Very confused #8..
Very confused #8..
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Joined: Nov 2014
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Hello, my question is about a misfire. So I have taken my truck a 1996, 5.2l auto, to my automotive teacher at high school. We tested the injectors resistance, the injector connection, the spark, firing order, coil, spark plug and wires. Still misfiring bad, no check engine light anymore after I replaced the cap on disturber. I don't know what it could be, ordered the plenum kit from Hughes, but I have a feeling that isn't the only problem (can see oil in bottom on intake). Truck ran find then randomly had misfire code a few days ago, then more cylinders then #8 were misfiring so I replaced the cap. We're doing a leak down test this week to see what's happening. It is using a noticeable amount of oil and my antifreeze is disappearing, could be an external leak on the antifreeze I haven't seen yet. When I took #8 out (Before changed the cap) it was fouled badly.(Changed plug) Now with the truck running I can disconnect #8 injector and have no difference in idle, no idle down or up but throws broken connector code. I'm worried the head is cracked, valve is burnt or head gasket blown out. Any ideas I don't want to throw any more money at this, just had the transmission rebuilt this year. The truck has new plug wires as well and no catalytic converter. I sprayed sea foam thru the intake about 2 weeks ago I don't know how that would cause a problem maybe it got on a sensor? Just throwing ideas out, thank again any help is greatly appreciated. Also the truck is starting to blow white smoke.
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Joined: Apr 2010
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From: Clayton MI
Rebuilding the top end won't cause blowby. That's a product of worn rings, which you may or may not already have. (compressions test please, dry, then wet.)
No real test for the PCM. About the only option there is to swap it out, and see if anything changes. Kinda an expensive proposition if it turns out NOT to be the problem.
No real test for the PCM. About the only option there is to swap it out, and see if anything changes. Kinda an expensive proposition if it turns out NOT to be the problem.
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You have a real physical defective issue with the engine that needs to be corrected and its going to take some work and money to make it right. That is just a fact. You will need to pull the heads at a minimum. At this point in time you need to focus on the tests and processes that are able to be done with the engine full assembled and running. Do a cylinder leak down test on each cylinder and then repeat it for all eight a second time so you are confident in the results. Do a compression test on all eight cylinders and then do them all again with 10cc's of engine oil added through the spark plug hole to check for the condition of the rings. Write down all of the test results. Repeat any test that you suspect was not accomplished properly. You might have a head gasket problem in addition to other problems. Understand that you'll probably find that the heads have valve issues and that these are repairable as long as you don't have any cracks but at the same time, you may have fairly worn piston rings and putting newly overhauled heads on to an engine with worn out rings is kinda dumb so take your time and thoroughly evaluate the engine before you pull it apart. Go to Walmart and buy a new white queen size sheet and put it under the engine while you let it run for a full hour to find out if you are loosing any antifreeze through an external leak. The water pump is the most likely suspect but understand that the investment to understand where the antifreeze is actually going is important to figure out before you take the engine apart. It is the nature of engines to wear out so consider everything with a clear head before you proceed. There is no reason to consider that you have a defective pcm. The plenum problem seems to pop up on every running problem post. I think its actually an inside joke that has gotten out of hand. I don't know you or your intuitive abilities. Understand the intent of the testing you are doing and ask questions of the local people you respect. Don't listen to your friends or people who haven't actually ever replaced a head gasket. Before you actually begin to disassemble your engine, get a good picture of the costs involved.