FIXD

[pete_c]

Thank you Jon!!
 
Yeah mom is close to 90 now  and only drives a couple of miles away from her home if anything.  Fills the tank may be once a month or two.
 
 
 
That said most likely the fuel additive will not be doing much considering that she never drives the SUV.
 
Decided today just to fix it in baby steps...first changing the spark plugs and wires...then maybe cleaning or purchasing new injectors.

 

[mikefamig]

Yeah here is a picture of my ODBII reader which looks like an old calculator; large and bulky still functional; just kludgy. I read a while ago that Innova was a commonly utilized brand. These showed up on Ebay a few years ago and I think I paid some $30 for it???
 

innova.jpg
 
The code here is related to mom's Lexus (just a tad over 100k).  Googling it says it times to replace plugs or clean injectors or replace injectors.  I know that it needs a tune up.  She never drives it anyhow.  That said I purchased some fuel cleaner for now to see if it clears the code.  Thinking that the injectors are easier than the plugs to replace...but the injectors are more money than the plugs.
 
 
The new ones now utilize WiFi and have a little web based diagnostic menu in software embedded on the wireless ODBII readers.  The option to shut it off and leave it in place is a good thing as I think if you leave it plugged it it stay on.  Such that I was looking for one with a front on and off button on it.  The old ones used blue tooth and were more just a serial to bluetooth device with the software on the phone or tablet.  Embedded web page is better.
 
Thinking too on my vehicles there is another diagnostic plug for a computer for the mechanic in the front compartment.  It is not all ODBII but wil talk to ODB2.  It is a round plug with many pins on it for the computer to plug in.  I have checked in to getting one of these and the diagnostic software which is MFG provided.  It is less than $1000 but a bit too much for the casual lay person to purchase.

 
a P0302 indicates that cylinder 2 is misfiring or has misfired. You have said that the engine is running smoothly. If the engine is still running smoothly that indicates that all cylinders are firing.
 
I would clear the error suing your OBD3 reader and run the car to see if the error returns.
 
Mike.

 

[pete_c]

Yes it the engine sounds fine except that I can feel the rough idle when I put my hand on the hood.  I cleared the codes a couple of times with the ODBII device.  The same code came back after running a few minutes.  Googling the code on the Lexus user forum the replacement of spark plugs / cleaning or replacement of injectors came up along with trying a fuel additive.  The issues here is that the SUV can sit for a month without driving it.

 

[mikefamig]

The next thing that I would do is to examine each spark plug. The plug should be a light tan color. Then determine if the spark plug in #2 cylinder is firing with a good blue spark. They make a tool that tests each plug wire for a spark. It just flashes a light each time the plug fires to show that you have good voltage to the spark plug.
 
You may not like this but what I do is to remove the spark plug, connect it to the spark plug wire, and then hold the metal body of the plug against the engine block or other good ground. Then have a friend turn the key and watch to see if the spark plug makes a good blue spark. If the engines starts just have him shut it off immediately. As long as you keep the body of the plug grounded and only touch the wire insulator you won't get a shock.
 
Mike.

 

[mikefamig]

If the engine has good smooth power under a load and is only rough at idle I suspect a vacuum leak affecting the idle fuel/air mixture. An air leak can be difficult to find. In my old cars here there are only one or two places that a vacuum leak can occur so a leak is easy to find but it's a lot harder on a modern car. Late model cars use intake manifold vacuum to control a number of things and there area lot of vacuum hoes and devices that can fail.

 

[pete_c]

Yes here will try the easy stuff first.  Once the engine cover is removed rest comes easy ; well sort of.  The SUV is at the 100K mark and never has had a tune up so I am hoping for the easy way here.  Did have a new timing belt installed by the dealer a few years back at the 90k mark. 
 
Vacumn leaks are a PITA as you have seen with my last endeavor and replacement of a cyclone valve.
 
IE: first it was the MAF (looked new), then upper intake rubber hose (looked new) then the fuel pump (looked new) and finally the cyclone valve....diagnostic was no tools and easy, part was reasonably priced and it was the replacement and all vacumn hose replacement which was most difficult.

 

[cobra]

I had a similar problem with rough running on a different car.  My local mechanic did cables and plugs first.  The car would be fine for a while, then at higher rpms would throw a misfire code.  Did it again and I took it back to them.  They found some mice had built a nest under the air cleaner/on top of the engine.  Might be something simple, especially if it sits idle for a while.  That's what happened with mine.

 

[linuxha]

Wow, it's been 30+ years since I worked on a vacuum problem. I recall that a spray of water helped localize the issue.
 
Of course my current auto has fewer miles than my bicycles so that sucking sound is just mean having a bad day. ;-)

 

[bucko]

From my old days as a mechanic, I learned a trick or two. Forget about injector cleaners, fuel dryers,etc. The one and only thing to add to your car is.......Marvel Mystery Oil. To all your gas engines. I add this every fill up, but actually that's overkill. Still, this stuff will keep your whole fuel system, top cylinders and valve faces in top new condition. Been using it forty years for everything. It just works.

 

[bucko]

Wow, it's been 30+ years since I worked on a vacuum problem. I recall that a spray of water helped localize the issue.
 
Of course my current auto has fewer miles than my bicycles so that sucking sound is just mean having a bad day. ;-)

When I bought my used Lexus, I drove it home, and although it ran fine my OBD threw a slew of errors. Before I even wasted time going through them, I spent the day and replaced every vacuum line with new hose. Seems like miles of hose. Then I drove the car, and all but 1 error was gone, which turned out to be a bad O2 sensor.
Vacuum has everything to do with engine function nowdays. No need to bang you head against the wall trying to run down some odscure leak. Then a week later another one. Just replace everything and start with a clean slate. Expect to do it again in a few years, depending on where you live.  

 

[JonW]

Based on the vehicle history you've described, you should replace the plugs and clean the injectors and you'll probably be fine.  If the problem still persists, look to coil packs.  If you have "coil on plug" coil packs, you can swap them from one cylinder to another to determine if the code follows the coil pack.  If it follows the coil pack, then you know what to replace.

 

[linuxha]

... to run down some odscure leak. Then a week later another one. Just replace everything and start with a clean slate. Expect to do it again in a few years, depending on where you live.

 
Oddly enough, that's what I did also. It was a 1975 Mustang II. As I started replacing bad hoses I started breaking to connectors (old and brittle). In the end I rerouted everything and cleaned it up. I also added a slightly large vacuum reservoir. I wouldn't recommend it for modern card (redesigning) but one hose had deteriorated the it's most like many more have also.  

 

[pete_c]

Yeah really not too concerned except that it'll have to pass emissions some time or another.