UPDATE 4age silvertop lean. VVT unplugged runs better

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SR85DET
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UPDATE 4age silvertop lean. VVT unplugged runs better

Postby SR85DET » Tue Jan 10, 2017 6:58 pm

Edited (I hate typing on cell phones)

Engine: Silvertop, Auto BT ECU, ITB trumpets, no emissions equip, 3sgte O2 sensor, sqe distributor relocation kit.
Possible culprits IMO: MAP, ignition timing, VVT, TPS, ?

Issue:
-Watching my wideband sensor I have an issue with the vehicle going lean most of the time when I hit the throttle. It seems if I'm at 100% throttle that the issue doesn't exists or only for a half a second or so. 40-80% is horrible and bogs down and goes off the chart lean. Haven't heard any pinging although there is a knock sensor.
-I know that my MAP inline dampener/filter(?) is missing at the moment. Could this cause my issue? What does this thing do?
-Originally my map sensor was tee'd to all four throttles and ran better around town but was horribly rich at idle (off the scales at less than 10:1)
-My biggest concern is that it could be ignition timing. I thought I set it correctly but it seems like it's a timing issue like it isn't advancing properly.
-VVT engagement. How do you know it's working properly?

This makes me want to go aftermarket ECU since that's what I'm used to but I would be happy with just a stock power output for now.
Last edited by SR85DET on Sat Jan 14, 2017 10:33 am, edited 3 times in total.

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Re: 4age silvertop lean EDITED

Postby SR85DET » Wed Jan 11, 2017 8:23 am

http://forums.club4ag.com/zerothread?id ... tid=693597

I always forget about the archive, at first. This thread has great info for anyone else having these issues. I'll keep you updated.

I'm hoping it runs better with the VVT unplugged. Does anyone know what that MAP sensor filter does though? I can't even find info through Google.

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Re: 4age silvertop lean EDITED

Postby Jeonsah » Wed Jan 11, 2017 10:07 am

I had a similar lean issue with my BT 20V and A/T ecu. It turned out to be the fuel pump. I just got a standard replacement for an 86 Corolla GTS at the local parts store and that fixed my issue. Another problem that can cause you to run lean is an exhaust leak before the O2 sensor for the ECU.

I am not sure about the map dampener. I have it hooked up on my car. I would suggest keeping everything as close as to factory on the 20V due to the ECU being so damn picky..
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Re: 4age silvertop lean EDITED

Postby jondee86 » Wed Jan 11, 2017 12:02 pm

ITB engines need a lot of extra fuel when the throttles are opened quickly. The ECU
should provide the extra fuel (acceleration enrichment) if it gets the correct information
from the key sensors... MAP and TPS. Additional enrichment is also provided by the
FPR which increases the rail pressure as the manifold pressure drops (gets closer to
atmospheric). So make sure the FPR is connected to a good vacuum source.

The pulsation damper is used to smooth out pulsations in the MAP reading when the
MAP sensor is sampling from multiple throttles. not having one for the moment will not
cause the leaning out issue you are having.

Cheers... jondee86
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Re: 4age silvertop lean EDITED

Postby SR85DET » Fri Jan 13, 2017 10:49 am

Jeonsah wrote: It turned out to be the fuel pump. I just got a standard replacement for an 86 Corolla GTS at the local parts store and that fixed my issue.


How did your engine run up top before fuel pump replacement? Mine will go back to running really well by the time it gets near redline.

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Re: 4age silvertop lean EDITED

Postby SR85DET » Sat Jan 14, 2017 9:17 am

Can someone help me understand something with TPS adjustment. The FSM says to "disconnect TPS sensor and insert feeler gauge between the idle stop screw and stop lever"
Ok so here is the problem, unless you use a vacuum pump to pull vacuum on the vacuum diaphragm or start the engine (which neither are steps in the procedure) then the stop screw will not be even close to touching the lever. Please don't suggest not messing with the TPS. The electrical part is easy but as person who writes military technical manuals for a living, the steps do not seem to cover everything.

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Re: 4age silvertop lean EDITED

Postby SR85DET » Sat Jan 14, 2017 9:20 am

Additionally, using the vacuum pump seems fair enough but if you are actually supposed to use the vacuum diaphragm throttle stop then this will change the TPS position. Also this will affect checking codes as the TPS won't read closed when sitting with engine off bc the diaphragm needs vacuum to close the throttles all the way. Thanks ahead.

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Re: 4age silvertop lean EDITED

Postby SR85DET » Sat Jan 14, 2017 10:22 am

UPDATE: reset TPS best I could and well as ignition timing a couple degrees. With VVT plugged in it runs about the same. Unplug the VVT and it runs MUCH better. Initial lean for fraction of a second that you can't really feel and then goes back to a richer than 14.7 and pulls well. So for the kicker... the VVT solenoid ohms out perfectly in spec.

ECU signal bad?

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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby jondee86 » Sat Jan 14, 2017 1:42 pm

It appears that your VVT mechanism is operating correctly, however the results
are not as one would expect :? Unplugging the VVT solenoid (preventing the intake
cam from advancing) improves mid-range performance, when you might expect
the opposite result. So it seems that your engine has all the intake cam timing
it requires without the extra advance supplied by the VVT system.

The logical deduction to be made from this information is that your intake cam
is installed too far advanced. Since I do not have a 20V engine, I have to rely on
anecdotal evidence that it is possible to rotate the VVT pulley on the camshaft by
hand when the timing belt is off the engine. And if this is true, then it may be
that your VVT pulley was accidentally moved from the zero advance position when
the engine was assembled and the cam timing set.

In the absence of any better theory, it might be worth checking you cam timing :)

Cheers... jondee86
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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby SR85DET » Mon Jan 16, 2017 4:49 am

This is a great theory Jondee and I will check the cam timing next time I'm in the garage. I do wonder though, as you mentioned, if you can turn the VVT by hand. I didn't see any mention of this in setting cam timing and I believe this would be important information as to not make this mistake by accident.

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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby Jeonsah » Mon Jan 16, 2017 5:47 am

If I remember correctly, it would run better at higher revs. It was doing it on idle and partial throttle. It was almost a year ago so it is hard for me to remember the exact details. Hope this helps. You could rent a fuel pressure test kit from a local auto parts store and check your fuel pressure. That will tell you if either your fuel pump or fpr is going bad.
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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby SR85DET » Mon Jan 16, 2017 12:01 pm

Jeonsah wrote:If I remember correctly, it would run better at higher revs. It was doing it on idle and partial throttle. It was almost a year ago so it is hard for me to remember the exact details. Hope this helps. You could rent a fuel pressure test kit from a local auto parts store and check your fuel pressure. That will tell you if either your fuel pump or fpr is going bad.


Well the thing is I have tested my TPS, FPR, O2 is new and wired correctly, engine runs great at high RPM with or without VVT plugged in. I have read a lot of info including the thread which I believe was yours where you had a surge tank and the pump was bad (I could be wrong about it being yours)

What this specific problem seems like is a Silvertop running with Blacktop ECU and VVT being controlled differently or operating under different parameters causing a bog. Or like Jondee suggested with the cam timing being off but I have not found any info with anyone else finding this to be true. It seems there is so much misinformation out there b/c of it being a complicated issue and so many other issues can act similar to this. I am at a loss at this moment and honestly thinking Megasquirt is the answer or finding a delay switch to switch over to VVT a half second or so later than it should be. I'm thinking in theory that this will run much better as its opening too early or just too advanced as Jondee suggests.
I have read that the STA signal has caused problems but I am 90% sure my signal is correct without rechecking. It doesn't make sense as to exactly what it does. I've heard it "wakes" the ecu which seems odd. I could see how it would turn VVT on during starting for ease of starting but if it if the signal is missing then VVT would be off. So despite people having issues missing the STA signal I'm extremely curious as to exactly what this feature does to the ECU or if indeed it just "wakes" it up. How does the ECU not know its awake when the engine is running????

Does anyone have the silvertop FSM pages for setting cam timing?
Does anyone have a map sensor pulse dampener as well?

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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby Jeonsah » Mon Jan 16, 2017 12:33 pm

Have you checked your cam timing yet?
Have you tested the STA wire for continuity and tried shaking it to make sure there is a good connection?
Sometimes you may not know how something works but you can test to make sure its input is not broken (in this case the STA wire).

There are multiple people I know who are successfully running a 20V ST on BT electronics. So I would say it is safe to say that you just have to find the problem with yours.

Here is the link for setting cam timing on a 20V:
http://forums.club4ag.com/zerothread?id=87830

One thing I have done is gone to the junkyard and pulled an extra set of sensors for the 20v. You cant get them all but you can get a majority of them. This can help you in the long run when troubleshooting problems. For instance, I have gotten map sensors, knock sensors, o2 sensors, and cops. I had an issue with my engine not revving correctly and bogging at high rpm. So I replaced 1 sensor at a time and test drove until I narrowed down the problem. During this process I labeled all the extra sensors as good or bad for future reference. Anyways, it turned out my ignition timing was too advanced and the ecu needed to be reset. I would highly recommend resetting your ecu once in a while on a 20V...

Here is an example to justify why I think resetting the ECU on a 20v is important (atleast BT ECU). In the problem described above, I had checked everything (except ignition timing) and nothing was solving the issue. My friend down the street had a running 20V ST with the same BT AUTO ecu as me (same part number). So we swapped ECU's and viola..... my engine would run correctly. This tells me that the stock ECU can learn itself into a position where it will not run the engine correctly. Once I put the engine in diagnostic mode and reset the ignition timing, the problem went away.
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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby jondee86 » Mon Jan 16, 2017 1:58 pm

Fkn interesting thread this :P

As said ^^^^ because the BT ECU has some learning ability, you do have to reset
it to clear any bad habits it may have learned. Downside is that it will also clear any
good habits, so the ECU has to re-learn any corrections it has to make to improve
the way the engine runs.

I have never seen anything that says the STA signal does more than just help the
the engine start. 12V is only present on the STA pin while the engine is cranking; at
all other times there is no voltage applied to the pin.

The BT and ST control the VVT solenoid differently. There does not seem to be any
concensus on exactly how the ST system works... most opinions say it is simply
ON/OFF at somewhere around 4000rpm. Maybe the switching point also changes
with engine load, but that is a minority view.

Opinion on the BT system says that the switching point varies with rpm and load, and
can occur anywhere between 1500 and 6500rpm. It is said to switch VVT OFF at around
6500rpm as high rpm performance is better without the extra camshaft advance.
I have read that the static cam timing is different between the ST and BT engines,
but since I understand that the same VVT pulley is used on both engines, I don't see
how performance would be affected by using a BT ECU on a ST engine.

There are almost as many "engine bogging" threads as there are 20V conversions :)
And there are many different solutions offered up on the interwebz. One of the more
unusual ones was curing severe bogging by changing the COR relay. This has some
traction, as should the COR be operating erratically due to badly arced contacts, the
fuel pump could be getting low voltage causing fuel pressure to drop and lean misfire
under load.

However, as I understand your car will run WOT to redline with the VVT unplugged,
you have no shortage of fuel and this will not be your problem. Keep digging...

Cheers... jondee86
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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby SR85DET » Mon Jan 16, 2017 2:54 pm

Ok, this is edited. I had pics but my cam timing is spot on. I doubled checked it and was a tiny fraction off the first time but all marks line up exactly.
Last edited by SR85DET on Mon Jan 16, 2017 4:18 pm, edited 1 time in total.

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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby SR85DET » Mon Jan 16, 2017 2:55 pm

I assure you the cam dots are lined up to the backing plate however the cams are not lined up to each other. That picture is more head on and accurate

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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby SR85DET » Mon Jan 16, 2017 3:55 pm

Can someone help identify the transistor pictured? All the rest on the back of the board say "GA 77". Now I think this is just linked to the COR relay based on tracing and the fact that I accidentally applied voltage to it and it no longer works :roll:


The article that is linked to the VVT transistor is not this transistor. That one looks completely intact. Right now my COR is always on while the key is on (for fuel pump) so could having no COR wire to the ECU cause VVT running issues? Stay tuned.... (help is appreciated)


Image
Last edited by SR85DET on Mon Jan 16, 2017 4:12 pm, edited 2 times in total.

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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby SR85DET » Mon Jan 16, 2017 4:00 pm

Jeonsah wrote:
Here is the link for setting cam timing on a 20V:
http://forums.club4ag.com/zerothread?id=87830


I thought this was just for a blacktop. If this is correct for a silvertop then I would be a tooth off as my cam marks are not aligned to each other but then my marks would not be aligned to the backing plate. But then my intake cam would be more advanced and I thought that negates Jondeea theory of being too advanced.

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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby SR85DET » Mon Jan 16, 2017 4:25 pm

Jeonsah wrote:Have you tested the STA wire for continuity and tried shaking it to make sure there is a good connection?
Sometimes you may not know how something works but you can test to make sure its input is not broken


My STA wire is spliced in with the starter signal wire. I actually cannot find the ST or BT wiring for this. The engine wiring diagram omits this. So I don't know if this is correct but it gets 12v when the Igntion switch is in crank position only. Just like the 16v ECU so it should be the same.

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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby jondee86 » Mon Jan 16, 2017 8:56 pm

SR85DET wrote:Right now my COR is always on while the key is on (for fuel pump) so could having
no COR wire to the ECU cause VVT running issues?

This getting a bit confusing now :? Without knowing what combination of parts you
are using, or exactly how it is wired up, I can only guess. The old style COR used in the
AE86 and ST has two coils... one only active when the key is in the CRANK position.
The STA signal is derived from this circuit. The other coil is active when the flap in an
AFM opens, or with MAP sensored engines, when the ECU detects manifold vacuum and
and switches FC to ground.

This strategy provides a way of turning off the fuel pump to avoid feeding a fire if your
engine stops suddenly when you hit a tree and you are unable to switch the ignition off.

However, from the few scraps of information available on the AE111 BT engine, it is
possible that the COR only has one coil controlled by the ECU. The ECU gets a STA
input and activates the COR. Providing the engine remains running, the COR remains
energised. But if the engine stops the ECU de-energises the COR which cuts the pump.

Getting back to your question... having the fuel pump run continuously whenever the
key is ON does nothing more than remove the safety feature of cutting fuel when the
engine stops. In no way can this affect VVT. On the other hand, having 12V applied
continuously to the STA pin (if this is the case) could cause the ECU to think it was
permanently in "starting mode". Thus supplying extra fuel and retarding the ignition.

Pure conjection of course... this would show up on your WBO2 and is easily tested by
making sure there was no 12V on the STA input once the engine is running.

Cheers... jondee86
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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby SR85DET » Tue Jan 17, 2017 4:58 am

I should have been more clear as to what I have going on. I have what can be considered a 100% stock blacktop wiring setup with the exception of the COR from the ECU out to the harness is cut and going to nothing AND all the wiring removed for things like body components, lights, etc.
I have 12v in run position applied to the COR wire (of the vehicle, controlling the fuel pump) instead of the wire that should be coming from the ECU COR signal.
The STA signal is only going to the ECU when starting as it is wired to just my starter signal, not 12v constant.
This wiring of the COR was taken from the partially translated silvertop wiring diagram combined with an 87 GTS which appear to work the same.

Do any electrical experts know what transistor I can purchase? I'm pretty sure based on being handy with a meter and the knowledge I've found that I can figure out if its a NPN or PNP resistor but do these have values to them? Thanks ahead.

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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby SR85DET » Tue Jan 17, 2017 5:01 am

I also have a perfectly good Silvertop ECU around 1991 and a fried Silvertop ECU from around 1993. Unfortunately neither have these exact transistors in them.

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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby Jeonsah » Tue Jan 17, 2017 9:27 am

If you can, please provide a list of your setup as well as a list of the things you have tested/checked. This will simplify some of the confusion.

1. What type of ECU are you running exactly. A BT M/T ECU or a BT A/T ECU? Part number helps too. I can crack mine open and take a look if you have an A/T ECU.

2. I thought the cam timing applied to all 20v but the thread mentions BT. So not quite sure on that.

3. Here is how I wired my STA and FC signals:
Image
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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby jondee86 » Tue Jan 17, 2017 1:37 pm

Can you pull fault codes from the ECU ?

Since the engine does (did ?) run with VVT active, and better without VVT, it
seems to me that the electrical setup must be OK. Leaking capacitors inside
the ECU are a frequent cause of problems on ST ECU's, but I don't think that
it is a problem with BT ECU's. You could check while you are in there.

So, right now the only diagnostic clue we have is that the engine runs better
with the VVT disabled. While I don't know and have no way of checking, I expect
that when VVT activates, the ECU also will make changes to the ignition timing.
If this assumption is correct, then some experimentation with ignition timing
might prove helpful.

For example... establish the current idle timing on a warm engine using your
timing light. IIRC it should be around 15-16 DBTDC. Then retard the timing by
(say) 5 degrees and go for a drive with the VVT plug connected. You are looking
for a change in the bogging problem, either better or worse.

If it gets worse, then advance the timing by 2 degrees from your original
baseline, and try again. Be careful to listen for knock and any signs that the ECU
is pulling timing on account of knock. This manifests itself as a loss of power, so
if the bogging gets worse under load with more timing, terminate the test.

The switching point for VVT on the BT is based on load, rpm and TPS angle, so
you need to test with (say) 1/2, 3/4 and full throttle and note at what rpm the
problem shows up. You don't need to be too scientific... it just helps to give
an idea of how bad the bogging is and perhaps a few more clues :)

Cheers... jondee86
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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby morgan » Thu Jan 19, 2017 9:45 am

SR85DET wrote:
Jeonsah wrote:
Here is the link for setting cam timing on a 20V:
http://forums.club4ag.com/zerothread?id=87830


I thought this was just for a blacktop. If this is correct for a silvertop then I would be a tooth off as my cam marks are not aligned to each other but then my marks would not be aligned to the backing plate. But then my intake cam would be more advanced and I thought that negates Jondeea theory of being too advanced.


its for both ST & BT

I recently have started having a bogging issue and am interested to see where this leads you. my cars in storage for the winter though, so Ill chime in best I can
haha cali...i got one of your 86's and you're not getting it back.
My turd of an 86
20v swapped 86 write-up

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Re: UPDATE 4age silvertop lean. VVT unplugged runs better

Postby SR85DET » Fri Jan 20, 2017 5:26 am

I'll be checking this out more this weekend I hope, although I have the ECU out currently. I'm also working on a T50 trans rebuild on an extra trans so who knows if i'll drive the car. Man, getting trans parts is a PITA. I have 4/6 of my large bearings and all my syncros and gaskets. I still need all the caged needle bearings and the center bearings on both shafts....

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