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ylekiot1

Car Idles File, But Once It Is Put In Gear The Whole Car Vibrates

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First off the idle control valve works, After it warms up you can see it lower the idle, then some more, then some more. I know that is working. I have looked over the whole fuel/ignition system that is easy to get to. No luck. I have the shop manuals and have gained nothing from them. Coil? Cap? Rotor? Wires are a year old. Plugs 40K. Car drives fine. Just the vibration at idle in gear. Is it quite noticeable.

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Check the condition of the motor mounts and transmission mount. Mine went bad at 98K before I bought it, and the repair order that came with the car's records described exactly your symptoms. It may well be the case that something else could be going on with your car, but that's a good place to start. After that it's time to check out the ignition system. Have the plugs, plug wires, and caps & rotors ever been replaced on your car? After that, things like a new fuel filter and a good fuel system clean-out will help. LexLS.com has tutorials on doing that stuff, if you're so inclined to DIY it.

HTH! :lol:

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Plugs and wires have been regularly replaced. Caps and rotors are probably original. Car has 230K miles. To do the caps and rotors, it looks like I have to drain the coolant and such. Yuck. I'll check the mounts then go to the cap and rotor and then check the coils. Thanks.

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To do the caps and rotors, it looks like I have to drain the coolant and such. Yuck.

Isn't necessary. I did mine and it mainly entailed getting the plastic off the front of the engine, which is a big time p.i.a.

I did have to pull the fan and shroud out though, but it's not a big deal to do. If you end up having to drain the coolant, this is one of the best engine designs I've ever worked with, as far as getting the air out of the system. Pretty much takes care of itself. Speaking of cooling systems, while you have that much taken apart, replace the thermostat. It's cheap insurance, and they tend to slowly open over time, allowing the engine to run cooler than it should. Make sure to use a factory thermostat. In my experience working on cars, I've found the failure rate for aftermarket ones to be about 75% vs. NEVER for any factory one I've used.

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Try checking the Ignition Coils. I had an idling problem that shuddered the car when in gear. I thought it was the TPS or fuel system at first. My plugs and wires were relatively new, I couldn't figure it out and took it to a Master Mechanic and he found that the RH Ignition Coil was bad. Car runs smooth now.

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And coils are notoriously hard to test by the DIY'er because the resistance values will appear within tolerance but fail under load. If they are original this would be a great time to replace them. The bad one (RH) on my '94 tested fine when simply checked with an ohmeter.

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We have seen this time after time...Do a full tune-up with OEM or parts recommended on this forum or sell the car. Jeez guys it is so easy to maintain a 400 if you would quit sparing the dollar..and change all the mounts at 100k miles. If you are over 100k miles there are a lot of issues you need to address and all are covered on this forum from experienced owners. A 400 will go forever if you put the money into maintenance and along the way you have to ask yourself..should I keep it or trade up? I, traded up because it was getting more expensive to maintain than the cost of a 430 overall, one year and not an issue. I have never looked back and do my maintenance schedule as declared. I understand some of you cannot move up and my point is to not cut corners on the maintenance of your 400. I also understand there are some of you late model 400's that are perfectly satisfied. Nice cars ;) This forum has a wealth of knowledge, experience and know how...Please use it wisely and remember a Lexus was built the best and deserves the best parts you can find..and a kiss on the hood never hurts. ;)

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Probably not applicable, but as I drove into my garage 2 days ago, the 94 LS was shuddering like crazy in gear, but OK when idling. I opened up the plastic covers and such on the engine, and found that the longest spark plug wire, which was only 5K old, was twisted. The installer (me) must have messed it up. Replaced the newer cable with an original one, and the problem was solved. I also found that the long plastic assembly that grabs onto the head of the spark plug was broken on the newer cable-a piece of plastic was missing.

Now it runs like a top-hope your solution is as simple as mine.

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