Diagnose my (Subaru) car.
I happened to drive to work today, needed to pickup the cylinder head for the Z car from the shop in Beverly this morning. On the ride home, with my superior from work, I noticed a throb to the car at idle with the clutch pedal down. Now, I had noticed I was low on gas leaving Cambridge about 1 hour/10 miles ago. That's right, one (1) hour. We had spent the last twenty-five minutes inching towards Swampscott from the Carroll Parkway/Lynn Shore Drive rotary.
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The throbbing seemed to die down as I released the clutch pedal and revved the engine. A____ mentioned, "Aren't you low on gas?" I said, "That's it, I'm about to run out of gas." I pulled over and parked the car by the Lynn/Swampscott Beach and we each walked home. We'll see if A____ ever accepts an offer for a ride again (we both had a 10min walk at that point).
After supper I returned with a gallon of gas. Starting up the car, I noticed the same problem. A throb at idle, that got better at higher RPMs. I drove the seven tenths of a mile back to the house, noticing on the drive that I had less power than I was used too. I sat idling in the driveway thinking, "I hope this isn't that spark plug that I misthreaded and had to be helicoiled back in place."
Opening the hood I was greeted with the sight of the engine rocking away. I had seen the engine run without a plug before, the engine was out of balance and vibrated similarly; all my plugs were in order. I also noticed the throbbing/pulsing/rocking noise was evident in the exhaust sound,.I didn't notice any exhaust noise from between the engine and the tailpipe.
In neutral, revving the engine seemed to alleviate the pulse I felt (did not have an assistant confirm that the engine rocked less).
* Bad engine mount? Then why the exhaust noise, and the loss of power?
* A hole in the exhaust system? Then why the rocking engine?
* Am I not firing on a cylinder? How can I confirm that?
* How do I get to Pep Boys so that I can fix my other car?
A) I've had a loss of power when my exhaust manifold failed in my Japanese car.
B) If getting a different exhaust system can fluctuate your horsepower by 5-10%, this also supports the theory.
C) You know you don't have a leaking gas line/fuel injector (right?), and your MPG seemed in line (right?)
D) I don't want this to be a major repair, especially if the Subaru intends to get Baltimore next weekend...
oops - I feel stupid - you guys are talking about 2 seperate cars...
It is entirely possible that when the car was low on gas, you sucked up some crud that was in the tank.
This happened on a 1986 Nissan Sentra I had with 170,000 miles. Car wouldn't go over 45 mph. We changed the fuel filter and it was fine.
The hole at the top of the gas tank probably doesn't have much to do with keeping crud out, does it?
Replaced the fuel filter. Seems to run fine.
I'm leaning towards exhaust leak. Cracked header?
His car (and my main competition for his affections) is a BMW, and his terminology is British, but I hope that helps...
Good luck!
Dizzy cap/rotor/leads is a good suggestion. Just like the fuel filter, start with the easy stuff.
I will still check distributor and such before limping to the garage.
Joe at the garage found a slightly used computer to pop in and it runs like new. So much for shade tree mechanicism. I'm not going to purchase a vehicle with EFI ever again.
Of course, they don't speak English, but that's fine.
Sorry, it's much more convenient than a shop in Somerville. Otherwise, I'd stick with my old garage in Cambridge (a 20 minute walk to work). Driving a car on three cylinders along the parkway into town isn't really an option either.