Engine running rough, slow acceleration.

[Mr.Biotite]

I wanted to see if anybody had any advice for diagnosing. My 93 Pathfinder sat for about a week, after starting it up it was running pretty rough (more vibration than normal). The acceleration is also much slower than normal. Sparkplugs and fuel filter have about 15,000 miles on them. Fuel pump seems a little louder than normal, but the fuel pump comes on just fine and the car starts right up. I ran some seafoam through it thinking maybe it was some buildup on the injectors but that didn’t make a difference.

Any advice?

[Slartibartfast]

I would check the plug wires, make sure nothing's been chewing on them. If nothing jumps out, pull one wire at a time (carefully, easy to shock yourself). If it makes the engine run worse, put it back. If not, then you know which cylinder is misfiring. Then it's a question of spark, fuel, or compression. Check that you've got spark at the plug end of the wire, check that the plug is good, check the resistance on the injector, and if none of that shows the issue, do a compression test.

 

I had this happen recently on mine. Checked resistance on the injectors and found that the injector on the misfiring cylinder was well out of spec. It somehow fixed itself when it cooled off so I've been ignoring it for now, but I imagine it'll remember that it's dead sooner or later.

[Mr.Biotite]

Thanks for the advice. I did find a vacuum hose was missing from the fuel regulator to the intake manifold. I also found some corrosion on the distributor and the cable that runs from the ignition coil to the distributor cap. I replaced all the spark plugs cables, ignition coil, distributor rotor and cap, vacuum hoses, and the PCV valve. Figured it was time since most of it was all original. Cleaned up the throttle body butterfly valve as well. It seems to be running better but still seems to have some issues. Fuel pressure test was good with and without vacuum, so I am beginning to think it is fuel injector issue or the timing is off. I am going to run it for a little while and see if it gets better. Maybe I’ll get lucky like you and it will fix itself. 

[gamellott]

My bet is that you are having an issue with a fuel injector now that you have looked into the rest of the culprits. 

 

I'm experiencing similar symptoms, and I'm pretty sure it's the injector, since, like you, it was only sitting a week or so when the symptom popped up, and I have localized it to one cylinder which will require me to pop off the intake... 

 

Good Luck!!