ISV voltage question... John Speake please take a peek :)
#31
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Hi, just reading along and I think I get what Dave and John were talking about a little. You said it is 'electrically connected', but I think in John Speake's earlier post he said that the ground to the engine through the mounting bracket is part of the circuit. This would explain why the one that you have 'plugged in' to your system but not mounted to the engine isn't doing anything.
Can you try grounding the housing of the ISV while it's plugged in and see if there's any difference?
Can you try grounding the housing of the ISV while it's plugged in and see if there's any difference?
Sorry, but I thought the grounding was relevant to the general discussion, I apologize for potentially hijacking the thread.
Rod
#32
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"Rod, D.R. has, or will have very soon, a new set of chips for your kit. Among other things the new set should lower the idle by about 150 rpm. Also, I've been working with John, off line to understand what 'the code behind the LH curtain' is doing so as to be able to better-tune the ECUs for the TS kit."
Dave, thanks. It's really painful to be dumb. I apologize for my vertical learning curve.
Rod
Dave, thanks. It's really painful to be dumb. I apologize for my vertical learning curve.
Rod
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The 928 SP TS kit uses two throttle bodies that are quite a bit smaller than the stock units. But, the idle behavior and the operational parameters of the ISV is almost independent of how much air is going through the throttle bodies and ISV bypass. Yes, I know that sounds weird - but its true. I've done several experiments with the TS kit in various configurations.
I have a number of theories as to what might be going on. But, we'll end up with more confusion than logic if we try to work through them in this thread. Let's go off line on the TS, ISV, and Shark Tuner interaction until we can gather some more data.
#34
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The ISV doesn't need a ground to the engine bloack, I didn't mean to give that impression :-) It gets all the electrical connections it needs through the two pin Bosch connector.
Rod, if you had one ISV in the air path but no power, then the loop is broken. Also, the second ISV with an electrical connection but airpath not connected is similarly ineffective.
The loop is - ECU detects idle speed is too high or too low, send a correction signal to the ISV, ISV responds, LH checks idle speed agian, corrects again as necessary, ad infinitum, many times a second...
Rod, if you had one ISV in the air path but no power, then the loop is broken. Also, the second ISV with an electrical connection but airpath not connected is similarly ineffective.
The loop is - ECU detects idle speed is too high or too low, send a correction signal to the ISV, ISV responds, LH checks idle speed agian, corrects again as necessary, ad infinitum, many times a second...
#35
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The ISV is not grounded through the body of the unit. The wiring diagrams are pretty clear on this. And they have notations for electrical items that are body-grounded - for instance the head light lifter motor - that do not appear for the ISV.
#36
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Under those conditions the second ISV, the one exposed and connected electrically but not by hoses, opened wide as soon as the engine started and stayed that way without modulating at all even though the engine was running at @ 850rpm's steady.
Does this scenario point to anything in particular?
Does this scenario point to anything in particular?
If I have some free time this evening I will do an independent check with one or more ISV setups that I do know work and will post the results.
#37
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I also note that the ISV appears to have a 3rd terminal for an additional unused input... anyone know about this one - it appears to have a secondary coil that may also need to be pulse grounded...? presumably this part was used on other vehicles - it would tend to impy two seperate control mechanisms though that would be rather odd in terms of a closed loop system. Maybe it was just an alternate configuration for a variable voltage control mechanism or an alternate coil spec? Anyone?
Alan
Alan
#38
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I did determine there is no short to ground from pin 33 on the LH connector, harness side.
#39
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Look very closely at the connector. You will see tiny numbers molded in the plug. The inboard set of 5 terminals is the "1" the out board set is the "2". The individual terminal are 1 through 5. So, W13 is the middle terminal on the inboard bank on the W plug. On your 88 W13 should have two red/yellow wires on it.
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The S3 ISV do have three pins. The S3 ISV is mechanically different from the S4.
Are you sure your not looking at the idle/WOT?
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#42
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Looks like harness problems are out.
I'm going to proceed with SharkTuning the map in the idle range like John suggested.
After checking the harness for shorts I plugged the ISV back in to be ready to do the SharkTuning and took a little ride to see how it behaved, with the engine warm the idle is smooth at 1000rpm's. If it is true to it's previous behavior it would start idling at 1200 rpm's once the car warmed up a touch more.
We'll see what the SharkTuner does for it. I don't want to be tuning to hide a symptom but it is already running great with the exception of the idle being high so it's not like I'm changing the WOT or even medium load part of the map.
The only wild cards I can think of at this point is the EZK has never been replaced...don't know that it could give me the high idle though...
And the replacement MAF is used so maybe it is the source...
I'll do some logging to see how the data looks at all stages of rpm's and load if the idle goes to normal after the tuning and if they look good then hopefully that will be the end of it!
I'm still open to any suggestions in the meantime, I like learning how this beast works!
#43
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EZK does not affect idle . Do some datalogging with the ST so you can evaluate what is going on.
Check out O2 sensor adjust and idle stabiliser on the System monitor screen.
Check out O2 sensor adjust and idle stabiliser on the System monitor screen.
#44
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No not the TPS - I do understand its not wired to on S4 models - but on the diagrams the ISV looks like the extra pin on the unit exits - see the 87 diagrams for the most obvious indication (pin numbers) - later diagrams show the internals but no Pin ID. On 85/86 models all 3 pins are wired & both grounding IPs are driven from the LH.
You'd think it might be the diagram is just a vestigial hold over - but it appears to be a newly drawn diagram for '87 with more detail...
Alan
You'd think it might be the diagram is just a vestigial hold over - but it appears to be a newly drawn diagram for '87 with more detail...
Alan
Last edited by Alan; 10-21-2008 at 08:03 PM.
#45
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It was idle stabiliser bouncing around 52% and the O2 was pegged on 20 too much so I just finished installing a new O2 sensor just to be sure. A quick drive didn't seem to change anything but the data logging will have to wait until morning, ran out of time