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

[lelandEOD]

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

I checked for this very thing over the summer when I had the harness on the ground. I'll make sure to double check for continuity at the check connector, but I don't think I have them reversed. I appreciate the reply though!

 

[lelandEOD]

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?

I'll try it and report what happens when I pinch the return line. I will say that I've noticed that it seems that the ECU does adjust the mixture whenever I try to meddle with it. For example, last night I installed one of the spare AFMs I had laying around (the one that someone drilled out the mixture adjustment seal) and I decided to play with it for s&gs. I could see the AFR going lean momentarily when I turned the screw counterclockwise and richer as i turned it clockwise. But, after about 4-5 seconds, it appeared that the ECU readjusted the mixture. No matter how much I turned the mixture screw, the AFR meter would momentarily swing lean or rich, then slowly return to the same 15.9:1 -16.3:1 range I've been trying to solve.

 

[LAMBCRUSHER]

have you had the AF meter calibrated?

 

[WILLD420]

If the ecu is adjusting mixture when it's supposed to be in open loop, like at idle? you have a problem with something telling the ecu it's needing to be in closed loop mode .

 

[White Stripe]

I'll try it and report what happens when I pinch the return line. I will say that I've noticed that it seems that the ECU does adjust the mixture whenever I try to meddle with it. For example, last night I installed one of the spare AFMs I had laying around (the one that someone drilled out the mixture adjustment seal) and I decided to play with it for s&gs. I could see the AFR going lean momentarily when I turned the screw counterclockwise and richer as i turned it clockwise. But, after about 4-5 seconds, it appeared that the ECU readjusted the mixture. No matter how much I turned the mixture screw, the AFR meter would momentarily swing lean or rich, then slowly return to the same 15.9:1 -16.3:1 range I've been trying to solve.

The afm only is used for mementary fuel adjustments or for open loop fuel when the engine is cold and the o2 hasn't warmed up yet. The o2 has the final say when its warm what the afr is. If your getting 16:1 afr then I would suspect the o2 sensor is the issue.

 

[Kleatus]

I'll try it and report what happens when I pinch the return line. I will say that I've noticed that it seems that the ECU does adjust the mixture whenever I try to meddle with it. For example, last night I installed one of the spare AFMs I had laying around (the one that someone drilled out the mixture adjustment seal) and I decided to play with it for s&gs. I could see the AFR going lean momentarily when I turned the screw counterclockwise and richer as i turned it clockwise. But, after about 4-5 seconds, it appeared that the ECU readjusted the mixture. No matter how much I turned the mixture screw, the AFR meter would momentarily swing lean or rich, then slowly return to the same 15.9:1 -16.3:1 range I've been trying to solve.

Your findings tinkering with the AFR mirror mine in that the 02 sensors will balance out any “adjustments” made.

It sounds like you might be down to coolant temp or the 02 sensors themselves. You mentioned you could hear it go into lean miss when it hit 170 degrees..? That is awfully warm, warm up enrichment should cease at 122 degrees - not too sure when it is supposed to switch to closed loop but I think it’s well before 170. That (as well as the questionable test voltage) would point to a temp sensor issue.

 

[Prairie Swamp]

Also - I think I read it mentioned that the location of the O2 sensors was not critical. I have to disagree with this. A college buddy interned in GM's emissions lab around the time this truck was built. They spent a lot of time determining the optimum distance from the exhaust manifold to O2 sensors. They want them up and functioning fast for emissions reasons so too far away is no good - but there is also a reason why they are not right at the manifold/header on every vehicle produced.

May be playing a factor here may not. But the custom exhaust and the closeness of the sensors to the manifold is a deviation from design intent.

 

[lelandEOD]

There are some awesome suggestions in this thread. I can't tell you all how much I appreciate everyone's help. You guys have probably saved me from lighting this truck on fire a couple times over now. I clearly don't understand as much about EFI as I'd like.

Your findings tinkering with the AFR mirror mine in that the 02 sensors will balance out any “adjustments” made.

It sounds like you might be down to coolant temp or the 02 sensors themselves. You mentioned you could hear it go into lean miss when it hit 170 degrees..? That is awfully warm, warm up enrichment should cease at 122 degrees - not too sure when it is supposed to switch to closed loop but I think it’s well before 170. That (as well as the questionable test voltage) would point to a temp sensor issue.

I think you might be on to something. I'm going to scientifically study the warmup cycle and report my findings here but I'm pretty sure I can hear two distinct drops in idle from a cold start up to fully warm at 199°. The first drop in idle is at about 130° as the idle drops from 1100rpm to about 850rpm. It's the second drop when the idle drops again from ~850rpm to 650rpm (at about 170°) that I can begin to hear the popping and sputtering emerge. The miss may be there before the idle drops to 650rpm but that's when it is pretty easy to hear.

I did inspect the temperature sensor last night. I checked the resistance between the terminals on the sensor and got 1.85k ohms. My IR thermometer said the sensor/aluminum thermostat housing was just under 73°F. Using the chart on page FI-73 it would appear the coolant temp sensor is operating correctly:

I'm going to re-check the coolant temp sensor resistance readings at dead-cold (overnight) and at operating temps to see if the values are also correct.

I also double checked continuity between the coolant sensor and the ECU. I got .02 ohms on E2 from the harness connector to ECU and .5 ohms from THW from the harness connector to the ECU. I'm not sure why the THW lead is different than the E2 lead as they are the same gauge and length wire or if this is even significant? The FSM doesn't tell me what to do if the voltage reading from the coolant temp sensor is out of range (1.59v @ 176°) but the resistance check of the sensor appears to check out.

 

[lelandEOD]

have you had the AF meter calibrated?

No, other than conducting the voltage and resistance checks in the FSM. I need to figure out why I am under the specified voltage on VS - E22 at the ECU (plate closed). I got 3.96v and was supposed to get 4-6v. Also on VS - E2 at the ECU (with the measuring plate fully open) I got .48v and was supposed to get .02-.08v. When I conducted the AFM resistance checks (page FI-62 and FI-63) the AFM checked out ok. So, I'm at a loss.

 

[Kleatus]

There are some awesome suggestions in this thread. I can't tell you all how much I appreciate everyone's help. You guys have probably saved me from lighting this truck on fire a couple times over now. I clearly don't understand as much about EFI as I'd like.



I think you might be on to something. I'm going to scientifically study the warmup cycle and report my findings here but I'm pretty sure I can hear two distinct drops in idle from a cold start up to fully warm at 199°. The first drop in idle is at about 130° as the idle drops from 1100rpm to about 850rpm. It's the second drop when the idle drops again from ~850rpm to 650rpm (at about 170°) that I can begin to hear the popping and sputtering emerge. The miss may be there before the idle drops to 650rpm but that's when it is pretty easy to hear.

I did inspect the temperature sensor last night. I checked the resistance between the terminals on the sensor and got 1.85k ohms. My IR thermometer said the sensor/aluminum thermostat housing was just under 73°F. Using the chart on page FI-73 it would appear the coolant temp sensor is operating correctly:

View attachment 1640143


I'm going to re-check the coolant temp sensor resistance readings at dead-cold (overnight) and at operating temps to see if the values are also correct.

I also double checked continuity between the coolant sensor and the ECU. I got .02 ohms on E2 from the harness connector to ECU and .5 ohms from THW from the harness connector to the ECU. I'm not sure why the THW lead is different than the E2 lead as they are the same gauge and length wire or if this is even significant? The FSM doesn't tell me what to do if the voltage reading from the coolant temp sensor is out of range (1.59v @ 176°) but the resistance check of the sensor appears to check out.

It might be jumping the gun to say the sensor checks out when only considering one data point on its operating curve. I’d suggest checking the resistance while its hot as well. If the resistance is out of range when gets hot, that will result in an incorrect voltage reading by the ECU which you seem to be seeing already.

 

[lelandEOD]

It might be jumping the gun to say the sensor checks out when only considering one data point on its operating curve. I’d suggest checking the resistance while its hot as well. If the resistance is out of range when gets hot, that will result in an incorrect voltage reading by the ECU which you seem to be seeing already.

Agreed. I'm going to re-check it stone-cold and at operating temp too.

 

[White Stripe]

Did someone say you have a custom exhaust and your o2 sensor is not in the factory location? How many wire o2 sensor does the 3fe have? Just one or more than 1?

 

[lelandEOD]

Did someone say you have a custom exhaust and your o2 sensor is not in the factory location? How many wire o2 sensor does the 3fe have? Just one or more than 1?

Yes, they are apparently much closer to the cast manifolds than the original FJ62 O2s. They are 4-wire heated O2s as well.

 

[White Stripe]

Yes, they are apparently much closer to the cast manifolds than the original FJ62 O2s. They are 4-wire heated O2s as well.

oh okay you should be fine then

 

[89BIGBLUE]

My coolant temp sensor tested ok, but I was still unsure, and always looking at it out of the corner of my eye. At temp, the truck seemed to run well. Cold starting was tricky. I replaced it, and it’s been great ever since. I think it’s worth putting a new one in, to rule it out.

 

[lelandEOD]

My coolant temp sensor tested ok, but I was still unsure, and always looking at it out of the corner of my eye. At temp, the truck seemed to run well. Cold starting was tricky. I replaced it, and it’s been great ever since. I think it’s worth putting a new one in, to rule it out.

You have no idea how much I'd love it to be something simple like the coolant temp sensor.

Unfortunately, I've now checked it for resistance at 40°F (4.5k ohms), 68°F (1.85k ohms), and 198° (245 ohms). All three values appear to fall within the curve specified in the FSM:

 

[lelandEOD]

I also recorded some pertinent data on the warm-up cycle from cold to operating temp.




Cold water temp: 40°F

Water Temperature Sensor resistance value: 4.5k ohms

Started engine: Vroom.

RPM: ~1090rpm initially, gradually slowing to ~990rpm over 2-3 minutes

Initial A/F: 8.3:1 - Slowly climbed to 9.3:1; then 10.3:1 during this period

Fuel pressure: remained constant at 40 psi

*No noticeable popping or sputtering from the exhaust




...After about 4-5 minutes of run time:

First RPM drop heard: 820rpm

Water temp: 101-110°

A/F: jumped immediately as the water temp came up. fluctuated between 14.9:1 to 15.9:1 - the AFR leaning out coincided with the audible idle drop - (going from closed loop to open loop?)

*No discernible popping/sputtering heard yet




After another few minutes of running:

Second RPM drop heard: 690-660rpm

Water temp: @167°F

A/F: same as above

Fuel pressure: 38.2 psi

*Popping/stumbling is heard at the tailpipe




Fully warm (dash temp gauge read 198°F; IR thermometer pointed at thermo housing said 170°F)

RPM: 650 rpm

Fuel pressure: 38.0 psi

A/F: same as above

*Popping/sputtering is heard at the tailpipe

Shut it down and checked the water temperature sensor resistance: 250 ohms (within value for temp)




I also made a short video that shows the exhaust sound from the first idle drop to the second idle drop where you can begin to really hear the miss. I also filmed the gauge cluster that depicts the AFR to show how it fluctuates from ~14.9:1 to ~16:1.

 

[Kleatus]

What about the 02 sensor voltages, at the diagnostic connector? Wonder if we can learn/compare anything there?

I’m skeptical of 15.9 being lean enough to induce a miss on its own without some other factors playing in.

 

[mwebfj60]

How about the air cleaner and AFM being mounted on the exhaust side...after it is warmed up and the idle drops down is the THA-E2 voltage at the ECU still within 1-3V? Just thinking maybe the intake air temp/ overall AFM temp might be higher than it should causing a variation in the AFM temp/resistance.

 

[4Cruisers]

Checked the oxygen sensor cross-reference (on just one website so far). The Denso part number for Toyota part number 89465-69015 is 234-4056.

UPDATE: Another website shows the Denso 234-4051 as equivalent to 234-4056.