Hi everyone,

I have scoured this forum looking for answers to my problem and nothing seems the describe my exact problem so appologies if this kind of a repeat question for anyone.

I have a 2003 Blazer 4.3 4x4 with 234K km's. The other day I was on the highway and I stopped at a red light, after driving for approximately 1 hour, and as I went to accelerate I essentially had no power. Flooring it would jump the rpm maybe by 200, and vehicle would lurch and I was moving maybe 5Km/h. I pulled over and it died finally. I tried to get it to start, it would crank very strong but wouldn't turn on. There was either misfiring or backfiring (I'm unsure of the difference) and sometimes it would start and idle extremely rough and die again. I sat at side of the hwy for about 10 minutes to start researching wtf was going on and when I tried to start it up again it held and I could rev the engine. I drove for about and 5 minutes and it died again in the middle of me crossing the hwy, luckily some dude helped me push it to safetly. This time I disconnected the battery and it fired up again and held for about a minute or so and then died. I sat for another 30 mins researching when a man on a motor bike came to help and asked me to show. It fired up again and I was able to drive it home without a hitch.

The following morning I turned it on and it fired up instantly and ran perfectly with the rpm's at a steady 500. Everytime I turn the engine on it runs fine now, but needless to say I do not want to drive it for any length of time until I figure out what is wrong.

I pulled off the distributor cap and rotor and they had some corrosion so i cleaned them, I changed the fuel filter, cleaned the throttle body, checked the air filter, and I did a fuel leak down test and pressure was at a steady 55ish and held for about 10 mins. I haven't done a compression test or spark test because I am afraid to drive anywhere to buy tools. I also pulled codes but I didn't get anything, I cleaned the MAF last year and it's still clean.

Here's a list of items recently replaced:

• Igntion switch (last summer)
• ignition coil (last summer)
• Spark plugs (3 weeks ago)
• IAC valve (last summer)
• All O2 sensors (last summer)
• Catalytic converter (last summer)
• Fuel filter (yesterday)

I experienced something very similar to this last year when my cat got clogged, then a local muffler shop straight piped my Blazer.

To summarize, it stalls, sputters, misfires and idles very rough or just dies when it is hot but starts and runs like a top when it is cold.

Thanks all,

Troy

 

Ill start simple and we will ratchet things up if this doesn’t do it.

Try To recreate the no start condition close to home with your fuel pressure gauge and a spark tester. Consistently failed is your friend. Intermittent problems can be very frustrating. As soon as it won’t start repeat the fuel pressure test. Then do a spark test at a couple of ignition wires at the plug end during crank. If no spark there repeat at the coil output and then the distributor output at a couple of the output posts. Your looking for 1” of strong blue spark in a consistent pattern. All no run problems are either spark, fuel or air. Let’s finout which one and then go from there

new components are no guarantee that you can ignore that area. One positive fuel pressure test does not rule out fuel delivery problems. It only tells you that the fuel pump regulator lines and filters are capable of proper pressure some of the time. It’s 100% if you fail but not conclusive if it passes at rest. When my fuel pump failed at around 100,000 miles it bucked and stalled a few times before it died for good despite good static fuel pressure tests. Also you don’t know what the fuel injectors are doing while running. Some guys tape the fuel gauge to the windshield and see what fuel pressure is doing when it dies. I have recently done that with a boat outboard with intermittent cutout problems. Key on fuel pressure is good but as load increases, fuel pressure starts to drop. I use a transducer on the fuel rail schrader and either a thin cable to a gauge or a wireless transmitter to an iPhone. These are other options.

let me know how you do.

George

 

Sure sounds like a fuel pump going out. Pressure testing when no start returns will let you know.

 

Did you replace it with an OEM coil? Sometimes the cheap ones dont last long.

Other than that.. as suggested, could be fuel related.

Either weak spark or weak fuel could do it. Had a Grand Am did the same thing. Never did find out what the issue was.

Check fuel and spark strength before we go further because I could think of a few other things it could be too, although I dont rhink your engine has a gathering problem so check those first.

 

I drove it around the block several times to get it up to temp but it didn't die on me. Unfortunately I'm going out of town today for work so I won't be able to fully test this and get back to you all until around the weekend.

I did test the fuel pressure again the it held but when I let the engine idle the needle was shaking back and forth with a variance of 5-10 PSI. I'm not sure if that is a faulty gauge (it's a brand new Innova) or if that has something to do with the injectors. Is there a way to tell if the injectors are bad without removing the intake manifold?

93S10Tahoe, I replaced the ignition coil, ignition switch and IAC valve last year with BWD parts. From what I have read they are fine. I try to go with AC Delco or Delphi for most things but I was in a pinch last year and that was what was available. The spark plugs are Delco.

 

There is a way to test the injectors as is, it’s called an injector balance test. There is a pulse generator box:



that generates a selectable pulse count. You probe into each injector connection after key on to charge the fuel pressure gauge and note the fuel pressure drop after the firing pulses. You recharge and repeat on each injector and note the uniformity of the pressure changes. If they are out of wack then you have an injector problem. If your problem is intermittent then it might not tell you much at that moment so passing may be inconclusive but failing is conclusive. As with my other suggestions, this test is also best during a meltdown. Let me know if you want some videos.

George

 

Okay after some more reseach and specific wording in google I came across an issure not specific to GM vehicles but to all. The coolant temperature sensor. I did find something on this forum about it damn near 10 years old. How likely is that as a culprit? It's sure easier and cheaper to replace/troubleshoot than the injectors.

 

There are a few sensors which if they get wonky can cause problems. Yes the ECT is one of them but so is the crank sensor, the O2 sensors, the TPS, the MAF, ... Of those the crank sensor is probably most likely when the truck keeps cutting out completely because no crank sensor output equals no ignition. This is why I’m guiding you to try nd establish if it’s fuel or spark because that’s how we start narrowing this thing down.

as as a general rule the best approach to a problem is to diagnose it properly and then do a targeted repair. I don’t personally like parts swapping unless I am 95% sure I know what the problem is and the part is cheap and easy or an intermittent problem is making me crazy and I can’t nail it down. The ECT does not come to mind but you can check the sensor value in live data on your scanner. While your there you can look at the O2 sensor output, the fuel trims, the TPS sensor output. As before though it would be best to catch it when the truck dies so also travel with your scanner.

George

 

Actually, if you want to try and rule out sensors then you can see live data output on your scanner for more sensors than I listed in the previous post. Additionally there is the MAF, manifold pressure etc. (don’t remember them all on the Blazer as I work on many brands and I’m not able to look right now). Once again you might get head faked if the truck is running good but you can record the values then and relook when the truck is dead. A wonky sensor might be off even when the truck is running so if you want to go this route then you can familiarize yourself with proper values.

Again I’m not a parts cannon guy but if you want to go that route, I would start with the crank position sensor. It would still be best to determine fuel pressure or spark at the next event.

George

 

Hey all,

I was finally able to get the vehicle to die on me again. I had my fuel pressure tester on me and as soon as it died on me I tested the pressure. I was only getting 30 PSI max. After about 5 minutes I tested again and I was getting 60ish PSI. So I now know that it's a failing fuel pump. I've never heard of a fuel pump intermittently failing like this. If somehow dies on me again I will be checking all of the other suggestions!

Thank you everyone