93 940 low gas mileage + sluggish
 

My 93 940 base is getting about 16 mpg. It's pretty sluggish overall, mainly at low speeds and with AC on. At higher speeds its less noticeable. Idle is stable but engine alternates vibrating to smooth.

Any help would be appreciated :P

~hawk

when did it last get a tuneup? new air filter? is the compression good in all 4 cylinders? is the timing belt off a notch? any 'check engine light' or diagnostic codes on the OBD (*)

is the air duct intact and leak free between the intake manifold and the air mass meter (AMM aka MAF) ? no leaking vacuum hoses?


(*) see Engine and OBD Diagnostic Codes to read the OBD codes

"Engine vibrating" means you have a misfire, an intermittent one by the sound of it. Just look at things like plugs, wires, dist, cap, etc. Yeah, what used to be called a "tune up"...

Spark plugs were in bad shape, changed those. Also changed the air filter which was dirty. Will update tomorrow when no traffic and can get up to speeds.

Thanks for the help thus far :)

when its dark out and you can park in a dark place (or in a garage, with the lights out), pop the hood and start the car, and look at the engine in near total darkness for any sign of blue sparks around the cap/coil/spark plug wires... if you see any of this, you likely need new plug and coil HV wires. I *highly* recommend getting the Bougicord brand wire set sold by IPD and FCP and others, as its the closest thing to the originals, and much higher quality than the pretty looking junk they sell at most car parts stores (including Bosch brand wire sets, much of which is chinese junk now).

Also pop the distributor cap and inspect the inside of the cap, and the rotor ... excess erosion of the contacts, too much black buildup inside the cap and you get arcing and weak sparks, time for a new cap and rotor (for this you DO want Bosch)

I like to put a little silicone electrical grease around the spark plug ceramic parts and the outside of the 'tubes' on the coil and cap that the wires go onto, it helps keep them air/water tight to prevent future corrosion, and it makes it easier to get them off a few years later.

Wow, its like a new car! Cant believe the power it has now!

Ill do the blue sparks check tonight, and ill check the cap/rotor also :P