the temp sensor on the thermostat housing/water outlet neck because the gauge malfunctioned in the dash so I replaced it with a mechanical type plumbed to that spot. The truck did NOT run strangely after this conversion (I dont think I removed the CTS for the computer?.) I do not think that an 02 sensor could have this type of effect on the truck even if its stuck in a closed loop. Am I wrong?

What else should I try?
I was thinking I may have some strange fuel delivery problem, possibly injectors? However when my vw's injectors went out the engine would never regain full power when surging. I haven't checked fuel pressure yet, but it doesn't make sense that it would be low because if I can get the truck past the midrange surge it normally runs fine towards the top end and high demand. Could be the ECM itself but I am not getting any trouble codes when I bridge the diagnosis box. Could a bad engine ground cause a midrange stutter? Anyone who made it this far have any ideas? I am completely stuck. Thanks in advance. I really appreciate it.


Andrew

scuba

You think its fuel..
Fuel pressure regulator...?

zclubhouse

That will be one of the next things I check. I haven't seen FPRs break, but I am sure they can. However, if the spring is shot and I am running full pressure all the time, would my idle ever be normal? Idle adj screw does work.

scuba

good question...Im really trying to think...
Also have you checked the idle air valve ?

Ezrider_92356

you could try adjusting your valve lash

abecedarian

TPS asjustment is fairly critical to engine operation. Besides telling the ECU how far open the throttle plate is so it can figure fuel mix, it also tells the ECU when you're at idle. When at idle, a few things happen such as timing is advanced over baseline to lower emissions, the O2 sensor is not monitored, etc. The TPS can be adjusted fairly easily without a meter. Loosen the screws just enough so that it will just turn with light finger taps- so a tap moves it maybe 1/10th inch at most. With the engine running and the diagnostic plug jumpered, turn the top of the TPS towards the front of the engine until the rpm suddenly drops. If it doesn't, turn it towards the rear of the vehicle until you hear the engine speed jump up a bit. Then tap it back forwards until you get that one tap that makes the rpms change back down low again, and lock it down.
After that, check your timing and idle speed. Timing should be ~5btdc, idle should be ~750. If you have to adjust one, check the other since adjusting one will affect the other. Also, make sure to use the air bypass screw on top of the throttle body, not the screw on the throttle linkage or dashpot.

The coolant temp sensor you pulled is likely one for an auxilary function, not your gauge. The gauge sender is on top of the intake, between #2 and #3 runners, next to the head, with a single wire plug on it, not on the thermostat outlet.

sometimes it idles fine, sometimes it idles low (~500)?
when on the gas, the engine sometime runs fine, sometimes acts as if you are switching the key off and on every .5 second?
when it's doing this, do you notice any smoke out of the tailpipe?
when you manage to get it above 4k, and it's running good, is the pedal floored, or are you at part-throttle?
does it run any different when the engine is cold compared to when it is warmed up?
are all the grounds to the engine in place- front of the engine block / battery side; where the upper and lower intake manifold bolt together; rear of head to firewall; around power steering pump, from alternator harness?

Ezrider_92356

if it was due to the tps it should still run fairly well, with the tps unplugged, i ran my Toyota with the tps unplugged for a couple months till i bought a new tps and it ran fine.

zclubhouse

No I haven't yet. I wasn't thinking IAC because idle doesn't wander. How would I look into that short of flat out replacing it? Had to work today and haven't made any more progress on the truck.

zclubhouse

I already have the TPS adjusted to where the idle drops when diagnostics is jumpered. The question is, should I adjust the TPS by the book (ohm meter resistance) or should I just leave it alone?
I have already tried adjusting my idle speed with the air bypass screw but I am happy with ~950 when cold because that is what that truck has always done.
I did pull the gauge with a single plug wire on it and now the gauge in the dash is completely dead. Just curious if the aux sender I pulled would affect the running at all? Is it the CTS that reports to the ECM or something else?

Yes it sometimes idles fine at 900, sometimes drops to 500. Doesnt change very frequently, normally switchs to 500 idle as a response to load (trying to drive it.)

No smoke out of the tailpipe. Condensation smoke cause its cold outside, but no fuel black or antifreeze white or oil blue (or flames for that matter! )

Runs above 4k regardless of throttle input.

No difference in running dependent on temp, however I haven't gotten it up to full operating temp in a while because it runs so poorly I generally shut it down in between working on it.

All the grounds are in place. I was thinking about changing the battery grounds because they are original, but I dont see any cracking, excess corrosion or broken pieces. I was thinking it might be a bad ground but I dont see any problems.

zclubhouse

I dont understand? Why? In response to the valve train nose or the truck running poorly?

eich75

my 88 22re does the same thing only in the first 3 gears tho... i thought it was the brakes hangin but i changed them and the springs... i also thought it was a dirty fuel filter until i changed that... if you let off the gas when it bogs down does it run fine? its only when i give it gas after a stoplight or something that it bogs down

abecedarian

950 cold means little if the idle isn't constant and consistant when warm. I keep saying this to people: the cold start system is secondary to the warm / normal operation of the engine. If it doesn't operate properly warm, it will never operate properly cold. Some things can mask various problems, but it doesn't make it correct. That is one reason the TPS must be correct. And if the TPS is significantly 'incorrect' it will affect things.

If the TPS is correct, with the engine running, inserting the jumper as required into the diagnostic connector should cause the idle to change, and the timing to change as well. Given that, when the coolant is approximately 180F (the thermostat has cycled at least twice), the idle speed should be approximately 750 and the timing should also be approximately 5 BTDC. Are both of those true?
You said you disconnected the plug on the thermostat / water outlet. To me, the coolant outlet is not between the #2 and #3 cylinder intake runners.
...I must be missing something here.
well, that does make a difference of sorts- if the engine doesn't fully warm up, there's no reliable way to set the idle or timing.

zclubhouse

Abe,
The idle is constant and consistent when warm. However, with response to load the idle often drops to 500 and sometimes goes back up to 900. It doesn't waver back and forth like a bad IAC. I know that it sounds like I am contradicting myself with the idle "staying consistent", but basically its either normal operating idle (cold or warm) or its 500 (cold or warm.) Its like the truck has 2 options on a switch and randomly switches back and forth between the two. If you leave everything alone it will generally stick with one idle speed or the other. It will sometimes recover to the 900 or drop to the 500, I dont know why. I havent had the truck up to full operating temp because it is cold enough outside that it doesnt really heat up at idle. I suppose I could try to stumble it around for a while to get it up to operating temp but I would want something new to check if that was the case.

The idle DOES DROP when the diagnosis terminals are jumped. I haven't been able to get a timing light yet. I will check back once I double check the timing.

I was trying to say that I replaced the coolant sensor on the water outlet that is also a single wire sensor. No confusion as to the location of the water outlet/ intake runners. Just asking if the sensor that I did replace would have anything to do with the running condition.

Thanks for the help. I will check the timing and see if its normal.

zclubhouse

No, my truck will bog and run poorly regardless of throttle position when engaged in gear. It only surges once I apply the throttle.

abecedarian

another dumb question- what is the temp rating on the thermostat and when was it last checked / replaced?

zclubhouse

It reads at 160 at the water outlet before the thermostat when its at operating temp, thermostat is rated at 180. Thermostat was replaced 2 weeks ago and last checked 2 days ago when I pulled the top of the outlet off so I could get to the bottom TPS screw and do battle

Ezrider_92356

the valve train noise tells me that that the valves have not been adusted in quite a while and if one of the valves is too tight it may not be letting it close completely when the motor is cold and that would cause idling problems, also its free rather than throwing money at something i prefer to try the cheapest posibilitys first, i would also start disconnecting sensors one at a time. if it runs better with a sensor disconnected (the computer will go into default mode and estimate what the sensor should be reading) then you know that sensor needs to be replaced

ozziesironmanoffroad

you know, mine did that and for the longest time i thought my fuel pump/TPS was gone. but i decided to have some fun with wires. so i examined the fuel injector wires, and i sat there scratching my head saying 'now i feel stupid'. there was a bit of bare wire showing on the fuel injector wire, and whenever it would hit the metal of the engine, would ground out, and misfire. i could get it to do it while idling, but it was rare. it did it while moving. it did what you described... shaking, bogging, etc. check your fuel injector wires and plugs. just for the hell of it, you know?

zclubhouse

Ok, I will look into that. I tried unplugging sensors to see what difference it would make and so far I haven't see a specific sensor make any difference to the trucks running habits. I will poke around a bit and let you know if I find any bad sensors. Im trying to pin point the cause of the bogging/surging more than the idle because I think the idle is another symptom of the main problem rather than the only problem. The bad idle fixes I have seen do not address the mid range powerband problems.

Excellent idea, Thank you. I've been away from the truck for a while but I was thinking about going through the fuel injectors and harness because something along those line could cause the problems I am having. Its a bummer they are so buried on this truck but I will do a visual inspection tomorrow and get back to you. That idea really makes sense to me.
Does anyone know what impedance reading the injectors should have on the truck? Im thinking it should be around 14-15 ohms but I want to make sure the injectors are not stuck in full loop.

zclubhouse

UPDATE:
Worked on the truck for a while today. Checked compression at 165-170-160-165. Adjusted the TPS exactly dead on with an ohm meter, didn't make any noticeable difference. Tracked down the culprit as cylinders 2 and 4 fuel injectors. When the truck would bog and run rough at 500rpm I unplugged cylinder 1 spark plug wire and it had spark, however, the truck would start to run even worse and die. Cylinder 3 had the same response. However, cylinders 2 and 4 had spark but no fuel. When I pulled the wire nothing changed. Listened to the injector firing and 2 and 4 were not firing at all when it bogged. When it recovered all injectors would fire. I pulled the upper intake today and inspected the harness and did not notice anything out of place. What would make 2 injectors stop working at the same time and start working again in tandem? I do not think it is an injector failure, but I do have access to other injectors and I could try those. I have an 87 22re with the low impedance (1.5-3ohms) injectors. Does my computer only work with the low impedance or could I put in the 89and later injectors? I think that it is probably something that runs the pair. What should I try or look for, harness or ECM problems or should I replace the 2 bad injectors? Thanks again