Surging RPM Problem At Freeway Speeds - Help Diagnosing

[00GTP4ME]

Hey all,

This is an annoying issue I've been dealing with for quite a while, but this weekend it got bad enough that I'm to the point that I really want it solve whatever it is.
The problem is strange and hard to describe so I'll do my best. It only ever happens when I'm going freeway speeds. Usually, I'll be driving along and for whatever reason I'll need to push on the gas to the point that it increases the RPM's, but not quite enough to make the transmission shift down (auto trans.). If I'm cruising along at 65-70, the RPM's are just barely over 2K. If I push on the gas and get it up around 2.5K, then the RPM's start surging up and down in an oscillating pattern- going up a few 100 RPM's and then down again quickly and the engine sounds like it's bogging down or flooding or something.
Now if I go back to just cruising along at 65-70; if I give it enough gas to shift down, it does so smoothly, I get great acceleration, and there's no sign of any problem. It's just when I stay within the gear I'm already in and give it more gas-but not pinning it.
This never happens at any other time - it idles very smooth and I have no clue what this could be. I'm sorry if this is not the most coherent explanation, but I just can't think of how else to explain it.

If anyone wants to take a stab or has any ideas of things for me to check, I would really appreciate it!...

[troy1]

Almost sounds to me like your TCC is not locking up correctly. Do you have a scanner?

[00GTP4ME]

Originally Posted by troy1

Almost sounds to me like your TCC is not locking up correctly. Do you have a scanner?

I have a code reader, but that's it. What's a TCC?

[HeMi101]

Im with troy, sounds like it could be TCC problems. TCC = Torque Convertor Clutch btw. Mine does the same thing on my impala, but my trans is a mess right now period.

[tblake]

TCC Indicision definatly.

One question, do you have any modifications to the throttle body area? How is your MAF screen? (still in place?)

[00GTP4ME]

Oh great.

What kind of a fix/cost would be required if that turned out to be the case?

I haven't made any mods to the throttle body and the MAF screen is in place. The closest thing to a mod in that area would have to be my cold air (kinda). The cone filter is still under the hood, but I have a lead pipe that goes behind the driver's side fog light. I used to have a true cold air, but I think the pipes were too small and the engine seemed like it wasn't getting air fast enough. So when I shortened the distance between the MAF and the air filter, that seemed to fix it.

I'm taking the car in tomorrow so this info really helps me. Is there anything else this could be? How would a shop go about finding out if this was a TCC issue for sure?

[tblake]

Remove the MAF and clean it with some MAF sensor cleaner

[00GTP4ME]

Ok, I'll give that a try. Is there actually a MAF Sensor cleaner or can I just use carb cleaner?

I've been doing some more searching on here and am surprised that others have experienced the exact same symptoms. It makes me laugh because I was almost quoting others verbatim when I thought there was no way I was making sense. The only down side is that I didn't see a common solution to these issues.

If cleaning the MAF doesn't yield anything, here is a list of things I've gathered that may lead to a solution:

• Tranny Code Scan
• TPS Sensor check
• TCC Solenoid check
• Excess valve body wear in the TCC valve area?
• Worn or shrunken teflon seals on the input shaft?
• A bad o-ring on the input shaft that seals in the torque converter?
• A faulty torque converter clutch?
• A bad pressure control solenoid?
• Worn out sleeve in the channel plate that supports the input shaft?
• Check pressure relief valve in the channel plate for debris

• Verify proper operation as commanded by the pcm is with a scan tool by viewing TCC slippage rpm, TCC duty cycle, EPC data, and checking any codes and making sure the engine is running properly and a misfire is not a false sense of a torque converter problem or shudder.

Possible Solutions:

• New or reman / repaired valve body?
• New EPC solenoid?
• New TPS
• New TCC Solenoid

Anything anyone wants to add to the list??

[richtazz]

Do not use carb cleaner on a MAF, it will ruin it. MAF cleaner leaves no chemical residue, carb cleaner does.

[richtazz]

On your surging issue, it's most likely a TCC valve or TCC control circuit/wiring issue. The TCC controls torque converter lock-up, and is a common issue in these transaxles and causes your exact symptoms when they start to go.

[tblake]

My car was doing it after I switched from my stock t-body to a ported zzp stage 1 t-body with no maf screen. As soon as I put the maf screen back in there, problem solved.

I almost wonder if the cone filter oil isn't gumming up your MAF sensor.

Like Rich said, you could also ohm check the TPS.

[00GTP4ME]

Well I'm running it in to the shop right now because I won't have time later. Thank you so much for the help guys and I'll report back later with what they say! Stay tuned...

[chrissbee77]

sorry to post on this topic. IF it is his TCC how much would something like that cost a transmisson shop to fix.

[00GTP4ME]

Originally Posted by chrissbee77

sorry to post on this topic. IF it is his TCC how much would something like that cost a transmisson shop to fix.

N/P. I'm wondering the same thing.

[troy1]

New TCC = rebuild.
Solenoid = $500
Wire = $300