Snap-on MT2500

[Steven Petersen]

There really isn't a "fast idle" spec on the .bin for a 7747 ECM. When you shut off your engine the IAC goes to its "park position", in this example it's 145. Then, when you start the engine, it waits 20 seconds before the IAC starts to decay to set position vs temp. Here's some of the tables controlling the IAC. In this case it calls for your IAC to be ~24 when warm and your idle s/b ~600 in Closed Loop.

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Agreed, your IAC position at warm idle appears to be high. Plus your idle is high too. As @Schurkey suggested, clean the IAC passages. Maybe they're choked down a little causing the ECM to open the IAC some more?

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Try turning off your ignition, wait about 15 seconds, then turn it back on and see where your IAC is. Theoretically it s/b ~145 steps in park position (I think, ha ha).

How old is your O2 sensor?

O2 sensor was replaced with new Delco 9 months ago, only because I bumped and broke the old one while working in the vicinity. The threads were bad and I had it tap the hole to get the new one in. Would an air leak at the threads be a possible problem?

Another thing I just discovered. The butterfly in the air cleaner was stuck in the open position, meaning it couldn’t shut and pull warm air from the manifold. I was able to free it and now it works properly. I’m hoping this helps during warmup.

 

[PlayingWithTBI]

Would an air leak at the threads be a possible problem?

Yes that could be an issue, it may be getting outside air making it think you're running rich. YYMV

 

[Steven Petersen]

Yes that could be an issue, it may be getting outside air making it think you're running rich. YYMV

This morning warm up was improved. It never stumbled and less surging. Still very slight maybe 25RPM. Higher O2 cross counts during warm up too. The only thing I’ve changed is freeing up the butterfly for the heat stove on the air cleaner.

 

[FrankieD61]

My son has a Solus Ultra he uses at work but he's never hooked it up to the 1227747 in my 88. I have a laptop with TunerPro RT software and an ALDL cable which has 2 jumpers - 1 direct short from terminals A - B, the other is a 10K resistor for older PCMs and TPI systems. Here's a screenshot of my real time feedback. You should be able to see most of these (maybe not all) with your MT2500.

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Just an FYI, here's a screenshot of a data log from the WUD (What's Up Display) used with the EBL Flash - running a little rich on the WBO2, LOL.

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I love this stuff

What cable are you using? ALDL to USB, or something?

 

[PlayingWithTBI]

What cable are you using? ALDL to USB, or something?

Yep, the 12 pin ALDL to USB.

OBD Diagnostics

aldlcable.com

 

[FrankieD61]

Yep, the 12 pin ALDL to USB.

OBD Diagnostics

aldlcable.com

Thank you!! You guys are awesome!

 

[blairbernard575]

I just picked up a Snap-On MT2500 to use on My 88 K2500. I've never used a scanner before so this is new to me. It came without any manuals so I have a few questions. I have the primary and troubleshooter cartridges. I hooked it up and the first thing I noticed is it keeps the idle at 1000 rpm. Is this normal? There are no codes stored so that's not an issue. It shows back and forth from exhaust lean to exhaust rich. Is this normal? Are there any other things I should check? Thanks for any guidance.

Bought the same snap on mt2500 but my question is what cartridges do I need for first gen tbi. I have a 1992 GMC Sierra

 

[Schurkey]

If you have a '92, you'll want a cartridge from '93 or newer up to '99. This will not be difficult, the '99-and-older cartridges were common on eBay; they may still be. You'll also want the correct cable end, and the cigarette-lighter power adapter. I had GM1, GM2, and GM3 OBD1 cable ends. The GM3 is--so far as I know--for ABS only, and only on certain vehicles. GM1 and GM2 are the more-used ends. I forget which one is 5-pin (early) and which is the more common, later adapter.

I ran an MTG2500 for ~20 years. I was using '99-and-older domestic, and a 6.2 software version (released in 2006, 2nd quarter, and good to 2005) Domestic and Asian cartridge which went back to...'96, I think. Similarly, I had the Fast-Track Troubleshooter cartridges up to...'94, maybe. I didn't use the Troubleshooter cartridges much. Maybe I should have.

 

[blairbernard575]

If you have a '92, you'll want a cartridge from '93 or newer up to '99. This will not be difficult, the '99-and-older cartridges were common on eBay; they may still be. You'll also want the correct cable end, and the cigarette-lighter power adapter. I had GM1, GM2, and GM3 OBD1 cable ends. The GM3 is--so far as I know--for ABS only, and only on certain vehicles. GM1 and GM2 are the more-used ends. I forget which one is 5-pin (early) and which is the more common, later adapter.

I ran an MTG2500 for ~20 years. I was using '99-and-older domestic, and a 6.2 software version (released in 2006, 2nd quarter, and good to 2005) Domestic and Asian cartridge which went back to...'96, I think. Similarly, I had the Fast-Track Troubleshooter cartridges up to...'94, maybe. I didn't use the Troubleshooter cartridges much. Maybe I should have.

So as long as it says 99 thru means 99-and-older domestic be the right cartridge for a tbi ob1 makes sense. First time I tried a scanner tool I just want to make sure I order the right cartridges for my truck..

 

[Schurkey]

'99 and older--"1980 1/2 thru '99". Not " '99 thru 2006" or whatever. So more "Thru '99" than " '99 thru xxxx"