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[Solved] 1993 Chevrolet S10 stalling when hot.

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1993 S10 Blazer 4.3 CPI

192,000 miles

4L60E automatic transmission

still has AC mounted.

 

Hello, Scotty and anyone else reading this post.

 

Note: I don't live in US, so OEM parts and even aftermarket ones are a bit hard to come by, mostly, it's double price and a whole month or two waiting for shipping. So don't get me wrong when I swap the parts for used ones. )

 

So my 4.3 CPI S10 Blazer 4-door squarebody caught a weird bug about a week ago and I'm still trying to figure it out.

I just started driving home after the car was sitting in the sun for half a day and after the first turn It stalled out on me. I fired it up again - and it died in a couple of seconds, again. Cranked it again - died, again. I used the momentum to park it and went to the gas station (thought the fuel gauge was just a bit off and I'm outa fuel). I filled it up - cranks, but no start.

So I thought It might've been the IAC valve (since it's been idling rough lately and lighting the "service engine soon") and replaced it from my other Blazer. It started almost right away but then it stalled after a little warmup, when I pressed the gas pedal to the floor. I fired it up again and tried to move - no problem there. But as soon as I made a U-turn and cleared the intersection - it stalled on me again.

The next day I came with a friend who had one of those old GM scanners. Idle was at 900rpm. It said the old error was about the IAC, now it was about the MAP sensor. So I took it from my other Blazer, cleaned it a bit and installed it. The error was gone. But then we had a thought about checking the other IAC valve if it was actually working. Swapped to the old one - no start, changed back to the other - same thing, no start. That got me thinking other directions.

I had a similar issue in December and have already changed the fuel pump and both filters, fixed the fuel line, replaced the coil and distributor assembly with brand new ones, changed the oil (10w40 since it served me well in other cars) and oil filter and that seemed to do the trick.

So I was sure it's not the ignition or fuel problem.

 

I narrowed the problem to this:

The truck stalls after reaching 210 degrees when I touch the accelerator while moving. Also, it's not a usual "clunk-clunk" stalling, but something like a silent turnoff.

 

I found a hole in the main intake hose, replaced that one and cleaned the temp sensor (checked it - working fine). Then I cleaned the EGR valve. No change.

Then I thought about vacuum leaks.  I noticed my vacuum line worked it's way off the cruise control actuator - I put it back on. Clamped the vacuum pump hose - no change in idle. Cleaned the PCV valve and replaced the rubber seal, since the old one was stone hard - no change. I didn't hear any particular hissing anywhere either.

I stumbled on some Youtube videos about Blazers stalling and found out the ICM unit was inside the distributor and thermal paste is necessary to be applied there - so I did, used the best computer thermal paste that was available. That certainly made the startup much smoother, but when I tried running the truck again - same thing, dies on acceleration when hot.

The next day I thought it could be the Oil Pressure Switch, since the fuel pump schematics include it and many people blamed it. So I managed to find a new one in my city and replaced it. At first, the oil pressure dial went berserk jumping up and down, then it settled after a while, still having seazures from time to time. I tried driving the truck - same problem.

Today the gauge seemed to behave. But I've messed up the distributor position while replacing the oil switch, so it idles pretty rough and I wanna address that in the next few days.

I'm also kinda thinking "bad wiring" but then - why only when hot? I found a video of a guy having trouble with the coil wire when engine got hot, so I'm replacing that tomorrow. I also think the ignition switch is worn, since a couple of times it tried to start before I fully turn the key to starter position. I'm not much of an electrician, so at this point I'm just guessing.

Also, some people on Chevy forums suggested that maybe the antifreeze\oil cooling system isn't working efficiently enough and that causes the ECU to shut down, but I don't know - seems plausible, since the summer just recently started and that day I turned the heater off. Also, I only got this truck in autumn, never drove it before in hot weather.

 

I'd really appreciate any useful practical advice coming from experience, got tired of those "visit the dealer" useless ones.

 

The only other thing that seems off with the truck is the Voltage gauge showing around 15,5 volts instead of usual 14 (this started couple of months ago, but goes away after a couple minutes of driving).

13 Answers
3

It doesn't sound like you've nailed this down to either a spark or a fuel delivery issue yet.

Why not grab an HEI spark tester and during the next "Crank NO Start" see if you're getting spark at the ignition coil?

If you are, spray some starting fluid into the intake and see if the Blazer starts for a second.

Your Blazer has GM's old Bypass Ignition system. So below 400 rpms the computer isn't involved in sparking the ignition coil. It's done by the pickup coil inside the distributor and the Ignition Control module.

When they're failing those pickup coils tend to stop producing a voltage signal when they get hot and then work again when they cool off.

Without that signal, the ignition coil won't produce spark and the ICM won't send a signal to the PCM to pulse the fuel injectors.

They're a pain to replace so most people just buy a new distributor.

Anyway, here's a link to a step by step tutorial to test all this stuff. (except for spraying starter fluid into the intake but if your coil is sparking you can squeeze that in before doing the rest of the stuff in the tutorial).

https://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/distributor-mounted-icm-tests-1

 

 

 

 

Dude, did you read my post? )))

The full distributor assembly and coil are brand new. I even put some very fine thermal paste on the ICM.
Also, my Blazer doesn't idle at 400, it stubbornly idles at 900.
I just finished changing my fuel pump to the OEM Delphi - my guess was correct, it DIDN'T help. )))

I'm thinking bad wires, at least on the coil. And probably should recalibrate the timing, tho I can't find the wire you're supposed to disconnect from ECM.

Oh, and BTW, I've been testing it out with the hood open for last several times, so It shouldn't get that hot to malfunction.

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Posted by: @bogdan

I fired it up again - and it died in a couple of seconds

Posted by: @bogdan

It started almost right away but then it stalled after a little warmup, when I pressed the gas pedal to the floor.

Posted by: @bogdan

The truck stalls after reaching 210 degrees when I touch the accelerator while moving

All these symptoms indicate to me it's a fuel delivery problem.

 

Posted by: @bogdan

OEM parts and even aftermarket ones are a bit hard to come by

 

You must use new OEM fuel pumps (AC Delco or Delphi) on these vehicles.

 
 

It runs and revs fine when cold, tho. And I had it running fine for months after the pump replacement even at 210 degrees.
Why exactly OEM ones? Isn't the exact fuel pressure match enough?

Also, why does it Idle exactly on 900rpm then? Shouldn't it be less or varying with a dying pump?

🤷‍♂️ Good questions. Maybe there is an answer on the internet.
I've heard this story over and over. Almost always this is the issue, and OEM pump solves it.

I'm sincerely curious about it but couldn't find any technically deep answer anywhere. (

And also, there's a practical reason for me, since not only those pumps are hard to get across the globe, but also someday their production will stop, especially with this EV craze.
So if I had the exact specs needed - I could try finding the best replacement possible from local manufacturers.

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There is difference between fuel pressure and fuel volume, just like there is a difference between PSI and CFM.  The injectors are very sensitive to fuel pressure (PSI) and fluid volume (CFM) or gallons per minute.  @mmj has what is probably the answer, OEM part.

Hm. I see.
I already had the Delphi pump ordered and it came a month ago. Tho, I didn't care to replace it since the truck was running fine. I'll check it out.

Though, being naturally curious - why did it run perfectly OK for several months when I put the other pump in? I'd reeealy like a technical explanation on this. )

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Posted by: @bogdan

What about other aftermarket US-made non-OEM parts? Are they any good?

it depends on what part you're talking about.

Sensors, electronics, pumps, motors etc ... never!

Posted by: @bogdan

my wallet doesn't like that math.

Simple. Don't buy overseas vehicles.

I Dont Know

My foolish friends buying Japanese imports have the exact same problems as you.

Well, what worries me, that if even the US parts are no good, the only alternative is Aliexpress, for the most part, since Ebay's shipping fee is a pain...

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Not very technical but a lot of after market parts just aren't built to the same standards as OEM.  Is the pump in there now after market?  Where did you buy it, Ebay,  Amazon, etc?  The heat insulating gel should have come with the new ignition module.  It's not really a paste.  Is the ingintion module OEM?

Don't really remember. Think it might've been Airtex.
I took it from my 3rd Blazer, which I use as a donor. It was running fine before i crashed it. It was a TBI, tho, maybe that's the thing...

I'm just really looking for a decent alternative out of local manufacturers, since a 100$ item becomes a 200$ item as soon as it crosses the Atlantic and my wallet doesn't like that math. ) If only I had the full specs...

 

The ignition module came with the distributor, it was a full assembly. But I read that their thermal paste was kinda "meh", so replaced it with the one I tested on my Alienware laptop - there it significantly decreased the temp. And the texture of the "gel" was exactly the same as of the thermal paste, btw.

 

P.S. What about other aftermarket US-made non-OEM parts? Are they any good?

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If you're gonna play, you've gotta pay. I only buys parts locally that come with a limited lifetime warranty, with the exception being the ones @mmj mentioned above.

Zippo claims their "lifetime warranty" works anywhere - not quite, depends on the place you're in. )))
Where d ya get the sensors and stuff, then? )

there are a handful of online retailers for genuine gm parts. But they aren't cheap.

Most of those don't ship overseas. So Ebay and Amazon, I guess..?
And what about those "performance" and "heavy duty" parts listed on Rockauto?

I tried comparing, but European and Asian ones not only use different measurements, but also list different types of characteristics when compared to US (like octane numbers on gas pumps - 92, 95, 98 - yours are "regular", "premium", etc...).

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Topic starter

So, for anyone who'd be running in similar problems - I fixed it!
Wanted to write sooner, but got stuck with other things to do and forgot. )))

Sooo. It was the darn new ICM the whole time.
What I didn't realize until I met a mechanic who's also a Chevy fan, was that those modules are quite often defective (even new ones!) and he had to order a whole bag of those just to find a couple that would work propperly.
So I did the same - ordered several ones from different brands (since the GM one is pretty expensive here and takes 2 months to ship) and voila, it worked!

Thx everyone who helped me with advice.

Glad you solved it and thanks for reporting back.
I'd say it's very likely that the defective "new" units are just salvage from wrecks that have been cleaned up and repackaged. That's what happens when you buy parts for a vehicle that came from the other side of the planet.

Not for nothing but I told you to test that 2 months ago. I even gave you a link on how to test it
.
You replied: "Dude, did you read my post?"
.
Anyway, I appreciate the belated "up vote" and I'm glad you finally fixed your S10.
.
Like MMJ said, thanks for coming back and letting us know how it worked out

Well, what I didn't know, that BRAND NEW ones are quite often bad from the factory. )
And, as I've stated before - the whole distributor assembly was replaced recently. So I excluded that possibility, considering the car's old and many other parts could go bad. )))
Fixed the air leak, wrong temp reading for ECU and rich fuel mixture on the way, so I don't really regret digging around more than I could. )

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Topic starter
Posted by: @mmj

Simple. Don't buy overseas vehicles.

I Dont Know

My foolish friends buying Japanese imports have the exact same problems as you.

Well, I gotta admit - it's kind of a passion. )))

Car culture is much weaker in Europe in general. And European cars feel kinda boring, same goes to Japanese, btw, since there's plenty of those (tho, parts are quite cheap here). But old US cars are pretty rare, which kinda makes you appreciate them more.

Besides, I have a weakness for old square designs and where else would there be such an array of those if not US cars... )))

I completely understand. But like every hobby horse, they require blood sacrifice. You have to pay to play.

I know, I know.
There's some passion in those cars. They look totally different, they're made totally different and I can also joke that my 0-100km(0-60Ml) is measured in liters instead of seconds. )))

I'm just worried that the recent pandemic shipping crisis might get me in a situation where I won't be able to get some parts even for a big fee, so I have to think "locally". )

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Topic starter
Posted by: @doc

There is difference between fuel pressure and fuel volume, just like there is a difference between PSI and CFM.  The injectors are very sensitive to fuel pressure (PSI) and fluid volume (CFM) or gallons per minute.  @mmj has what is probably the answer, OEM part.

I had another thought - could it be, that the alternator giving more voltage than it should causes the pump to malfunction?

no

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Topic starter
Posted by: @bogdan

since it's been idling rough lately and lighting the "service engine soon"

I also forgot to mention that it still lights up the "service engine" light when it warms up ONLY on idle (press the gas pedal - it's gone).

Can this indicate some extra issue connected to the situation? As I've mentioned before - it always idles on 900rpm and I can't figure out why. Or is that also the fuel pump to blame?

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Topic starter
Posted by: @mmj

You must use new OEM fuel pumps (AC Delco or Delphi) on these vehicles.

Just as I thought - didn't help. I installed a Delphi pump which I ordered before and had sitting around - nnnope, still dies on acceleration when hot.

Only the "service engine" light was gone now... I think...

that's too bad, but I still think you're better off with a reliable pump.
Other things that are affected by heat are electronics (ICM, PCM etc) and injectors.
You might also consider the catalytic converter. Remove the O2 sensor in case there's a restriction.

Yeah, it's much quieter, but that doesn't help much. )))

I asked a bunch of people and opinions have split:
Some say it's the spider or the fuel pressure regulator - but then, why only on hot and it stalls when rpms drop after stepping on gas.
Others blame crank, camshaft or coolant temp sensors.
Third (where I tend to lean) blame wiring and relays. Since my alternator tries givin out more voltage than needed, I might as well go down that road and swap it out.

As for the CAT - it was deleted years ago before me, so no problems there.

Could you please update my post on that matter and those discussed here?
Maybe someone will have an answer to that problem.

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Posted by: @bogdan

I think it might also be the alternator relay regulator.

disconnect your alternator, and hook up the battery to another vehicle

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Topic starter
Posted by: @mmj

I'd say it's very likely that the defective "new" units are just salvage from wrecks that have been cleaned up and repackaged. That's what happens when you buy parts for a vehicle that came from the other side of the planet.

Besides, it's too small of a module to be saved, to my opinion. If it's fried - it's fried.

And what are the chances of thousands GM ICM's to end up exactly in Chinese garbage piles intact brought from abroad? It's much more likely that they salvage separate parts like transistors\capacitors or whatever and make something out of those. Or even more possible thing - they just sort materials to be melted (it'd be much easier and cheaper that way).

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