Ive been messing with a problem on a S4 NA engine for about a week now and would really appreciate it if you guys could help me out. I bought a low mileage S4 engine to swap into a 84 GSLSE. I got the engine in and all the wiring done and just ran the engine two weekends ago. The engine starts up quick but idles rough and lopes like its been ported, if I rev the engine it shakes back and fort really bad and kinda sounds like its running on one rotor. I have done a compression test, its kinda hard to read accurately but the needle for sure bounces above 90, I pulled both leading plugs and can hear nice strong steady *psssts* pulses as I crank the engine over. I have pulled all 4 spark plugs and cas and I can watch all 4 plugs spark as I rotate the cas. I also can hear and feel both primary injectors *click* as I rotate the cas. Im still going to pull the primary injectors and rig up a way to see if they are squirting fuel and possibly swap them with the secondary's. I also noticed that the conector for the tps has some corrosion in it and might not be making good contact, I plan to clean that good as well. Is there anything else that could be possibly causing the engine to run like this?
Thanks, Joe

 

Is this only when cold? Warm? Both?

It almost sounds like you have a vacuum leak, or your timing is off, have you verified timing and thats its right?

Anything else about this s4 engine? Or is it bone stock? Emissions removed etc

 

+1 on vacuum leaks. check all vacuum lines and UIM/LIM gaskets.

 

The engine is all stock. I did have to put a GSLSE front cover and water pump so that it would bolt up. I didn't run it long that way so I can really say if it does it when hot or cold. When I shut the engine off the block was warm to touch so maybe both? It still has emissions, I figured I have a small vacuum leak some where because there are some loose hoses that I tried to plug up. With the way the engine shakes when its revved it makes me think its more than just a vacuum leak? I have not tested timing with a light yet. I have been stabbing in the cas by lining up the first mark (no color on them, first one to match up when rotating the crank the normal direction) on the crank pulley with the pin and lining up the dimple with the raised boss on the cas. Next time I get a chance to work on it (tomo or this weekend) I will check timing and look for vacuum leaks.

 

I did find a video on youtube that seemed to be running similar to mine and it was diagnosed with the ecu going into limp mode... ???

 

bro, spray some carb cleaner or starter fluid around the engine bay when its running. If you have a vacuum leak, the idle will change.

 

hold on, you had to change the front cover (obviously) when you took off the front pulleys, did you keep the s4 pulley's or put on the GSL-SE Pulleys. Granted the timing marks SHOULD be the same between the two, but they may not (I'm not sure, a 1st gen guy would know)