95 Riv chugging at 45mph to 50mph?? HELP

I have a 95 Buick Riviera supercharged with about 150,000 and at 45mph to 50 mph it has like a chug or bucks back and forth. It has new plugs, tps, egr purge valve. I thought maybe egr valve, but they are like $150. I wanted some more opinions on what it could be first. Does anyone have an idea?
Yes the sevice engine light comes on after running for e few minutes. The wires are about 2 to 3 years old. They are xact 8mm lifetime wires. They looked good when I checked and put the new plugs in.. It did it before I did plugs also.

If the SES light is coming on, have you had it read for code(s) ?
That's the first place to start. Most auto parts store will read the codes for free.
Doesn't sound like the typical symptoms of a bad EGR though. More like ignition problem. But why speculate when you can get the code and go from there.

mine also chugged alot, it turned out to be a intermitent failure of 1 of my coils.....pull the wire at the coil while she is running and see if u get a weak spark or none @ one of the coil terminals......ps after replacing the defective coil the problem went away. after the simple shadetree test. buzzed the hell out of my hands though

you really should find a way to get the codes read before you start replacing parts, but most auto stores cant read 95's OBD 1.5 pcm.
i would swap out the wires to acdelco wires and junk those "lifetime" ones.

it is somewhat normal to have a almost chugging feel right when OD kicks in and the engine is at a high tq load and low rpm.
That said, it puts a strain on the ignition system, so if it is doing it more than it used to then replace the wires and plugs then test coil packs.

I always forget about the 95 being the oddball when it comes to reading the PCM.
If you know someone that works in the auto industry (technician) they will have the scanner capable of reading your car and there is always the dealership.
It can be cheaper to pay someone to read the codes than replacing expensive parts.
But I would follow the others advice and look to the ignition system i.e., wires and coils breaking down under load. You can get coils from a junkyard cheap to help you with diagnosis if the wires don't solve your problem.

Try a fuel filter.. Fixed my issue similar to this

45-50 mph is when the torque converter locks in 4th gear, and the engine is under the most strain. This is where any ignition fault will reveal itself. I know you say it has new plugs, but check them all again. It is easy to crack a plug on installation and it won't show up until that heaviest load sometimes. It could also be a bad wire or coil as has been mentioned, but TRIPLE CHECK your spark plugs.

deekster_caddy wrote:

It is easy to crack a plug on installation and it won't show up until that heaviest load sometimes. but TRIPLE CHECK your spark plugs.

Go ahead ask him how he knows. !!!!!!!!!

Hell I'll dive in anyway, this might be useful for somebody.

Rick I finally figured out today why I have been cracking so many spark plugs lately. It seems that my spark plug socket is not deep enough! The plugs I've been installing are longer than my socket, if I pull the extension or ratchet out of the socket the plug fits snugly. If I have the extension in I'm barely grabbing the flats to tighten the plug, and the tip of the plug is no longer held centered.

But I also can hear the tiny 'crack' sound when I'm doing the installation. I know every time it happens. The only time I didn't realize what it was, I was working on my '94 Regal (3800 N/A) years ago and it did exactly what the OP is describing. Unlock the torque converter, or step on it hard, and the misfire would go away. But at low RPM cruise, it would buck like crazy. Then I realized what that 'crack' was that I heard when I was putting the plugs in.

I have 3 5/8 spark plug sockets, and they are all doing the same thing. I have been working on cars for ages and just recently started cracking plugs. Did they change the length of the ceramic part of spark plugs recently or something?

deekster_caddy wrote:

I have been working on cars for ages and just recently started cracking plugs. Did they change the length of the ceramic part of spark plugs recently or something?

somebody's been eating their spinach.


how tight are you putting the plugs in? They only need to be snug, not super tight.

Haha nice! If anything my arms are getting weaker as I've been driving a desk for almost 9 years now. Machine shop = awesome forearms! Desk = flabby and weak So I don't know why, but for the last month I've been cracking plugs left and right. The same spark plug sockets I've had for 20 years.

I used to overtighten everything. Then I got some torque wrenches and stopped snapping off bolt heads and stripping threads.

deekster_caddy wrote:

Hell I'll dive in anyway, this might be useful for somebody.

Rick I finally figured out today why I have been cracking so many spark plugs lately. It seems that my spark plug socket is not deep enough! [much omitted] Did they change the length of the ceramic part of spark plugs recently or something?

maybe - maybe not. Maybe you are just missing the little rubber tube that goes in the spark plug socket that grips the insulator.

Albertj

albertj wrote:

deekster_caddy wrote:

Hell I'll dive in anyway, this might be useful for somebody.

Rick I finally figured out today why I have been cracking so many spark plugs lately. It seems that my spark plug socket is not deep enough! [much omitted] Did they change the length of the ceramic part of spark plugs recently or something?

maybe - maybe not. Maybe you are just missing the little rubber tube that goes in the spark plug socket that grips the insulator.

Albertj

I have tried with and without the rubber boot. I find the rubber boot a PITA because it keeps coming out.

Maybe it's just time for a new socket.

I was going to suggest that. heck, it's not like they cost $50.00....
Even a good one from Snap-On will pay for itself if it helps stop from breaking Spark Plugs.

CHECKED ALL PLUGS All in good shape and non cracked. I have also been working on cars since I was 12. I am going to do the fuel filter first and check the plugs wires again and make sure thecoils and modual have good conections. Also I have been driving the car in Drive or 3 when doing 50mph or under and still does it.

Rickw wrote:

I was going to suggest that. heck, it's not like they cost $50.00....
Even a good one from Snap-On will pay for itself if it helps stop from breaking Spark Plugs.

i dont know about that, this spark plug socket from snap-on is $73

Sorry about all the side discussion clogging up your thread. The fuel filter will create a lean condition at full throttle, but not this bucking. The torque converter will still lock in third gear. Does the bucking go away if you step on the gas and get the torque converter to unlock? If so, it's ignition related.

I had the same problem with my 95. It ended up being a coil. My dad has a regal 3.8 SC. I pulled the coils off of his car and swapped them. It ended up being the middle coil.