Serious Shudder / Surging - 2004 LeSabre

Just recently I developed a really serious problem with my 2004 Buick LeSabre. After I've been driving a while and everything comes up to temperature the car will buck and shudder on gentle grades at about 45mph under steady throttle. When I press the accelerator down it seems to smooth out until I get up around 4000 RPM and then it begins to surge and drag. If I'm driving along and I decide to floor it, the car begins to surge and choke out around 4500 RPM, it feels like the engine is losing power or a clutch is slipping. I don't see the RPM's bouncing around the way I'd expect that they might if it were a clutch slip event. My first instinct was to assume the TCC was failing so I decided to pursue some further diagnostic.

I have an AutoEnginuity Scantool system setup on my laptop. Using the scantool I took a look at the converter slip speed and TCC signal while reproducing the failure. When the computer commands the TCC to engage the slip speed drops steadily and remains low even throughout the shuddering event. I don't see any evidence of a TCC slip in the slip speed data although the event is sort of an instantaneous finite occurrence that may not show up in the slower streaming data. I.E. the data may not be refreshing fast enough to catch the instantaneous slip. On the other hand when I monitor engine management data I'm seeing consistent misfire data streaming in when the problem occurs. Cylinder 2 consistently reports significant misfire events when I am experiencing the failure.

My plan is to start by replacing the spark plugs and wires, as well as the belt and fuel filter (basic tune-up). These maintenance items have never been serviced on this car and I have about 116K miles on it now. I'd like to know if it's possible for the engine to report misfire data in the event of a TCC slip or shudder. I know the PCM monitors misfire events by looking at the slight changes in RPM that occur when the particular cylinder fires. I'm thinking if the TCC slips and sends a shudder back through the powertrain the computer might actually see that as an engine misfire and retard the spark timing by mistake.

I'd also like to know if anyone knows of a good way to monitor spark events while driving. In other words, I have a real basic inline spark tester, but it’s only practical to use it while the car is sitting in the driveway. I'd like to rig up something that would give me a spark indication while actually road testing the car. If the ignition is grounding out periodically I'd see a dead spark on the affected wire when the failure occurs. I'm going to monitor fuel pressure with a fuel pressure gauge and possibly swap out an ignition control module that was replaced recently with an AutoZone brand unit to rule that out. Please let me know if there is anything else you can think of?

Does anyone know whether a failed TCC could have any impact on drivability under WOT conditions at high RPM? I can understand how the TCC could slip momentarily under gentle consistent throttle and mild to medium load on a gentle slope, but could the TCC possibly be doing anything at WOT under extreme load? I have trouble during both driving scenarios. I'm also reluctant to suspect the TCC or transaxle because the problem came up so suddenly. This car has never had a hint of transmission trouble before.

If you are getting misfire on # 2, it sounds like a secondary ignition problem to me. See what happens when you replace the plugs & wires with ACDelco parts. I am surprised that your wires have lasted this long!

It is exactly the same problem we had with our 2000 two years ago, and with my limited old school knowledge, was convinced it was the lockup torque converter, certainly something in the transmission. I expected a big repair repair bill. I believe it was HotZ28 who said change the plugs and wires, which I did...problem solved. As he states, make sure it is AC plugs..

Yeah, I sure hope so, Haha. BTW I should have mentioned I did buy the plugs and wires at the dealer, along with the new accessory belt and fuel filter. I wouldn't mess around with aftermarket parts in this case. GM uses Iridium plugs as the stock plugs on this car, they seem to be excellent.

I have to wait a little bit to swap them out because I'm in the middle of a head gasket replacement project on my mother's Ford Taurus. Once I get her car cleared out of the garage I can pull mine in and get at those pesky rear plugs. If it were warm outside I'd just do it in the driveway.

I've done plugs and wires on previous LeSabres three or four times in the past. Does anybody have any good tips for removing the rear bank plugs on this car? I typically jack it way up on stands and come in from below with extensions and swivel links. I've heard of some other people having success with tilting the motor forward by disconnecting the mounts. Just wondering if there are any other tricks I should know about?

Like you, I have used all kinds of extensions, swivels, and various body contortions to get the back bank out. Sorry no tricks that I know of, other than patience, and the promise of several large adult beverages once complete.

Hah, well out of curiousity I checked with the dealer about what I'd have to plunk down to get a nice reman Goodwrench trans for this car. After subtracting the core fee, the price is 2400 out the door with a new torque converter included. I was also happy to find out that they give you a 3yr / 100k warrenty on the thing. If I've got problems in the valve body with the TCC valve and TCC apply I'm going to just throw the whole trans out and get a new one at the dealer.

I'm going to be teed off if I go to the trouble of replacing these plugs only to find out the issue is with the trans. LoL from past experience rebuilding a trans on my 2000 I know how easy it is to access the rear bank plugs with the trans out of the way. Frankly, I'll be shocked if plugs and wires solve the problem, the drivability of this thing is basically zero right now. Something is royally fouled up and it happened really suddenly... We shall see. I promise I'll post results and progress when I work on it, but it may be a few days while I finish up with the Ford Vulcan head gasket project. For now it just needs to get me back and forth to work.

The dealer told me they take the wheel off and reach up, the plugs are easy to acess from there. I looked at it AFTER I did mine and it sure looks easier.

Chris.

That's a really unique and interesting suggestion, I'm going to try it. That could solve my garage conflict if I could apply that method in my driveway I might be able to knock this job out tonight before it snows like the devil outside HAHA.

I should clarify my earlier post, I was just joking about being irritated if the plugs and wires don't work out. I hope no one took offense, I'm totally on board with the idea of doing a basic tuneup first, theres no reason to jump into the big stuff right away. I'm guessing I finally got a misfire code today as the SES light came on while it was acting up and started blinking (typically indicating a continuous misfire condition). I'm just concerned because my shifts seem really sluggish.

When I get home from the office I'm going to take a look at your suggestion about removing the wheel to get at the rear bank plugs, that could really help but they might be using that technique on the lift. They may come up from below and behind the wheel. I'll update as I dig in.

One more thing I remembered. I'm left handed and tried all morning to get to the plugs. Could not get them. I switched to right hand (left was exhausted), it was still hard, but I finally got it. If your left handed, they designed it for Right Handed People.

Chris.

One more thing I remembered. I'm left handed and tried all morning to get to the plugs. Could not get them. I switched to right hand (left was exhausted), it was still hard, but I finally got it. If your left handed, they designed it for Right Handed People.

Chris.:screwy: I am right handed & remove the plugs with my left hand - no problem! I guess it depends which side of the car (or middle) you are working from! :rofl: The first thing you need to do to access the rear plugs, is to remove the strut tower brace! I do not use universals or swivel sockets, only a 3/8 in ratchet with a 3" wobble extension and plug socket! One other hint - remove #2 & 4 from passenger side & #6 from the drivers side (all from above & with tires/wheels in place) :smooch: Should be a 15-min job, once the wire boots are removed! :smokin:

Just to update everyone, I have confirmed that the problem is related to the ignition system. I need to provide a little background info first. About three months ago the car suddenly developed a serious and constant misfire condition. The misfire occurred under all circumstances, idling, cruising, and accelerating... everything. At the time I diagnosed the problem as being related to the Ignition Control Module.

REF: http://www.automotiveforums.com/vbulletin/showthread.php?t=972121

Back when the original misfire condition occurred I solved the problem by purchasing a replacement ICM at AutoZone. The car ran normally for all this time until the most recent misfire problem started to occur. This past weekend I decided to go ahead and replace the spark plugs, wires and accessory belt. Sometime in the process I made the decision to go to AutoZone and swap out the ICM I had purchased. After getting a replacement ICM at AutoZone, I finished installing the plugs and wires and took the car for a test drive. It seems to be running normally, although if I pay really close attention I feel like I'm still getting just a very slight hesitation during WOT acceleration. Interestingly enough after swapping the ICM three months ago, I never road tested the vehicle with scan tool connected, at the time it seemed obvious the problem was solved.

Now that I've drastically improved the behavior by swapping the ICM, plugs and wires, I'm going to go on an extensive road test with the scan tool. I'm curious to see if the engine is still reporting misfires during heavy acceleration and if so, I know that I need to pursue further diagnosis. Interestingly enough, my transmission is suddenly shifting normally and with its usual firmness. After replacing the ICM the first time, it took a few drive cycles before my shifts were adapted properly. Perhaps what I have is a really crummy ICM from AutoZone that simply can't withstand the conditions under the hood on this car. I might also have a coil pack that shorts intermittently and causes premature failure of the ICM.

Thankfully I've been able to at least zero in on the ignition system as the source of my troubles. My primary goal this past weekend was to simply identify the failing system. I wanted to rule out major transmission and engine mechanical problems first. Now I can focus on the ignition system and try to restore original performance and ideal drivability. I didn't have much time to do further testing over the weekend as I didn't complete my head gasket project on the Taurus until late Saturday night. I'm glad to have that project finished successfully so I can put more time into the Buick.

After having trouble with the second Autozone ICM I eventually purchased an OE replacement from the dealer and the problem has been resolved for about a year and a half now. Just another bunch of time and money wasted on aftermarket junk.

Thanks for posting what you found in the end. That will help others here in their diagnosis of similar problems.