: Brougham shudder



caddieboy
01-31-06, 11:45 AM
When I'm driving my Brougham on the highway, if I'm cruisin on cruise control or just staying the course lightly pressing the gas, the car starts to shudder a bit and stops right away if I press the gas slightly harder. It doesn't always shudder but often enough. The shudder shakes the car as if I'm suddenly driving bumpy pavement. Are the tire balances off? I just got the car and this is the only point of concern.

More about the new car soon. Thanks in advance!

Katshot
01-31-06, 12:42 PM
It's possible that the trans is the source but before I condemn the trans, I'd make ABSOLUTELY sure that it isn't an ignition misfire.

caddieboy
01-31-06, 12:50 PM
It's possible that the trans is the source but before I condemn the trans, I'd make ABSOLUTELY sure that it isn't an ignition misfire.

I accidentally forgot to put the parking brake on while on Lombard street (rushed out to take a photo) and there was a hard clunk when I put it into gear. Could that have done it? If it's the trans, will driving her 3000 miles have an ill effect?

How would I diagnose a misfire? I'm filling her with Regular. The car was checked out thoroughly beforehand.

I was hoping it would be badly balanced tires. Certain speeds seem to be more troublesome.

Katshot
01-31-06, 01:58 PM
The shudder you describe is very common on these cars (and many others too). I generally find it's caused by a bad plug, plug wire, or ignition coil. When at cruising speed with the TCC locked, the engine is at a fairly low rpm and when you give it just a little gas, it puts a pretty big load on the ignition system and can cause a misfire. Once the TCC unlocks and the trans downshifts, the engine isn't under such a load and the mis goes away. There's a few things that can contribute to this. An overly lean condition, and/or any weakness in ignition secondary insulation can contribute to or cause this misfire. The only reason I point this out is that I have seen people get their transmissions overhauled only to find the shudder still there. Expensive screw-up.

caddieboy
01-31-06, 11:05 PM
The shudder you describe is very common on these cars (and many others too). I generally find it's caused by a bad plug, plug wire, or ignition coil. When at cruising speed with the TCC locked, the engine is at a fairly low rpm and when you give it just a little gas, it puts a pretty big load on the ignition system and can cause a misfire. Once the TCC unlocks and the trans downshifts, the engine isn't under such a load and the mis goes away. There's a few things that can contribute to this. An overly lean condition, and/or any weakness in ignition secondary insulation can contribute to or cause this misfire. The only reason I point this out is that I have seen people get their transmissions overhauled only to find the shudder still there. Expensive screw-up.

TCC? I'm guessing something Cruise Control.

I noticed that it tends to shudder more when a slight incline comes. I tested it on cruise control

The light load on the ignition system sounds like what we're talking about.

How serious is it to drive with this shudder? I can avoid it by avoiding Cruise control and not lightly pressing the gas. I'm 2000 miles from home and would prefer to deal with it at home, but if I can find a good mechanic on the drive home (Friends are 700 miles away and may know someone).

I'd appreciate any info on the harm I'd be causing and why, if you please. If it's something I should take care of ASAP, considering the distance.

If it's the trans, I have a new one at home I can use. :)

N0DIH
02-01-06, 01:45 AM
I'll back up Katshot on ignition. My 91 Bonneville would do that when one of the 3 ignition coils was going bad, the worse the coil got, the worse the shudder was, only when I would get on the gas. Enough I couldn't drive the car. It got pretty violent when it was nearly dead. But when it was not under power, it idled fine. Cold start was a little tough, but once started it was fine.

Weak fuel pressure can do something similar too.

Tires are NOT engine rpm sensitive. Switch gears, like OD vs D at 55 mph. If it changes, it is engine, if not, suspension/wheels.

I had a bizzare vibration in my T/A once, only under power, not under coast/decel. I eventually figured it was the engine/trans bolts. When I pulled the engine and reinstalled, I didn't tighten them down tight enough and it came loose. The top was ok, but the bottom got loose and was nothing but problems.

Katshot
02-02-06, 11:24 PM
TCC? I'm guessing something Cruise Control.

I noticed that it tends to shudder more when a slight incline comes. I tested it on cruise control

The light load on the ignition system sounds like what we're talking about.

How serious is it to drive with this shudder? I can avoid it by avoiding Cruise control and not lightly pressing the gas. I'm 2000 miles from home and would prefer to deal with it at home, but if I can find a good mechanic on the drive home (Friends are 700 miles away and may know someone).

I'd appreciate any info on the harm I'd be causing and why, if you please. If it's something I should take care of ASAP, considering the distance.

If it's the trans, I have a new one at home I can use. :)


TCC = Torque Converter Clutch
The point I'm trying to make is that an ignition misfire will give you the shudder you describe. There are many things that can cause an ignition misfire but the bottom line is that lugging the engine and increasing the load on it is a prime time for an ignition misfire. Anything that contributes to an overly lean condition in the combustion chamber can cause a misfire (known as a lean-miss). Have a lean condition, add a load to the drivetrain, and you are putting a MAXIMUM load on the ignition secondary system, and it can produce the shudder you described due to an intermittent ignition misfire.
If your ignition system is not PERFECT, a lean condition will generally cause a misfire under load.

N0DIH
02-03-06, 02:00 PM
The reason the misfire feels so rough it is a low rpm miss, under heavy load, and that beats the living tar out of the rods and rod bearings. Drop out of OD, see how much it changes. It migh be more visible there. Don't fear rpm, that car has 2.56's with OD, and it was common place back in the 70's to get cars w/o OD and 2.73's to 3.23's w/o OD and would last all day at 100 mph, you will not rev the engine too high at all. You can run it like that for weeks with no ill effects short of less mpg..... and only maybe at that....

caddieboy
02-04-06, 01:51 AM
The reason the misfire feels so rough it is a low rpm miss, under heavy load, and that beats the living tar out of the rods and rod bearings. Drop out of OD, see how much it changes. It migh be more visible there. Don't fear rpm, that car has 2.56's with OD, and it was common place back in the 70's to get cars w/o OD and 2.73's to 3.23's w/o OD and would last all day at 100 mph, you will not rev the engine too high at all. You can run it like that for weeks with no ill effects short of less mpg..... and only maybe at that....

Thanks, I've been avoiding shudder by either no gas or heavy gas. And if I do feel shudder coming on or it does come I press the gas fast. I hope I'm not doing a lot of damage to the rods and rod bearings. Only 1000 miles to go before I get home and have it looked at. Thanks again.

caddieboy
02-04-06, 01:55 AM
TCC = Torque Converter Clutch
The point I'm trying to make is that an ignition misfire will give you the shudder you describe. There are many things that can cause an ignition misfire but the bottom line is that lugging the engine and increasing the load on it is a prime time for an ignition misfire. Anything that contributes to an overly lean condition in the combustion chamber can cause a misfire (known as a lean-miss). Have a lean condition, add a load to the drivetrain, and you are putting a MAXIMUM load on the ignition secondary system, and it can produce the shudder you described due to an intermittent ignition misfire.
If your ignition system is not PERFECT, a lean condition will generally cause a misfire under load.

Thanks for all your advice and explanations! I've ruled out the transmission being the problem. It's so incredibly smooth and shifts like a dream when accelerating rom a stop.

I was driving through a part of the country where I didn't realize that Regular gas is 86 Octane (I'm used to reg being 87, which is recommended for these cars) so I added higher octane and it's better, but not gone. At this point the gas mixture is definitely higher than 87.

Thanks again for everything!

Katshot
02-04-06, 09:37 AM
Most likely, if the ignition system has no malfunctioning items, fattening up the miture a little will cure your problem. It's most likely caused by a combination of things but a little richer A/F ratio would probably elliminate the whole problem.

caddieboy
02-04-06, 10:09 AM
Most likely, if the ignition system has no malfunctioning items, fattening up the miture a little will cure your problem. It's most likely caused by a combination of things but a little richer A/F ratio would probably elliminate the whole problem.

A/F ratio? Auto-Fuel? I'll add some higher octane and see what happens.

Katshot
02-04-06, 02:47 PM
A/F ratio? Auto-Fuel? I'll add some higher octane and see what happens.

Air/Fuel Ratio. If it's a little lean, you run more load on the ignition system so it's more likely to have a misfire.

caddieboy
02-05-06, 10:17 AM
Air/Fuel Ratio. If it's a little lean, you run more load on the ignition system so it's more likely to have a misfire.

Tried to figure out the difference between lean and rich. Is lean low octane and rich high octane?

Katshot
02-05-06, 04:01 PM
Tried to figure out the difference between lean and rich. Is lean low octane and rich high octane?

Lean = less fuel
Rich = more fuel
A leaner mixture in the combustion chamber requires more power from the ignition system to ignite, so it can tend to cause misfires.

caddieboy
02-05-06, 10:02 PM
Lean = less fuel
Rich = more fuel
A leaner mixture in the combustion chamber requires more power from the ignition system to ignite, so it can tend to cause misfires.


Less fuel means higher octane? More fuel means less octane? Sorry for not knowing this. I feel I should.

Katshot
02-06-06, 10:04 AM
Less fuel means higher octane? More fuel means less octane? Sorry for not knowing this. I feel I should.

Sorry dude, I don't have time to get into this. Go do some research, or maybe someone with some time can enlighten you a little. sorry.

caddieboy
02-06-06, 10:19 AM
Sorry dude, I don't have time to get into this. Go do some research, or maybe someone with some time can enlighten you a little. sorry.

Don't be sorry, I figured it out. Thanks tons for all your help! Last thing you should be is sorry dude. I'm the one who's sorry. :)

N0DIH
02-06-06, 07:25 PM
Mine started to do some missfiring last weekend that seemed like a shudder, bad gas.... My Suburban filled up at the same place, same time, and the sub got out ran by a 90's Dodge Neon.... Something is really wrong there....

the3rdalien
02-24-06, 10:28 PM
Thanks, I've been avoiding shudder by either no gas or heavy gas. And if I do feel shudder coming on or it does come I press the gas fast. I hope I'm not doing a lot of damage to the rods and rod bearings. Only 1000 miles to go before I get home and have it looked at. Thanks again.
My car had the same exact problem, And I think we are not alone. But no one on this sight could figure it out. Amazing to me. I spent over a grand with all these tips and a lot of wasted time. I thought this sight could save me from the dealer prices to fix it. Makes me wonder who is employed by GM, etc. to sell parts. And you can't tell me some of you aren't. So now the car is getting a new engine it probably doesn't need, Will let you know.

caddieboy
02-28-06, 01:08 PM
Mine started to do some missfiring last weekend that seemed like a shudder, bad gas.... My Suburban filled up at the same place, same time, and the sub got out ran by a 90's Dodge Neon.... Something is really wrong there....

It's never fun to get outrun by a Neon. :eek:

caddieboy
02-28-06, 01:11 PM
My car had the same exact problem, And I think we are not alone. But no one on this sight could figure it out. Amazing to me. I spent over a grand with all these tips and a lot of wasted time. I thought this sight could save me from the dealer prices to fix it. Makes me wonder who is employed by GM, etc. to sell parts. And you can't tell me some of you aren't. So now the car is getting a new engine it probably doesn't need, Will let you know.

What did you do to try and fix it? How many miles on the engine? It's never fun when you try to fix something and nothing helps. I'm crossing my fingers the new plugs, spark wires, distributor, rotor and ignition coil will help things. I'll let you know how it goes.

the3rdalien
03-01-06, 06:21 AM
What did you do to try and fix it? How many miles on the engine? It's never fun when you try to fix something and nothing helps. I'm crossing my fingers the new plugs, spark wires, distributor, rotor and ignition coil will help things. I'll let you know how it goes.
Intake gaskets, new distributor, complete tune-up, coil, timing chain&gears, fuel pump,filter,injectors,fuel pressure regulator, every sensor and vacumm line. Nothing helped. Everyone here tried to help, but nothing changed. I hope you have better luck.

caddieboy
03-01-06, 11:35 AM
Intake gaskets, new distributor, complete tune-up, coil, timing chain&gears, fuel pump,filter,injectors,fuel pressure regulator, every sensor and vacumm line. Nothing helped. Everyone here tried to help, but nothing changed. I hope you have better luck.


Thanks! I hope so too! I'll let you know how it goes.

the3rdalien
03-29-06, 06:21 PM
Thanks! I hope so too! I'll let you know how it goes.
I put a new enginge in the car and have the same problem still...so its definitely in the transmission.

caddieboy
03-29-06, 06:30 PM
I put a new enginge in the car and have the same problem still...so its definitely in the transmission.

I have an almost new transmission in my 87 Brougham I *think* would fit in my '92 Brougham, so it might be an idea to swap them. I'll try the other fixes first though.

What will you do if you change the transmission and it's STILL there? Heheheh

caddieboy
04-10-06, 12:31 AM
Well, today I changed the Fuel Filter, Spark plugs and wires, rotor, distributor and ignition coil and the chudder problem is still there. BUT!!! It's doesn't shudder nearly as often. I even thought it was fixed because I was testing it under certain conditions under which it was GUARANTEED to shudder but it didn't.

Then it finally did, and I found I could eventually get it to shudder if I tried. Even so, the fact that it's improved leads me to believe it might be something I changed that helped. Could the increased flow from the cleaner fuel filter be a reason? Maybe it's the fuel pump not delivering enough gas? But light pressing on the gas? Nah, probably not it.

Just to remind, the problem is that when I press the gas very lightly to maintain speed, the car would eventually shudder. Doubly so when on an incline. Speed under 40 MPH result in no shudder. Above 45 and it's not too hard to accomplish shudder.

It sucks not knowing the reason why this is happening. I have the Tranny off my 87 Brougham which I could swap for the tranny I have in there now, but I'd raher avoid doing that if at all possible. Not even positive the 87 Brougham tranny would fit the 92 Brougham with the 5.7.

N0DIH
04-10-06, 01:13 AM
FWIW, GM did have at least 3 versions of software for the 94 PCM's on the LT1's, one of which was to fix the "chuggle" problem around 40-50 mph. It IS possible the problem may lie in software.

Granted, it does it now and didn't do it before....

Yup, the trans will fit, but you might find some significant differences, like THM700 R4 to a THM200 4R. Many preach the 200 R4 is weaker, while technically that is so, the 200 4R can be built to handle much more than the 700 R4. Primarily due to the 2.74 first gear vs the 700's 3.06.

What is base timing set at? It is possible it is set too low and that is causing some problems. You can try to disable the EGR valve (this won't affect the PCM triggering EGR operation, which leans mixture and increases timing), but with the lack of EGR (it might ping, be cautious), might have some good effects.

Fuel pump could be, if you can check pressure that is very helpful.

fleetwoodss
04-10-06, 02:55 PM
I had the same DAMN problem. AND ALL IT WAS.... Is the PCM needed to be reflashed. And It was GONE...Believe me she SHUDDERED all the time on the freeway.

caddieboy
04-10-06, 03:52 PM
I had the same DAMN problem. AND ALL IT WAS.... Is the PCM needed to be reflashed. And It was GONE...Believe me she SHUDDERED all the time on the freeway.

This isn't shuddering all the time though, just when I lightly press on the gas with a bit of an incline. Or even going straight on the highway with super light pressure on the gas to maintain speed and she'd shudder. Letting go of the gas pedal or pressing harder and it would go away.

It is better after what I did, could the PCM cure it all the way? How much does a PCM reflash cost? Or is it easy to do?

PAGEJR
04-10-06, 04:06 PM
Has Anyone Tried Replacing The Tcc Solenoid?

caddieboy
04-10-06, 04:09 PM
Has Anyone Tried Replacing The Tcc Solenoid?

I haven't. You think that might do the trick?

PAGEJR
04-11-06, 09:33 AM
YEAH I THINK SO. IM GONNA TRY THIS WEEKEND. CHECK OUT THIS LINK. IT SEEMS TO MAKE SENSE AND IS EXACTLY WHAT MY CAR IS DOING(http://www.montecarloss.com/TCC_Solenoid.html#Definition (http://www.montecarloss.com/TCC_Solenoid.html#Definition))
. :thumbsup:

caddieboy
04-11-06, 12:25 PM
I can't believe this! Look what I found in the owner's manual!!!

If you're using fuel rated at 87 octane or higher and you still hear heavy knocking, your engine needs service. But don't worry if you hear a little pinging noise when you're accelerating or driving up a hill. That's normal, and you don't have to buy a higher occtane fuel to get rid of pinging. It's the heavy constant knock that means you have a problem.

I recently put 89 octane in because I'm used to putting that in my old 90 Fleetwood which need 89. The thing is, this is shudder, not pinging. I don't hear pinging, or knocking for that matter. The car just shakes.

I think this might be a fuel thing as I was unknowingly putting 86 octane in when I first noticed the problem because I wasn't used to the pumps I encountered driving her from the States. 86 is where 87 is on our pumps. We don't have 86 here in Canada.

I'll report back when I have a closer to 87 octane mix. Just need to go as empty as possible on this tank and fill her up with 87, then see what happens.

N0DIH
04-12-06, 05:56 PM
If you are finding lower octane at higher altitudes, this is ok. You reduce your octane requirement 1 point per 1000 ft of elevation gained.

So having a tank of 93 octane at 6000 feet is like 99 octane at that altitude.

caddieboy
04-12-06, 06:01 PM
If you are finding lower octane at higher altitudes, this is ok. You reduce your octane requirement 1 point per 1000 ft of elevation gained.

So having a tank of 93 octane at 6000 feet is like 99 octane at that altitude.

That makes sense. I didn't know Vegas was that high up though. Anyhoo, I'm not that high up here at home, right about sea level as far as I know, and I certainly shouldn't be putting 89 octane.

I just need to get into the habit of 87 after so many years of 89. I'll save some coin too!

N0DIH
04-13-06, 12:41 AM
Even barometric pressure has some effect. Higher humidity reduces octane requirements.

caddieboy
04-13-06, 12:47 AM
Even barometric pressure has some effect. Higher humidity reduces octane requirements.

Interesting! I can't go lower thaan 87 octane, so even in the summer, I should be OK.

Buick61
04-09-09, 09:44 AM
I'm having this problem in my '96 FWB. The shop is recommending a full tune up (the car has over 90,000 miles, so I suppose it is time). Thoughts/opinions?

I'm HOPING this will solve the issue. It's been getting steadily worse over the past year.

Also, is it advisable to replace the water pump at this time?

N0DIH
04-09-09, 10:36 AM
Lean mixture will shudder and most commonly, weak ignition. So check the coil, but 90K, is coming up on cap/rotor replacement. I am NOT a fan of Opti replacing, but yet to do cap/rotor and ALL SEALS (from GM!!!!!), and if you are in there, a WP can't hurt, I had no problems with a NAPA rebuilt that got me 60K+ miles without a peep or seep....

Ohm out the coil and see if it shows ok, if ok, likely it is, then start to dig on the Opti. You can replace it, but in reality rarely does it need it, it is often cap/rotor. People seem to think they can't see a cap/rotor and try to drive it a zillion miles and think it should be ok. Would you let your old non EFI car with a cap/rotor be completely untouched for 100K? Didn't think so, Opti is no different. But there are seals that need replacing too, if not, and water gets in, it will damage the Opti and you will need replacement. Also, rebuild or replace Opti vacuum harness, I would check mine periodically, it used to be $12 from GM, now it is >$40.

Buick61
04-09-09, 03:59 PM
Lean mixture will shudder and most commonly, weak ignition. So check the coil, but 90K, is coming up on cap/rotor replacement. I am NOT a fan of Opti replacing, but yet to do cap/rotor and ALL SEALS (from GM!!!!!), and if you are in there, a WP can't hurt, I had no problems with a NAPA rebuilt that got me 60K+ miles without a peep or seep....

Ohm out the coil and see if it shows ok, if ok, likely it is, then start to dig on the Opti. You can replace it, but in reality rarely does it need it, it is often cap/rotor. People seem to think they can't see a cap/rotor and try to drive it a zillion miles and think it should be ok. Would you let your old non EFI car with a cap/rotor be completely untouched for 100K? Didn't think so, Opti is no different. But there are seals that need replacing too, if not, and water gets in, it will damage the Opti and you will need replacement. Also, rebuild or replace Opti vacuum harness, I would check mine periodically, it used to be $12 from GM, now it is >$40.

Thanks!!! I'll have to memorize that when I bring the car in so it sounds like I know what I'm talking about.