that could be it.
When I adjusted the throttle voltage it changed my shift points, no memcal needed.

I too had an 87 olds 98 with the 3800 that had the SAME PROBLEM. I replaced the plugs and wires and still no help there.



Now I think I am going to go get some fresh wires and plugs right now just to prove it is not that.

I am FAIRLY sure this is a transmission related item though. It feels like a random misfire but seems to only do it in 3rd gear and light to moderate throttle speeds.


The car shifts VERY smooth BTW for a GM product.


How do I adjust the shift points on a 4t60e??, I thought this was done electronically.


When you say "adjusted the throttle voltage" what do you mean by that? Are you refering to the TPS, since I beleive on the L27 TB they are FIXED, not adjustable like prior versions.







57chevythunder:
I did not know you lived over in WY, I lived there just outside of Jackson Hole a few years ago....with the same car as you had lol.
http://memimage.cardomain.net/member.../255551_41.jpg
http://memimage.cardomain.net/member.../255551_18.jpg

I've been there too with the shuddering problem.

An EGR valve that'* starting to fail can cause this, as it only functions during part throttle cruise driving. Mine is dying. I unplugged it for the time being. You might wanna try this to check and see if your EGR valve is contributing to the shuddering.

Also, dying coil packs can cause a similar problem. The tranny, in my opinion, is fine. As you stated it happens between 32 and 40 mph. the torque converter dilemma that we've all discussed here cannot be the cause. It is not in lockup under 37 mph anyways. Your tranny is most likely fine. When the TC locks up, all the tranny does is amplify the shuddering due to the "uncushioning" of the torque converter, which softens that shuddering when not engaged. I would also have to rule out bad fuel delivery because those types of problems usually occur when the demand for fuel is high like in a WOT run.

I'm gonna go with my gut feeling and say your EGR valve has seen its better days. Unplug it and see what happens. If your problem goes away, the valve is most likely bad, or the EGR passages are restricted. Mine is bad, I unplugged, and the shuddering went away. If it doesn't go away, you've got maybe an ingnition issue. I wouldn't worry about the tranny. As long as you don't beat the snot out of them, they should last, especially even at 110k mile so far.

Yes I was refering to TPS voltage. Anything is adjustable if you modify it.
My GM book gives a range that the scan tool should see on a 96 K motor at idle.
I just set it to the center of the range which I think was .47 for 96.
assembled reading from the factory was .41

All this stuff is worth a try, Hans. I'll be installing my tranny cooler in the next few weeks, so we'll see what happens with my car. As I'm sure we all know by now there are MANY different problems that can manifest themselves in similar symptoms. This surging problem can probably be caused by five different things. In my case I'm putting my money on overheating tranny until I'm proven wrong.

By the way, how long has your car been doing this? Is it only when the car has been driven for a while or when the weather is warm, or was it problematic during the cold winter months?

I've had this problem on two GM cars (maybe three, can't remember if the Bonnie did it or not), and a set of plugs and wires has always fixed it. It could well be transmission problems, but I'd put on a set of wires and then plugs first and see if that helps.

-Ryan

First of all i SHOULD CORRECT MYSELF.


The problem ocours ONLY at 38-45mph on the speedo.

KEEP IN MIND that my speedo is off in that range about 3mph so that is actually 35-43 or so.


It feels like a misfire but it ONLY happens at those speeds.

There is NO hesitiation or stumbling or surging, or studdering or whatever you want to call it at ANY OTHER SPEEDS that I can tell.

It goes into overdrive fine and smooth.


Starting out on a COLD day it runs perfect and has never even TRIED to sound like it was "stalling".


I would say the problem is most apparent at 42mph on the speedo to be exact.


anyway.


I replaced the plugs and wires 2 days ago....


here are the battle wounds to prove I changed the plugs...for the second time this year...Yes I made sure they were gapped three...yes 3 times.



here are the new wires.


I also unplugged the egr valve today to see if that helped...



and all that does is set off this light:





The problem is still there no matter what I try.


What should I do next?

at this 42 mph, is the TC locked or unlocked?

As stated above too, you could dealing with one of like 5 different things. Throwing all the plugs and wires at the car in the world isn't going to do anything for a car that is suffering from bad coil packs that start to break up when they get hot. MAy not be the cause but damn well worth a try. Before going into cardiac arrest over the tranny, try swapping out the coil packs with someone'* whose are known to be fine. I'm just recommending easy inexpensive things to try first to help narrow it down. Without having a FSM or advanced tools like an engine analyzer/scope, I'm afraid this is all we can do is try different things.

the TCC is unlocked at 42 on a flat road light throttle, it will lock at about 48

I was thinking maybe he was in TCC lockup in 3rd gear instead of 4th..... Hans, what RPM are you running at 42mph?