Weird vibration

[Wahugg]

Engine braking.... it's where the throttle body closes, causing a vacuum which makes the engine slow down the truck like a brake, hence the term engine brake.

The selector must be in 1st gear, otherwise the second you take the foot off the gas your car shifts to a higher gear, minimizing this effect.

Put the shifter in 1st, accelerate until about 40mph (this will put the revs right near 6000rpm) and then take your foot off the gas. You will not coast but experience a sizable resistance and slow downdue to the engine brake effect.

Let us know if the vibration is still present while engine braking.


Also a small google search provides much insight into this topic.... the first link in fact.

https://www.google.com/#q=engine+brake

[02_chevy]

Oo no the vibration goes away the second I take my foot off the gas


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[Wahugg]

but did you try this locked in 1st gear? This is crucial

[02_chevy]

Yes first and even tried it in second


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[02_chevy]

Yes first and even tried it in second


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[02_chevy]

I'm changing my fan clutch Tm and will update on situation then thanks for all the feedback!!


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[02_chevy]

So I changed the fan clutch and it's still there -_- checked the motor mounts and they're still good. Any other suggestions


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[KingBird]

I still think it has to do with fuel delivery or it's a vacuum leak.

[02_chevy]

I've had vacuum leaks on my cars before and it doesn't feel/sound like that. My next step is checking the cat o2 sensors. There's no easy way to check a fuel pump so that's my last step


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[KingBird]

I'll say this, when my cat was clogged after I fixed my fuel pump, the truck ran like shit!

[02_chevy]

You said you had a hollowed out cat right? How does the truck pass inspection? I have no cats on my camaro lol but Idc if that passes or not


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[Wahugg]

Honestly at this point I would bring it to a trusted mechanic.

All you are doing is guessing and spending money or are just going to make a new unrelated problem.... not the wisest thing. It's okay to bring it to the proper person once you've exhausted your personal knowledge or are just plane old stumped. That is exactly what Mike did with his K2500 and he is one of the more knowledgeable people on this forum.

-Wahugg

[02_chevy]

Honestly everything I've replaced so far needed to be replaced, I'm going off of what I've done in past with other similar cars/trucks I've owned. If i can't fix it after I've exhausted all my resources then ill bring it to a shop. Bad experiences with multiple shops by me


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[KingBird]

I live in Texas, no sniffer on the inspection. I agree with Wahugg, everything I did, I did because of trouble codes on my dash with the exception of the cam timing solenoid or whatever it's called. The reason why I replaced that was because it was causing a nasty oil leak. I strongly believe that you have an issue with the fuel pump, but I'm not willing to bet your money or time on it. The reason for that is because you don't have a CEL saying lean condition.

OK, back to Occam's Razor, what has been done to the vehicle? Details are important here.

[navigator]

so only in gear
only while accelerating
only noticeable above 3k rpms.

what if you hold the brake and get above 3k rpm in drive, do you get it then?

did you try this?

This could rule out all rolling components (driveshafts, ujoints etc).

[02_chevy]

Just a recap here.

I replaced:
both cv axles
both wheel bearings
both strut assemblies
fan clutch
waterpump
spark plugs 41-103 acdelco
Cleaned the throttle body
drank a few beers <-- very important

Symptoms:
Only happens in gear above 3000 rpm
if i hold it in gear and rev high it happens
does not happen if in park or neutral

The truck has a bds lift on it with z71's and thats it.

Next step is to check cat fueling and if all else fails bring it to my uncle who a mechanic for 28 years. and before anyone asks no i cant ask him for help right now otherwise i would have lol

[navigator]

if i hold it in gear and rev high it happens

so this should rule out driveshafts, CV shafts, ujoints, wheels, brakes, any rolling components.

Just a recap here.
does not happen if in park or neutral

this would lead me to eliminate anything engine related(fan, pulleys, pw pump, ac compressor etc) unless it is possibly due to the extra load of being in gear.

My next thought would be tranny/torque converter related.

[Wahugg]

The Torque converter will still turn even if the tranny is in Neutral or Park, granted it would not be under any load.

This could possibly eliminate the torque converter and push it further back into the transmission, but then again this whole situation doesn't sit well with me; just doesn't seem to add up.

[02_chevy]

The Torque converter will still turn even if the tranny is in Neutral or Park, granted it would not be under any load.

This could possibly eliminate the torque converter and push it further back into the transmission, but then again this whole situation doesn't sit well with me; just doesn't seem to add up.

exactly how im feeling right now. it just doesnt make sense

[Trail X]

It sounds to me like a failure of full ignition in one or more cylinders under higher load. Either you're not getting proper compression of the air, improper spark, or not enough fuel.

Does it seem to get worse as you ask for more throttle at the over 3k rpm stage? IE, does it only vibrate at full throttle? Does it vibrate but less at less throttle? Does it vibrate more as you get past 3k rpms?

Have you done a compression check?

If your compression check comes out properly, and you're sure you're getting good spark, the only last thing is a check of your fuel delivery. Have you changed out your fuel filter? I'd then do a check of the injector resistance to for check balance.