I just bought a 1997 saturn sl with 160k 5 spd man sohc. I bought it with a misfire and figured it was something easy like plugs or wires. I've done the following to figure out the problem.

new plugs/wires
I took out the ign mod and swapped the coils to see if the misfire moved from cylinder 4 to a different one...it didnt.
I compression checked the engine 4-170 3-185 2-170 1-175
I then went to start checking the fuel system....the injector electrical connection of cylinder 4 was half unplugged. I plugged it in and the misfire is a lot better but still flashing on the dash.

it is now intermittent. When i come to a stop...the misfire will go away and I can drive through the first 3 gears till 3500-4000rpms before it misfires. It will then misfire all of the time until I come to a complete stop.

I was about to pull the fuel rail and move injector 3 to 4 and vice versa to see if that is the problem. I noticed that injector 4 has a lot of play in it...i can spin in a lot both way...were as the other injectors dont have much give...could that be a problem? Do these injectors have normal o rings?

thanks for the help...sorry for the long detailed post.

:::addition.... cylinder 4 spark plug it white...which i believe is a lean condition...all of the other plugs are a dark color with some slight carbon on them.

 

Check for an intake leak at the head.

 

could the leak come from that #4 injector o ring failing possible? I find it weird that is the only injector that moves..Its dark out now...i'm going to have to mess with it tomorrow. thanks

 

or intake manifold

 

It's very possible that you need to replace the o-ring on that injector. You shouldn't have that much play in it. But I also agree that it could be a vacuum leak. Check for that and replace the o-ring and report back, please.

 

I finally had the time to get the fuel rail off and the auto parts store sold me the wrong o rings...had to go back and get more. finally got the fuel rail back on and everything back together. I also swapped the #3 and #4 injector to see if it would misfire on cylinder 3 instead of 4. well...its still missing on cylinder 4..so the injector is not the problem. I looked around for vaccum leaks...couldnt find anything. Any common areas to check? thanks!

 

I think someone said to check for an intake leak, thats done by spraying carb cleaner around the intake as the car is running. Any changes in idle and you found your leak.

 

thanks...i will give that a try tomorrow

 

Just curious, are you labeling your cylinders in the right order? The number 1 cylinder is closest to the passenger side of the car and the #4 is closest to the drivers side. The transmission is on the drivers side.

The reason I ask is these engines have an issue with the intake manifold gasket around the #1 cylinder. That port only has three bolts around it, nothing holding the upper outboard corner, and the there is no bridge between the #1 and #2 intake ports to support the gasket.

Spray a little carburetor/fuel injector cleaner or even WD40 if that is all you have around the #1 port and see if the idle is affected. If so, replace the gasket with a felpro gasket. The GM gasket does not have enough stiffness for a gasket that does not have the support provided by the mission bridge. The felpro gasket has a metal core and is better suited.

 

Last Post on this was the 7th. Good problem. It will be interesting to see the solution.
Compression is good, no problem there. The spark plug is probably not part of the problems. What happened when you moved the injector, swapped 3 and 4? did they tighten up? I wonder what you would be able to see if you installed a vacuum gauge?