falconsman

the cel is not on, the tranny was rebuilt 5000 miles ago, how ever when my car is in drive and I am sitting at a traffic light, the vibration is like a train passing, as soon as you let off brake and press the gas it runs great, it does calm down abit when i cut off the ac but still vibrates, any ideas on what this could be? Timing? Idle needs adjusting?.......

01tl4tl

the ecu takes care of all that stuff now, changes timing,,,

go to a parts store for a free code reading,,dont care if you havnt seen a warning light--bulb may be burnt out~

what rpm is the idle ac off, does it go up slightly when you turn the AC on?
ever done the egr port cleaning, and TB service of Idle Air Control valve
status of tune up parts- plugs?

could even be a front or rear motor mount-(front often found bad at trans time)
broken vac boosted mounts will affect idle- causes mystery vac leak

a 99: is that single coil and plug wires cap/rotor ,,or the 6 coils system
I dont know everything! (please dont tell my wife)

01tl4tl

just read in other thread you recently did the egr cleaning
if this issue started after that, it may be a result of that,,the upper gasket can be flipped upside down and cause problems by blocking a needed port

or vac line damage,, split end allowing leak,,
brakes ON pulls vac from its booster,,eventually from engine vac..rough running

falconsman

thanks, i has been doing this long before i cleaned the egr ports, even before the tranny was rebuilt, it idles around 700-750 rpm with ac off, when on it 750-800rpm and thats when it vibrates like is about to fall apart, as soon as you put it in N or step on the gas is runs fine. The shop wants $89.00 just to look at it.

fsttyms1

So it does it with or without the AC on?

When was the last time you had motor mounts replaced? Does the tach fluctuate or drop below 750 rpm when it does it?

falconsman

will check motor mounts, they have never been replaced, if they are bad would it only be at idle, and not any other times? and it is slightly noticeable with the a/c OFF but a back massage with it on. and the RPM stay in norm range. thanks

01tl4tl

the front and rear mounts are vac boosted (most years) so at idle they cause a small mystery engine miss
sounds like more than just that, but its a starting point
Look for bad vac connections at brake booster and master vac port at TB

recheck everything you did on the egr cleaning
has it done this since that work=like right after?
if so- take the top cover of the manifold off- flip the gasket over
It will appear correct if placed on engine side, but ck against cover side and its blocking an important port,,