I'm sorry if this is a little bit off topic, but I figured the All-Motor guys might be able to help with diagnosing my issue. Thanks, and I apologize if this is out of place.

Motor setup-
B18c1 OBD 2
Mild port/polish
CTR Intake/B17 Exhaust Cams
ITR Valvetrain

I was driving on the freeway the other night and out of nowhere, my CEL started to blink. Immediately, I let off the throttle and exited. As I made my way off, the car sounded like it was running on 3 cylinders, or as others would describe it, like a WRX.

Once getting the car back to my place, I checked the CEL and did a compression test. My CEL blinked a 72 and 74. I checked the compression and blew 215 across all cylinders except for cylinder 4. Cylinder 4 barely blew a reading on my gauge.

I checked the lash on those valves in cylinder 4 and they were within spec, none too tight or loose. I put the valve cover back on and still, no compression on cylinder 4.

Now, is this likely a bent valve or is there a chance that this could be fixed without removing the head? I did not over-rev the motor prior to this happening and no mis shifting at all. The car has been running fine and strong since the headwork was done about 45K miles ago. This is all surprising for me. Any help is more than appreciated. Thanks!

 

is there a noise that goes along with the behavior? sounds like you might have
over revved the engine at some point and valves might have touched. do you
have adjustable cam gears and if so what settings have you been running..?


Modified by MikeSarr_GSR at 10:11 PM 1/18/2007

 

No, cam gears are OEM, no adjustments.

The noise sounds like there is a misfire occurring, but nothing like valves slapping or anything. Its really hard to tell with the car misfiring and sounding like a WRX motor. I've never had any issue prior, nor have I over-revved the motor at all. The ecu is not modified and rev limits are at oem cutoffs and what not.

 

Bump for more insight?

 

Ok, just updating to hopefully help someone else in the future... and to see if maybe someone else can chime in with a better diagnosis -

Ok, pulled the head from my motor, and checked the block...


So far so good, least I didn't have to change a piston...

So next, flipped over the head to check the combustion chambers....


A close up of each combustion chamber helps finding the culprit...


So there you have it, the loss of compression and reason for misfire was due to a chipped exhaust valve in cylinder 4. The exhaust valves had a thick layer of black buildup on the backside of the face and continuing about 1/5 of the way up the stem.

***<U>NOW - More questions :</U>***

-Why do my exhaust valves have all that white build up forming on them?



Modified by EnjoyTheRideDC2 at 1:31 AM 2/18/2007

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnjoyTheRideDC2 &raquo;</TD></TR><TR><TD CLASS="quote">

So there you have it, the loss of compression and reason for misfire was due to a chipped exhaust valve in cylinder 4. The exhaust valves had a thick layer of black buildup on the backside of the face and continuing about 1/5 of the way up the stem.

***<U>NOW - More questions :</U>***

-Why do the exhaust valves have all that white build up forming on them? </TD></TR></TABLE>

Still have not come up with an answer myself...

 

well it looks like **** on your valves..hEhE one side looks like its running really rich or eatting oil..

how did the spark plugs look?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b16nonoy &raquo;</TD></TR><TR><TD CLASS="quote">well it looks like **** on your valves..hEhE one side looks like its running really rich or eatting oil..

how did the spark plugs look?</TD></TR></TABLE>

Actually after talking to someone who built engines in the past, the cause was my car was running extremely lean. The oil stain looking stuff is just carbon build up.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnjoyTheRideDC2 &raquo;</TD></TR><TR><TD CLASS="quote">

Actually after talking to someone who built engines in the past, the cause was my car was running extremely lean. The oil stain looking stuff is just carbon build up. </TD></TR></TABLE>

when I read your first post the frist thing I thought of was a bernt vavle, meaning the car was running too lean......you stated no misshift or over rev so that had to be the problem with number 4.

So yes the engine builder you talked to is right on the money....the car was running lean, looks like lean during part throttle. I would fix the head and look into having the car's A/f ratio checked while driving and see if there is anything you can do to make adjustments, I know your OBD2 so the only way to go about it is a FPR or a fuel controller, unless you go OBD1

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RedZone &raquo;</TD></TR><TR><TD CLASS="quote">

when I read your first post the frist thing I thought of was a bernt vavle, meaning the car was running too lean......you stated no misshift or over rev so that had to be the problem with number 4.

So yes the engine builder you talked to is right on the money....the car was running lean, looks like lean during part throttle. I would fix the head and look into having the car's A/f ratio checked while driving and see if there is anything you can do to make adjustments, I know your OBD2 so the only way to go about it is a FPR or a fuel controller, unless you go OBD1</TD></TR></TABLE>

Yeap, it was mentioned to me to tune at part throttle with my obd-1 p72. i finally bit the bullet and picked up a conversion harness. But since you mention it, would using a fuel controller be effective in helping with making the a/f mix richer?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnjoyTheRideDC2 &raquo;</TD></TR><TR><TD CLASS="quote">

Yeap, it was mentioned to me to tune at part throttle with my obd-1 p72. i finally bit the bullet and picked up a conversion harness. But since you mention it, would using a fuel controller be effective in helping with making the a/f mix richer?</TD></TR></TABLE>

your going the correct route...use a p72 and have it tuned with Crome by someone that knows and is comfortable with doing it.

a fuel controller is ok, but not great, your going a much better way of doing it.