MACEDON

All

When I'm on the highway between 70-140mph I tend to have this vibration especially vivid when I get on the pedal a bit more. Sometimes I'd be cruising between 70-80mph and the vibration is non existent, other times it feels like the car is bouncing up and down at the engine bay, I can feel it in the gas pedal as well.

How can I determine what it is? If it's a missfire???

It seems to fall under the same range that I have a vibration at idle (in park that is) between 1800-2400 rpm which to me seems like either one of the pistons/cylinders is damaged or I have a missfire of some sort.

No codes whatsoever. Again the weird part is that sometimes the vibration is there sometimes it isn't. I also have a leak at the rear main seal if that helps...

I have new poly mounts, they were installed at a shop though so I can't make a comment. I think the vibration was there even with the old mounts.

nanayaw6

I was going to say mounts but you mention you think the vibration was there before. If your old mounts were shot it would explain that and the new poly mounts I expect would have a slight vibration to them as though especially in colder weather.
Also, how fresh are your plugs? Also possible, a failing coil pack.

MACEDON

The plugs were done in May/June actually, had em done at the best indy shop in my local area and he used the Bosch stock specs complete with wires. I haven't pulled them since to check them out, I should try it.

I'm afraid it might be the cyl 8 starvation issue adding to it all, the car was driven with a 180mm crank pulley and no cooling mods in Miami FL for a WHILE before I got my hands on it and put in a PLM cooler, so keep that in mind.

It has SLR cams on top of it which I didn't know so not sure how much that makes a difference.

How can I test the coil packs?

Could it be a voltage issue?

Could it be a fuel supply issue?

I have yet to check the voltage and fuel pressure with a gauge, the car is down with the airmatic compressor currently.

oneslow55

Welcome to the world of solid mounts and ill effects.

MACEDON

This was happening before the mounts

PieRat

What r ur fuel trims doing then its doing this at idle?

oneslow55

no offense car is a load of problems!Get the car checked by a pro and be done

MACEDON

Ltfts are at 5.5%

MACEDON

I tried to, he told me "it's norma" aka he has no ****ing clue

oneslow55

He’s a shoe maker then not a tech ..Find a master shop or dealer man

check ball joints and flex disc

MACEDON

Ball joints I will check then. It's weird that it might be that...


Flex discs are brand new OEM parts too.

Sometimes like I said though the vibration isn't there, it's smooth sailing even if I gun it. I don't get it, it's like some vibration just appears, maybe like the engine is starved of oil?

You know how racecars need to be warmed up with revving otherwise they develop a vibration? Maybe it's something like that. At any rate this is straight up killing me and makes me feel like I shouldn't invest any more money in the car. I will have to go to another shop and investigate.

oneslow55

Before you give up,I would take it to a real tech to dig into it

C32owner

Do you have headers on the car? Under WOT these can vibrate pretty bad feeling it through the footwell. Doesn't explain the vibration though when you not on the gas.

SICAMG

Man you are all over the map as usual with this poor car. First off you state that you don't even know if the problem was there before the mounts so could be mount related.You also say the car is "bouncing" up and down. That could be tire related if the car is "bouncing".You also say the car "seems" to vibrate at idle. Doe's it or not? A leaking rear main seal / No bearing on any thing like a vibration. Dead cylinder number 8? YES ! A miss fire WOULD more than likely be an issue.
Make sure all the coil pack connectors are on tight. Did you check the compression and compare it to another cylinder? If it's dead the block/piston are all done and would really suck.

WideRide

+1 on all this. Have to be as specific as possible to nail it down. Way too many moving parts. Driveshaft carrier bearing, flex discs, etc. should all be checked. I had a loose coil pack that corrected a modest vibration recently...found it by dumb luck poking around the engine bay but it was VERY loose. No idea how it got that way.

SICAMG

Me too on the coil pack. Only did it on hard accel AND would show a code for that particular cylinder. Normal driving....perfect.

MACEDON

between 1800-2400rpm in P the car vibrates

Sometimes at WOT or cruising between 70 and 140mph the car does not vibrate

Sometimes at WOT or cruising between 70 and 140mph the car vibrates

It's not the wheels I had them checked

It might be a bearing that plays along at times?

It might be a ball joint?

Or it might be a missfire

MACEDON

I had the coil packs removed on the driver side not too long ago and inspected the passenger side as well they all seemed tight in place as well as the wires. The carrier bearing was replaced as well at basically a dealership along with the sparks, flex, valve covers, and tranny service.


Mine shows no code.

What I've read though is that there are multiple people with idle vibration between 1800-2400rpm which turns out to be the exact rev range I seem to have issues. This happens while I'm cruising and WOT, there's not real distinction. Sometimes it does, sometimes it doesn't. If I drive the car nicely there won't be a vibration, if I start flooring it around then it'll appear on the highway. Truly something I can't wrap my mind around.

What should be my course of action? Remove all spark plugs and look at them? Is there an efficient way to test the coil packs?

oneslow55

Sounds like a bent rim

tlambert

Get rid off those “solid” engine mounts you said you installed. Put new OEM mounts on. And relax all the engine/trans/exhaust mounting points on the car. Someone recently posted the thread on the process. Then see if it’s still there......post your findings when you’re done.