bad gas, possible engine damage?
10-29-2007, 02:46 AM
#1
bad gas, possible engine damage?
I'm working with an 02 lq4, excellent health, running castrol synthetic, 85k miles. Has always had the "gm sewing machine" click-clack at idle.
Recently out of the blue, the truck would not start the first time of the day, sounded like it had no compression from the first turn of the key. I actually had to look at the belts to see if the engine was spinning, I thought it might be a bad starter motor. Well, it was turning.
I finally feathered the throttle and after several attempts and lots of sputtering and misfiring, and a little starter fluid shot into the throttlebody, it finally roared to life, vibrating to hell and popping/sputtering and smoking out the exhaust heavily. I had to apply throttle to keep it running at around 2000-2500. After it came up to temp a bit, it began to smooth out one cylinder by one, and finally was back to normal. The rest of the day it drove and restarted 100% perfectly.
I thought I had a little bad gas, but as there is no drain on the tank and it was only 1/4 tank, I figured I'd just drive it almost empty to get rid of it all.
But, I wasnt able to drive it all out that day. The next day, same thing, wouldn't start, ran very rough for the first couple of minutes, then was fine. Again I wasn't able to run all the suspected bad gas out as I was only making a short trip and didn't have time to screw around with it.
Then today, the same thing. Had to use starter fluid again as it was NOT going to start on it's own. Had a couple or 3 small backfires through the intake (I could see my air intake jump, as the hood was up) and finally got it going, held it at 2500 and it smoothed out. But, today it wouldnt smooth out fully, it's as if one cylinder is not firing. IT does idle pretty normally, but once you get it up around 1500-2000, there is a strong vibration, and you can feel the lack of low end power when trying to move in gear, as I drove it gently around the neighborhood.
Also there is a considerably louder noise in the engine, reminds me of a lifter. Not the standard click-clack it's always made, but about 3x as loud and more rapid. You can hear it over the exhaust considerably. When driving around the neighborhood it sounds like a steam locomotive with this noise. I actually thought that maybe a sparkplug was loose in it's hole or something.
Anyway, I actually removed the fuel pump and pumped ALL the gas out of the tank, then sucked the little remainder out with a shopvac. Put in 3 gallons of fresh gas, sprayed out my fuel pump strainer with compressed air, and put it back in. It fired immediately to life but ran a little rough still, and has the vibration and the noise in the engine even after warming up.
Tomorrow I plan to change the sparkplugs in case I fouled one, compression test each cylinder as I do, and probably change the fuel filter. I am also thinking that one injector may be clogged so I may pull those off and have a look at the screens and perhaps blow them out with air too.
Even if an injector or spark issue turns out to cure the vibration and lack of power due to cylinder misfire, that wouldn't explain the loud noise...
I guess the compression test results will tell me if I somehow did damage to the engine trying to start it this morning with the bad gas/starter fluid, but I don't see how I could have.
Any suggestions or thoughts? I wonder if a valve could be burned or broken? A compression test would show if this were the case, correct?
Recently out of the blue, the truck would not start the first time of the day, sounded like it had no compression from the first turn of the key. I actually had to look at the belts to see if the engine was spinning, I thought it might be a bad starter motor. Well, it was turning.
I finally feathered the throttle and after several attempts and lots of sputtering and misfiring, and a little starter fluid shot into the throttlebody, it finally roared to life, vibrating to hell and popping/sputtering and smoking out the exhaust heavily. I had to apply throttle to keep it running at around 2000-2500. After it came up to temp a bit, it began to smooth out one cylinder by one, and finally was back to normal. The rest of the day it drove and restarted 100% perfectly.
I thought I had a little bad gas, but as there is no drain on the tank and it was only 1/4 tank, I figured I'd just drive it almost empty to get rid of it all.
But, I wasnt able to drive it all out that day. The next day, same thing, wouldn't start, ran very rough for the first couple of minutes, then was fine. Again I wasn't able to run all the suspected bad gas out as I was only making a short trip and didn't have time to screw around with it.
Then today, the same thing. Had to use starter fluid again as it was NOT going to start on it's own. Had a couple or 3 small backfires through the intake (I could see my air intake jump, as the hood was up) and finally got it going, held it at 2500 and it smoothed out. But, today it wouldnt smooth out fully, it's as if one cylinder is not firing. IT does idle pretty normally, but once you get it up around 1500-2000, there is a strong vibration, and you can feel the lack of low end power when trying to move in gear, as I drove it gently around the neighborhood.
Also there is a considerably louder noise in the engine, reminds me of a lifter. Not the standard click-clack it's always made, but about 3x as loud and more rapid. You can hear it over the exhaust considerably. When driving around the neighborhood it sounds like a steam locomotive with this noise. I actually thought that maybe a sparkplug was loose in it's hole or something.
Anyway, I actually removed the fuel pump and pumped ALL the gas out of the tank, then sucked the little remainder out with a shopvac. Put in 3 gallons of fresh gas, sprayed out my fuel pump strainer with compressed air, and put it back in. It fired immediately to life but ran a little rough still, and has the vibration and the noise in the engine even after warming up.
Tomorrow I plan to change the sparkplugs in case I fouled one, compression test each cylinder as I do, and probably change the fuel filter. I am also thinking that one injector may be clogged so I may pull those off and have a look at the screens and perhaps blow them out with air too.
Even if an injector or spark issue turns out to cure the vibration and lack of power due to cylinder misfire, that wouldn't explain the loud noise...
I guess the compression test results will tell me if I somehow did damage to the engine trying to start it this morning with the bad gas/starter fluid, but I don't see how I could have.
Any suggestions or thoughts? I wonder if a valve could be burned or broken? A compression test would show if this were the case, correct?
10-29-2007, 05:11 PM
#2
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I think your heading in the right direction by checking the plugs and the compression check. The check should reveal any problems in your valvetrain. You might want to pull the valve covers off and do a visual inspection also.
10-29-2007, 06:28 PM
#3
I just finished the compression check, and I'm kinda baffled by the results.
All 4 cylinders on the driver side bank were even at around 170-180psi cold, and all the plugs looked pretty normal (they were recently replaced).
The front 3 cylinders on the passenger side bank, the plugs all had oil/fuel on them and were brown/black. These 3 cylinders showed compression in the 210psi range.
The rear cylinder on the passenger bank had a normal looking plug and showed 175psi compression.
I pulled the injectors/rails off and started to test them using a spare fuel pump in a jug of fresh gas, lines to the rails, battery to run the pump and trigger the injector, measuring cup (cc) and stopwatch. I checked 4 of the injectors and only one of them was flowing anywhere near stock (24lb, 250cc/min) from what I have been able to research) while some were only flowing 125cc/min.
I've put in new plugs and also ordered new injectors, which should be here Wednesday. I also got a new fuel filter.
The loud tapping noise was present when I would crank the engine prior to removing the injectors. Now, it does not seem to be present, as I was running the compression test.
This is wierd.
All 4 cylinders on the driver side bank were even at around 170-180psi cold, and all the plugs looked pretty normal (they were recently replaced).
The front 3 cylinders on the passenger side bank, the plugs all had oil/fuel on them and were brown/black. These 3 cylinders showed compression in the 210psi range.
The rear cylinder on the passenger bank had a normal looking plug and showed 175psi compression.
I pulled the injectors/rails off and started to test them using a spare fuel pump in a jug of fresh gas, lines to the rails, battery to run the pump and trigger the injector, measuring cup (cc) and stopwatch. I checked 4 of the injectors and only one of them was flowing anywhere near stock (24lb, 250cc/min) from what I have been able to research) while some were only flowing 125cc/min.
I've put in new plugs and also ordered new injectors, which should be here Wednesday. I also got a new fuel filter.
The loud tapping noise was present when I would crank the engine prior to removing the injectors. Now, it does not seem to be present, as I was running the compression test.
This is wierd.
10-31-2007, 08:10 PM
#7
So, in other news, the USPS blows goats. I paid 30 bucks in shipping cost alone on Monday afternoon to get my injectors overnighted from PA to TN (about a 7-8 hour drive). Tuesday goes by with no injectors. Wednesday goes by with no injectors. WTF?
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11-01-2007, 04:23 PM
#8
Well, put on the BRAND NEW fuel injectors and rails today, and also a new fuel filter. So the fuel system is now 100%. I also have the new plugs installed. Fired it up and it ran the same...slightly rough idle, rougher around 1500-2000rpm with a pronounced vibration, and a distinct loud rattle/clickclack on the top end of the motor.
I could use some ideas here guys. I guess I can plan on tearing the intake off and checking out the valvetrain, and possibly removing the heads.
I could use some ideas here guys. I guess I can plan on tearing the intake off and checking out the valvetrain, and possibly removing the heads.
11-01-2007, 04:44 PM
#9
Bad gas can stick intake valves and cause a number of valve train problems. Such as bent push rods, broken rocker arms, tore up lifters, flat cam ect. You asked if bad gas could cause engine damage, so I assume you suspected that you were running bad gas. How long has that fuel been in the tank? Usually bad gas stinks real bad, did it smell different?
Maybe you have bad valve stem seals or really loose valve to valve guide clearance and its leaking oil into the cylinder while the motor sits. This could foul plugs and cause it to run like crap until that stuff is cleaned up.
Valve train trouble could result in screwed up valve to valve guide clearance.
Maybe you have bad valve stem seals or really loose valve to valve guide clearance and its leaking oil into the cylinder while the motor sits. This could foul plugs and cause it to run like crap until that stuff is cleaned up.
Valve train trouble could result in screwed up valve to valve guide clearance.
11-01-2007, 05:31 PM
#10
Pulled off both valve covers and got to checking rocker arms and valves. Turns out those 3 cylinders that showed higher compression in my test, all have SEVERELY bent pushrods on one side. One of the pushrods actually looks like an S.
I wonder if this fubar'd my lifters or valves? One of the bent rods took a small chunk out of the hole in the head that it goes through, but it doesnt look like it would hurt anything structurally.
Unless one of you more experienced guys has other advice, probably what I will do is throw in another set of pushrods to replace the bent ones and then see how it acts. Do another compression test and test drive, and if it still seems out of wack I will plan to pull both heads, replace them with used or rebuilt ones, and replace all the lifters.
Any advice is appreciated.
I wonder if this fubar'd my lifters or valves? One of the bent rods took a small chunk out of the hole in the head that it goes through, but it doesnt look like it would hurt anything structurally.
Unless one of you more experienced guys has other advice, probably what I will do is throw in another set of pushrods to replace the bent ones and then see how it acts. Do another compression test and test drive, and if it still seems out of wack I will plan to pull both heads, replace them with used or rebuilt ones, and replace all the lifters.
Any advice is appreciated.