i have a weird vibration in my 99 as well.

Transmission and motor mounts are new.

Vibrates a hell of a lot more on a cold start, but i can still feel the vibration at idle when it's warmed up.

Vibrates even when in park.

Can't figure out exactly what the problem is, no misfire codes. Only the occasional "system too rich bank 1 " code.

I am thinking the next thing to replace / clean is the injectors. Fuel filter has been replaced, upstream o2 sensors replaced, airmix path cleaned.

Any suggestions?

 

Scraape...the thought in my mind is one of the ignition coils or spark plug, the leads to the coils too.

 

good suggestion. I seem to be getting the system too rich code pretty frequently on bank 1. I think that may be my issue. I have replaced the 4 coil packs on bank 1 with no change .

I will check the spark plug gap . Something I forgot to do when replacing them.

any other ideas ?

 

i read on these forums somebody mentioned they had an issue with their MAF connector , so I made sure to check mine.

When I wiggled the connector and the car was running, i noticed the idle jumped when i messed with the connector !

Just replaced the connector and seem to not be shaking or misfiring anywhere as much as before. Hoping I fixed my issue. I haven't got the "system too rich bank 1" code in awhile.

Will report back

 

This part...?

 

yup! I got a connector with pigtail off ebay

 

Have you checked the air mix passages? Are they clean enough?

There are totally 8 passages. Each banks have 4 of them and there are 2 holes connected to these lines at the top side of the throttle body. 4 lines are connected to each injectors.

When one of them or more is/are clogged or partially blocked, a strange vibration often occurs. The passages only send the air and when those are blocked, there doesn't go enough air and the ratio of A/F(Air to Fuel) becomes rich. The engine has a MAF but there are 2 banks. A single MAF can't control unbalanced 2 banks well enough and this causes a vibration.

 

after replacing the maf connector and unplugging battery I now have a misfire on cylinder 2 . Which I am honestly happy about because that is most likely the issue I was having with bank 1. I'm guessing it's spark plug or injector ?

 

These drawings show the passages.

 

Kinda sounds like a coil issue. Have you pulled the coils in that bank lately? The tube seals in the valve cover can leak which eventually takes the coil out and fouls the plug...

 

Then you need to check the spark plug first and if it's OK, I'd try swapping the ignition coil with other cylinder one.

 

Thanks for the diagram Yamae it's a big help. I had no idea the pathways are so extensive!
What's the best way to clean these for forum members who don't have access to professional shop equipment? An aerosol spray like throttle body cleaner or something in liquid form, poured slowed into the holes, like Seafoam?

 

yes Yamae, i have cleaned my air mix passages on my vehicle. Unfortunately this seems to be a separate issue

 

I actually have checked the coils on bank 1 and swapped the 4 of them out with a set of *used* ones.

I also changed the spark plugs at the same time.

I will check the spark plug and coil and report back

 

Update: pulled cylinder 2 plug and it seemed fine .

replaced cylinder 2 coil pack.....

haven't got a misfire code as of yet..

i need to drive more to see if the issue goes away, but when I started it up cold it was shaking and misfiring a bit , as it was before.

I guess with 257k an injector is always a possibility? 😣