I have a 91 ES250 with 155K on it.

About 3 weeks ago the engine started running really rough. Felt like it wasn't firing on all cylinders. It wasn't constant and this happens at idle, in park, neutral, accelerating and running. It seems to have a little less power but at high RPM I still have pretty good acceleration. It has gotten progressively worse. It started as a short term problem, after a couple of miles the car ran fine and now it seems to be pretty constant problem.

This came on suddenly. Engine was running fine. I thought it might be something with the transmission because it felt like there was a jerk forward (like more power coming on) then back to the rough run or idle, but it seems to run fine in all gears.

I have run regular gas in it, premium and even used an octane booster. It still happens.

I did have the timing belt and water pump changed several months ago and it ran fine up to about 3 weeks ago. It seemed to coincide with the time I put octane booster in. I do smell a little gas in the exhaust at start up so it might be running rich at start but I do not smell it after the car warms up.


Any ideas?

 

Some Additional Info.

I was looking around the engine compartment today and found that all of the vacuum hoses were not connected to the BVCVs. The ES250 has two of these valves with 2 vacuum lines each. All of the connection points are broken on the valves. Could this cause the misfiring, really rough idle and drive?

 

Certainly any kind of vaccuum leak will cause the car to not run correctly. The more leaks you have, the worse it will run. It doesnt seem to make sense that those connections would be broken and suddenly it runs bad. Something has to have happened to cause these items to break, then subsequently cause the car to run bad. I highly doubt it was the octane booster, in fact, i can pretty much eliminate it. Is your coolant level low at all? Smoking on startup, or while driving? How old are your plug wires, cap, and rotor?

 

Thanks for the quick answer.

I am taking the car into the shop today to have the plugs, wires, distibutor and rotor replaced, throotle valve and injectors cleand and timing/ignition checked. They are also going to try to change out the vacuum control valves although these things are something Lexus cornered the market on and are hard to find other than through Lexus. All of this for about $500-$600 (I don't know if this is a good price, but it doesn't sound unreasonable).

I filled my tank with 93 octane this morning and the engine seemed to be running fine again, at least no bucking and it seemed much smoother with more power. It sounds like all cylinders are firing again. This happened before. At about 2/3 full it started missing and bucking and I would not have expected that to change this time. Hopefully the tune help will prove me wrong.

I do not see any smoke out the tail pipe but today of all days I did see a little out of the engine compartment (after I filled the tank). I am thinking (hoping) maybe the other cylinders were not previously firing are smoking slightly as they get back into the game.

 

Another add-on question: Does anybody know if a BVSV from a 1991 camry V6 2.5L can be used on the ES250 engine? I thought they were essentially the same engine. I had a tech guy at a parts store tell me they were not interchangeable. Of course the lexus valve is more expensive than the camry valve.

 

no time to really get into it, but the problem you describe sounds like an ignition problem, specifically with the way it degraded over that time period, as well as feeling like it still has power... the system is much more transparent and problems not as noticeable under full load / higher throttle positions, especially on a non-turbo car...

 

Thanks for the info.

Quick update: Took the car in and had new plugs, wires, distributor and rotor put in. Oil change also. Seems to be running great at the moment. We'll see what happens when I reach 2/3 tank.

I have to change out the BVSVs and hope that might help even more. The car still seems to run hot (mid-way up the temp guage). Maybe the new BVSVs will help.

Any thoughts?