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Discussion Starter · #1 ·
So I built a DIYPNP for 5.0 mustangs, its for another project but I figured I'd get the kinks worked out on my 90 LX. So here are a few factors that may be working for/against me. My IAC does work with the A9L, Unplugging it changes the idle and I can hear it step up and down. Sometimes it does hang a high idle though (2000rpm). My thermostat is probably not even there, the car never gets above 160F.

So I run VE Analyze and have pretty good luck other than some pinging under load. I come back in to dial it back a little, and the idle works its way up to 1200+ rpm. I have tried all the IAC and PWM settings and it doesn't seem to do much. The IAC Test doesnt seem to do anything either. Am I missing something? I'm pretty new to this, its only my second MS and the other was a GM throttle body that worked without issue.
 

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I don't have your .msq of course, but a careful look at your tables and settings will often reveal something weird. Like a bunch of advance where it shouldn't be, or a wonky CLT or IAT curve that it dips into only occasionally. FE may be on it if your CLT does not come up as 'normal'. I assume you've already done that looking, so...

The PNP would be a Jerry or Matt answer, but my first eye twitch is an intermittent grounding of your TIP122 through the mounting screw, insulator, leg, close solder bridge or something. If the case gets ground, it will throw full 12v at the idle valve.

Another common one I've heard of is simply that the PNP has taken the valve beyond where it's been for 20 years, smeared goo around, and it's just sticking a bit. A quick clean-out may prove that one. Otherwise, I'd call DIY and they probably have the right answer without thinking about it.

David
 

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Discussion Starter · #4 ·
You're right FE I'll get a t-stat in there...maybe tomorrow...but I've only had this one about a week, just haven't had a chance.

I looked through the tables, didn't see anything crazy, but I went ahead and reset some of the lower idle tables to their beginning setting and restarted VE analyze. What I DID do is find THIS LINK and cheated and loaded those settings into my car. I had to modify one of the curves to match the max 165F temp, but I could verify the idle drop with the PWM output PID. Then, I disconnected the IAC with no idle change, and set the idle screw to around 800. Went and drove it with no issues, just some pinging.

Anyway I'll drive to work and keep tuning and post any changes in this tune or situation, thanks for the help!
 

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Discussion Starter · #5 ·
So I drove my car with the DIYPNP today, and the idle worked fine. Guess I was jumping the gun on that one. I put a t-stat in it, it stayed at 195 and I was actually able to get it to pass a dyno state inspection with the DIYPNP. It's a stock motor but I thought the results might be of interest.

HC(PPM) MAX 174 READING 168
CO% MAX 1.12 READING .60
CO2% NO VALUE READING 13.6
O2% NO VALUE READING 1.1
NOX(PPM) MAX 1258 READING 737

DILUTION >6 READING 14.2

This is a two speed test, 15mph under a medium load and 25mph under light load, any gear as long as rpms are between 1000 and 2500. Both sections had similar results and both were right around 1800rpm. This car has rust on the spark plugs and could probably use some ignition parts...maybe explaining the HC. But the rest look really good!

Had to go ahead and put my stock ECU back, We're hoping to have this other car done this week...but maybe I can sell my A9L and offset the cost of my own!
 

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Nice! :tup: Yeah, aftermarket ECMs are fairly easy to tune for emissions testing, as long as they aren't borderline radical. Actually, with your HC good but high, if you just retard the ignition a few degrees, the NOx will drop like a rock. I've had a few that were close to failing, and a bit of extra fuel along with retard would bring the NOX right down. It's a balance between high HC and high NOx. It was so bad on one (1990 Lumina van), that it would hardly run with a huge amount of retard, making maybe 50hp WOT. But, it passed like that, and then we added timing just to get it home. LOL

BTW - how do you like that VE Analyzer tuning program? Makes it stupid easy to tune fuel on-the-fly, eh? :D

David
 

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Discussion Starter · #7 ·
That VE analyzer is slick, the VE Analyzer Live is unbelievable. All the guys at the shop are like "what's the big deal it, looks like it does all the work for you"...and its hard to argue. Does it adjust PW only or does it do the timing also? I'm having trouble trying to find that answer.

In any case, I'm sure you're right with the timing, I am running a little more timing than i need at the dizzy, and it seems that I'm unable to set the trigger offset to a negative value, so its actually building up about 3 degrees advance (by my logic). I think the nicest part about having this hooked up to my car was being able to see live data and log all of the sensor operation.
 
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