‘92 5.7 tbi stalls after tach goes crazy

[Ninety-two]

I’m new to posting here but not to reading. I’m also not a great mechanic, at least I’m not great at diagnosing, but I can wrench a bit. Anyway please excuse my ignorance. I’m trying.

5.7 tbi in a ‘92 K1500. My work truck. I recently threw a bunch of parts at it. Surging idle and crap mpg, I figured some deep-tune parts I could do myself might actually be an inexpensive place to start. Cap, rotor, plugs, wires, O2 sensor, TPS, MAP sensor, fuel filter and a thermostat because I needed it.

Much improved….for about 20 miles. Then following a warm start it stalls. Starts right up but stalls again. And again. I notice the tach is bouncing up and down really fast, faster than the flywheel would actually let the engine rev, but stalls when tach crashes. Couldn’t find a vacuum leak with propane. I’m absolutely stumped. I’d be so disappointed to call a tow after I did all that….

 

[PlayingWithTBI]

Then following a warm start it stalls. Starts right up but stalls again. And again. I notice the tach is bouncing up and down really fast, faster than the flywheel would actually let the engine rev, but stalls when tach crashes

It happens only when the engine is warm right? This sounds like the proverbial Ignition Control Module going out. It may also be related to the Pickup Coil in the distributor. Unfortunately, you can take them out to test and they can prove it's bad but, they can't prove it's good. There's a lot of back and forth about who's still making quality parts but, stay away from cheap parts, only buy quality ones. If you see an ICM on Rock Auto, Summit Racing, etc. Then see one on Flee Bay for $49.99 less, be skeptical! HTH

 

[1997]

any codes?
OBD1 can set codes without checkeck engine light coming on.

 

[Ninety-two]

It happens only when the engine is warm right? This sounds like the proverbial Ignition Control Module going out. It may also be related to the Pickup Coil in the distributor. Unfortunately, you can take them out to test and they can prove it's bad but, they can't prove it's good.

Thanks for the reply. As below, I didn’t know it might store codes without a check engine light, so I’ll see if I can get anything that way first.
I read in a related thread that the tach jumping around might indicate something in the distributor. I had meant to ask what the tach is actually metering but maybe that’s my answer. You’re right about ICMs though. Cost varies insanely. From $18 to $105.

 

[Ninety-two]

any codes?
OBD1 can set codes without checkeck engine light coming on.

 

[Ninety-two]

No codes via paper clip method, other than confirming diagnostic mode. Runs smoothly warming up. Once warm, stalls with no warning. Tach-but not rpm’s- jumps around a bit then crashes with stall. ICM?

 

[Ninety-two]

…and if new distributor @$145 with new ICM @$100 should I just do the distributor?

 

[PlayingWithTBI]

Runs smoothly warming up. Once warm, stalls with no warning. Tach-but not rpm’s- jumps around a bit then crashes with stall. ICM?

As I said, that'd be my guess.

…and if new distributor @$145 with new ICM @$100 should I just do the distributor?

Your call. I can say, I bought a Spectra Premium distributor and the ICM went out in less than 2000 miles. I now have the ACDelco D1984A in that same distributor for 4 years now.

Another member here bought a lifetime guarantee distributor from O'Really, I haven't heard of any issues since. YMMV

Also, your Ignition Coil may be going bad too which CAN take out the ICM. When I bought the Spectra Premium distributor, I also bought a Pertronix Flame Thrower which went out about the same time - putting the cart before the horse here? The coil only caused a stumble, the Spectra Premium ICM caused surging at cruise speeds once warmed up. The tach would jump up to 4,775. That's how I caught it data logging.

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Here's the coil, I found this by spraying water on the ignition parts until the engine tried to die. Note the burn marks in the circle...

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[Ninety-two]

Seems like smart money says do it once. I’ll probably do distributor and coils. Coil is fairly inexpensive and I’ll already be there. Delphi new distributor over AC Delco reman, or what?

 

[PlayingWithTBI]

Delphi new distributor over AC Delco reman, or what?

Again, your call.