I have a 1995 sidekick soft top with the 1.6 16 valve engine in it. The engine has always run a little twitchy with the occasional misfire. About 2 months ago I did a full rebuild on the engine. There is also a new O2 sensor, spark plugs, plug wires, distributor cap, rotor, air filter, fuel pump and filter, and a new exuast system from the downpipe to the tip. The engine still has a little bit of a jiggle to it. Every 10-15 seconds it will misfire. Occasionally the engine will run flawlessly. But that usually only lasts about 5 min. All the engine sensors check out fine at all temperatures and engine speed ranges. If I remove and plug the vacuum line from the fuel pressure regulator the engine runs a tiny bit smoother. If I also unplug the coolant temp sensor as well as the idle air control valve (to prevent the computer from going to cold idle) I can get the engine to run near perfectly. This richens it up and is what leads me to believe that my misfire is caused from a lean condition. I have checked the engine for vacuum leaks 100 times over with every method under the sun. There are no leaks. This problem is annoying me to no end as I need the engine to run smoothly so I can sell if for what its worth. I would greatly appreciate any help I could get. Thanks.

By the way, I'm new here. My name is Kyle.

Fuel Pressure might be low.
Pinch the return line, does this help?

I will have to try that tomorrow. I also forgot to mention, at about 1/4 throttle when accelerating the sidekick surges just ever so slightly. Once I hit 4000 rpm or I romp on the gas pedal the surging goes away.

I pinched off the fuel return line. The idle speed increased about 50 rpm and it ran smoother. There is still a little bit of a twitch to the engine. It almost seems to be as if one cylinder is only firing at 80%. Could I possibly have a clogged injector? I have had the injectors cleaned about 2 years ago. Compression is exactly the same in all cylinders. My compression tester is not accurate by any means. I have no idea how far off it is. The reading I had was 170 per cylinder. I can only tell if the numbers vary from one cylinder to the next.

Injector cleaning is not really needed, but
you might have something plugging the
inlet of the injector, or a faulty injector.

You can energize the injectors with straight
battery voltage, if you can do this with the
fuel pump "hot wired" but not the engine
running, you can pull the injectors and look
at the spray pattern and if they are working
correctly.   

I just did this, and found a bit of crap was stuck
in the injector, by holding teh injector wide open
for several seconds it blew the junk out and works
fine now, you might try this before replacing injectors

I have access to an injector tester. It pulses the injector for a specified time without burning it out. I will definitly try that. Do you think it would be easier to take off the intake manifold as a whole unit? This way the injector and fuel lines are tight and in place. I just don't want to have the fuel rail out and also try to keep the injectors in place while there is 40psi in the fuel lines. I'll keep posting with my results. Thanks for the idea.

I just looked at the spray pattern for the injectors. They all look the same. On monday I will have to get the injector tester and a fuel pressure guage. Then I can do an injector balance test. I hate engine problems. I really don't want to sell it while it's running funny.

Right now I am trying to do a fuel pressure test. The pump will turn on for 2 seconds then off. As soon as it turns off, the needle rushes towards zero. If get someone to turn the key on for me and I pinch of the rubber supply line as soon as i hear the pump stop i can get the gauge to stay steady. So... the leak is either internal at the pump or somwhere between the rubber line near the fuel rail and the pump. Could this cause my problem or would this not affect pressure while running. I can't run the vehicle right now as there is no intake manifold on it. I am going to continue to diagnose and will update when i find something.

I GIVE UP I can't fix this piece of crap. It frustrates me so much. I have checked everything. I put the manifold back on and it ran perfect. I then test drove it and when I came to a stop it was back to it's crappy self. Thank you for trying to help me I really do appreciate it. No offence but I need a honda. Thanks again.