Steering wheel vibrates visibly while in Drive when stopped, less in Park, and even less in Neutral. I'm concerned about the level of vibration - no other cars I drive are even close. Is this engine mounts, transmission problem, timing, or something else?
Engine mounts.
Check the "dog bone" engine mount on the top of the engine that connects to the strut tower. Look carefully for any signs of cracking. These are usually the first of the engine mounts to show wear. If this one goes, it puts more stress on the others and you'll need to check them more carefully. I'd guess if the one on top is good, or you replace it at the first sign of incipient cracking, the others are OK as well because the "dog bone" mount constrains engine movement. The correct factory name for the part is "engine moving control rod." Use Redline complete fuel system cleaner. One bottle in the tank with the first fill up, then one tenth of a bottle with each subsequent tankful. Do this for around two years and report back. Really. The in line four is inherently less smooth at idle with 180 degree crankshaft throws (offset between connecting rod bearing journals), and the steering rack is mounted close enough to the engine to transmit vibration. Also, any imbalance in tuning and maintenance is amplified. Check to see that the secondary electrical system is in top operating condition with original equipment parts. Aftermarket wires and distributor caps have been know to have significantly shorter service lives. Standard test for spark plug wires is test less than 25,000 ohms each. The secondary ignition voltage on Toyota's electronic systems is quite high so you may not notice an slight miss with weakened wires in normal driving, but it can be more noticeable parked at idle. I had some hesitation on harder acceleration at higher engine speed, but the car seemed to run perfectly fine during normal smooth acceleration. Trying out a new DMM (digital multimeter) I discovered two wires' resistance tested infinite, and one had burned the spark plug boot shorting to ground hidden inside the spark plug tube in the valve cover. The Redline CSFC is recommended because extensive testing by BMW qualified it as the only factory approved fuel injector cleaner of any on the market. Also, contains no harsh solvents that can damage components, plus contains synthetic upper cylinder lubricant. Does take a long time to affect improvements in contaminant reduction on the intake valves, but worth being patient. Read their technical information and study the graphs. There is an example for a four cylinder Toyota. One of the ways the Toyota engine generates additional power is through the use of four valves per cylinder. This has an effect roughly equal to turbo charging, in that it greatly enhances engine breathing and volumetric efficiency (plus reducing valve train wear with lighter components). If the intake valves become fouled with residue, they still open just as far, but the flow is restricted. That's why you'll notice an improvement in power with the Redline over time. Can take 15,000 to 20,000 miles, but it does work. Back to the original question, this will also help smooth the idle parked in Drive because it balances the power output between individual cylinders. Many fuel injector cleaners and gasoline additives make these claims, but I know this one works. Have had little to zero results with others. Finally, the oxygen sensor, takes what amounts to an average reading at the exhaust manifold such that if one injector pattern is less than ideal and output is restricted in the least, the feedback loop signals the ECM to richen the mixture to all injectors to compensate. By having each individual injector operating at peak efficiency, this will also help to smooth the idle parked in Drive.
Spark plug wire resistance ranged from 6500 to 12,000 Ohms, so that looks ok; did find one loose spark plug--which scared me. Is there some trick to getting the right torque and making sure the compression ring on the plug is seated right? Rubber on the dog bone is slightly cracked, so I will look to replace that -- manual says to support engine while doing this, but that doesn't seem necessary (?) I will try the Redline, I use a FI cleaner a few times a year, since I can't see the injectors and don't want to pull them.
That should be fine.
did find one loose spark plug--which scared me. Is there some trick to
Seems obvious to me - use a torque wrench. The inexpensive beam type for around $20 at Sears will work just fine. Head is aluminum alloy, so correct torque is important. When re installing a plug use a small amount of anti seize compound on the threads to ease removal later. If you have a few dollars extra, those 10" extensions with the locking button on the end are nice to ensure the socket doesn't come off at the bottom of the spark plug tube.
Rubber on the dog bone is slightly cracked, so I will
That's the perfect time to replace it - before the rubber cracks all the way through. I found no additional engine support was required. Just unbolt and replace. There again, there are torque values you can use when installing. Best to use the torque wrench on everything - that's why torque values are given. Although after years of practice you get a good sense of how to tighten things, it is still best to use the exact values.
I will try the Redline, I use a FI
Absolutely unnecessary to remove the fuel injectors, and unlikely you could see anything without checking spray pattern. With continual use (one tenth bottle at each fill up) the Redline CFSC will clean the intake valves over time and is safe for continual use, but you need to use it continuously to improve idle smoothness. May never get back to "like new" but you should see significant improvement if you stay with it. My steering wheel used to bounce up and down at idle in Drive, but it doesn't do that anymore. You can feel the power pulses from the engine coming through the steering wheel at idle, but they're relatively mild and not objectionable.
I also noticed that after a few hours of highway driving, then stopping, my idle RPMs dip about a needle's width below 750, and extra vibration/shuddering occurs. Usual city driving idles exactly 750 RPM. Does idle ever need to be re-set? (not that I have a tach)
I use duct tape on the socket to extension and also a strip overlapped inside the socket to help grip the plugs -- ugly, but it works.
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