‘95 5.7 runs poorly when warm. I’m reducing myself to being a parts-changer.

[PlayingWithTBI]

The ignition modules are absolutely prone to fail with heat. But my experience has always been that they either work great or not at all. I’ve never had a drivability issue related to an ignition module other than a complete no-run condition.

The ICM can cause drive ability issues too. The Ignition Coil and Ignition Control Module work hand in hand AND one can cause failure to the other. Again, as everyone says, only buy quality electronic parts. Yes they're expensive but, you get what you pay for

A GM Original Equipment Coil (GM PN19418995) and ICM (ACDelco D1984A) are still available, you just have to hunt for them I will always change both at the same time!

 

[df2x4]

There's also the "GMT400 Community Scan Tool." Last I heard it was still making the rounds, you could get on the list to borrow it for free. It's a Snap On MT2500 that will do OBD1.

https://www.gmt400.com/threads/gmt400-community-scan-tool.60565/

 

[any4xx]

The ICM can cause drive ability issues too. The Ignition Coil and Ignition Control Module work hand in hand AND one can cause failure to the other. Again, as everyone says, only buy quality electronic parts. Yes they're expensive but, you get what you pay for

A GM Original Equipment Coil (GM PN19418995) and ICM (ACDelco D1984A) are still available, you just have to hunt for them I will always change both at the same time!

Good to know this. I’ve literally never experienced a module issue other than a complete failure. I have the “Genuine GM” module on the way now.

 

[HotWheelsBurban]

Good to know this. I’ve literally never experienced a module issue other than a complete failure. I have the “Genuine GM” module on the way now.

I have a new module and coil for the Burb (bought last fall around the time I ended up replacing the fuel pump. If they are the same as the '97 I might install them before our trip. I don't like it idling rough....

 

[any4xx]

OBD1 to USB cable + laptop / phone + software is the way.

I have an ancient memory of owning something like this a million years ago when I had an ‘86 Corvette. If I remember correctly I never could get it to work properly. Hopefully the cables/software of today are a bit better?

 

[Komet]

It wasn't too big of a deal for me. Had to make sure the cable was coming in on the right com port. I had success datalogging with tunercat on a laptop and also aldldroid on my phone. I think most people use tunerpro but I haven't done that one.

 

[any4xx]

IAC for the win! Since replacing the coil cured the heat-soaked performance issue but not the off idle stumble I figured it was time for another guess. Today I put a new IAC valve in and my off-idle stumble is now completely gone.

I figure that three good guesses in a row tells me it’s time to shop for a lottery ticket.

I‘ve only had the truck for six weeks now and I’m happy to report that it’s now free of drivability issues. The last 12 years of being parked were pretty hard on it but it’s rebounded quite well.

 

[any4xx]

Hah! Not so fast there Dummy!!! This morning I was out driving and realized that while my off-idle response was greatly improved with the replacement of the IAC valve, there was still the slightest of an off idle issue. After playing for a while I realized that I could cause a stumble at any speed (even while parked) by carefully opening the throttle and holding it somewhere around 2% to 3% open. So that pointed me to the TPS.

A quick stop at a parts store and I installed a new TPS in their parking lot. NOW I’m unable to cause ANY type of stumble under any condition. Acceleration is smooth from gently off-idle to foot-to-the-wood slamming it.

So for those who haven’t followed along from the beginning: The no-start was fixed by replacing the fuel pump. The horrible acceleration when warm was fixed by replacing the coil. The vast majority of the off-idle issue was fixed by replacing the IAC valve. The last small remnant of the off-idle issue was fixed by replacing the TPS. So FOUR issues all stacked up together. Loads of fun…

And just for entertainment value, after all of this I got my very first SES light on my way home while everything was running smoother than ever. WTH!?!. I pinned the A/B on the ALDL when I got home and got a Code-32. Huh? Popped the hood and found that I had pulled the vacuum line out of the EGR valve while changing the TPS this morning. Ugh…

NOW it’s running perfectly! Hopefully I’m done with this saga for a while….

 

[HotWheelsBurban]

IAC for the win! Since replacing the coil cured the heat-soaked performance issue but not the off idle stumble I figured it was time for another guess. Today I put a new IAC valve in and my off-idle stumble is now completely gone.

I figure that three good guesses in a row tells me it’s time to shop for a lottery ticket.

I‘ve only had the truck for six weeks now and I’m happy to report that it’s now free of drivability issues. The last 12 years of being parked were pretty hard on it but it’s rebounded quite well.

Glad you got yours sorted out; that makes me wonder if the coil isn't the problem on my crew cab. We've had warmer weather lately in Houston (we tied a record high today at 87°) and it's idling more roughly than after I replaced the TPS and IACV. Somewhere in there I also replaced the spark plugs; they weren't bad looking but after 127,000 miles and 27 years I figured they needed changing. Everything on this truck is most likely original parts except for what I've changed. And it also wasn't driven much in the 3 or 4 years before I bought it. I was told by the man I bought it from,whose grandfather was the original purchaser/owner, that once grandpa passed, the rest of the family didn't drive it much. He mainly used it to tow a small boat and trailer a few times.
I think I'm going to replace the coil and install some wire separators; on the passenger bank there's a couple of places where the factory should've put some(because the wires are closer than they should be). Hopefully that takes care of it....

 

[HotWheelsBurban]

I've been told that TPS and IACV frequently go out around the same time. I guess if they're original or really old, the solution is to replace both? I've not been able to afford to do that on either truck though....