Aqueon

Last weekend, my wife's RX300 started running rough, with a flashing check engine light. Eventually, it stalled at a red light after we had gone to get the trouble codes read. At the time, the only thing showing on the report was a cylinder misfire: P0301, Cylinder #1.

I read some of the (extremely helpful) tutorials on this site and was able to replace the offending ignition coil / spark plug. The vehicle ran fine again...

...for about half an hour, at which point it started the same vibration and uneven acceleration that had showed up the first time. The CEL started flashing again, and we rumbled back into the auto shop to get the codes checked. This time, we got the following list:

• P1150 - AF Sensor
• P1354 - VVT?
• P0300 - Random/Multiple Misfire
• P0302 - Cylinder #2 Misfire
• P0306 - Cylinder #6 Misfire

Around here, the parts to make that repair will total $774.14. In my current financial situation, that's quite a chunk of change!

Now, I'm assuming based on my extremely limited knowledge that the CEL readings are suggesting I replace the VVT, the AF sensor, and all the spark plugs / ignition coils. Do you have any other suggestions for diagnosis?

I'm willing to get my hands dirty, and have a reasonable mechanical aptitude, but would very much like to confirm that I'm replacing the right thing before I drop that kind of money (and invest the time/blood/sweat/tears).

carguy07

You will not need all of those parts to fix. Clear the codes and check to see what code pops up first. You can have several, but the first one usually helps point to the problem.

fastnoypi

IMO, i would start with a vvt replacement out of the possible sensors to fix. Not only it is a cheap part for a DIY replacement, it does affect timing which might be the root cause of the misfires.

Baetke

Does your brake pedal get "hard" like you've lost your power brakes when the engine is running rough? This happens when the VVT malfunctions and you lose vacuum which is needed for the power brakes. If you have this symptom this is a pretty good indicator that the VVT is the culprit.

Aqueon

After shopping around a bit and inciting a bidding war between auto shops, I was able to get the cost-for-parts down to about $250, so a little under $300 after tax. I bought new plugs, coils, a VVT, and an AF sensor, and will probably install all of them this weekend.

I appreciate your advice, carguy, but decided that - since my wife got the car used and the original owner had never done a tune-up, I should go for the gusto! That way, if anything else breaks down the line, I'll know what's been worked on and what hasn't.

fastnoypi, I'll probably end up doing that one first. It seems like most of the sources I'm reading are in agreement on that point.

Baetke, I haven't noticed any problems with the brakes just yet. It's been misfire- or ignition-related symptoms only.

One thing I forgot to mention is that - when driving the vehicle back from the parts store - the engine would occasionally stop accelerating for a moment. I would just keep my foot at the same pressure on the accelerator and wait for the motor to "re-engage" one second later. (NOTE: This is one literal, not figurative, second. My wife timed it in case that mattered.)

carguy07

That sounds way too cheap for OE parts. I would not put any aftermarket (other than Denso or NGK) parts in the mix.

Aqueon

The plugs, VVT, and AF sensor are all OE. I'm not sure about the coils but will see when they show up. The local places didn't have more than one or two on the shelf.

fastnoypi

Aqueon.. just curious, approximately how many miles do you have on your RX?
I do agree that your parts total, does seem very low considering you ordered coils. I would hold off on installation of those and swap the factory ones around and see if you can chase a code that specifies the coil.

Aqueon

I'll have a look at the odometer when I get home this afternoon.

It does, I admit. The savings mostly came from the coil pack, which I suspect is not OE. That said, I'm beginning to doubt that the coils are the actual problem. Those will be going in last, if at all; I plan to follow your earlier suggestion and install the VVT first. If that fixes the issue, I'll be sad that it took so much time/effort/expense to realize how easy it was.

Aqueon

The odometer currently sits at about 132,000 miles.

Changing out the VVT seems to have sorted the rough idle, but I am currently getting a burning-oil smell while the car runs. There is no smoke from either the exhaust or the engine compartment, though. Could it be that the (relatively small) amount of oil that dripped while I was changing out the VVT and oil filter is burning off? That would certainly be my preferred answer... I have not yet taken the vehicle on a long drive, since I turned back once I noticed the smell.

I also have not yet installed the new parts, beyond the VVT.

fastnoypi

very possible that you dripped a little on the exhaust manifold. If you dont want to take the time for it to burn off, bring it to a diy car wash..let the engine cool a bit and hit the probable areas with their engine foam or get a can of Gunk engine brite. Careful to limit spray on the electrical components when you treat it and rinse.

carguy07

Is the CEL still on?

Aqueon

Now that I've got my pay for this next month, I'm back at work on the RX300. The oil smell hasn't gone away, and - after some sleuthing - I found out that the front valve cover gasket has sprung a leak. I don't think I caused that, but I'm gearing up to fix it.

The CEL has disappeared after I disconnected the battery to reset it. The rough idle stuck around, though.

This evening, I'm going to take a stab at the valve cover gaskets. From the DIYs I've seen, it's going to be a trip through the engine's innards to get that switched out, so I'll go ahead and install the second VVT, the AF sensor, and some other new gaskets while I'm under the hood.

matts6887

As far as the rough idle goes; from what i have learned from several other members; that most likely points to the IACV(idle air control valve). That could have heavy deposits on it causing the vehicle to idle very rough. Also; I would take some cleaner and thoroughly clean that iacv; then button everything back up and see if that solves the rough idle issue.

Aqueon

After three months, the aftermarket parts seem to be holding up just fine. The idle still feels a touch rough to me, but nothing serious seems to be going on, and the gas economy is OK.

Now it's on to the failed door lock actuator and air mix servo, I suppose.

Thank you very much to everyone in this thread! You've all been a huge help to me.

EDIT: I forgot to mention that - after using some engine cleaner - I was able to get rid of the burning oil smell and the valve cover leak. Changing out the valve cover gasket was a serious pain, but it's worth it to restore the wife's transportation.