I have an 89 toyota camry, 4cyl, automatic. Recently the car started to struggle from a stop on hills. My first thought was the transmission but then it started to pulse at certain speeds on flat freeway drives (this can be remedied by pressing on the accelerator pedal). So I thought maybe I had bad gas because I had gone to a different gas station. I filled the rest of the 3/4 empty tank up with a higher octane and still no change. The car has gotten progressively worse and now pulses almost all the time, however the gas is also now on empty (related?). I took it the mechanic who told me that it was definately misfiring and recommened a full tuneup including spark plugs, wires, air filter, and distributor cap. They tried to tell me that the wires looked bad but I personally just replaced all that about 25,000 miles ago. Everything still looked okay to me and the plugs are platinum tipped bosches. I have a hard time with the mis-firing diagnosis especially since the car drives fine when cold. Any suggestions would be helpful.
Jody

Regardless of it being warm or cold and age of components, everything they are telling you could be true. One red flag I see is Bosch plugs. I've never used them but, many on this and other forums have reported problems with them.

Can you hear the engine miss when idling in your driveway? That alone would eliminate the transaxle. One trick you can try is on a dark night open the hood and watch for arcing near the spark plug wires. It indicates degraded/chaffed wires.

Other possible causes could be a vacuum leak, an EGR problem, a fuel pressure/injector problem etc.

You say you replaced "all that 25,000 miles ago". Exactly what was replaced, where did you get the parts, and what time frame ago was this?

The car idles fine all the time. The engine sounds great. I bought the parts from checkers a little over a year and a half ago. My personal opinion is that it is something to do with the fuel. On hills it feels exactly like the times when I've accidentally ran a car out of gas (sputters and then kicks in).

OP,
As noted, check for vac leaks, especially in the intake ducting. Also, look at the air filter and verify that it does not require replacement. You may also want to replace the Bosch plugs with Denso or NGK.

"I personally just replaced all that about 25,000 miles ago."

I have seen cheap aftermarket plug wires break down in as little as 1 year or the mileage you already have on them. If you have a digital volt/ohmeter available I would check them for resistance through the distributor cap.

"I have a hard time with the mis-firing diagnosis especially since the car drives fine when cold."

This makes me think O2 sensor, since the O2 sensor is out of the loop until the engine reaches a certain temperature. It also makes me think of the coil inside the distributor, since they can also cause problems when they get warm. Check these 2 items.

Mike

If you have a digital volt/ohmeter available I would check them for resistance through the distributor cap.
Mike

Do you put the red end in the rubber boot contact and the black end of the voltmeter on the distributor cap? it should read 12 Volts, right?

Do you put the red end in the rubber boot contact and the black end of the voltmeter on the distributor cap? it should read 12 Volts, right?

It doesn't matter which probe goes where in this case, but you are checking for ohms, not volts. Download the factory service manual stickied at the top of this forum and go to the ignition system section for the procedure and the specifications you should read.

Mike

The Bosch platinum plugs are not gap-adjustable since the ceramic insulator surrounds the middle electrode. As it wears down into the electode insulator, the effective spark gap increases but you cannot readust them because the ceramic prevents taking an accurate gap reading. Denso or NGK are the appropriate plugs, though I've had good experience with Autolite platinum (not +2, +4, or fancy dbl platinum money-suckers).

This wear, along with oxidation build-up on the distributor terminals inside the cap and rotor can result in significant power loss. Hope this helps!