Tonyrodz's Tahoe Build Thread

[Snowbound]

I'll give it a shot. Afaik there's only 1 coolant temp sensor which is located on the ds head. How can you tell if it's open or closed loop? Will it say it?

Yes, the Tech2 will list loop status. And also look at the coolant temp and see what it says and if it’s close to where the gauge says temp is.

 

[Tonyrodz]

Is there 2? One for gauge and one for ECM? See if it’s showing a reading with the scanner. The STFTs should be constantly adjusting based off pre-cat O2 sensors. Scan the O2 readings and coolant temp. Also see what the status says if it’s in closed loop or open.

This is idling around 2000 rpms, closed loop. Warmed up.

 

[Tonyrodz]

O2 sensors--

Whatever this is--Inactive.

 

[Tonyrodz]

Fuel trims at idle, which is low--high 400's.

 

[Tonyrodz]

Just numbers instead of the graph. Like "Cyl 1 = 35" "Cyl 2 = 13" etc. There seems to be an issue with higher misfires on cyl 1.

Rare that the instantaneous STFTs would be steady at 0; are your upstream O2 sensors working? Do you see a change in the STFTs?

If they continue at 0 then the LTFTs should eventually come down closer to that. LTFTs are an average of the STFT over a longer period of time. Seeing your LTFTs over +10% means that the ECM has been adding fuel for a while to compensate for a lean condition. Generally you want the sum of the ST and LT fuel trims to add up to something lower than 10%.

So if your STFT Bank 1 is 2%, and the LTFT for the same bank is 6%, 6+2= 8% which is generally acceptable.
Same issue if the sum of the same bank trims is negative. Goal is between -10% and +10%, but closer to 0 is best.

Seeing the trims at the higher rpm could help determine if there is a vacuum leak or something else.

EDIT: bump your idle up to 600 rpm or so for the low reading. That's a really low idle you have there.

This is the history--

Coolant temp sensor seems to read in the range--gauge and tech2.

 

[Tonyrodz]

At around 600 rpms.

I'm sorry I'm all over the place, I'm still trying to figure this tech 2 out and I'm posting the info as I find it.

 

[Tonyrodz]

Now it's not doing anything! WTF!

That was around 600 rpms.
This one is at idle, under 500 rpms. It just keeps going--misfiring.

 

[Fless]

Let's just ignore the history misfires. You likely had a problem at one point but it sure doesn't show up in the current misfires, at least at 618 rpm, for this ignition cycle.

Do you know why your idle is so low?

 

[Tonyrodz]

Let's just ignore the history misfires. You likely had a problem at one point but it sure doesn't show up in the current misfires, at least at 618 rpm, for this ignition cycle.

Do you know why your idle is so low?

I sure don't. It started about 2 1/2 yrs ago. I've had a random misfire since I bought it 4 yrs ago. I can't afford to take it to anyone so I'm hoping I could get some good advice. My check engine light has been on steady. Weird that it's not misfiring at 600 rpms. This van is a POS!

 

[Fless]

I sure don't. It started about 2 1/2 yrs ago. I've had a random misfire since I bought it 4 yrs ago. I can't afford to take it to anyone so I'm hoping I could get some good advice. My check engine light has been on steady. Weird that it's not misfiring at 600 rpms. This vzn is a POS!

Next time you have the Tech 2 on it see if the desired RPM is close to the actual RPM.

 

[Snowbound]

Seems like the CTS is ok and it’s going into closed loop as long as you didn’t command it. Future reference, nobody cares about heater numbers on O2 sensors. That is just for getting sensors up to temp faster for emissions garbage and nobody cares about emissions. Not being a smart ass, just letting you know don’t worry about heater circuit. All we care about is MV numbers but a screen shot isn’t gonna tell us if they are going rich to lean. 100’s to 700’s 800’s even. It should be swinging low to high.
injector pulse width at 2.43 ms is standard base number in the tune. When I see 2.43 ms that tells me fuel is not adjusting. That is right in line with STFT being at 0. I’m wondering if this is just at idle. If desired idle is 680 and your idling under that, it could be just running on a preset table like it’s in open loop. If your idle issue was due to stepper motor on throttle body, I would think it would also have a flat spot or stumble off idle. In think I would start simple and remove throttle body and clean the shit out of it. Put it back on and do a relearn.

 

[pwtr02ss]

Good stuff @Fless and @Snowbound

hell, I'm learning something. Thanks dudes

 

[Tonyrodz]

Seems like the CTS is ok and it’s going into closed loop as long as you didn’t command it. Future reference, nobody cares about heater numbers on O2 sensors. That is just for getting sensors up to temp faster for emissions garbage and nobody cares about emissions. Not being a smart ass, just letting you know don’t worry about heater circuit. All we care about is MV numbers but a screen shot isn’t gonna tell us if they are going rich to lean. 100’s to 700’s 800’s even. It should be swinging low to high.
injector pulse width at 2.43 ms is standard base number in the tune. When I see 2.43 ms that tells me fuel is not adjusting. That is right in line with STFT being at 0. I’m wondering if this is just at idle. If desired idle is 680 and your idling under that, it could be just running on a preset table like it’s in open loop. If your idle issue was due to stepper motor on throttle body, I would think it would also have a flat spot or stumble off idle. In think I would start simple and remove throttle body and clean the shit out of it. Put it back on and do a relearn.

I swapped the tb 3 different times, no change. I also did the relearn procedure with no changes either. What does "MV" mean?

 

[Fless]

millivolt reading of the O2 sensors. Tells how active they are and how they're adjusting.

 

[Tonyrodz]

Pretty sure these fuel trims are with a higher idle.

 

[Tonyrodz]

millivolt reading of the O2 sensors. Tells how active they are and how they're adjusting.

The van was completely warmed up, so I'm assuming the O2's are working ok? It doesn't really have power. I do haul alot of weight, but I have to floor it on the highway if I want to move. I don't smell any gas fumes either.

 

[Rocket Man]

I see your bank1 sensor 1 has 150 mv while bank 2 sensor 2 has 870. Might be a problem with 1 of them, I’m not sure what range they should be in. Somebody else here should know.

 

[pwtr02ss]

I see your bank1 sensor 1 has 150 mv while bank 2 sensor 2 has 870. Might be a problem with 1 of them, I’m not sure what range they should be in. Somebody else here should know.

I noticed that too. Maybe bank one sensor is bad?

 

[Tonyrodz]

I noticed that too. Maybe bank one sensor is bad?

Damn. Maybe I should've asked @Scottydoggs when he came by to help me with the Tahoe if he could've plugged into the van with his laptop.

 

[Fless]

I see your bank1 sensor 1 has 150 mv while bank 2 sensor 2 has 870. Might be a problem with 1 of them, I’m not sure what range they should be in. Somebody else here should know.

Good eye; I missed that graphic and detail.