Ight I have a problem with the car. It started a week ago. Monday I put a new k&n air filter on the car (old one went missing ) drove home from the rents house and it drove fine. Got up tuesday morning and left for work and got half way there and it started to misfire. Now the car has sat for a week and as soon as I turn it on it doesn't run right at all. What should I look at?

-I'm thinking plugs and wires should be my first stop. Plugs are fairly new. Wires are old probably 6 years or so. But my car doesn't get driven a lot at all. I might have put 7k on the car since I did them.

-The coil is a couple month old msd blaster coil ( it shouldn't be this but weirder things have happened)

-Immediately thought opti but shouldn't that throw some sort of code? (its about 4 years old now and there is probably only 4 to 5 thousand miles on it)

-Don't think it could be the o2's cuz they have always thrown a code plus it does it right when the car is started and they aren't being read yet

-Could it be my msd6al ignition? Or if that was broke would my car start at all?

_Thought the k&n oil might have got on the maf so I cleaned it pretty good so I think all is well there. Plus I unplugged it to see if that helped but it didn't change at all.

Could it be anything else? Map sensor?

What do you guys think?

Thanks Joe

 

Do you have any idea how long the old filter was missing for? I would think it could cause problems if any debris got inside the engine. To many things could be wrong. Need to start with the basics and the cheapest ones first.

 

No idea how long it was gone. But it ran fine with it off, noticed no problems or misfires. It only started the morning after I put the filter back on.

 

Look for a dead cylinder

 

how will I look for that? I have free scan but didn't see anything out of the norm there. There are no Trouble codes set in the computer and no SES light on the dash. Its ran for about 40mins or so now with it misfiring so I'd think that would be long enough to set a code.

 

Oh yeah the car runs rich as hell. I started it up after about a week of not cranking it and i could smell the unburned fuel. I know it'll run like crap for a little bit after not being started in so long. But there was black smoke just rolling out of the exhaust for a good 5-7mins.

 

These days of scanners and codes have left some people with an "I don't know what to do now" euphoria. Kind of like learning how to do math BEFORE you buy the calculator.

First of all, prior to 96, there will be no codes for misfires. Sorry, gona have to go back to the "old" method of finding that one.

Second, once you run rich, several things will get screwed up which inturn usually causes it to run even richer. You foul plugs which now don't fire. See the point. You mess up the O2 which, if it was working before, it won't work now. Then, if you had a good cat, which you don't say, (I assume you don't), it would have been cooked also.

If the problem is the high voltage side of the opti, as you questioned before, it would not throw a code for that. Remember, it doesn't know it's misfiring.

One other thing that bothers me is you said "Don't think it could be the o2's cuz they have always thrown a code plus it does it right when the car is started and they aren't being read yet"

Are they still throwing a code for O2's? What is the code?

Remember there are 2 things that are required to burn the fuel coming into a cylinder. Spark and compression. Take either one away and it runs rich. So you start by checking spark at each plug. Spark can leave any cylinder at any time once the wiring/plugs gets old by allowing the spark to jump from the wire to the block instead of traveling to the plug and across the gap. One notorious spot is behind the alternator. If you haven't seen that spot yet, you're in for a treat.

You can check for a dead hole several ways. One is to remove the plug wire while the engine is running and see if the way it runs gets worse when you pull the plug wire off. If it does get worse when you pull it off, it was firing. If it does NOT get worse when you pull it off, you know it was NOT firing.

But since it's hot down there and it's hard to get to the wires without burning yourself, you could do the same thing with the injector wiring. Same deal, unplug the injector and see if it gets worse or not.

The other way is by monitoring exhaust temperature. This was can be confusing if the manifold has been allowed to get warm prior to checking. I like to do it only with headers and only when it's dead cold. When it's first fired up, check the temp of each primary tube near the head and see how fast the temp rises. The one or few that stay behind, are the ones that are not firing. I use an IR thermometer to measure the temp but some have done it with water spray to see how fast it evaporates. Thermometer is obviously better.

 

Thanks man I appreciate your help on this.

As far as the 02's go there is no code being thrown for them at this time. So thats why I don't think its them. Plus when they'd go out the exhaust would stink pretty bad kinda hard to explain but i've replaced about 6 of them in the last coupe years. I'm correct in thinking that the 02's aren't being read during start up correct? So even if they were bad it wouldn't cause a prob until it went to closed loop right?

There are no cats on my car. I have hooker long tubes with a catless ypipe.

I'm well aware of the mess behind the alternator and you are right its a PITA.

Damn I should have thought to just start pulling injectors off to see if it gets worse.

I'll see if I can find someone with a temp gun.

Thanks man.

 

mabe you have some bad gas.

 

UPDATE:

Went out and started pulling injector clips and I have at least 4 cylinders that when I pulled them the car didn't change idle at all. The other 4 when I took them off the car automaticaly idled down and got worse. Pulled the plug on 3rd cylinder back on the driver side (cylinder 5 correct?) and it didn't look terrible there was a tiny spot of white on it and it smelled like BP 93 octane.

EDIT: 3rd cylinder back was one of the ones that didn't make the car idle worse.

 

So with that being said am I suppose to start looking at the optispark? Cuz like I said this just happened. It was running fine then all the sudden it was running like crap. And I have a hard time believing I messed up 4 spark plugs or 4 wires all at once.

 

I've had two cases of bad misfires on my car, one was the opti, other was a burned spark plug wire. First thing you need to do, obviously, is check the wires for burns or cracks. One bad wire can throw off everything else. Being a 94, your PCM might not throw a misfire code.

It's hard with the vehicle on the ground, but try to crawl up under there and take a look at the opti. The water pump has a hole at the bottom of it. This hole leaks coolant as an early sign of a dying water pump, which happens to then leak on the opti (awesome planning GM ).

But don't just go replacing the opti, it could be something really simple that you're missing. I would also check for vacuum leaks in your intake.

 

Shouldn't be the waterpump since I have an electric one the weep hole gets sealed up.

I'm definetly going to check the wires first. A friend also suggested i might have broken a spring. I have CM single springs (forget the #) and they've been on my 224/236 cam for about 4 years now and have maybe 5-8k on them

 

Ttt

 

Good idea to check the wiring first. Obviously the plugs will need changing. AS will the O2's.

But I doubt you have a spring problem. With more than one cylinder at the same time?

However that does raise an interesting point. In order for valves to cause a misfire, it would have to effect compression. Therefore, it's wise to do a compression test. Be sure to pull the fuses for the injectors before doing so.

And no more TTT