Sometimes it runs, sometimes it no-starts and pops through intake!

[homerthefish]

My old girl is a 2001 5.2 with 183,000 miles on it.

A few months ago it threw a sensor code and had loss of power, the code cleared on its own and the truck drove fine for a few weeks, code came back for a day, clearned...came back, I bought the sensor, cleared for a few weeks (of course!), but then came back on and stayed on. At this point I finally started having some mild driveability issues where there was loss of power, sometimes at low RPMs it would shut off (would always restart) and there was an occasional pop through the intake. Finally, she died in my driveway (which I thought was very polite) and that's where the story begins.

The code was for the crankcase sensor, which I bought first. Once I did some googling, I decided to replace the pickup in the distributor first since it had similar symptoms and seemed like a much easier job. While I was at it, I replaced the cap and rotor. The truck still wouldn't start, so I tackled the crankcase sensor (allen wrench and a ***** bar - nothing to it!!!). The engine code cleared, but it still wouldn't start. My ex suggested checking the fuel pump - he has a history of throwing every part at a car until it finally started so I was reluctant to believe anything he said - BUT the truck would 'run out of gas' even if the gauge said 1/4 tank and I wasn't hearing the pump kick on when I turned the ignition. Lifted the bed, replaced the pump and hit the key - SHE STARTED!!!! Yay! And ran great! I let it idle for about 5 minutes, shut it off, restarted several times. Feeling accomplished, I put the bed back on, cleaned up and decided to take a test drive for ice cream. Crank but no start. DANGIT!!!!


I finally phoned a friend who comes out, scratches his head and says it seems like it skipped a gear in the timing chain. The truck cranks, then when you let off the key it tries to turn over but pops and smokes gas up through the intake. On a whim he checked plugs which were gross. He left saying replace the plugs - it may not be the issue but they need done. So I replace the plugs and the truck fires right up. Yay! Drive it down to the barn, up to the house, shut it off, start it up, drive it some more - life is great. For an hour. Then back to crank, no start, pop and smoke. The truck starts when the moon phase is correct then runs great, and then goes back to the crank and pop on a whim.

I am NOT mechanically inclined but can youtube most fixes, assuming I know what the issue is. HELP!!!

 

[Dan98]

My old girl is a 2001 5.2 with 183,000 miles on it.

A few months ago it threw a sensor code and had loss of power, the code cleared on its own and the truck drove fine for a few weeks, code came back for a day, clearned...came back, I bought the sensor, cleared for a few weeks (of course!), but then came back on and stayed on. At this point I finally started having some mild driveability issues where there was loss of power, sometimes at low RPMs it would shut off (would always restart) and there was an occasional pop through the intake. Finally, she died in my driveway (which I thought was very polite) and that's where the story begins.

The code was for the crankcase sensor, which I bought first. Once I did some googling, I decided to replace the pickup in the distributor first since it had similar symptoms and seemed like a much easier job. While I was at it, I replaced the cap and rotor. The truck still wouldn't start, so I tackled the crankcase sensor (allen wrench and a ***** bar - nothing to it!!!). The engine code cleared, but it still wouldn't start. My ex suggested checking the fuel pump - he has a history of throwing every part at a car until it finally started so I was reluctant to believe anything he said - BUT the truck would 'run out of gas' even if the gauge said 1/4 tank and I wasn't hearing the pump kick on when I turned the ignition. Lifted the bed, replaced the pump and hit the key - SHE STARTED!!!! Yay! And ran great! I let it idle for about 5 minutes, shut it off, restarted several times. Feeling accomplished, I put the bed back on, cleaned up and decided to take a test drive for ice cream. Crank but no start. DANGIT!!!!


I finally phoned a friend who comes out, scratches his head and says it seems like it skipped a gear in the timing chain. The truck cranks, then when you let off the key it tries to turn over but pops and smokes gas up through the intake. On a whim he checked plugs which were gross. He left saying replace the plugs - it may not be the issue but they need done. So I replace the plugs and the truck fires right up. Yay! Drive it down to the barn, up to the house, shut it off, start it up, drive it some more - life is great. For an hour. Then back to crank, no start, pop and smoke. The truck starts when the moon phase is correct then runs great, and then goes back to the crank and pop on a whim.

I am NOT mechanically inclined but can youtube most fixes, assuming I know what the issue is. HELP!!!

What code are showing

 

[homerthefish]

No codes now. Honestly I don't remember the number, but it was something like 'crank shaft sensor bank 4' or something like that.

The thing is possessed - some days (hours?) it will start the first time you hit the key and run great. Other times you hit the key, it cranks and when you let off, sputters, coughs and starts. Most often it will crank and sputter, but won't start. Sometimes when you rev the engine quickly it breaks up, other times it revs just fine. Sometimes you have the RPMs up and let off the gas, it drops below 1,000rpms and bounces back up. Other times it dies. Sometimes its fine.

At this point I"m ready to 1) let the 15-year old kid catch it on fire, or 2) see if I can limp it to the $$$ shop.

 

[JDSR]

I believe the coil is bad, test it and test the plug wires, if bad put some new plug wires on seeing you never mentioned them.

 

[JDSR]

Ya might also check the timing chain slack, which you can do without tearing it apart

 

[Spike95]

When you said you replaced the crankcase sensor, I am assuming that you meant the crankshaft sensor which it had produced a code for before. The issues you are having with it popping and smoking sound like the spark timing is way out of wack at times. I can see how your friend could think that the timing set jumped a tooth. You are saying that sometimes it runs perfectly though... Usually when a hard mechanical part like a timing chain set has an issue, it is not intermittent.

I would go back to the original issue with the crankshaft position sensor. The ECM uses info from that sensor to adjust the ignition timing. So a faulty signal on that circuit could definitely make it pop and smoke and not want to run. Since it has acted the same way with the old sensor and the new replacement, it is not likely the sensor itself that is the issue. I would be looking for a problem in the harness attached to it. Could either be a short or a bad connection somewhere. Next time you try to start it and it gives you problems, try unplugging the harness from that sensor and then plugging it back in. Then try to start again. You may want to do this a couple times to see if it makes a difference. If it fixes the issue, then the most likely culprit will be loose and/or dirty female connections inside the harness plug. If that doesn’t change anything, then follow the harness away from the sensor and study it for any worn or cracked insulation on the wires. All it takes is a tiny spot with barely worn insulation to cause an intermittent short that will drive you crazy.

 

[fireflymedic]

Take a close look at any wires going to sensors that throw a code that they don't have insulation eaten off by rodents.

 

[ViolentMouse]

Could also be a lean pop. maybe the bed got set down on the fuel lines? or the wiring for the fuel pump?
You need Fuel, Air, Compression, and spark to run an engine.

You have air, as long as you have compression, as stated above mechanical failures are RARELY intermittent, so mechanical timing is out of the equation, so air/compression check.
fuel and spark are the only things you need to diagnose.

Spark is controlled by the computer, which gets it's signal from the crankshaft position sensor.
Fuel is controlled by the computer, which gets it's signal from the camshaft sensor in the distributor.

Crankshaft sensors usually work or they don't, and given the popping from the intake, I would take a guess, that you either got a spark plug wire crossed, two plug wires routed so close they are cross talking (arcing between two wires). or you moved the distributor when you did the cam sensor.

Go back to basics, verify the firing order. make sure you do not have plug wires parallel to each other without some protective sleeving on the wires.

Sadly you cannot check timing without a scan tool that can see cam angle. Do NOT attempt to manually set the timing on these motors without a scanner. The computer controls the timing, and the distributor controls the fuel/cam angle. Moving the distributor can end up being a much bigger pain than it's worth.

If wires, and firing order are all in order, then put a fuel pressure gauge on it. see what the pressure is key on engine off, cranking, idling, and 2500 rpm.

Let us know how it goes.

 

[Daw14]

No codes now. Honestly I don't remember the number, but it was something like 'crank shaft sensor bank 4' or something like that.

The thing is possessed - some days (hours?) it will start the first time you hit the key and run great. Other times you hit the key, it cranks and when you let off, sputters, coughs and starts. Most often it will crank and sputter, but won't start. Sometimes when you rev the engine quickly it breaks up, other times it revs just fine. Sometimes you have the RPMs up and let off the gas, it drops below 1,000rpms and bounces back up. Other times it dies. Sometimes its fine.

At this point I"m ready to 1) let the 15-year old kid catch it on fire, or 2) see if I can limp it to the $$$ shop.

What is the result ?