Car shuddering periodically

[petraman]

Ok, I'll admit, ever since I owned this car I've been EXTREMELY paranoid about it. Whether something' seems wrong, or whether something seems like it's going to break or whatever, it's totally ok. But I'm pretty sure this isn't, since not only I noticed it, but a friend just pointed it out to me today as well. That never happens . So, and this is only periodically, shifting has not been very smooth lately... In fact, it shudders pretty bad, but here's the twist. Sometimes it does and sometimes it doesn't. I haven't noticed that it's any particular time. Sometimes it's when ithe engine's cold, sometimes it's when it's hot. So, idk. Any thoughts? It's going in to Intense this week because I think the shift algorithms from the PCM might have caused this...

[petraman]

Nobody??? C'mon...

[lowrider0308]

Does it shudder when slowing down for a light like the engine is doing it? My mom 01 SE has started doing that but we havent had the time to work on it.

[petraman]

No, but it does do that sometimes. I think it's just the transmission downshifting to first, not really worried about that... I'm gonna try to take the Intense shifting tables out of my PCM and try a shift kit...

[BlackHawk99]

At what speeds does this occur? What gear are you in? TC locked up?

Don't jump to conclusions just yet that the tranny is causing these issues. The shuddering transmission maybe the result of an ignition issue.

[petraman]

See, that's the thing. It happens at all speeds, in all gears. And I was thinking it was an ignition issue, but didn't know how to check it... I think it might have done it a few times when the TC was locked up, but then again as I said, it happens in all gears...

[petraman]

Question, how can I check if the ignition system is working right? It's gotten better lately, but it's still there

[petraman]

Bump! Seriously, no one has time for me? sad...

[Jrs3800]

Do you have a scan tool or access to a scan tool?

[petraman]

No, but that's been next on the buy list for this car... What can I use that for?

[bruce]

you may have some "hidden" codes. There won't be a check engine light displayed but when you scan it there might be a few that where hidden.

search P1811

[swampthing]

my car had some weird things that it did during acceleration in the course of all the ignition components i changed the MSD coils really helped, I read on another forum that mismatched coils can cause weird things where one coils resistance is drastically different then the other, just trying to help gearheads please correct me if i am wrong...

[petraman]

Oh I forgot to mention this in the post, I have no clue what it was, but it stopped doing it a few months ago. I think it might be that the plugs and wires needed time to settle or something, because I'm almost sure it was an ignition issue...

[clm2112]

If you have acquired a scan tool, now would be the time to use it and see what the values look like while the car is running correctly...so you can compare against it when something is wrong.

A random shudder at all speeds sounds more like a transmission timing problem instead of an ignition problem. Like a sticking valve or a clutch. Hard to diagnose since you can't recreate it at will.

[petraman]

"lalalalalala, I'm not listening"

I don't want to hear the "t-word" mentioned. Been there, done that, got the tshirt...

[clm2112]

I don't want to hear the "t-word" mentioned.

I know, I know...at least the problem has gone away for the moment. Just out of curiosity (I don't know the car's history) but was the transmission rebuilt previously? Random thought of a rebuilt tranny is one of the clutch packs or band on a rebuild may have been installed dry, got glazed, and chattered a bit when applied until the glaze wore off.

[petraman]

The transmission was replaced a year ago with a unit from a 2003 Impala, and it had around 50k miles on it. I switched over the PCM to a 2003 so I can get the updated valve body, solenoids, etc...

[petraman]

Just out of curiosity, Curt, but would a sticking clutch affect all the gears or just one? I'm just kinda curious, I don't really think I'm going to do anything about it. Maybe I'll get a shift kit when I get my refund check, we'll have to see. I'm not driving it nearly as much as I used to, so it's kinda at the back of my mind. I've always thought it was an ignition problem because of some of the other minor issues. Like running kinda rough when it's humid outside. It also never shudders during WOT runs or anything, so idk. As I said, I'm not worrying about it, just curious

[clm2112]

Just out of curiosity, Curt, but would a sticking clutch affect all the gears or just one?

It would effect various shifts depending on which one sticks. Each clutch is not for a single specific gear. For example, one clutch may hold a planetary gear still in both 1st and 4th gear. (I'm at work and don't have access to the ATSG manual's table of which clutches are in play on each gear.) That's what makes diagnosing a tranny problem such fun, a problem with a clutch might cause a 1-4 upshift instead of the 1-2 upshift that was supposed to happen.

[2000Silverbullet]

When was the last time you replaced your ignition wires?

Be sure that the back plug wire is not touching the O2 sensor or wire.