Nefarious Posted December 8, 2012 Share Posted December 8, 2012 Hey everyone. I just ran a compression test in my gfs truck and I'm seeing some variance in a cylinder. Most cylinders were between 170-175 psi but one (#6) read about 157. We just got the truck and have been tuning it up, done all the regular stuff...fuel/oil/air filters, fluid changes, o2, spark plugs, oil seals, timing belt, waterpump, tensioner... but it still has a slight miss... I'm wondering if the compression numbers are too far off or maybe its something else? There is a tick in the motor and also a miss which is noticeable mostly on decel (the reason I ran compression) . The miss is heard in the exhaust especially when the motor revs down under no load and the ticking noise sounds like its coming from the middle of the valley between the heads. I'm thinking injector(s)... Checked codes...55 so all good. Next I'm going to clean the maf and ohm test the coolant temp sensor, as well as the injectors.... is there anything else should look for while I'm there? The liters seem good, I ran some wynns engine tune through it and I inspected the lifters and when the valve covers were off no noticeable impairments... doesn't sound like lifter noise but maybe.... Any advice is welcome! Need to take this thing in for air care so my gf has a winter ride! Thanks Link to comment Share on other sites More sharing options...
Precise1 Posted December 8, 2012 Share Posted December 8, 2012 The difference is listed in the FSM, I can't recall it right now. I do recall that the overall compression wasn't the concern, mainly the deviation between cylinders and the recommended 'allowable' amount wasn't much. If you haven't downloaded the FSM, go to the Garage section, a link will be posted in the thread pinned at the top of the section. B Link to comment Share on other sites More sharing options...
adamzan Posted December 8, 2012 Share Posted December 8, 2012 According to page 46 of the em part of the fsm the standard compression is 173, the minimum is 128, and the limit for difference between cylinders is 14. Link to comment Share on other sites More sharing options...
Alkorahil Posted December 8, 2012 Share Posted December 8, 2012 According to page 46 of the em part of the fsm the standard compression is 173, the minimum is 128, and the limit for difference between cylinders is 14. Most cylinders were between 170-175 psi but one (#6) read about 157. At 170 then 157 is within tolerance. However, the cylinder miss when reving down makes me think before injector of: 1) spark plug 2) distributor cap and rotor 3) fuel filter 1 Link to comment Share on other sites More sharing options...
5523Pathfinder Posted December 8, 2012 Share Posted December 8, 2012 (edited) Or carbon buildup on the valves. You might want to perform a wet test in just that cylinder and see if it changes much. This would help you determine if the rings are not sealing, but I don't think that's what you have going on. Edited December 8, 2012 by 5523Pathfinder Link to comment Share on other sites More sharing options...
Nefarious Posted December 8, 2012 Author Share Posted December 8, 2012 Okay, I did notice the distributor has a bit of play in it, ill try swapping the good one from my truck over and see if that helps. is it possible an injector is bad even with no codes?? There is still quite a loud ticking sound from the middle of the motor, and it runs a little rich. has new spark plugs gapped perfectly, fuel filter, air filter, o2 sensor. I just cleaned the cap connections of corrosion and inspected the rotors which lead me to the play in the distributor. I compared the lower gear teeth to my good one and the gears do look more rounded off and worn than mine. it has about 1/4 inch or maybe a little less of play. I guess this could be the cause of the slight miss hey? Just the ticking noise now, sigh I'm not looking forward to pulling the upper manifold again to ohm test the injectors... Link to comment Share on other sites More sharing options...
sewebster Posted December 9, 2012 Share Posted December 9, 2012 Might be a way to test injectors at a connector... 1 Link to comment Share on other sites More sharing options...
Nefarious Posted December 9, 2012 Author Share Posted December 9, 2012 Ya thats not a bad idea... I never even thought to ohm test the connection at the other end of the injector wire rather than test the injectors themselves... a couple foot run of wire isn't going to affect the overall resistance by much if any. I should have thought of that considering I just finished semester 1 of electronics tech school! Lmao Link to comment Share on other sites More sharing options...
devonianwalk Posted December 9, 2012 Share Posted December 9, 2012 Link to comment Share on other sites More sharing options...
Nefarious Posted December 10, 2012 Author Share Posted December 10, 2012 Well I put most of a bottle of seafoam in the gas, cleaned the maf, swapped in my good distributor...fired it up and after a bit of a drive she purrs like a kitten!!! Has awesome power, drives great and no miss! Thanks for the help!! Link to comment Share on other sites More sharing options...
Alkorahil Posted December 10, 2012 Share Posted December 10, 2012 thats great! Link to comment Share on other sites More sharing options...
Nefarious Posted December 11, 2012 Author Share Posted December 11, 2012 Ya man ! Once she is on the road ill post some pics of my gfs 400$ mint 93 SE with my 3.3 swapped beast Link to comment Share on other sites More sharing options...
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