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Engine tick/knock after bad gas

2K views 9 replies 3 participants last post by  ejstruchen 
#1 ·
I have a 98 Ext Cab 1500 with the 5.2 auto and was the victim of bad gas. She wouldnt start normally and then when she did, she would spit and sputter until she finally started. Took a minute or two but it would finally start running smooth. I put some octane boost and seafoam in the gas and topped it off with premium. I then proceeded to run the gas out of the tank.

After a few days, went to get into it after work and it gave the same problem with trying to start. Finally, after some huffin and puffin and spittin and sputterin, she started, but now she had a terrible tick/knock coming from the drivers side. Then, the CEL started flashing. I stopped and check with a code checker and it said that #7 was misfiring. Limped her home, checked/changed the plug and wire. No improvement. I was down to less than 1/4 tank so I refilled with premium and put an injector cleaner into the tank.

Im on my third tank with injector cleaner and the CEL stopped flashing all the time. It only comes on when under a heavy load. I seems to be idling ok and no backfiring, just the annoying tick/knock on the driver side of the engine. Code checker still reads #7 misfire code.

I have read and looked all over the forum and havent read anything like this happening to anyone else. I know it was the bad gas that caused the initial problem, but I need to know where to go from here.

If I drive it normally, the CEL never appears, but the ticking remains. It does seem to get a little more quiet at idle, but not much.

Any ideas or suggestions would be appreciated!

BTW, she has 152K on the odo and just had her oil changed recently. This problem didnt show up until after the bad gas. Thank you all for any assistance you can provide!

Tim
 
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#4 ·
These things can run for quite a while with a bad gasket. Performance will degrade as it gets worse. Oil consumption will increase. As more oil is consumed, more contamination of the cats will occur. The stress on the reciprocating assembly is increased from mis-fires. These are very stout assemblies and can absorb quite a bit of that sort of stress. It's not like an overnight disaster, but should be dealt with soon as possible.
 
#5 ·
Thanks for the reply!

So, I looked on the forumz and found that the gasket will have certain tell-tale signs if blown. Please correct me if I am wrong or have missed something.

1. Increased oil consumption
2. Oil pooled at the bottom of the throttle body
3. Vacuum at the oil cap/crankcase fill
4. Ticking noise on top end
5. Check engine light with a cylinder misfire code(s) (sometimes flashing)

So, I checked the oil and it is fine. It has been run approx 300 mi since this problem showed up. I also checked the bottom of the throttle body. There was no oil pooled at the bottom. There was a little residue and some carbonation, but nothing to write home about. Checked the oil cap for vacuum while running. Nothing like one would expect when the plenum gasket has failed. I still have the ticking on the top end, but the CEL only comes on under a heavy load.

So, I disconnected the #5 and #7 fuel injectors to see if there was a difference in idle. There was an immediate difference with both, so I dont think the injectors are bad.

So, Im down to valve springs and rockers. Gonna pull the valve cover and find out this weekend.

Does it sound like Im on the right track, or are we still thinking plenum gasket? Any assistance is appreciated!

Thanks again for all the advice and great information

Tim
 
#6 ·
On the symptoms, oil consumption gets incrementally worse. At first it isn't much. In that it's just supposed to be filtered air going through the throttle body, the residue you saw is an early indicator. Pooled oil would be a really bad leak. Vacuum at the crankcase fill? Maybe on a really bad one. Spark knock can occur due to the oil getting into the cylinder. The vacuum leak can also cause a lean run condition which can also cause knocking. It would be unlikely to have a broken rocker or spring, but nothing is 100%. I'd pull the plugs on the knocking side and read them. Do they all look exactly the same or is one maybe a little different? It is also possible that you could have a collapsed lifter.
 
#9 ·
All looks fine and back together. Running great now. All I can figure is the misfire was at the right time to cause the damage. Bent it about 45 deg but no other damage, thank goodness!

Gave her a bath and loaded her up for the trip to my daughters college tomorrow (move in day).

Thanks all for your help and I hope this helps someone else too!

Tim
 
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