Hello Everyone. Found your great site looking for info on what my truck is up to. I bought this truck 2 years ago. Ran great and never let me down. It is a 1993 S10 Blazer Tahoe with a 4.3 Vortec and 4X4. A few days ago it started to jerk when cruising. Almost felt like the tranny was slipping and slamming back in. Its an automatic by the way. I would punch it and it ran fine. Just when cruising at 55 steady it would lerch. The next morning I went to work and it just stalled. Almost like no spark or fuel stopped. I went to turn it over but no fire. I shot it with starting fluid and it fired up. So I took it home to inspect. Had great fuel pressure, great spark but looked weak ? So new plugs, wires, cap and rotor. It stalled again when driving and would not fire. I rebuilt the distributor and no luck. Checked and swapped out the coil. No luck. Now if I feel it starting to stall, I can pop it up in to neutral and it will run right. Just when I engage in drive it does this spell. My best friend and also my mechanic took it to his shop. He rechecked everything and cant see whats wrong ? Not throwing codes ?? He checked the fuel pressure and it was good. He popped off the plenum and checked the spider. Everything checked good. Now I don't know where to go from here ! We checked to obvious and still nothing. He is thinking injectors. I am thinking a sensor. Anyone have an idea where to start.

Thanks for any help at all !

John

 

Sounds similar to the problem I've been having. My car drives fine for about an hour, then the power abruptly and intermittently cuts out and (usually) immediately returns, the check engine light sometimes flashes, sometimes the tach needle swings around, etc. It feels like the car goes from idle to wide-open throttle and back again. Sometimes the car suddenly stalls without warning and is hard to restart. Just letting it sit for a couple minutes always makes the problems go away for a short while. Happens more often in warm weather than cold, but there's not a strong correlation with temperature.

I had a bad injector once and the car behaved similarly, but not as dramatically. This time, however, the swinging tachometer needle (when engine speed is constant) is telling me that the ignition is involved. Replaced the coil and distributor+ignition module and pickup coil, but it didn't fix the problem.

Recently, I noticed that when the car is acting up, I can turn it off but put the key back in the "on" position with the car not running. The check engine light should normally be on like this, but when my car is acting up it will instead blink rapidly and erratically--almost as if you connected a lightbulb to a wire and dragged the wire across the battery terminal. At the same time, the injectors will buzz and click in a random way. All the other electrical systems, however, are unaffected. I checked all the wiring, but I now believe it's a bad computer. Automotive computers are usually extremely reliable, but there's not much left to blame.

Don't know if it will help you or not, but it might give you a couple other indicators to look out for in case we're having the same problem.

 

if the ses light is flashing it usually means a misfire..get the codes read.....possible crank sensor at fault too

 

Is that directed at me?

I pulled the codes. There are no stored codes. The light flickers with the engine NOT RUNNING. That's not a misfire. The light should stay on since it's not receiving pulses from the distributor. My car doesn't have a crank sensor, it has only a camshaft sensor. As I already stated, the ignition module, coil, distributor, and pickup coil that the cam signal is derived from were all replaced with new parts. And the fuel injectors buzz and go crazy.

Thanks anyway.

 

Ok here is what I did after work every night. I took off the plenum and checked for leaks. There was a wee bit of gas under the send/return lines. So I bought a new set and installed. Again checked for leaks. Everything looked good. Put everything back together. I started it up and idled fine. Let it warm up for 20 minutes. Drove around in a parking lot down the street. Lot more power than before. It stalled when I came to a stop coming out of the parking lot. But it started right up ? So I drove down the street and it started to spit and sputter. I turned around asap to get back to my home. It stalled at the stop sign. Would turn over but no fire. So I shot it with starting fluid. Started up but died out in a few seconds. Waited a few minutes smoking a cig. Shot it again and it fired up and I boogied home. Took some skilled motoring to keep it running lol. Foot on the brake and pedal to the floor.
Thinking my fuel pump my be going out ? Or maybe the temp sensor (not temp gauge sensor). I am at a loss !! Love this truck but dont want to put part after part into it. 61.00 at Napa for the fuel lines for the intake. 6.00 for gasket. Does anyone have any idea at all ??

Thanks for the help !!

 

I would think if you had a sensor failure you would through a code. Since no codes let me throw some ideas/tests out there for you that don't cost $$$:

• Check the battery and the connections. Weak batteries or bad/loose connections can create all kinds of system symptoms.
• Either leave the fuel pressure gauge connected while you test drive or take it with you to attach when the engine sputters or stalls. Your symptoms really sound like loss of fuel pressure. Needs to maintain between 55-61 psi
• Check the primary and secondary coil wires (wiggle test).
• Dirty EGR valves can cause rough idling and stalling.
• Has the fuel filter ever been changed?

If you want to test for ECT sensor there is a procedure at autozone.com as well as these forums.

Good Luck and let us know.....

 

I have a brand new battery I bought when this first started. Connections are tight. I was thinking about the pressure gauge while driving and seeing if the fuel pump is starting to go or shorting out. That might be my next step. Also going to try to swap out the coil with my spare. (My motorcycle did that last summer when it warmed up, the coil would die out.) But I dont think it is that seeing how I can spray starting fluid in the intake and it fires up every time. Cleaned out the EGR and it is fine. Changed the original fuel filter this spring.
Going out in the shop now to see about the pressure. Let it warm up and go for a short drive. Keep it on while I am driving. Does the fuel pump have some kind of check valve ?? It is odd to me when it stalls out and I try to turn it over, it will not fire. But I shot it with starting fluid and it fires up but dies out on the first attempt. Then I shot it a 2nd time and I could keep it running ??
Ready to buy a horse and buggy lmao ! or a 1970s Chevy truck w/ 350 (i grew up with them and easier to me on fixing or diagnose.)

Thanks Licklog

 

So far today I put the pressure gauge on. Started it up and waited for it to stall out. Then tried to start it but it would not fire up. Looking at the pressure gauge it stayed at 60. But I did notice on the gauge when I first turned the ignition to on(not starting), that the gauge went to 70psi for the first 2 seconds of pressure build up from the pump. Then back to 60 when the pump stopped pressure.
I have read the manual ( I have 3 ). Following and double checking, it tells me that the fuel reg or spider is junk. Was so hoping it to be the fuel pump lol !! So should I replace the fuel reg first and test it again. Or while I have the plenum off just replace the reg and spider.

 

If your pressure is above 60psi, there is nothing wrong with the pump. If your pressure holds steady after the pump shuts off, then the regulator and check valve assemblies are fine.

Your problem sounds more ignition related than fuel. Have you tested for good spark when you are getting your no start condition? You may want to remove your ICM (ignition control module) and coil and have them tested.

 

The pressure held great. I have beautiful spark when it is in the no start condition. After it died out, I turned it over for 20 seconds. Pressure gauge still read 60psi. I then pulled the coil wire of the distributor cap. Put a spare plug in and wedged it under my wiper so I could see the spark in the drivers seat. That looked nice and blue ! I then put the wire back on and pulled #2 spark plug wire off the plug. Tested that with a spare plug. Again there was nice spark ? I just had the distributor rebuilt (new ICM and coil).
I bought a spider injector off Ebay last night. So I will put that on and see if that helps when it gets here.