Guys,

I have a couple of newbie questions, my first problem is that my idle pulsewidths are insanely high. As the engine settles into an ~800rpm idle the PW creep up to 4-5ms! I even had one quick blip of 8.xms yesterday with a factory GM AUJP chip. This is killing my spark plugs. I put roughly 2k on my last set (mainly 'cause I spent a lot of time lately just idling). Once the TPS is greater than 1-2% the PW drop down to 1.xms, it's just the idle goes super rich and the idle gets choppy. Can anyone point me in the right direction as far as where to make changes in the PROM using TunerCat?

Also, does anyone know if there is a place in TunerCat to change the VSS signal from the electronic pulse of the '90+ electric speedos to the pulse of my '89 cable driven speedo? I thought the VSS switch in the ECM switch table would do it but nope.

And finally, I was curious, in TunerCat it seems like the ranges on the tables are awfully short. Some rpm ranges stop at 4800rpm, some speed ranges stop at 100mph. Is there a way to extend these tables beyond these values? If not what does the ecm do for VE values at 5000rpm on up?

Thanx in advance!

Drew Skinner
'89 IROC L98/A4 HOT cam, headers, exhaust,
127730 ECM conversion

 

On a cold start the pulse widths are long, 4msec at a hot idle, you have a problem, need to looks of vac leaks I'd imagine a mechanical problem. With out the VSS then the IAC is screwy
To fix the VSS change location 0018 from D8 to 98 and the use C-6 for the optical speedo input
After 4800 just uses those same calcs. I personally never seen an area the needed changed after that

 

Does your message imply that your TPS is reading less than 1-2% at idle? Have you gone through adjustment procedures for the TPS and base idle? This is on a 730, so what kind of vacuum are you pulling at idle, and how does it compare to the MAP sensor signal?

Just some thoughts, entered as such.

 

I made some Diacom runs tonite, and yes it appears that at idle my TPS output is .65V and throttle position is 0%. Vacuum (according to the MAP sensor) is 15-17"Hg at idle, I need to pick up a gauge to verify that figure. I noticed something odd when I recorded a highway punch from 40-80mph tonite. As soon as I go WOT MAP plateaus at 29"Hg, shouldn't vacuum go to 0 when at WOT? I never noticed it before, but I have never seen vacuum go UP at full throttle, only down to 0. Anybody clue me in here? Also my 02 don't plateau at the usual 88xmV like they usually do, instead they just oscillate like normal part throttle conditions. Fuel pressure is solid @ 43psi, but the 02 sensor is doing weird stuff, it's a brand new heated 02 also.

I'm figuring I should resolve my VSS issues before anything else in order to get that variable out of the equation. Thanks for the help so far guys!

Drew
'89 IROC L98/A4 cam/headers/'730 convert

 

Yes vacuum does go to or near 0 at WOT. The reading you are seeing in Diacom is absolute pressure, not vacuum.

MAP 29"Hg = Vacuum 0.5"Hg = MAP 100Kpa


See, http://www.geocities.com/MotorCity/S.../prog_101.html for the conversion table.

 

Grumpy, what kind of program are you using? I looked up 0018 in the s/w that came with the pocket programmer and everything is 0 at that address. I know I must be doing something wrong here. Delco_edit says the same...

Thanks,
Drew
'89 IROC L98/A4

 

Just so we are at apples and apples look at a AUJP 0018 should be D8
I use Hex Worshop for stuff like this.

 

Thanks Grumpy, got it fixed.

I'm still having problems, I've checked and double checked for vacuum leaks, reset the TPS to .55VDC (was .65VDC) and I've reset the IAC per the service manual procedure. I'm going to thoroughly clean the throttle body and IAC passage then reset the IAC again. Just to eliminate any doubt.

I posted a few files on the web, so if anybody feels like taking a gander hit: http://lonestar.texas.net/~drews/efi/

"idlepoor" is a Diacom buffer that clearly shows the decaying idle quality.
"1_aujp" is the bin.

Thanks,
Drew
'89 IROC L98/A4

 

400+K gads
L8r