[90coug]

Fellas,

I have really poor compression on cylinder #3 and want to know if there are any tricks to help emissions within BE.

I'm getting high hydrocarbons (unburnt fuel). Wondering if I could run the one bank lean enough to pass? Or can I adjust the fuel injector on the one cylinder to produce less fuel? I'm seeing LAMBSE around 17 on this bank while the other one is doing fine around 14.7. KAMRF on the bad bank is about .7 while the other bank is good at 1.

I did adjust the plug wider for a better complete burn. Car runs fine but this cylinder (rings) was damaged running some nitrous. I'm seeing about 60psi on #3.

Thoughts or ideas??


95 tbird sc
tj41
czaw0

[decipha]

that makes absolutely no sense, a bad cylinder should read lean not rich, you probably have a stuck injector in that cylinder which is what killed it not the n2o

[90coug]

Decipha,

How the hell are ya?


Well the cylinder is bad for sure no doubt about that. As far as running too rich, man I don't know but it's a fact. You want to see datalogs?

My theory is the rings are shot so all the air is escaping pass them and leaving no air to burn the fuel. In fact it's pressurizing the crankcase so bad it's pushing past the valve covers gaskets and leaking oil. I have to disconnect the tube that runs from the driver side valve cover to the air intake because it just sucks so much oil into the intake, or better yet it's pressurized so it's just forcing oil. Yea anytime I step on it I have to redo the valve cover gasket if I want a clean driveway. It sucks but the car will run, just idles crummy.

I think your wrong on running lean, only thing leaving thru the exhaust is unburnt fuel, the air goes right by the rings into the crankcase and out the valve cover gasket (path of least resistance). It's not the cylinder running rich or lean, the O2 is seeing a rich condition.

[cgrey8]

Note there's a difference between being rich and "reading rich."

If you have unburned fuel, the mix might be rich. From a CAT's standpoint, unburned cylinder charges will definitely be rich. However from an O2 sensor's perspective unburned air charges will register as lean. We make the assumption that a lean O2 reading is lean. In the case of unburned cylinder charges, there'll be quite a bit of oxygen present regardless of what the actual AFR was.

However if you are not getting lean readings and instead actually getting rich readings, then perhaps your assumptions of what's going on are wrong. No doubt, there is something wrong with the cylinder (stuck injector, bad rings, hole in the piston, whatever). So that'll need to get looked at.

But I don't think you are going to overcome an emissions issue related to that cylinder by telling other cylinders to misbehave in some counter-effective way. The closest option you have would be to run the engine as best you can and shove as much smog pump air into the cats as you can to compensate for unburned fuel conditions. However I'm doubtful this will pass an emissions test.

[90coug]

Well, I don't know what to think now. If either of you have a chance to take a look at this datalog that would be way cool. This is from my drive into work this morning and it actually didn't seem as bad as it normally does. Am I reading this right?? LAMBSE are around 10- which tells me the ECU is commanding more fuel???

At any rate, I know the cylinder needs to be looked at. I built and installed the damn thing but I've lost motivation to do it again. If I destroy it even further, so be it.

[cgrey8]

Another option I just now thought of might be to disconnect the cylinder altogether and just run it dead. This means the engine will have to either run Open Loop (difficult to pass emissions with that) or run the engine off the "other" bank's O2 sensor...the bank with all good cylinders.

The only downside here is you'll get a substantial portion of unburned oxygen in the exhaust. Some emissions tests require that the percentage of oxygen not be above a certain amount. Other tests require that the percentage of CO2 not be below a certain amount. Although due to smog pumps, that threshold might be high enough you can get a pass if you are lucky. I've never heard of it passing, but if you are bound and determined to try, that's something to consider. Of course, it's going to run like there's a dead cylinder. But it shouldn't hurt anything.

[90coug]

Funny you mention that, first emission test was with the engine only running on the one O2 sensor that was good. It didn't pass, in fact, the hydrocarbons were way above the limit. I'm thinking I should take it back with it running normal. I changed the O2 and plugs and the car runs fine oddly enough. I must have fouled the last one with too much gas or something. The car would bog down and I would lose signal from that O2 on the bad bank.

I should probably just park it and give it a ring job but if I could get another two years outta of it that would be awesome.

[90coug]

Anyways, thanks for the ideas.