A Super-Ultimate 3FE Diagnostics Thread - Let the Battle of Wits Begin (3 Viewers)

[lelandEOD]

you do not mess with any screws when checking timing.

I read it was a technique to get the idle at the correct rpm without having a helper. I can't easily hold the timing light, rotate the distributor and hold the throttle. If this is a bad idea, let me know and I'll recruit the wife.

and you really should do the ecu voltage and continuity tests...you'd be amazed at what kind of resistance builds up at connector terminals...

I've run through the ECU voltage test on page FI-29 and reported the results on the first page of this thread. I found that the coolant temp sensor (THW-E2 was slightly out of range and I also got an under-volt and over-volt reading on the VS-E22 terminals from AFM to the ECU.

just adjust the tps you have on there correctly. stop. test. re-evaluate. go back and readjust till it's dead on, or move on to the next issue. systemically rule out possibilities. right now it seems that we are simply enumerating them.

tps is far more responsible for overall performance than anyone gives credit for. and much more difficult to adjust than I can imagine, apparently.
afm is a fickle beast that should require NO MUCKING with by any one.
ISC controls air flow for idle functions.
distributor returns an engine position and speed value to the ecu.
O2 sensors return exhaust tract A/F values to the ECU> their position in relation to the head is important
ECU sends voltage pulses to injector banks front and rear and controls pulse width of fuel burst (3 cylinders each bank, simultaneously)
none of these thing can talk right if there is any issues with the wiring.

the ECU voltage test will reveal any issues with the wiring. Testing the ECU will ensure you that your head is on straight.
testing the O2 sensors should prove that they recognize the changes in A/F levels in the exhaust, AAAND that those values are reaching their destination, because you have proven the harness and ECU already.
Distributor needs next to nothing other than to be installed correctly, and on time. you verified its info is being delivered and you can check it off the list. ( you might need to hook the EGR in if you are unable to eliminate this issue with any other avenues of investigation, but I never noticed untold behavior when I had my egr system disabled.)
ICS is prolly not a contributor, but if it is not functioning properly, you might get extra air during running, or less than normal air during idle
make sure there are NO places for air to get in. even the VC gasket, oil cap, dipstick, galley gasket... ANY UNMETERED air will put this donkey into the dirt.
AFM- just use one that has not been played with. use one that has a good seal, no extra holes, and bench tests good per FSM.
(there is the tiniest possibility that you might need to make a SMALL adjustment to an AFM but if and ONLY if you are able to prove that the A/F IS OFF TRACK. most people who mess with them have not ruled out all the usual suspects before ****ing up a perfectly good instrument, and find it was not their issue, only to have to source a new instrument.
tps...well, this bugger is pretty much the HMFWIC in the EFI department. and he's very specific about his position in life. if you put him off his throne just a red hair, he'll never let you forget that he warned you not to...


at the end of the day, I think you're reading too much into the equation. You've got added steps in your diagnostic process that aren't called for in the book. you think you have an understanding of the players in the band but there are a few places where translation has been lost. I can totally understand- as you have spent prolly spent weeks of minutes trying to get you investment to give you a reach around without any joy. it makes a man grasp for things he can understand, and shy from things he cannot.

step back.
breath
remember it is just metal, rubber, and plastic
go back to the beginning of the troubleshooting guide, and systemically check things off the list in the order of appearance. do not go down the chain till you have spent the link you're on. this system is dead simple. Toyota has already done all the research. just don't color outside of those lines.

your intake duct appears to be longer than stock. I wonder if the metal duct is also contributing to adding heat to the A/F charge. I wonder if the length and bends have created too mush static resistance to airflow.
your O2 sensors are too close to the dump. that could be affecting the type of signal the sensors read
you need more drive time with the tps to get it dialed in...people say adjust it... I say calibrate it.
you MUST check the harness for cracks, melting, poor connections.
you may need to add the EGR back to rule it out as a contributor. Yes, I said so you can rule it out...

Good post.

I'm going to focus on the TPS adjustment until I am absolutely certain it can be eliminated from the suspect list. I'll be doing that today, assuming it gets warm enough in the garage!

Thanks everyone!

 

[mwebfj60]

The only manual I have is the 3FE Engine Supplement. If there is another, please let me know.

I have the 88 Repair Manual, has the same checks you’re finding in the supplement.

 

[Kleatus]

Just throwing this variable into the heap—

The 3F-E (or any fuel injected engine) is dependent on its O2 sensors to tell it what to do about the air fuel ratio. Normally there is an air pump (smog pump) pumping extra air into the exhaust and the ECU accounts for this extra oxygen.
If the air pump is removed, the exhaust will have less (zero) oxygen in it (as can clearly be seen in any smog test report) & the O2 sensors will report this back to the ECU. The ECU without a smog pump is being told that the engine is running too rich (although it's not) so it will lean out the mixture too far.

I could be understanding this incorrectly, but I can't see how a fuel injected engine can run properly without the smog pump functioning.

Just wondering

If the air pump ran all the time yes, that line of thinking would be spot on.

As the 88 New Features manual explains things however the air injection is only operational under certain conditions- fuel cut off (deceleration) and warm up. During these conditions the ECU isn’t relying on the 02 sensors for feedback because it’s running in open loop. This is also mentioned in the section about air-fuel feedback under the conditions when the engine is running in open loop (when AI is on and temp is over 104F).

So the air pump doesn’t influence A/F ratios via the 02 sensors, assuming it’s working properly.

The air pump is strictly for emissions. The catylytic converters back then weren’t as good as they are now, and required supplemental oxygen to keep emissions in check under certain conditions, hence the air pump. Many cars of the era had nipples right off the cat itself that air was injected into. You don’t see this anymore.

 

[60Works]

This thread is loaded with good information. Thank you all.

Is there a component in the system that comes on at 1800 rpm and shuts off at 2500?

Perhaps something emissions related that is triggered to only run when the engine is relaxed in the mid range but turns off if you're excellerating hard above 2500?

 

[cruiser88]

Are u getting a code 51? I know the temp sensor plug on a 62 needs checked often. On a 62 its not usually any one thing but several little issues.

 

[lelandEOD]

Are u getting a code 51? I know the temp sensor plug on a 62 needs checked often. On a 62 its not usually any one thing but several little issues.

The ECU is not throwing any codes. That's a big part of the frustration as it leaves me guessing...

 

[Kleatus]

Following along and throwing things out here because I have gotten tons of great info from here that has helped me be able to DD my 62 for the last several years- I’ve been through some frustrating issues myself and have had to dig into and figure out quite a few issues over that time..

When I had a bout of weird issues with mine once, it ended up being the part of the harness that ran next to the air rail. It was cooked brittle and insulation had cracked off and I had coolant temp sensor and injector wires exposed inside the harness. I have had similar wires in the past “pass” checks with a meter and still give issues.

Hows your harness..? Maybe hone in on those wires to sensors that were out of range in your previous tests?

 

[LAMBCRUSHER]

Coolant temp sensor.

Are u getting a code 51? I know the temp sensor plug on a 62 needs checked often. On a 62 its not usually any one thing but several little issues.

 

[LAMBCRUSHER]

Do you have access to a known good ecu?

 

[LAMBCRUSHER]

i mean to rule out a code not being delivered... really outside chance. And my line of thinking is why I know how frustrating this must be. I’m thinking if there were a code that for some reason wasn’t being sent when it should be- worst case quirk of bunk ecu- it would be nice to stick a goodun in there and verify that it wasn’t sending any codes under similar fault manifestation. Just to have a baseline sanity check. But don’t let this suggestion distract you from step by stepping it. Just maybe put it somewhere on the list if you need to...

 

[lelandEOD]

I have a spare and will throw it in there this evening. Thanks for the suggestion.

 

[lelandEOD]

Following along and throwing things out here because I have gotten tons of great info from here that has helped me be able to DD my 62 for the last several years- I’ve been through some frustrating issues myself and have had to dig into and figure out quite a few issues over that time..

When I had a bout of weird issues with mine once, it ended up being the part of the harness that ran next to the air rail. It was cooked brittle and insulation had cracked off and I had coolant temp sensor and injector wires exposed inside the harness. I have had similar wires in the past “pass” checks with a meter and still give issues. View attachment 1638964

Hows your harness..? Maybe hone in on those wires to sensors that were out of range in your previous tests?

I had this exact same problem two years ago when I discovered that one of my O2 sensor leads had melted together and shorted out.

The harness on the truck now is freshly inspected and wrapped so I don't think this is the culprit in my case. I just had it out last week when @jonheld was helping me diagnose a broken circuit in between the AFM and ECU. Excellent food for thought for others though!

 

[lelandEOD]

Also, I think I can answer at least one of the reasons why there are different part numbers for the '88 TPS and the '89-'92 TPS:

 

[lelandEOD]

Another quick video with some Toyota TPS Adjustment Life-Hacks!

 

[lelandEOD]

Ok, I swapped the ECU tonight to make sure one wasn't failing to disclose an error code; no change to the air/fuel ratio - no codes displayed.

I also swapped out the flippin' brand new fuel pressure regulator for a spare used one I had on hand. My fuel pressure at (warm) idle went from 33psi to 40psi and it now retains pressure after shutdown, unlike the brand new one. No change to the air/fuel ratio.

I also spent a significant amount of time adjusting that throttle position sensor. I am very confident that it is now within the specs listed in the FSM. No change in the air/fuel ratio.

The engine runs very smooth at high idle during the cold start sequence. I can literally hear the lean-miss begin to emerge as a subtle sputter/pop from the exhaust pipe as soon as the coolant hits 170° and the idle begins to drop.

There are still several FSM diagnostic tests that I need to accomplish and there are still discrepancies from completed voltage tests that must be unraveled.

I've also ordered a set of new O2 sensor bungs so I can relocate the sensors further down the exhaust stream.

 

[pandasfj]

just a thought but after you relocate the o2 bungs try swapping the o2 sensors, might have them crossed?

 

[Kleatus]

So, it might be running OK prior to switching over to closed loop? What happens with the O2 sensors unplugged entirely? Running condition and AFR?

Did you ever try pinching the return and seeing if the computer/02 sensors are picking up on and reacting to that, and how much reaction can you get?

 

[IBFJ62]

From experience, the 02 sensors do seem to be exhaust-side specific. Why, no idea. But when they got switched by the exhaust shop, the truck ran like s***, hesitating and no power. Also, the AFM. A new reman. might be in order.

 

[FJ40Jim]

Why move the O2 sensors? They like to be close to the engine.

As mentioned above, having the O2 sensors mixed up will cause bad running.

Maybe the ECT sensor is out of range? The mixture leans out as temp increases. If ECU thinks ECT is 300*F, then mixture will be very lean.

 

[lelandEOD]

Why move the O2 sensors? They like to be close to the engine.

As mentioned above, having the O2 sensors mixed up will cause bad running.

Maybe the ECT sensor is out of range? The mixture leans out as temp increases. If ECU thinks ECT is 300*F, then mixture will be very lean.

That's an interesting idea, Jim. When I ran through the battery of ECU voltage tests, I believe the coolant temp sensor gave me a voltage reading that was indeed out of range. I read 1.59v on ECU between terminals THW -E2 with the coolant temp @ 176°. The FSM said I was only supposed to get .1-1v. I am constantly getting the coolant switch and coolant sensor confused with regard to their function. I thought the THW was just got tell the ECU to go into closed loop at a sufficiently warm temp so I didn't think the 1.59v reading being off was too big a deal. But, that's the coolant temp switch, right?

Sure sounds like I need to conduct the water temp sensor resistance test found on FI-73...