valve lash adjustment
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Junior User
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valve lash adjustment
i had my heads rebuilt a few months ago, one of them replaced due to a crack, but the problem is that my engine has got this miss to it. it seems to do an excessive amount of shaking. i have replaced all spark plugs, distributor cap and rotor, coil and tfi, and it still seems to have the same "miss" problem. the timing is perfect. a few nights ago i replaced my spark plugs again and noticed the number 5 cylinder with oil on the plug. i hadn't noticed any problems when i had rebuilt the heads...the cylinders looked fine. even now i am blowing no smoke through the exhaust. i was told that this problem could have been as a result of a poor valve lash adjustment when the heads are rebuilt. i have run the codes on the ecu and have only come up with 02 sensor says engine runs lean. any help would be greatly appreciated.
george
george
Senior User
Joined: Sep 2001
Posts: 210
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From: Lincoln, Rhode Island
valve lash adjustment
I am not totaly sure it is valve lash but it could be if the valves are adjusted too tight causing the valve to be every so slightly open. This could create conditions that could compromise the seal of the valve stem seals. Thus allowing oil and air to be sucked in and creating creating a lean reading on the 02 sensor, and fouling the plug out and/or lack of compresion. It could also be the head gasket allowing oil into the cylinder which means you would also have a compression problem in that cylinder causing irratic idle and miss firing. I would do a compression check and possibly a leakdown test. Also use a vacum gage and watch how it fluctuates that might help.
I hope this might help.
400m
85' bronco II
86' f-150 (400 w/edelbrock power pack, 6" lift, 4-speed)
I hope this might help.
400m
85' bronco II
86' f-150 (400 w/edelbrock power pack, 6" lift, 4-speed)
Senior User
Joined: Feb 2000
Posts: 482
Likes: 1
From: Connecticut
valve lash adjustment
You stated the #5 plug looked suspicoius. Check to see that the injectors are functioning. Check the wiring to them, especially #5. A plugged or defective injector will cause a miss similar to what you are experiencing. I had a similar problem. I disconnected the injectors one at a time and noted the rpm drop to locate the defective ones. My fuel system was contaminated with rust like debris causing several injectors to become restricted.
Some may disagree with disconnecting the injectors with the engine running due to possible driver transistor damage on the engine computer from inductive spikes created when they are disconnected. These devices are normally protected with a diode to prevent this type of damage, I had no problems.
Mark
Some may disagree with disconnecting the injectors with the engine running due to possible driver transistor damage on the engine computer from inductive spikes created when they are disconnected. These devices are normally protected with a diode to prevent this type of damage, I had no problems.
Mark
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valve lash adjustment
ill check the wires on the plugs. i replaced the plugs a few thousand miles before the heads, but it could be a bad connection. the reason i see this a little unlikely is because it really seems more like oil on the plug than anything else, which i don't get of the plug was not functioning. as for a bad valve seat, the head i put on was a world cast because the stock head had a crack. it doesn't seem too likely, but im still waiting for my buddy to hand over his compression tester. thanks for all the input and ill check both out. if anybody has any other suggestions though, im still up for it. ill try anything
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valve lash adjustment
sorry i meant injector, not plugs in some of the parts. an injector that has a frayed wire is seeming to be like a more and more likely problem, but i haven't had the chance to check it yet. i always get excited when i think i have come close to fixing the beast. thanks
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