Highway speed problem

[Venum]

Hey guys, my car tends to do weird things on the highway, here's what happenes:

I took a road trip out to Nebraska and the 1st day my car drove fine, but the next day I was cruising about 85 and my cars starts to shake- like a rough vibration of some sort. It's not something that is unbalanced b/c it only shakes when I am barely on the gas (to maintain a constant speed). When I floor it or let all the way off it's fine. She even did it in 4th gear when I was going slower. The range that it happens at is from 70-95mph (in 5th).

I've cleaned out my throtle body with carb cleaner, but that didn't do the trick.

The odd thing is that it takes a little bit before it does this, it's not right away when I get up to speed, maybe 30 min or 45 after I'm maintaining a constant speed.

Any ideas? Anything would be greatly appreciated, thanks.

 

[mitsuclipsegsx]

do all of ur tires have the same tire pressure?

 

[Venum]

Yes they do have a ll the same pressure but I don't think that it has anything to do with something being unbalanced because it only does it when I am barely pushing on the gas (to maintain a constant speed). So that makes me believe that it has something to do with the engine of some sort. Any ideas? Any feedback is greatly appreciated.

 

[mitspro]

balance tires?

 

[92awddsm]

Check plugs and wires. Sounds strange, I know but ive seen it before.

 

[blcknspo0ln]

are you running a larger pump? i've noticed my 190 pump will give bad partial throttle response once in a while. also might wanna check for boost leaks.. dont know why but it does this also...

nm you're NT... thus i have no ideas, but i'll second the plugs.wires check

 

[Venum]

:laugh: ^^ I was gonna say....I don't have boost, . Plugs and wires huh? You think that are getting old or shot? I'll do that, I hope it fixes the problem. Thanks for the responses, if anybody else has suggestions let me hear em.

 

[RoasT BeeF]

I am with the guys above.....plugs and wires were my first thought.

 

[Venum]

Roast Beef and I replaced my valve cover gasket and put in some double platinums (thx again Brent) I had oil all over the valve cover because I had a leaky hose, also I had some oil down near plug #1. You could see the oil on my original plugs when we took them out too. So we cleaned her up real nice and put her back together, so far no problems. I'll let you all know if I get that shaky feeling on the highway or not. Thanks for the responses.

 

[rtp03]

I have been having the same issues you do with your car. When barely on the throttle in 4th or 5th gear at about 50 mph in 4th and 65 in 5th. I replaced almost all the driveline parts and it does not change. I have had the problem for 4 years + and it has not been getting worse or better.

Things changed - Rear End
Front axles
Front Wheel Bearings
Switched transfer cases
Right and left motor mounts (new)
Driveshaft balanced
All 3 U-joints replaced
New wheels
New tires and balanced

What else can cause such a vibration in the body and seats?


It sure is frustrating, I have had 3 mechanics and driveline specialists look at it and they can not find the cause.

 

[Omega]

It sure is frustrating, I have had 3 mechanics and driveline specialists look at it and they can not find the cause.

You seem to have tried everything mechanical.. what about electrical?

Try the usual plugs/wires as mentioned. Also, check the coils. If they test fine, they could be acting up when they get hot.

Have either one of you logged the car while it's doing this? If so, can you see any erratic spark, O2 readings, things of that nature?

 

[Venum]

I don't log, I'm N/T so I don't think I have the convenient hook up you guys do. And rtp03, I can't believe you've changed all that and nothing helped! That's not a good thing, makes me wonder if it'll ever be resolved.

Maybe we should try electrical, if you log and see anything unusual let me know man.

 

[harjms]

dude that sucks...it must be our nebraskan weather....but anyways, double plat spark plugs...i thought plat. sucked for spark plugs...u should be running the NGK BP7es or whatever they are called....(well this is for my turbo...dont know if its the same on N/T)

 

[Venum]

1st of all, harjms- dude I live in Bellevue! Where you at? I live real close to the Bakers (in the gateway park apartments) PM me man, we could chill.


And 2nd- For N/T's you want hot slugs such as double plats (that's what I got) on turbo's you want the plugs to relativly cold (from my understanding).