shudder at 50-60mph

[gabequest]

Dropping it into 3 does stop the shudder. In 3 I was able to occasionally find a spot where it felt a bit more lurchy than a shudder, but it was subtle. That feeling felt more like timing or something plug/etc. related. Last year the cap and rotor were replaced by GM after an early morning tow, where I thought it might have been fuel pump. Did not do plugs and wires at that point.

[LiftedAWDAstro]

Pull the cap and check for corrosion or moisture. I would plan on changing the plugs and wires as well if you don't know when they were done last.

[gabequest]

The leads DID have some white corrosion on them. There was also a bit on the rotor tab. I scraped the ends and the van did a bit better during same conditions. Did not have much opportunity to test. Just once onto the highway before an exit (grocery getter today). Interestingly, a pending code P1153 disappeared. There is still a damn P0157, which is annoying because I just wired another sensor in and had the PCM reconfigured for it. I have to check for ground. I have my appointment with the California referee on Thursday to clear the van for smog. A bit nervous but hopefully it all comes together soon.

Any idea why corrosion after 1 year on this cap? Should I just try to clean them better or do you scrape away a bit of material and decrease the connection. I'll wait to order cap and rotor until further advised.

thanks again!

[LiftedAWDAstro]

These vortec engines only seem to run best on GM cap and rotors. I have never had any luck trying to clean them.

[gabequest]

By GM do you mean AC Delco?

[LiftedAWDAstro]

Yes. They seem to be the best quality for these ignition systems.

[gabequest]

Replace cap and rotor cap: minimal improvement.
Replaced plugs and wires: more improvement and SES light off....then passed CA SMOG!! WOOHOO!!

Still shudders a little with gentle acceleration once at 40-55mph. Distributor? Could this be from plug screens in the distributor?

[gabequest]

I changed plugs and wires and the SES turned off...for a few days :-k Long enough for me to pass SMOG!!
The shudder is now hardly there at 50mph+ and easy to drive right through that window, but still comes on some at 40ish when going up small hill (i.e onramp). Something about that load kicks it on. I'm wondering if the contact of my exhaust manifold may be it...but this didn't happen for a while after the engine swap, or subsequent motor mount swap.

The SES light is back on, but haven't scanned it yet.

:-k :-k ](*,) :-k ](*,)

[gabequest]

Finally, the shuddering saga comes to an end. It was the damn torque converter. I got some info from a tranny shop....gently apply break during said shudder and if it stops, its probably the TC.

Good news: my answer
Bad news: the part is under warranty but labor is not, which means for the 2nd time in 15months, I've dropped the tranny!!!

the shudder is gone, but my van cont's to earn his name!!!!!!!!! TROUBLE

[MountainManJoe]

What was wrong with the TC?

[gabequest]

I dont really know for sure; may have been the clutch slipping as it tried to engage. Some one else may be better able to answer that, but I THINK thats what the tranny guy said when he advised I should change it. I feel kinda bad for not bringing him my business...but not bad about saving $600 by doing it myself!

[T.Low]

Could be the torque converter, but I'd think you would had replaced it when the trans was rebuilt.

I'd try a new filter and change the fluid with an exchange machine to be sure it was all new, and add a BIG cooler if you don't have one.

What fluid are you running?

The TCC can act up and shudder as described with the wrong fluid. I can't remember which fluid, though.

Maybe have a trans shop verufy that the converter is locking correctly, and that the TCC solonoid is OK.

Sorry to hear that you're having problems, and can't wait for the new pics!!!!

=D> =D> =D>

Glad ya gotter fixed, GQ.