Misfire, head or intake gaskets?

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dz2a8r

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Ive got a 98 Hoe i bought from a buy here pay here lot, bought the service plan they offered for $200, covers most major parts, seals, and other stuff for 5 mos 5500 miles. Well driving a good distance approx. 100 miles or so it started misfiring and the CEL started flashing. Found po300 and p0420 codes. hooked tech two up and verified cylinders 5 and 7 were misfiring under a load. Replaced all the usual suspects, cap, rotor, plugs, and drove it home from work. still misfiring. Returned to work the next day and pulled out 5 and 7 found them white on the electrodes, which made me suspect they were burning coolant. Stall tested it while it was hot and it began to misfire on cylinders 5 and 7 after about 10 seconds or so, and began to spit coolant from under the rad cap and gurgling into the overflow canister. Compression test was fine running and just turning it over, did use a block tester on the radiator cap and it failed, meaning exhaust gases are getting in to the cooling system. I believed it to be a head or a head gasket problem, called them, and of course they have to have their guy look at it and yada yada. Told them everything i did and what the problem was on wed, and they called me on friday to tell me that their guy said it was just the intake gaskets, and that they would be covered. Got it back today @530 and brought it home after driving it a while i pulle dover and stall tested it.........you can guess what happened next....after about ten seconds spitting coolant out of the radiator cap, gurgling, and missing its A$$ off.......anyone else think it might have a head or head gasket problem??
 

BattelWagun

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What gaskets did they use? What ignition parts did you use? I would like to see the parts they replaced, and also check your compression again. It's beginning to look like the heads. Are the oil/coolant contaminated at all?

also, just to be safe, mist water over your plug wires at night to see if you have any electrical arching.

are you losing a lot of coolant? white smoke/excessive water out of pipe?
 
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dz2a8r

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What gaskets did they use? What ignition parts did you use? I would like to see the parts they replaced, and also check your compression again. It's beginning to look like the heads. Are the oil/coolant contaminated at all?

also, just to be safe, mist water over your plug wires at night to see if you have any electrical arching.

are you losing a lot of coolant? white smoke/excessive water out of pipe?

used delco parts, misted plug wires no arching, its obvious they changed the intake gaskets, no oil contamination, coolant looks like @$$ which i would expect with 130k .......i just bought it about a month ago just havent gotten around to flushing it. compression on all cylinders was around 155 if im not mistaken. no white smoke out of the tailpipe, or excessive coolant loss....ive only put about 2800 miles on it since i bought it....runs fine at an idle, cruising 65 down the interstate, but when you kick it down to pass, at about 70 it begins to miss its A$$ off and the cke flashes at me. only misses under a load.....im thinking its a head or headgasket issue still, gonna call them in the am and see about getting it back to them........they wouldnt let me fix it at work because it would be a conflict of interest with me being the owner, but thats fine they can buy another set of intake gaskets, oil change, coolant and have someone else do it for the second time
 

BattelWagun

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Yeah it's sounding like gaskets unfortunately. They're leaking, just not enough that's it's noticeable all the time. Good luck! Tell us how it works out


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SunlitComet

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Total head gasket failure is imminent (enter sound of klaxon siren here):imo: save the engine before major damage occurs.

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dz2a8r

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Yeah i know, but they have to send it to their guy and get verification from him, so as of last week i dropped it off....they said it was intake gaskets, they replaced them i picked it up, stall tested it when i got home, took it back to them the next morning......stopped by the shop today at lunch and they were going to do a block test on it.......theres only one way exhaust gases can enter the cooling system and that is at the head, just cant seem to get them to understand that
 
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dz2a8r

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stall tested in front of them last tuesday when i took it back......he only seemed concerned with telling me how hard i was being on the trans, and not with the misfiring going on with the engine. they finally called me back yesterday and told me they put a stronger radiator cap on, and ran a block test, and could not find any other problem with it..... i told them to have it ready for me i was coming to get it. If he cant diagnose a head gasket problem within a weeks time then he doesnt need to be working on cars. Im going to call the sales manager from the lot i bought it at and see if i can get anything done through them
 
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dz2a8r

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has a 16 lb on it now, claims it had a 7 psi on it, that would absolutely explain it burping from under the cap, but not the misfire.
 
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