yotalaz

my 1990 4runner, runs good when cold but when its hot outside and i have the ac on its a pig. and it seems to loose power after the engine gets to running temp. any ideas what this could be?

thook

Does it still run poorly with the a/c off while being hot outside? What I'm trying to determine is how much of a factor the a/c is in the problem. If it's doing anything, it may be just exacerbating the real issue. So, if I were to take a couple of guesses, I'd say possibly the cold start timing switch or the coolant temp sensor. You're probably running too rich once the motor has reached temp because either one of those components are signaling for fuel when the motor doesn't actually need it. If the a/c is posing any problem, while running, the motor's not feeling strong enough to meet the demand of the pull on power.

BTW, have you looked in the factory service manual troubleshooting guide, yet?

hilandfrog

Doesn't the IACV give more air when cold and block off when hot effecting idol?

Repo

thook

Yeah, but I'm not sure what you're getting at. Maybe the IACV is stuck open?

sb5walker

If you want help with your engine, it really helps to know what engine you have.

But basically, when cold, the ecu runs the motor in "open loop" mode, where it uses preset values for mixture & timing. When the ECT (engine coolant temp sensor) signals to the ecu that the motor has reached operating temp, the computer switches to closed loop and begins to use signals from the O2 sensor to set mixture. If it runs differently when hot than cold, then the engine coolant temp sensor is probably working. Since it runs poorly when in closed loop, I would check the O2 sensor first. If it's over 90k miles or a Bosch or it's fouled, it should be replaced. If less than 90 miles and not a Bosch, it may be worth checking its switching rate - there are instructions in the fsm.

The problem with the A/C on could be that the A/C idle up vsv isn't working, or you need to adjust the idle speed higher (big hex-shaped plastic screw). See the fsm for location.

Other than that, these suggestions from a previous post may help you get it going right (they apply to both 22re & 3vze):

1. Check for codes. The CEL doesn't always light up, so you have to check. Address any issues highlighted by the code(s). See post #2 of 'Massive Truck Info' sticky.
   
2. Check compression. If it isn't in spec, no sense spending another dime until you address the mechanical problem.
   
3. Check that IDL & E2 terminals of throttle position sensor (tps) have continuity when throttle is closed (idle position) and don't have continuity when throttle open. If not, try adjusting position of sensor - follow instructions in fsm (easiest to remove throttle body 1st) or use this technique from 4crawler. If you can't get the terminals to make contact at idle, replace the tps:
   http://www.toyotanation.com/forum/sh...44#post3111544
   
4. Perform a tune-up: Replace plugs, cap and rotor with new factory spec Densos. Replace wires with a Denso cable set if hard, inflexible, cracked or tracked up with carbon. Replace air filter with one from Toyota. Adjust idle speed as near to spec as possible, then set TE1 - E1 jumper in check connector and set timing to spec. On 22re, adjust valves if not done recently, and check the timing chain guides while you're in there. Replace O2 sensor if over 90k miles with direct fit Denso - (part # from sparkplugs dot com and search 'denso' and part # on amazon for best price - that goes for other Denso parts, too.)
   
5. Read the old plugs (keep track of which plug from which cyl) and post their appearance here to get help with interpreting if needed. Normal is light tan or gray deposits with slightly worn electrodes (the older the plugs, the more worn the electrodes). See this page or this one.
   
6. If plugs are all flat black, the engine is running rich which may be due to bad O2 sensor, corroded O2 sensor connector (try cleaning it up), bad ECT (engine coolant temp sensor - test procedure in factory service manual), out of adjustment vafm (air meter - test procedures in fsm), or too high fuel pressure (rare).
   
7. If plugs are white, with worn, rounded electrodes, the engine is running too lean, which may be due to clogged injectors, timing too advanced, low fuel pressure (could be bad regulator, clogged fuel filter, possibly low voltage at fuel pump due to corrosion or tired pump), cracked or leaking air hose between vafm & throttle body, incompatible O2 sensor, exhaust leak, or possibly vacuum leak. If one or two plugs are white and others are normal or black, almost certainly the lean cyls have clogged injectors. Try running through a bottle of an injector cleaner that contains polyether amine - Red Line SI-1 Complete Fuel System Cleaner or CRC's "Guaranteed to Pass Emissions Test Formula" are the only two left that do. If that doesn't work, send injectors to witchhunter.com to be professionally cleaned and flow tested. They do great work for a very reasonable price and turnaround is very quick.
   
8. Clean throttle body if needed with throttle body cleaner, rags, toothbrush, getting back of throttle plate and being careful not to get any solvent on or in the tps.
   
9. Temporarily pull and plug the vacuum hose off the EGR valve to see if that improves the running - the vsv or modulator may be bad or vacuum lines misrouted. It's important that the EGR be functioning properly as it helps keep combustion temps down and helps prevent blown head gaskets, burnt valves and pinging. It doesn't cost any power because it doesn't operate when near or at full throttle, and it actually improves gas mileage by a small amount.
   
10. Check air hose between vafm & throttle body for cracks or leaks.
    
11. Check for vacuum leaks by passing unlit propane torch along all vacuum lines and throttle body & intake manifold joints and listen for increase in rpm.
    
12. Check tps, vafm, ect & O2 sensor to make sure all values are within factory spec. Procedures & specs in fsm. For VTA in the tps and VS in the air meter make sure resistance changes smoothly as you open & close throttle/vane with no spikes or dropouts. There are two ways listed to check sensors: one, to check resistance in the sensors themselves (see the relevant chapters in MFI SYSTEM section; tps is in THROTTLE BODY chapter), and the other method is to check voltage on ecu terminals when ignition is on. That not only checks operation of sensors but the ecu's connection to them, which is important. Instructions in the ENGINE - MFI SYSTEM - TROUBLESHOOTING section. You'll need backprobe adapters for your multimeter test leads or you can push needles into the connectors and hold test leads against those. For the O2 sensor, follow procedures in fsm ENGINE - MFI SYSTEM - OXYGEN SENSOR section to check O2 sensor switching to make sure sensor isn't "lazy" which is a sign of it being fouled. That work is done on terminals in the check connector. Don't just check O2 sensor resistance - that only verifies that the heater isn't burned out, but you would get an ecu code if it were.
    
13. Check resistance of both circuits in coil - best to do when hot (of course, use the hot specs). Disconnect it before checking. Instructions in the IGNITION - ON VEHICLE INSPECTION section.
    
14. Check resistance of signal coil(s) in distributor and check clearance between signal rotor lobes and signal coil projection(s). Clean up the igniter's ground (mounting bolts). Instructions in the IGNITION - ON VEHICLE INSPECTION section.
    
15. Make sure coil to distributor cable is not shorting out on something.
    
16. If catalytic converter is original, it could be clogged. Best way to check is to remove it and look through it - you should see light through it fairly easily. If clogged, replace with a direct fit Magnaflow - get part # from their website, then search ebay for magnaflow and the part number for the best prices. You'll need two 2" o-ring exhaust gaskets - the ones from the dealer, if they are the Toyota ones, are better quality (of course).
    
17. Run a Seafoam and/or water treatment to clear some of the carbon off the piston heads and valves. http://www.toyotanation.com/forum/sh...70#post2946870 If you use Seafoam, do it before changing plugs, O2 sensor or cat.
    
18. Check that both engine & chassis have good grounds to neg batt post and E1 term of ecu has good ground to chassis and E01/E02 terms have good ground to engine.
    
19. Check fuel pressure and volume. I think the necessary fitting is a M8*1.0 banjo bolt. See this thread: https://www.yotatech.com/forums/f116.../#post51210586 Also these articles may help: http://www.aa1car.com/library/fuel_pump_diagnose.htm . http://www.import-car.com/Article/39...me_checks.aspx
    
20. If hesitation only occurs when traveling and never when stopped, could be bad speed sensor (only with the cable-type speedometers). On older 4runners/pickups the vehicle speed sensor (vss) is a mechanical reed switch in the speedo, and when it gets worn, the signal can get noisy, which is interpreted by the ecu as excessive speed and so it activates the governor (fuel cut) feature. Here's a tech article on the issue: http://www.motor.com/article.asp?article_ID=271 And some info on identifying the vss wire: http://www.the12volt.com/installbay/...TID~98493~PN~1

yotalaz

wow! give me a bit to take it all in.

yotalaz

ok it runs good when its cold then the power drops off a bit. with the ac on its worse. i was gettting a code for the o2 sensor but i replaced it a couple of months ago. i reset the code but after about 60 sec the code would reappear, ever since then i gave up. this 3vze has no cat. i havnt dont most of the stuff on this list. that would keep me busy for a good weekend checking all that stuff. i have a compression tester but no timing light. ill have to go and get the denso o2 sensor. just to be sure i know its not a bosh but its some other brand. ive done many seafoam treatments.

sb5walker

Which O2 sensor code are you getting? There are a few different ones indicating different problems. Also, check the appearances of the plugs - that will tell you how it's running, mixture-wise.

thook

Sorry, guy, I don't see how Bosch has anything do with the O2 sensor function. I know I've read where others had issues, but I've had one on my '92 3vze for a long time without issue. So, that's debatable.........though I'm not going to debate it.
Also, I don't see how the motor running differently when hot than cold necessarily means the ECT is probably working fine. IOW, it can and will dramatically affect performance if it's not sending a proper (lower) voltage signal to the ECU and is most defenitely noticed once the motor has reached operating temps.

yotalaz......Even though a CEL is showing an O2 code, it doesn't necessarily point to the sensor itself. It could be doing it's job just fine. Given that it's new, it probably is. But, like sb5walker said, which O2 code your CEL is throwing will tell a lot. The ECU does have to have an O2 signal. There's a way to check to see if you're in closed loop mode once the motor's is warm. You have to check the voltage at the diagnostic port.

http://www.autoshop101.com/

Look in technical articles: Article 27 Engine Controls #4 - Diagnosis.pdf

sb5walker

Anything is debatable. I don't doubt your report of your experience, but there are many examples of people having persistent code 21 with the Bosch sensors, which can mean either bad O2 sensor heater OR, reading doesn't change for 60 seconds or more for two consecutive trips. This last appears to be the case with the Bosch sensors. Normally, the computer adjusts mixture back and forth between slightly rich and slightly lean, and expects the O2 sensor to reflect the changes - it's called "switching" and when the sensor is working properly it's at about once a second between above .45 V and below .45 V. When a sensor gets fouled with carbon, its switching rate slows down (called a "lazy" sensor) and the ecu throws a code 21. Apparently, since the Bosch sensors are so much shorter than the OEM Denso, and the sensor flange stands the sensor up and away from the pipe by a quarter inch or so, the short Bosch gets much less exhaust flow past the tip and does not switch as quickly. There are many reports of mixture/code problems with Bosch sensors that were solved by replacing with Denso:

https://www.yotatech.com/forums/f116...l#post50849557
https://www.yotatech.com/forums/f116.../#post51072210
https://www.yotatech.com/forums/f116.../#post51248025
https://www.yotatech.com/forums/f116...06/#post936034
https://www.yotatech.com/forums/f116...l#post50779151
https://www.yotatech.com/forums/f116.../#post50898016
https://www.yotatech.com/forums/f116...r-woes-164595/
https://www.yotatech.com/forums/f116.../#post50896986
https://www.yotatech.com/forums/f116.../#post50707951
https://www.yotatech.com/forums/f116...-calif-222662/

So, again, I don't doubt your word that the Bosch is working for you, but I think in the spirit of trying to help the folks who will search and find this thread, it's good to report this fairly substantial body of experience with that type sensor.

You're definitely right that an O2 sensor code does not necessarily mean bad O2 sensor - many other conditions that cause the motor to run too rich or too lean will cause the rich or lean codes, so yotalaz, it will help to know what code(s) you're getting.

As far as the engine running differently not being sufficient evidence to validate ECT performance, that's true. I should have said if the change in running happens exactly when the motor reaches op temp and the cold idle bypass valve shuts, bringing idle down, then probably the ECT is correctly reporting op temp to the computer, which then switches to closed loop mode where a faulty O2 sensor can introduce poor running. But a direct test of the resistance of the ECT (or voltage at the ECT terminal of the ecu) will be the definitive test.

thook

Well, I know how the O2 works, and with the 22re the sensor flange is an issue. I've posted about it myself in atleast several threads (the first link you provided), and I have a Denso unit on my 22re for that very reason.(An NGK unit is identicle to Denso, btw.) But, the flange is not an issue with the 3vze. Plus, the whole idea that the sensor being too short is kind of a shabby theory, in my opinion.....flange issue aside. The probe can be shorter...and is, just not much....but, the exhaust system is pressurized. The sensor is going to get enough exhaust to read it.... provided it will seal correctly on the manifold, of course. If it won't seal right, it will be drawing oxygen from outside the system which throws everything off. So, no Bosch for the 22re, but okay for 3vze. I'm in line with the spirit trying to help, for sure. But, you've probably been around long enough to know that even on YT there's enough erroneous, half baked troubleshooting theories to leave room for further clarification. I'm guilty of it myself even though my intentions were/are honest. Hell........I've deliberately gone back to older threads/posts of mine to make corrections when I learned I was wrong.......in the spirit trying to help knowing the info will be found on a search.

Anyway........hehe

Surely you realize the operation of the cold idle air valve is independent of ECT and ECU relationship and functions? IOW, just because the idle drops doesn't mean the ECT is correctly reporting to the ECU. And, certainly under driving conditions, idle air valve functioning or not functioning is moot regardless of engine temp. As well, and lastly, a static test for the ECT is not definitive. Certainly you can test for resistance under cold conditions and at operating temp. But, if it passes those tests it can still fail under change. IOW, you have to watch the meter as the temp is changing. Of course, the only way to do that is in a pot of water. The motor won't run without the ECT plugged in.

sb5walker

Yes, I do surely realize there's no electrical or functional connection between the AAV & ECT-ECU-Closed Loop systems. It's the timing of events that connects them. When the coolant gets hot enough to close the AAV, it is probably hot enough to trigger an operating temp reading from the ECT. Not at the precise moment, but close enough.

Yes, by all means you have to test the ECT when hot as well as cold. You can do this without the pot of water by back-probing the THW & E2 terminals of the ecu with ignition on. When at op temp, the voltage should be between .2 and 1 volt. When cold, there should be less voltage. See page EG2-185: http://personal.utulsa.edu/~nathan-b...86troubles.pdf If someone doesn't have backprobe adapters for their multimeter, they can push needles into the connectors and hold the test leads firmly against them.

The advantage of testing at the ecu (aside from the convenience of not needing to remove the sensor) is that you also are verifying that you have good wiring between the ecu & sensor. If the voltage isn't up to spec, then you would want to remove the sensor to check its resistance (probably it will be bad and will need to come out anyway - but if not bad, then you know to check wiring).

thook

Yeah, you're correct, there. Many ways to test something sometimes. I was just giving one example specifically for ohm testing. I've already read about the method you've posted on autoshop101.com. Do you know about that site? If not, I think you'd like it.

Also, I have to apologize. I suppose it depends on who you talk you and timing of events as what to what you're told and what you think you've learned, but I'm dead wrong on all counts with regards to Bosch vs. Denso O2 sensors. For any Toyota design, as I'm told, all Bosch sensors are poorly designed (too stinkin' short) to correctly integrate with Toyota systems..... 3vze included. The sealing is not an issue with the 3vze, though. I can atleast say that.

I spoke with a service tech at the local dealership just a little bit ago. Apparently there's an "informal" service bulletin about it, and technicians are advised to replace Bosch units if they are present in the vehicle. Dang. The good news is, though, I think this is going to improve my mileage and power more than what is present. I'd been blaming it on bad gas and tire size. 31's.

thook

I did some reading today and last night. I think I finally understand what you're trying to say. If the system has gone into closed loop mode, chances are great that the ECT is working properly? But, doesn't the ECU still rely on a constant low voltage signal from the ECT when the motor has reached temp and/or in closed loop mode? And, if the voltage signal is not low enough, then it will cause poor operating conditions?

I'm sorry to hijack this thread. But, I'm having to review some things I studied a while back and now realize I've remembering wrongly and getting some things mixed up. Maybe you and I, sb5walker, can exchange in some other way? I have access to technical materials, but no one to really bounce things off of on such a technical level as this. Only if you care to, though. Otherwise, I'll make do on my own.....no problem.

thook

Okay, now I remember why I'd come to the conclusion the O2 being Bosch wasn't really an issue.......or the length of the probe, for that matter. I went back read some old threads I'd posted in while I was in the midst troubleshooting my own issues and doing some homework. I'll find the thread and post the link in a minute, but one fellow ran Bosch sensors in his 22re without issue passing CA smog tests for 4 years without his. His opinion about delayed response issues was the length of the wiring used in the system. More wire = more resistance. So, his suggestion was to keep the length of the wire as short as possible........enough to allow for movement.

Okay, maybe I'm debating now. But, for a little while I'd been down on myself for being a bit dunce. So, now I'm just supplying info for contrast. I'm still not sure what's correct, but certainly a meter and volt readings would say for sure Bosch or not. That and/or smog tests........which we don't have here in AR.

sb5walker

PM sent.

thook

Got it. Thanks. I'll be replying soon enough.

Okay........soooooooo, I called up the local dealership to speak to the head technician himself about this Bosch vs Denso thing. Turns out he had a T-100 in the shop not a week ago that the assigned tech couldn't figure out what was wrong. The head tech, Donnie, took one look under the chassis and saw a brand new Bosch sensor pre cat. He unplugged it and viola!!! the truck would run just fine. Sooooo, I decided I'd unplug mine on the '92 once the vehicle reached operating temp and went into closed loop. Definite improvement. Of course, the CEL came on, but the engine idled smoother, she had noticeably more power, and accelerated more smoothly and easily. In conclusion, I didn't believe it was a problem (and, it may not be for everyone given what I said before about the fellow without issue......for over 20k miles now. I just spoke with him last night over the phone), but it is. So, I'm getting a new Denso ASAP.

sb5walker

Takes a man with integrity to make the kinds of posts you've been making - you don't see too many of them on forums. Props to you.

For Denso direct-fit O2 sensors, sparkplugs.com and a related site densoproducts.com have good prices, but their shipping can sometimes be a bit much. If you get the Denso part # from those sites & search for denso and the part number on amazon you can sometimes find a better price or the same price with free shipping. I see at the moment they're very close.

thook

Lol.......yeah, I found a post of yours (rather my wife did) over on Toyotanation for the amazon deal. That's where we're looking at the moment.

Thanks for the props. I'm not sure what you mean by the "kind of posts I'm making"....haha. But, if I were to guess, I'm making admissions when I'm wrong. Ego, schmego.....there's a purpose for having one, but it shouldn't get in the way of be willing to expand a little on one's self.....though, I know it can be challenging. Don't know anyone that doesn't have one.

mojo4x420

sorry, I don't understand what unplugging the o2 sensor tells you... If you unplug it doesn't the ECU realize it's gone and goes into open loop mode, so it doesn't use any of the sensors and just uses it's basic fuel mappings... I thought all this told you is that some sensor is not functioning, not which one.