What Would Make This Mechanical Jolt?

[96gstdsm]

I have posted about this before, but i thought then that it was bogging. After driving it more it definately feels like something mechanical is knocking or something. It happens alot usually around 3k rpm's As soon as i give it full throttle i feel a kinda grind and then a loss of power. Feels like a slipping action. I do not believe it is clutch as the rpm's don't raise at all. It happens in all gears as well except 1st i think. I have never felt it in that gear. What would something transmission like cause this? It really does not feel at all like a bogg anymore. It is also getting worse than it was a week ago. It used to happen only once in a while, it now happens it 2-5th gear and atleast once in every gear. Usually like 2 or 3 times it jolts in each gear under wot.
Any ideas what i am in for? Would a misfire feel something like this? Also what is the correct firing sequence on a 96 gst?

---Ryan.

 

[2gGSX]

I'm having a similar situation actually, although not as frequently as you and only in WOT situations. The firing order is 1-4 and 2-3.

 

[eclipsh]

Sounds like one hell of a boost leak. If you haven't done a boost leak test yet, you'd better. I had a hole blow in a coupler and it felt just like I'd blown my tranny or worse. Made an awful noise under boost, somewhere between a tranny chewing itself up and a tire chewing up a fender.

http://vfaq.com/mods/ICtester.html

 

[96gstdsm]

Sounds like one hell of a boost leak. If you haven't done a boost leak test yet, you'd better. I had a hole blow in a coupler and it felt just like I'd blown my tranny or worse. Made an awful noise under boost, somewhere between a tranny chewing itself up and a tire chewing up a fender.

http://vfaq.com/mods/ICtester.html

Would a boost leak make it feel like something was "clunking" together possibly? It does not feel at all like it's bogging anymore, although it is losing power when it happens. It feels like a slip, but i know it's not the clutch. When it jolts, i can feel something hitting together, or atleast thats how it feels. It does seem to happen along side with certain boost levels. It happens alot around the 3-4k rpm range. Seem to not have much or any boost above 5 so dont know for sure if it happens there. But when i put it in 5th gear going about 50 and then step on it, when it get's to like 3k every time i can feel it. I know that how you test for a clutch slipping too, but the rpm's dont go up just for like a second the clunk and jolt type of thing happens.

 

[eclipsh]

Yes actually, it can feel like a clunk. That'd be detonation in your engine from it running way to rich (not as much air in engine as ECU thinks so it runs way too rich and detonates). That detonation makes the car keep retarding the timing until you are running so little advance that it can't detonate (explains the knocking sound disappearing at about 5k and the poor acceleration.) 3-4k is when you are building boost the fastest so it explains why it feels funny then. I'll bet if you stomp on the gas around 4500rpms you'll get the same effect.

Check for leaks. At the very worst you will eliminate that as being an issue and can move on from there.

 

[96gstdsm]

Yes actually, it can feel like a clunk. That'd be detonation in your engine from it running way to rich (not as much air in engine as ECU thinks so it runs way too rich and detonates). That detonation makes the car keep retarding the timing until you are running so little advance that it can't detonate (explains the knocking sound disappearing at about 5k and the poor acceleration.) 3-4k is when you are building boost the fastest so it explains why it feels funny then. I'll bet if you stomp on the gas around 4500rpms you'll get the same effect.

Check for leaks. At the very worst you will eliminate that as being an issue and can move on from there.

Alright thanks alot. I guess i will have to do a boost leak test. The only things i have changed on the car are a 1g bov and a new intake that would effect that so would most likely be one of those things. For the bov i have a metal to metal contact without a gasket. Should there be a gasket for the 1g bov and the bov adapter flange? It did not come with one an i dont know if they make one or not. I know metal to metal contact is usually not that good at making a complete seal.

 

[No_Skillz]

Buy some "make your own gasket" material from pep boys.

Although usually you get knock from running lean, not rich, I suggest you still do the BLT to rule out some common possibilities.

 

[96gstdsm]

Ok well i guess i'm just an idiot. I had checked the spark plug well and didn't see any oil or anything but i guess the oil had gotten past the washer around the spark plugs. I put new spark plugs in today and when i removed my old bosch plugs i noticed 2 of them had lots of oil and stuff around the spark area. This was due to a real crappy oil cap i bought off ebay that did not seal any oil from getting out, thus it leaked onto my valve cover and then into my spark plug well. Just drove it around now and goes up to 80 with no problems what so ever in any gears!! Pfffew i love easy fixes! It really felt like it was something in the engine or tranny. Must have been from not sparking and i guess thats why i smelt alot of fuel recently as well. Hopefully that was an all in one fix! Should have checked this earlier but did not have a gapper for the plugs until this weekend.

 

[eclipsh]

Glad to hear you got it fixed