Took the C5 into Honda today to check out what was wrong with my rough idle. I was hoping something simple like loose hoses? However, I guess they said there was a problem with Cylinder 3 reading 50! The rest are 175 (4), 175 (2), 185 (1). Watching them redo it so I could see, they only cranked it a few time and I asked if they were stepping on the gas. They said you don't need to. Can some verify this for me before I let them take apart my head and send it out? Anything else I can check out before going back to the dealer? Thanks!

 

I belive you are supposed to go full on the gas with 5-7 cranks.

Bump for someone who may know for sure.

I know there are step by step intructions but I dont have a link.

 

Hey thanks, that's what I thought too. Any other help would be appreciated.

 

Here you go: http://www.c-speedracing.com/h...t.php

 

5 cranks at wot.

 

my buddy who works for GM says that in school they were taught a minimum of 4 cranks is sufficient (but thats GM of course), then i know the Helms manual states that a minimum of 10 is correct.

As to your problem at hand....there may be several things that are possible wrong. You could (A) need a valve adjustment, (B) have a burnt valve seat (C) the valve guides could be loose, which i learned is very typical of our Heads especially if beaten on regularly. You'll know more when you rip off the head but i wouldn't be surprised if its an easy fix. Did the dealership comment as to whether or not the plug in the weak cylinder was clean or sooty?

 

I have done it BOTH ways. And it barely makes a difference to be at WOT (especially if you go a bunch of cranks).

Give up man, #3 is gone.

-Chris


EDIT: I've measured #3, and said to myself "oh jeez it's low", then done it again at WOT to get the same result. Wishful thinking, but a compression test is NOT rocket science, and rather difficult to mess up to the point where you'd get a low reading twice in a row.

 

Hey guys thanx for the help! I looked at all the spark plugs and #3 looked extremely sooty compared to the rest. (sigh) I guess, I can't do much but take it apart and see what happen's!

Would this cause the rough idle and the car dying as well?

 

could be the problem, any misshifts or overerevving lately?

 

looks like pistons rings are gone in that one cylinder. and headgasket could be blown for your intire other cylinders. compression on my stock usdm itr is 240 all across with wot. without is about 210. Good luck hope its nothing major.

 

un-plug distributor, throttle wide open, crank until the needle stops moving.

sie consistancy between cylinders is more important than the actual numbers having the throttle plate closed shouldn't give you "bad" numbers, but it MIGHT.

Look for all the numbers to be within 10% of each other - it is usually pretty obvious if one cylinder is bad because like you saw at the dealer, it will be like 200-200-50-200 or something.

make sure you have a strong battery, i have a lightweight battery and it has JUST enough juice to do a compression test then start teh car back up afterwards...

 

Hey guys, thank again! I'm just dreading the results. Hopefully a leakdown will prove beneficial before doing anything major... and expensive!