96 blazer stalls when hot

[mcdon26]

Ok. As requested I'm starting a new thread. I've seen a lot of people who have had this issue throughout several different forums but no one has ever posted a resolution that I have found.I bought the blazer last September. 4.3l spider injectors had 175k miles when purchased and super clean. Last summer on hot days, and only after driving 15 - 20 miles the engine would start to hesitate on acceleration. The more gas pedal I would give it, thee more it would hesitate and lose power until it eventually stalled completely . I could let it sit, cool down for 30 minutes and it would restart. This happened 4 times last summer on hot days and each day it was back in the shop from where I purchased it. Fuel rail pressure is always good. Leak down test was done on the fuel rail and it held. The only code I would get was an intermittment small evap leak. Fuel filter was replaced. After several revisits to the mechanic he replaced the ICM (supposedly), then we entered the fall season, the weather cooled, and I never had the stalling issue. I did however sporadically get the small evap leak code come up when I was always below a half tank of fuel. I'd fill up and and next diagnostics cycle the SES would go off. Fast forward through the winter, no problems other than sporadic SES WHEN UNDER HALF TANK. motor was replaced 2 weeks ago with a new one. 500 miles on the motor and we had our first 80 degree day here in Maryland. Blazer started fine in the morning and starting fine in the afternoon. In traffic, and after sitting at a stop light for a few minutes the problem restarted. No SES light. From a stop gave it gas, it accelerated fine until I gave it more gas pedal to accelerate faster. Vehicle hesitated badly so I backed of the gas and it felt normal. I had to keep backing off the pedal to keep it from hhesitating until it final stalled completely. Had to let it sit for over an hour. Check the fuel rail and it had pressure. I couldnt tell exactly as i had no gauge. Turn key back on and pressure built back up. It hesitated and was hard to restart but ran for another 4 miles before doing the same thing again. Let it sit two hours restarted and got it home 5 miles away. Although I still got no. SES light I noticed a discoloration on the ignition coil and replaced it as well as cleaning out the MAF sensor in case it was dirty. But again no codes. This morning started fine and I'm now sitting at the shop. This never repeats itself for any mechanic. Just likes to leave me stranded. Thank you in advance for your help.

[Scrapper]

i seen what all you done except the cps sensor or it just might be your cat is plugged?

[MT-2500]

Originally Posted by mcdon26

Ok. As requested I'm starting a new thread. I've seen a lot of people who have had this issue throughout several different forums but no one has ever posted a resolution that I have found.I bought the blazer last September. 4.3l spider injectors had 175k miles when purchased and super clean. Last summer on hot days, and only after driving 15 - 20 miles the engine would start to hesitate on acceleration. The more gas pedal I would give it, thee more it would hesitate and lose power until it eventually stalled completely . I could let it sit, cool down for 30 minutes and it would restart. This happened 4 times last summer on hot days and each day it was back in the shop from where I purchased it. Fuel rail pressure is always good. Leak down test was done on the fuel rail and it held. The only code I would get was an intermittment small evap leak. Fuel filter was replaced. After several revisits to the mechanic he replaced the ICM (supposedly), then we entered the fall season, the weather cooled, and I never had the stalling issue. I did however sporadically get the small evap leak code come up when I was always below a half tank of fuel. I'd fill up and and next diagnostics cycle the SES would go off. Fast forward through the winter, no problems other than sporadic SES WHEN UNDER HALF TANK. motor was replaced 2 weeks ago with a new one. 500 miles on the motor and we had our first 80 degree day here in Maryland. Blazer started fine in the morning and starting fine in the afternoon. In traffic, and after sitting at a stop light for a few minutes the problem restarted. No SES light. From a stop gave it gas, it accelerated fine until I gave it more gas pedal to accelerate faster. Vehicle hesitated badly so I backed of the gas and it felt normal. I had to keep backing off the pedal to keep it from hhesitating until it final stalled completely. Had to let it sit for over an hour. Check the fuel rail and it had pressure. I couldnt tell exactly as i had no gauge. Turn key back on and pressure built back up. It hesitated and was hard to restart but ran for another 4 miles before doing the same thing again. Let it sit two hours restarted and got it home 5 miles away. Although I still got no. SES light I noticed a discoloration on the ignition coil and replaced it as well as cleaning out the MAF sensor in case it was dirty. But again no codes. This morning started fine and I'm now sitting at the shop. This never repeats itself for any mechanic. Just likes to leave me stranded. Thank you in advance for your help.

It needs to be tested when it does it.

Run a full fuel pressure test.
Hook up a fuel pressure gauge and drive it untill hot or when itn does it.
Post back fuel pressure reading and readings when it stalls.
If fuel pressure is up to specs when it stalls then check for lose of park to plugs.

Also tap computer for stored or history codes.
If any post back code no.

[mcdon26]

I was at the shop when I posted the original message and the new mechanic went through everything again and it all checked out. Actually I've replace the cat and muffler 3 weeks ago so a no go on that. I went ahead and replaced the ICM two days ago as it didn't look like it had been replaced as I was told. I had mentioned to the previous mechanic about ensuring there was grease between the ICM and the heat sink. When I pulled the old one off, it looked like silicon grease was on it. Not the white grease supplied with the new one. I took the heat sink and ICM off, cleaned the heat sink extremely well and reinstalled. So far the weather here has not gotten out of the 60's so everything has been running fine. I went on a 100 mile round trip adventure yesterday without incident. It's supposed to be 80 tomorrow so we'll see how it fairs.

The issue with having it tested when it happens is I'm usually alone, or with my 5 year old son when it occurs. Within 30 minutes to an hour the problem dissipates. Not enough time to contact a tow company, wait for them to respond and transport the vehicle to the garage. By that time, the vehicle is operating again. Frustrating.

By CPS, you mean the Cam Position Sensor? How difficult is that to replace?

As I mentioned before, lots of people having this problem but I haven't found anyone following it all the way through to the end. At least I'd like to complete this thread to resolution.

Parts replaced so far:

Motor
Cat
Muffler
Ignition Coil
Ignition control module (cleaned heat sink and replaced grease)
Distributor, Cap, Rotor, wires
took apart and cleaned MAF sensor
Replaced air filter (was very dirty)
Thermostat

Current MPG average is 17.3

[mcdon26]

Alright, that didn't work guys. Got to my son's daycare, turned off the vehicle and it wouldn't restart. Left it sit 30 minutes and it restarted, drove perfectly fine and got me the 10 miles home. Although, this time it did throw a code directly on startup. I can't get it anywhere now though as it won't restart again. Before I cut the vehicle off and put it in park and gave it some throttle and the throttle response response was terrible and eventually dwindled down to nothing. I don't have anyway currently of pulling off the codes so I'm hoping to let it cool down and run it up to autozone. Guess I will start pricing a code reader out.

[inafogg]

has anyone tried the old tap test.... bang on the computer??
just a thought,lots of money spent!!

[mcdon26]

Originally Posted by inafogg

has anyone tried the old tap test.... bang on the computer??
just a thought,lots of money spent!!

I haven't heard of the old tap test

[viggy58]

well, not so much a tap test, but start unplugging harnesses and checking for corrosion. spray em out with contact cleaner.

[MT-2500]

Originally Posted by mcdon26

I haven't heard of the old tap test

The old Tap/twist it was used on the older PCM computers to check for circuit board problems.

Not any way to do it on the VCM computers.

As said before it needs tested when it does it.

One test you can do by yourself is hook up a fuel pressure gauge and tape it to outside mirrow or outside windshield and watch fuel pressure while driving and when it does it.

If fuel pressure hold up to specs driving and when it acts up then it is other problems.

But still needs tested when acting up.

Find a good repair shop that will test it for you.

[maxisp2000]

I am having the exact same problem with the exact same symptoms. The failure of the engine sets no codes!!! I have replaced the: fuel pump, fuel filter, rotor, plugs, wires, coil, distributor cap, ICM, plenum gaskets, intake manifold gaskets, fuel regulator, alternator, water pump, coolant temp sensor. I cleaned all connectors and pins. Because of these repairs, the air blend damper door actuator failed (it broke the main gear inside). To repair that consisted of removing the entire dash, replacing the inaccessible part, and reinstalling the dash. Replaced temperature control dash panel. I cleaned all connectors and pins.

In the winter that car runs perfectly.

I am starting to think it's the VCM because the high speed blower setting on the HVAC will not run sometimes too.

Now I think it might be the spider and the MAX injector.

Anyone know how to tell for sure??

HELP!!!

[MT-2500]

Originally Posted by maxisp2000

I am having the exact same problem with the exact same symptoms. The failure of the engine sets no codes!!! I have replaced the: fuel pump, fuel filter, rotor, plugs, wires, coil, distributor cap, ICM, plenum gaskets, intake manifold gaskets, fuel regulator, alternator, water pump, coolant temp sensor. I cleaned all connectors and pins. Because of these repairs, the air blend damper door actuator failed (it broke the main gear inside). To repair that consisted of removing the entire dash, replacing the inaccessible part, and reinstalling the dash. Replaced temperature control dash panel. I cleaned all connectors and pins.

In the winter that car runs perfectly.

I am starting to think it's the VCM because the high speed blower setting on the HVAC will not run sometimes too.

Now I think it might be the spider and the MAX injector.

Anyone know how to tell for sure??

HELP!!!

PROPER TESTING WILL TELL FOR SURE.

But best to start your own New Thread/Post.
Saves on hyjacking expense.
And give all information on yours.

You have a lot of replacing but no metion of what has beed tested or what brand of replacement parts or why parts were replaced.

Have you tested fuel pressure?
Have you tested everthing when it is acting up?
Have you put it on a engine capable scanner and read out sensor data and checked for history/past /stored /present codes?
Remember not all problem will set check engine light and hold it on?
Any flashing check engine light when driving?
Does the check engine light come on key bulb check on and go off engine running?
Was your replacement parts AC Delco and Delphi fuel pump?
Auto matc AC controls or regular?
How did your repair break blend door?

[mcdon26]

What year is your blazer? And let me say, I feel for you and know it's been frustrating. I'd kinda like to work in conjunction with you, compare what we've done versus what we haven't. I actually think having both threads may limit the info we get together, or I'll just have to keep a watchful eye open for your's if and when you open a new thread.

I took the vehicle to my local GM dealer yesterday and basically got a shrug of the shoulder. Hooked up a engine scanner and no level out of spec were discovered. I had discussed with the service mechanic the possibility of the spider injector and nut kit replacement and the basic answer I got was it was worth a shot. I went in to talk to the parts people and they just confused me. 2 different parts guys told me my vehicle doesn't show it has the spider injector. WHAT!?!?! I'm now confused. they price me out 6 injectors and a body kit (?) for $991.00. Woe. Not what I expected. The body kit was $140 so I'm wondering if that may be the actually spider assembly. They didn't have one in the shop so I couldn't look at it. So, do I have the spider connector or not? Sure thought I did based on the research I had done. I don't want to open up the intake and find out I have the wrong part and no one has it in stock.

The nut kit was $40. Weather seems like it will be getting no higher than 70 for a while so this will not repeat itself until it gets hotter. I am going to purchase a fuel pressure gauge as suggested and leave it on and taped up so I can watch the pressure during all range of RPM. Pressure tests have been done by a previous mechanic with passable levels at idle. I leak down test was also done according to the previous mechanic and fuel pressure maintained.

I also want to put out there a few things I had not previously mentioned because I didn't want to be chasing a ghost and this was not the major symptom and as every mechanic I have talked to does not seem to think this is a symptom, but I always have. RPMs when I first start the truck cold are about 800. After the engine has warmed up and stopped at a light with the trans in gear, the RPMs are somewhere inbetween 550 and 600. This is not a rough idle by any means, low, but not rough. I do however get a slight loping of the RPM while stopped and in gear. The RPM will lope from 550 to 650 or any where within that range every 5 seconds or so. It isn't consistent and does it whenever. When driving at 60mph, my RPMs maintain a consistent 2000. I may feel a slight hiccup, and I mean ever so slight. If I wasn't paying so close attention to everything because this thing left me on the side of the road so many times, I would miss it. Also, at this RPM range - 1800 to 2000 throttle response os very poor, seems I can move the gas pedal half the distance without any response from the engine and then it drops down a gear flies up to 2500 RPM. And one last thing, after the truck is warm, and I have gotten somewhere, turned the motor off, put it in park the idle jumps to 750 RPMs then gently falls back down to 550 -600 RPMs. When I come back and restart it, same thing, 750 down to 550. But when I put it in gear, I have virtually no change in RPM idle is not rough, just low.

Just trying to throw everything out there.

MaxisP, don't forget about me if you end up finding a solution, please.

[maxisp2000]

OK! I was trying to be brief. My failure mode is exactly the same as the OP. I have 177,000 mile on the engine.
1996 Chevy S10 Blazer 4x4 4.3 Vortec Vin Code W.
The air blend door actuator breaks because the door cycles each time power is removed and applied. Think of the carriage assy on a printer when you power up. Mine broke the main gear inside and was stuck with the heater full on.
Brand new fuel pump.
Cannot test anything when engine will not start.
It sets no codes. Every now and then I get evap codes, because of the gas cap.
No check engine lights for this problem.
Replacement parts are from Autozone usually.
Why would I open a new thread for the exact same problem?

The car runs fine when the ambient is less than 80 degrees. I went from Las Vegas to Phoenix and back last week when it was in the 60s.

I ran across a mechanic who said their kid had the same car, and it had the same problem. He said that they spent an entire day chasing wires under the dash to fix this problem. When I pulled the dash, I cleaned all the contacts I could find. I thought that would fix any wiring problems under the dash. I found two relays I did not take the time to identify. One was stuck on the HVAC covers and was wide and rectangular. Another was wrapped in foam and installed into the fascia. I think one is the HVAC high fan speed.

Also, I don't know if this is a hint, but my HVAC fan will stop running at the high speed setting when it gets warm too. This is a new fan, and fan speed regulator and control plate.
Another hint is opening the hood seems to cool off whatever is stopping the engine, so I think it's under the hood , not the dash wiring. That's why I thought it was the ICM to begin with. I replaced that last summer and drove from Las Vegas to Tucson and back in the heat of the summer. So I thought I had fixed it.
That's why I am thinking maybe the VCM or spider and injector.
I also know that I need to change my 4X4 vacuum switch, but that's unrelated.
An expert would help here.

[maxisp2000]

Sorry in advance.
Also, the HVAC high speed fan did not use to come on at all. I replaced the fan and the fan control inductor and the switch. Did not make a difference. Then I changed the engine coolant temperature sensor, located near the thermostat and the high fan worked again. Until it gets hot outside.

That is leading me to the VCM. There appears to be a logic command to the high speed fan relay that allows the fan to run when it's colder outside. Then shuts off if it is outside the allowed temp range. Maybe the VCM is doing the same for the ignition or injector, to prevent a perceived overheat problem that doesn't exist.

I don't know.

To repeat, my symptoms are the same as the OP. Only when it's warm outside. It feels like vapor lock, or running out of gas. Car runs until the problem starts. If you press accel too much it dies off, but runs at idle until it stops eventually. Open the hood to cool off and the car starts right up, no codes, no saved codes, no problem until it does it again. Turning the key runs the fuel pump until the relay shuts it off seconds later. But the car does not start.

This is a very common problem on the internet. But no solutions.

Experts?

[MT-2500]

Originally Posted by maxisp2000

OK! I was trying to be brief. My failure mode is exactly the same as the OP. I have 177,000 mile on the engine.
1996 Chevy S10 Blazer 4x4 4.3 Vortec Vin Code W.
The air blend door actuator breaks because the door cycles each time power is removed and applied. Think of the carriage assy on a printer when you power up. Mine broke the main gear inside and was stuck with the heater full on.
Brand new fuel pump.
Cannot test anything when engine will not start.
It sets no codes. Every now and then I get evap codes, because of the gas cap.
No check engine lights for this problem.
Replacement parts are from Autozone usually.
Why would I open a new thread for the exact same problem?

The car runs fine when the ambient is less than 80 degrees. I went from Las Vegas to Phoenix and back last week when it was in the 60s.

I ran across a mechanic who said their kid had the same car, and it had the same problem. He said that they spent an entire day chasing wires under the dash to fix this problem. When I pulled the dash, I cleaned all the contacts I could find. I thought that would fix any wiring problems under the dash. I found two relays I did not take the time to identify. One was stuck on the HVAC covers and was wide and rectangular. Another was wrapped in foam and installed into the fascia. I think one is the HVAC high fan speed.

Also, I don't know if this is a hint, but my HVAC fan will stop running at the high speed setting when it gets warm too. This is a new fan, and fan speed regulator and control plate.
Another hint is opening the hood seems to cool off whatever is stopping the engine, so I think it's under the hood , not the dash wiring. That's why I thought it was the ICM to begin with. I replaced that last summer and drove from Las Vegas to Tucson and back in the heat of the summer. So I thought I had fixed it.
That's why I am thinking maybe the VCM or spider and injector.
I also know that I need to change my 4X4 vacuum switch, but that's unrelated.
An expert would help here.

Why would you open a new thread for the exact same problem?


For one reason it saves on hyjacking cost.

When you hyjack another person's post having two different vechicals and usualy two different problems it gets very confusing.
I very seldom find two differnt vechicals problems with the same answer.
First thing on yours.
If you have a no start you can check fuel pressure for up to specs and loose of spark to all plugs to start with.

If you want expert help try all a data DIY online sub.
And go threw the proper testing.