Excessive engine vibration

toyota
tacoma

#1

My 4 cylinder Tacoma vibrates a lot when it is idling, especially sitting in “drive” at traffic lights. My regular mechanic has tried various things to remedy it but none has really worked. He suggested the valves may need to be adjusted. Is this plausible? Or is he off-base? And is it really expensive?


#2

You haven’t provided much info to work with. Year, mileage, any codes present, compression test run, etc, etc.

If valve lash is suspected to be the caue of rough running then yes this can be the cause of rough running.
Valve lash inspection and adjustment is not very expensive.
However, repairing damaged cylinder heads due to tight valve lash is expensive if the tight lash is on an exhaust valve.

The first step in diagnosing an engine performance problem is a compression test. This will reveal if there’s a problem with piston rings, cylinder head valve issues (the lash), etc.
A vacuum gauge could also be quickly connected to the intake manifold. This would reveal in a heartbeat if there’s an issue with compression. (again, valve lash too tight)


#3

Thought the year was in there. It is a 2000 Tacoma but it has very low miles, about 54K. Hard to imagine it could have major engine problems with such low mileage. They checked for codes and none were present. Did not check compression or vacuum that I know of. Should I take it to a Toyota place or try my regular guys again? They seem to be honest, but I don’t know how well-versed they are in foreign cars.


#4

A vacuum test and compression test are very basic things that any mechanic should be able to do.
In theory a very low miles truck with only 54k miles should not have a compression problem but those problems can and do happen.

I’m not privy to your guy’s line of thinking and procedures so I have no idea how he arrived at the valve lash conclusion.

Quite a few years back car makers recommended a valve lash check at anywhere from 1k to 5k miles from brand new and this was often paid for by the car maker. After the initial check it was recommended that this check be done every 15k miles.
The bean counters took hold (goodbye to the 1k/5k check) and the PR department took over the 15k mile check as part of the ongoing effort to whitewash maintenance costs.

The problem with tight lash on an exhaust valve is that it only takes comparatively few miles for damage to be done to the valve face and seat. Once discovered, adjusting the valve(s) may be a temporary fix and down the road in months or even years it will surface again and no adjustment will cure it the second time.
Hopefully tight lash is not the problem here and it’s something more minor, although sometimes finding the minors can be difficult.

If a compression test is run you should be seeing about 180-190 PSI on all cylinders. If a vacuum test is done you should see a rock steady reading of about 17-20 inches of vacuum if everything is good in there. (The vacuum reading will vary based on altitude, barometric pressure, any engine wear, etc so it’s not a certain specific figure.)
Hope some of that helps and good luck.


#5

The vacume gauge would be an excellent thing to use to check into these theories…then again besides me and OK45 and maybe a handful of others on here…Having the knowledge to decipher what that gauge is telling us is starting to seem like a lost art. Hope the op has a good mechanic nearby to do this test It would reveal mucho. Aside from what the vacume gauge can tell us the next thing to look at is the ignition system.

I would be looking for a miss meself…