Dead cylinder - how noticable is it?????

[bloopbloob]

I just ran a cylinder balance test with my scanner. i got code 70 3 times in a row, which it says indicates a very weak or dead #7 cylinder. i'm just waiting for it to cool down so i can check my plug, but it has me worried! i ran the test just to check... it runs strong and i never thought there was a problem... if it were a dead cylinder, would it be noticable? i'm just wondering if its been this way since i bought it, so i have nothing to compare it to??? what all should i be checking besides the plug? how hard is it to test an injector?

 

[iwashmycar]

also check the plug wire and the injector harness, and then maybe try it again

 

[BlooDReigN]

Why not do a compression test? It's pretty simple to do a 5.0.

 

[bloopbloob]

k well i couldn't get the spark plug off with my crappy spark plug wrench, so i guess i'll pick up a good one that uses a ratchet tomorow. is a dead cylinder noticeable though? won't it shake the engine at idle or anything??? what all would i need to do a compression test? never done one before....

 

[BlooDReigN]

You need to get a little kit to do one. They are pretty cheap. Basicly what it is is a gauge with a hose and a fitting on it that will screw in to your spark plug hole. You put the gauge in the spark plug hole and turn the engine over a few times with the starter (make sure the plus arent getting any spark by disconnecting the plug wire from the distributor) and the gauge will give you a reading. Generally you will get a reading in the mid 100's in PSI and you want all your cylinders within 10% of each other as a rule of thumb. It's not a bad time to replace your spark plugs if you haven't done it in a while either, seeing as you gotta take em all out. The whole thing shouldnt take more than 45 min - 1 hour.


Oh, and cylinder 7 (incase you didn't know) is the cylinder 2nd from the back of the engine on the drivers side.

 

[Roland69]

I use a snap-on modis scanner and use the lab scope function with a low amp clamp over the starter wire and it will show a graph of the amps from the starter.....if all 8 cylinder's are good the peak of all 8 amps will be close but if one is dead or weak one will show on the graph that it took little to no amps to turn the compression stroke of that cyl. Hard to explain but if all 8 are good the graph will look like this

^^^^^^^^

and if ine is dead or low on compression it will look like this

^^^^^^-^ kinda

 

[bloopbloob]

ok well the one i have does the test and if somethings wrong, it shows up as a code. then you run it again within two min., and if it shows up again, it's more severe, and then the third time if it shows up, it's a dead or near dead cylinder i guess... and that is what i got... i'm still suprised that nobody can comment if a dead cylinder would be noticeable or not! i think something that severe would be obvious, right???

 

[TomCat]

Run it while it's all connected, shut it off and pull #7 spark plug wire. Start it up and compare! If there isn't much difference at all, try it with another plug. Say... #4. Then take all your data, compare and see whether or not it's dead! lol, it'll give you a little more info at least.

 

[DEFWISH]

i have been told to crank it for 4 *POOFS* . it is supposed to be a full cycle. so that's always how i do it. also it is best to have all 4 plugs out of a side . 1. easier cranking and 2.it is better to help diagnose problems . ( more accurate )

 

[93GTosu]

i'm still suprised that nobody can comment if a dead cylinder would be noticeable or not! i think something that severe would be obvious, right???

you'd think running 7 of 8 cylinders would be noticable!!

just wondering, what scanner are you using? one with a display or one that beeps/flashes? i have an actron scanner that beeps and flashes. reading through the booklet, it says that on a cylinder balance test a 77=throttle movement and to redo the test. maybe you were mistaken with the code? if you arent using this type of scanner--ignore me

 

[hemi_fan]

Yes, you will deffinitely notice if only 7 cylinders are firing. The most prominent thing you will feel is crazy shaking from the engine not being in balance. There will also be a power loss, but mine wasnt that noticeable surprisingly.

 

[302RollinHard]

take the suspect cylinder and put a few drops of oil in the cylinder and retest. If pressure increases you have bad rings.

 

[Mr. Rustypwnz]

a dead cylinder is noticeable, it will feel sluggish off the line and on shifts, what temps is the coolant getting to lately? i had a plug wire make love to the header after a hard 150mph run down the highway one night and didnt notice it till i got it to the house, but it was getting very hot on me, and the next day going to work, in the 210-220 range!!

 

[bloopbloob]

ok... first of all, my scanner has a digital screen that shows the codes, and came with a book, so i'm sure of what the codes i'm getting mean. pulled the plug, and it looks fine. pulled #6 also just for reference, and they look the same. both have gaps of about .042. they are ac delco plugs. is this close to what they should be set at? i bought a plug wire tester (pretty cool dealy if u ask me!!!) that i'm gonna go try in a couple minutes. i dont think its the wires, because they are FRPP wires i just bought a couple months ago, and i havent put many miles on the car. i disconnected the #7 wire, and fired it up. it was a little different than normal at idle, but not much, definately not what i would expect from a missing cylinder!!!!!! i thought it would shake like crazy but it didn't.... barely noticeable than what i'm used to. does this mean i may have been running on a dead( nearly dead) cylinder for a long time? or is this normal? i just think that maybe i don't have a normal baseline to compare it to!
any other suggestions?

 

[bloopbloob]

update. just more confused now! first of all, the 'neat little spark plug wire tester' tool i bought is garbage. didn't work on any wires... only $10, but still garbage. taking it back when i get a chance. so after i reinstalled the 2 plugs i removed and gapped to .042 (what #6 was at, & #7maybe off by .004), i went and did another cylinder balance test, and i passed on the first try! i don't get it! how could i fail 3 in a row before, (each fail indicates more & more severeity in the problem), and then change nothing, and pass? it still sounds and runs the same as always....
ideas??? but still i'm confused, it runs (at idle) almost the same with #7 wire un hooked as when its connected. i'm kinda busy lately, but i plan on unhooking other cylinders to see if its the same. kinda forgot to try that when i was at it....

 

[Roland69]

did you try adjusting the rocker's...maby give that a try it's easy and could very well be your peoblem.

 

[bloopbloob]

ooooooooh! how hard is that? i'm just the avg. backyard mech. type guy!. i like to do as much as i can by myself, and love to learn, but i know when i'm outta my league!!! i also live in an apt., and it's my dd, so my options are limited...

 

[Deleted member 87397]

You would notice a dead cylinder more as rpms increase. The shaking of the engine should get worse if it's completely dead. I had a plug wire fall off once on a V-6 ranger I had once and it was shaking like mad. Maybe with a V-8 it's not as noticeable? Don't know. Hope you get it figures out.