No close loop on 88 7MGTE

[supraguy31]

Ok... So I go and Install a 190 stat, It takes longer for the fans to Kick on which is good I suppose but one they come on, they dont want to go back off. I use a Muiltimeter on the T1/E1 and its a Solid 4.99 with engine at 2500rpms. A/F is 17.4 at Idle but its not Sputtering like it did before when I let it sit there Idling.

So what should I do now since Im actually getting a 4.99 reading now instead of that 0.02....

 

[jdub]

Talked to Supraguy on the phone...resolved a couple issues

Some more info on Vf:
- Its a AFR learned value output in 5 stages on the 7M
- "Normal" is 2.5 volts
- Higher than 2.5 volts...the correction coefficient is on the "increasing" side (richer)
- Lower than 2.5 volts...the correction coefficient is on the "decreasing" side (leaner)

Here's an interesting tidbit...the idle adjust screw (the one I told you to screw all the way in) has an impact on Vf. If it's moved too quickly, AFR feedback will halt. Let it go like we talked about for a couple days...you may need to do another ECU reset.

The output waveform of Vf has a constant period of ~32 milliseconds...when Vf is measured with a multimeter it will show a constant value. This explains why you are seeing a constant voltage on your digital meter. It's also why you would see the fluctuations on an analog (needle) meter when you do this:

Check Vf at the diagnostic block:
- Warm the engine to at least 180 deg F
- Multimeter (set on DC volts) connected to Vf (+) and E1 (-)
- T and E1 jumped (like you're setting timing)
- Warm-up O2 sensor...run at 2500 RPM for at least 2 minutes
- Maintain 2500 RPM and check Vf voltage on multimeter...it should fluctuate 8+ times in 10 seconds.

Vf may very well be working, but your ECU is trying to push the coefficient more lean based of the voltage you are seeing. Remember, the voltage between T and E1 isn't telling us anything about Vf...it simply puts the ECU in diagnostic mode. What is the voltage between Vf and T without having T and E1 jumped?

One other thing I dug out of the TCCS book...the ECU uses what it calls "voltage correction" to compensate for the time delay between sending an injector signal and when the injector actually open. If the voltage of the battery drops, the delay increases. The length of time the injector remains open becomes shorter as a result, causing an initial lean condition. The ECU compensates by lengthening the injector signal by the time corresponding to the delay.

Why am I telling you this?
When you go to boost, you show a initial quick lean on the AFR gauge, followed by a fast correction to 11.5 AFR.
Make sure your battery is fully charged

 

[dumbo]

One other thing I dug out of the TCCS book...the ECU uses what it calls "voltage correction" to compensate for the time delay between sending an injector signal and when the injector actually open. If the voltage of the battery drops, the delay increases. The length of time the injector remains open becomes shorter as a result, causing an initial lean condition. The ECU compensates by lengthening the injector signal by the time corresponding to the delay.

Why am I telling you this?
When you go to boost, you show a initial quick lean on the AFR gauge, followed by a fast correction to 11.5 AFR.
Make sure your battery is fully charged

very good too to know. my battery is dead after it has be sitting for the build(have to jump it, and i know it kinda hard on the alt), and i get a quick lean condition when i step on it, i was just gonnna increase fuel with my maft but maybe i'll get a bat, even though i have no "proper" throttle linkage (its in the mail) and its gonna snow any day.

 

[supraguy31]

jdub,

Im correcting all of those things that we talked about and Im making sure the other things arent clogged. I also as you mentioned think its a Harness Issue but once I get all the little things corrected, We will see where it ends up at. I need to email the Person that we talked about and see if he did what he said he was going to do since I already paid him and his payday was today.

 

[jdub]

After doing a bit of reading, I'm wondering if it is a harness issure or not. Vf *may* be working (it's a correction value after all). I'd like to see what you have for voltage at Vf and E1 without the jumper installed on E1 and T.

Like we talked about, let it go for a bit. I would make sure the battery is fully charged though

 

[supraguy31]

Yeah, I will get you those readings tomorrow, After Adjusting that screw as we talked about It started up pretty good without the Stumble like usual. Doing the PVC hose as we Speak so that is correct. I need to find another EGR Valve assembly as I have the back Plate but I cant find the Assembly part between the intake and Side of the head.

 

[jdub]

Just to put the info in this thread:

On the top of early model 7M TBs there is an idle adjustment screw (the book calls it an air bypass screw). Since idle is controlled by the ISCV, this screw should be all the way closed. It is common for it to have been messed with...I mean it's there, so Toyota must have put it there to use...right? In the case of a 7M, the answer is NO. The 89+ TBs do not have it for this reason. Adjusting this screw out will simply induce a source of pirate air into the system.

Robert also has hit a lean condition at part throttle under load, going into boost. I've beat the EGR issue (and why you want to keep it) to death. The USDM ECU expects the EGR to be there and is tuned for it timing/fuel wise...removing it creates a lean condition due to the additional air in the cylinders. Under load this can cause detonation...not good.

 

[supraguy31]

So I took a reading without the jump connector.

VF and T voltage is 4.93 consistant. I still have the car Idling so as soon as the fans Kick in I will check the voltage again to make sure that the engine is completely warm.

VF to E1 right now is a Consist 0.03v and A/F on wideband is reading 17.2 at 700rpms.

 

[jdub]

It looks like Vf is attempting to push AFR feedback to rich (makes sense...that voltage indicates a lean condition).

Did you adjust the AFPR by any chance?

Might want to check the MAFT Pro to make sure it's not pulling fuel at the low end.

 

[supraguy31]

Adjusted the AFPR from the 40 psi to 35 psi as we talked about.

Low tune on the MAFT Pro is 00 across the board so Im not pulling or Increasing as I see.

 

[jdub]

Put the FP back to 40 psi...a 17.2 AFR idle is too lean.

 

[supraguy31]

Will do,

Changed it back to 40 and it didnt make any Difference really, Still Idle at 725rpms showing a A/F ratio of 17.1 or so and Im getting a faint pop sound from the Exhaust which Im assuming its the a/f

 

[3p141592654]

Vf can be confusing to decode. Read the attached link to make sure you are interpreting it correctly.

http://www.well.com/user/mosk/Vfsignal.htm

 

[jdub]

That brings up a good point...any new codes stored now?

 

[grimreaper]

have you ruled out an exhaust leak? the smallest of pin holes has thrown mine off by a full 1.0 af ratio

 

[supraguy31]

That brings up a good point...any new codes stored now?

Only codes now is the Code 43 (Starter Signal) which we talked about that already.

I Checked VF and what Im getting is that At Idle with fans on Im getting 0.17 with A/F at 16.8, Now if I sit there and with my hand hit the throttle really Quick the VF Signal will go from 0.17 to 0.00 and pick back up to 0.17 so I think that this is a good thing.

VF/T1 is showing 4.82 with fans on. I know the fans being on is pulling current so this might be irrelivant.

 

[jdub]

The Vf/E1 voltage indicates a lean condition (which your AFR confirms)...it also means the ECU is "pushing" AFR correction rich (which it should).

Checking Vf/E1 in the diagnostic mode (E1 & T jumped) is the only other valid measurement and should be checked at 2500 RPM. That will give the the O2 sensor cross count (needle fluctuation)...the voltage will indicate rich or lean. Rich = 5 volts (or close)...Lean = 0 volts (or close).

There is a concern...when a lean condition continues longer than a predetermined time, it kicks the ECU out of AFR feedback (goes into open-loop). If your lean readings continue on the AFR gauge, reset the ECU again....leave the FP at 40 psi.

The fan voltage draw should not have an effect on idle readings...voltage correction discussed earlier should only come into play under heavy acceleration. Make sure the battery is charged

 

[supraguy31]

hehehe.... Its all good,

VF and E1 is 0.04-0.05 and bouncing between them, Engine completely warm

 

[supraguy31]

Jet, Try anything at this Point. I have another harness coming if the guy will ever ship the dam thing out. As of today, nothing yet.

 

[jdub]

VF and E1 is 0.04-0.05 and bouncing between them, Engine completely warm

Is that with T & E1 jumped at 2500 RPM, engine warm?