Thanks Tom,
I scored the Bondo EZ Bumper fix.
I'm fixing the front nose right now, as it's raining (wet sanding made easy!!).
That Bondo stuff works great!
I await full on D/A effort on the front nose, to see how well paint holds to this Bondo EZ Bumper fix stuff!
Thaks for the call.
Now for tech!
My car still bucks, only if cold so far.
Is car/cold engine operation - open loop or closed loop?
The car bucking is not as violent as before, tho.
Seems to "fix" itself quicker (back to normal smooth acceleration).
Still throwing no codes.
I await Sunday for a longer drive to see if I can duplicate the bucking sensation (upon partial throttle application)
Same story as before.
IF I floor gas pedal, problem is gone.
Only on partial acceleration does this occur. If I "kiss" gas pedal, no bucking sensation, at all.
I've checked all manifold bolts (just top, so far, tight).
Checked most hoses & they seem all ok.
Problem got much better after I reused the original air inlet assembly for Firebird.

 

you have to mich timming. bucks when the TCC come on right ?

 

I wetsanded my car way back when there was a nice rain storm I hope it doesn't rain tommorow, I'm going to be erecting my shop. Does it buck at a certian mph?

 

car should be in open loop @ WOT & I think for the first couple minutes after stating to allow the car to warm up & the cold start emssions to get w/the program.

edit due to fat fingers

 

There's gotta be a joke somewhere about erections and rain... (laughs)

Karl, glad to hear you found the stuff. I went to the local Strauss Auto today for some brake pads (Bendix, mkd-154's) and swung by the body repair aisle- they're still selling the bumper repair epoxy. I think i'll have to pick a few up; they're cheap enough, and leave one unopened in a cool, dark place.

 

I wish it was only the TCC that caused the bucking problem.
I solved that original bucking problem by lubricating the entire speedo cable assembly.
That literally cured the TCC problems.
I believe my current bucking problem is EGR related.
I will test my theory by bypassing the EGR on my 1985 ride & see what happens. I read about my "answer" in the latest Chevy High Performance.
During a break in the rain cells, I shaped the damaged area on the front nose piece.
Soon I apply the final amount of the EZ bumper repair.
Yet, I must await warmer days.
Then bring front nose to a friends shop that has lts of compressed air and spare air tanks to hold the volumn needed for a DA sander.
Can't wait for an early morning drive to see if bypassing the EGR cures this partial throttle acceleration problem.

 

Cold engine, EGR system runs in open loop. WOT is also open loop as Project said. Car stays in open loop until it hits a certain minimum engine temperature, AND until the O2 sensor is heated up enough to give a fluctuating reading. Cold O2 sensors give a steady signal because they're not working yet.

Since WOT clears the problem, maybe, just maybe, your car is trying to go into closed loop on a cold engine? Sounds pretty improbable to me, but hey, if you're looking for what if's....

 

Let me explain further to help all & perhaps, myself.
It's been raining to day. This bucking problem reared it's head, during a brief drive. Engine was still cold.
I assume it may repppear during when engine is warm, tho., too.
I can only say tomorrow before I take my drive, I am plugging up the hose to the EGR. To see if the problem is gone.
First time I made this problem disappear is when I changed my hokey air inlet set up to the factory air inlet constriction system.
Drove all day, with the factory air inlet set up, problem was gone. Then it came back again, today, the bucking problem.
SO FAR, Today, only drove in cold engine operation.
Thus my question for open or closed loop operation.
Bucking Problem dissappears when I floor the car, engine cold or warm.
I will offer more details upon longer drive during Sunday.
I believe EGR is the problem. Luckily I have a spare one handy, already to go.

 

Be sure to let us know man! I'm curious.

PS-Does it ever stall? Or just buck?

 

tps? again????

 

No Not TPS.
WHY?
It was checked by the Snap On Sensor as we drove. The genius who owns that tool, knows his tool.
He agreed with me.
Never WASH your engine with a TPS.
NEVER readjust it, if necessary
Never touch it.
I'll find out this AM shortly.
I have to meet a contractor for work on my other house.
I'M VERY CURIOUS if I found the problem, too!
This simple plug it up test will tell the answer.
Yes, It BUCKS! Pretty violently, too.
BUT if ya floor accelerator (while the car bucks), it GOES!
IF ya let off the accelerator while it bucks, the problem "can disappear" and if ya then "kiss" the accelerator" the car still goes fine.

Does it stall, No.

 

What the hell is the Snap On Sensor?? Some sorta gadget that taps into the sensor output and shows it to you so you can monitor it while you're driving??

 

Ya got that right, Red Rider.
Also includes sensor cards for "a wide range of engine computer management systems".
It hooks into the ALDL, ya drive & ya can scroll down to see action/reaction - readings, etc.
Way cool toy.
I drive 25 miles just to get this used on my car for a fun drive & my charge a 12 pak of Corona Extra.

FYI, I provided them with tons of Factory Helms books & a note book (4" thick) of Q & A print outs from Corvette Forum, for help in this shops fixing a 1967 Corvette. And I provided one guy a beautifully restored set of 1967 Camaro Tail light housings w/RS lenses for $40! He has a 1967 & was using 1968 tailight housings. I couldn't stand it! Had to help him at a realistic cost. And I had a spare 67 pair of tail light housings for selling.

 

try dropping the base timming by 1-2 degrees. if that dont work check into the blm/int what are those values. also i highly doubt its egr related. just wouldnt seem sensiable. egr is on or off from about 120f or so. depends on alot of conditions. i think its timing. thats my 2 cents. make sure the balancer hasnt spun.

 

also i highly doubt its egr related. just wouldnt seem sensiable. egr is on or off from about 120f or so. depends on alot of conditions.

WRONG!
WRONG
WRONG!!

Yet kinda close, as it wasn't EGR related.
GUESS WHAT?!?!?!
On my 1985, I have the Vacuum Regulator Valve and a hose that connects to the Vacuum Switch.
AS I EXPLORED AT THE EGR area (I tried plugging the EGR & still the bucking problem), I brushed against that hose to the Vacuum Switch and hose fell off the vacuum switch.
I examined it closey and switched hoses (for a better seal) drove home.
THE CAR WAS SMOOTH AS BUTTER!!!!
Incredible.

IF ya had read my details, I kept stating that this happened upon partial throttle, not full acceleration.

Reading Chevy High Performance lead me to the answer, as the mag had an article about the EGR & how it can cause a hesitation in acceleration.
Again I have proven my theory that our MPFI rides need 100% sealing of the vacuum routing system to operate proper. Mine had a leak/bad seal at a vacuum switch and the results were this bucking upon partial acceleration problem.

 

And Tom, if ya still reading this trhead,
I just applied another layer of the Bondo Bumper EZ filler repair. I can't wait to now sand smooth and bring this nose to a buddy with larger air tanks than mine to sand whole front nose piece. Then rattle can spray paint the nose Body Shop Beige & attach to car. After I fix the oil leak & front brake hoses.