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Old 10-18-2007, 01:09 PM   #1
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Default Awkward idle 99 MSI w/High Imp 550s

Trying to get my 99 to idle right with the new injector install, stock ecu controlling idle MS is wired in parallel. Having some issues with it though. It warms up wonderfully, though it does so very rich (12.3-5:1). That I can deal with, the warmup is great but as soon as the engine reaches 160+ degrees it is no longer in warmup enrichment and I get a crazy oscillating idle.
Then I can turn the A/C on to put it under some load and it smoothes right out with much less hesitation.
I have two datalogs, one with the A/C on another with A/C off. I also attached the msq. I have all enrichments turned off unless I missed something and I'm just trying to get it to idle right.

99 MSI in parallel, stock ECU controlling idle.
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Old 10-18-2007, 01:21 PM   #2
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Most likely it is hunting btw your kpa rows 20 and 26. Change both them to the same value and see if that makes a difference. Why exactly do you have the 2 rows 26 AND 20. They are so close together I hardly see why both are needed. My car runs perfectly NA on only 4 rows total.
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Old 10-18-2007, 01:21 PM   #3
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Quote:
Originally Posted by cjernigan View Post
Trying to get my 99 to idle right with the new injector install, stock ecu controlling idle MS is wired in parallel. Having some issues with it though. It warms up wonderfully, though it does so very rich (12.3-5:1). That I can deal with, the warmup is great but as soon as the engine reaches 160+ degrees it is no longer in warmup enrichment and I get a crazy oscillating idle.
Then I can turn the A/C on to put it under some load and it smoothes right out with much less hesitation.
I have two datalogs, one with the A/C on another with A/C off. I also attached the msq. I have all enrichments turned off unless I missed something and I'm just trying to get it to idle right.

99 MSI in parallel, stock ECU controlling idle.
what AFR once you go out of warmup enrichments?

with batch you can't tune to stoich, more 13.5:1. I can't get that lean as I've such a small PW at idle the smallest step change means I stray into 14.5:1 and the idle wavers

EDIT: I ask as I can't view at work.
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Old 10-18-2007, 01:32 PM   #4
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Well I can view at work but only in Excel...

why do you have such a large advance at 500rpm? Unless I'm reading wrong it's 20deg at 500rpm, ramping down to 17 at 1k?

The only way I could get a stable idle was with a much lower advance at idle, like 10deg.
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Old 10-18-2007, 01:32 PM   #5
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Originally Posted by neogenesis2004 View Post
Most likely it is hunting btw your kpa rows 20 and 26. Change both them to the same value and see if that makes a difference. Why exactly do you have the 2 rows 26 AND 20. They are so close together I hardly see why both are needed. My car runs perfectly NA on only 4 rows total.
Would you mind throwing your msq up, I'd like to check it out. My tables are formatted the same as DIYautotunes, only reason they're that way. When idling it hunts around 26 and 34, never even gets into 20, so that small jump in ve values didn't affect it. I had all 6 of those cells the same until last night when I was mesing with it.

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what AFR once you go out of warmup enrichments?

with batch you can't tune to stoich, more 13.5:1. I can't get that lean as I've such a small PW at idle the smallest step change means I stray into 14.5:1 and the idle wavers

EDIT: I ask as I can't view at work.
I've been trying to tune it to around 13.5 because it idles much better there like you say. The ve values I have in the table now have produced the best results, i'll bump those two cells back up to 60 as well for measure though.
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Old 10-18-2007, 01:34 PM   #6
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Well I can view at work but only in Excel...

why do you have such a large advance at 500rpm? Unless I'm reading wrong it's 20deg at 500rpm, ramping down to 17 at 1k?

The only way I could get a stable idle was with a much lower advance at idle, like 10deg.
That timing map is from DIYs 94-95 PNP, i'll knock the timing down to see what i get, that makes sense though. Gonna go try it now.
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Old 10-18-2007, 01:49 PM   #7
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Yeah 20 degrees might be to much to remain stable. FWIW i noticed when i got my spark **** stable and in the range of 10 btdc it ideled alot better. That and realy cranking my AIC closed helped me a bunch. I can now idle with AC on easily where as before the oscilations would kill me or stall the motor out on stock ecu i think it was the ecu trying to compensate timming to quickly causing the AIC to hunt. Have you tried to get it through most of warm up and put it on a static 10 or 12 btdc and see if that helps?
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Old 10-18-2007, 02:16 PM   #8
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Hi Chad,

The VE table looks pretty stable, but the AFR is bouncing around like a rubber ball. I wonder if the IAC is opening and closing, and the stock ECU is thinking the injectors are doing something they don't? I'd try disconnecting the IAC as an experiment, and adjusting the throttle stop screw to see what happens.
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Old 10-18-2007, 02:59 PM   #9
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Hi Chad,

The VE table looks pretty stable, but the AFR is bouncing around like a rubber ball. I wonder if the IAC is opening and closing, and the stock ECU is thinking the injectors are doing something they don't? I'd try disconnecting the IAC as an experiment, and adjusting the throttle stop screw to see what happens.
I retarded the timing at idle to 10* and it helped for a while, took the car out for a drive, came back & parked it, just went out to mess with the IAC valve and it was oscillating again like before.

I started the car up and unplugged the IAC, adjusted the throttle stop screw so the butterfly was opened up a little more. It idled better, didn't fluctuate like a huge SIN wave like it had before though it was still rough, i'm sure that could be turned out.

I was going to adjust my IAC valve but it appears the previous owner stripped the allen head in the end of the valve. What an imbecile.
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Old 10-18-2007, 08:53 PM   #10
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My 2000 motor with 440s (standalone, not piggyback) idles fine stoich at around 20 degrees timing (more timing doesn't seem to hurt, either), when it's warm. Of course, it didn't run right on the stock 94 ECU (because it had 2000 injectors which were smaller than 94), and it's been so long since I've experienced a stock idle, maybe it's not as good as I think it is.

I'll look at your log tonight, but what's your pulse width doing at idle? If it's twitching by .1ms, that's actually a pretty big difference in fuel, and could cause issues.

-Mike
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Old 10-18-2007, 11:12 PM   #11
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Well as lame as this sounds i think i might have a leak on the underside of my upper intake plenum. I'm going to fix that tomorrow hopefully, that is most likely the source of all my problems.
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Old 10-19-2007, 05:25 AM   #12
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Well as lame as this sounds i think i might have a leak on the underside of my upper intake plenum. I'm going to fix that tomorrow hopefully, that is most likely the source of all my problems.
Vac leak will definately cause a wonky Idle, so if you have a leak that's the casue

good spot mate!
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Old 10-19-2007, 10:05 AM   #13
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More like lame spot on my part.

Now will RTV sealant cause any problems? I thought i remembered reading something about not using RTV in certain situations because it puts off a fume that kills O2 sensors. Is there any truth in that I could be confused with ABS piping.
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Old 10-19-2007, 10:43 AM   #14
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More like lame spot on my part.

Now will RTV sealant cause any problems? I thought i remembered reading something about not using RTV in certain situations because it puts off a fume that kills O2 sensors. Is there any truth in that I could be confused with ABS piping.
RTV, is that instant gasket?

i used gobs of the stuff on my Dummy Throttle Body, no issues here.

I don't see how the gasses would survive combustion anyway
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Old 10-19-2007, 11:41 AM   #15
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Yeah RTV is a instant gasket. Worth a try then. I don't feel like waiting for a new gasket
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Old 10-19-2007, 01:06 PM   #16
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chad it depends is it a leak in the flange that meets the head then RTV is a no no. But if it is just a addon part or something small rtv will do just fine for those bigger items like the manifold itself get a new gasket trust me i rtved mne originally and it last maybe 500 miles
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Old 10-19-2007, 01:21 PM   #17
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chad it depends is it a leak in the flange that meets the head then RTV is a no no. But if it is just a addon part or something small rtv will do just fine for those bigger items like the manifold itself get a new gasket trust me i rtved mne originally and it last maybe 500 miles
wait you used Instant Gasket instead of a metal gasket? I'm surprised it lasted 500 miles!

Instant gasket is meant to replace card/paper gaskets....
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Old 10-19-2007, 01:29 PM   #18
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I guess i'll just order the metal gasket and be done with it. Considering the metal gasket is the failure point. Wish we had a local dealer, life would be much easier.
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Old 10-19-2007, 01:50 PM   #19
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I used it and reused my stock gasket that is why it lasted so long.
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Old 10-20-2007, 04:34 PM   #20
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Well i took the intake mani apart again and put high temp sensor safe RTV on the upper and lower then reused the stock gasket. I don't think I have a vac leak anymore, though I do still have the same idle issues. Posting the new datalog and MSQ though. I lowered my ignition timing at idle, made sure my AIT enrichment was turned off as well as everything else I could possibly think of.
I thought it might be going crazy due to the AIT sensor getting heat soaked but it does the same thing at 90*+ and 78* which is about ambient outside. I'm running out of possibilities.

Maybe I should take my IAC valve off and see what I can do to get that adjustment screw out. Maybe all i need is to adjust the valve though that is something I've never done.

In the datalog you can see where I started it up with the AIT sensor heat soaked and then got on the highway with the AIT going back down to where it should be. Then later in the datalog you can see where i came back to a stop with the AIT much lower and it was doing the same thing.
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