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Re: Racing up and down at idle

Posted: Tue Aug 27, 2013 6:50 pm
by woody90gtz
Losing battery power should not be a problem. There must be something else going on.

Cheapest cable I know of from a very good DIY tune forum: ... LDL-Cables!

Software is free: TunerPro RT

Definition files are available at Gearhead: ... rmation-A1

And that is all you need if you are just logging. For a factory stock car that should be all you need. If you want to dip into the calibration to customize there is everything you need

Re: Racing up and down at idle

Posted: Sat Aug 31, 2013 9:50 am
by No Quarter
Ok, time for a status update. Not going well. After the GM session it ran fine for a couple of days, and then it started acting up again. Last night I had an idle at 2200 rpm. Not nice.

Here's a summary of how it behaves and what I've done, I need to get it fixed or drive it off a cliff.

It sometimes races up and down at idle. If I cut the battery, it's usually fine for a while, and then gets worse and worse. It also has a very slight hesitation, especially when cold. Comes and goes.

I've looked for vacuum leaks, no luck. The following has been replaced:
PCV valve
I've had the computer out, PROM out, all connections look fine.
None of these things have helped, the only thing that seems to help is cutting the battery, that helps for a while.

I've bought on ebay an ALDL cable and SW, but I don't understand the crummy SW manual. I bought the USB version, because my laptop doesn't have COM ports, but the manual still only talks about COM ports. I can't get the TunerPro RT to connect. And BTW I can't find a Chevy 90s 3.1 engine, only Buick/Pontiac. It was mentioned that " PM Woody he has the software and the definitions to log you just need to source a cable if you have a laptop you can work with." PW Woody, are you reading this?

A desperate guess: Since resetting the ECM always helps, I need a new ECM?


Re: Racing up and down at idle

Posted: Sat Aug 31, 2013 10:41 am
by Money pit Beretta
Cutting the power sets everything to stock tune. So it sounds like the computer is fine and that you have a sensor problem or major vacuum leak. Happy hunting!

Re: Racing up and down at idle

Posted: Sat Aug 31, 2013 1:24 pm
by woody90gtz
"PM Woody" translates to "private message Woody"...which is me. haha

What is an "SW" and why do you need it? My ALDL cable is USB and works fine with TunerPro as a COM port.

Here is the .ads definition for $A1 from the link I posted earlier. ... 1323218432

What brand o2 sensor did you put in it? I had a brand new Bosch sensor cause this same problem with my car. I replaced the Bosch with a Denso and the problem disappeared. Check the o2 millivolts carefully when you log it, just because your sensor is new might not mean it is good.

Re: Racing up and down at idle

Posted: Sat Aug 31, 2013 1:28 pm
by woody90gtz
Here is a link to another thread I started recently that helps explain the datalogging/tuning process.

Re: Racing up and down at idle

Posted: Sat Aug 31, 2013 2:07 pm
by No Quarter
SW is my short for Software

Re: Racing up and down at idle

Posted: Sat Aug 31, 2013 2:24 pm
by No Quarter
Woody, tried looking at your links, some require pw. Sorry, I'm a bit slow on this, I need firm instructions. The good news: I have a cable that fits the Beretta port. And I have the TunerPro RT on my laptop. But I can't connect, and if I could I don't know what I'll see.

It's now running so strange I may have to park it and drive my old Jeep instead

Re: Racing up and down at idle

Posted: Sun Sep 01, 2013 2:46 am
by No Quarter
After reading the help sections, here's where I got to:
If I in Preferences Data Acq and Logging use Use Plug In, I get no connection. If I use AutoProm/MAFTPro, I can connect, but if I start Start Data Scan, I'm disconnected.

Bottom left corner says Not Emulating and Hardware not found.

What am I doing wrong? BTW, I use 1989 - 90 3.1L, V6 LH0 Buick & Pontiac $6D.adx, is that the right one for my 90 Beretta 3.1 GT?

Any help will be appreciated. When started this morning it has a 2100 rpm idle. Took the opportunity to wiggle all the wires and sensors best I could, no progress.

Re: Racing up and down at idle

Posted: Sun Sep 01, 2013 9:53 am
by woody90gtz
Using just an ALDL cable it will always say Hardware not Found and Not Emulating...that is normal. When you click the configure plug-in button you need to match the com port there to the com port your cable is installed to. Mine set up for use plug-in and is at Com 4.

I think your car should be $A1.adx. I tried to attach it to this post but the extension is blocked. Send me a message with your email and I will send it to you.

Re: Racing up and down at idle

Posted: Thu Sep 19, 2013 11:49 am
by No Quarter
Status update. Changed the MAP as well. Found no vacuum leaks or ignition problems.

But to the point! I think I've found the culprit. Sort of. When removing the two bolts holding the TPS and turning it so the ALDL tool computer shows 1.18V, the racing at idle stops. If I move it ever so slightly it shows 2.35V and the engine starts racing up and down. So I've now adjusted it and it runs fine right now. can this be? I changed TPS and the problems was similar before and after. And the only way I could get the bolts in when the TPS was at the right place/angle was to enlarge the holes quite a bit. Is there a mismatch between the TPS axle and the throttle blade? When you by hand push very gently on the throttle in the engine room, the TPS axle moves just a millimeter before the throttle blade starts to move. Are they misaligned, can that be adjusted? If (guessing now) we're talking that the problem is that the TPS moves first so the ECM thinks the throttle blade has moved enough to open for some air, could that have been worsened with time because of build up of goo around the throttle blade?

As always any suggestions will be appreciated. It runs fine now, but for how long?