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The Newest Problem with no DTC...

NaturallySmashed

NaturallySmashed

New member
okay so once again, right before i take my car on a road trip.. i have a problem arising and no trouble codes to help me out. so let me TRY to describe this problem for you and perhaps you may know what it is that's causing it.

When driving the car generally 40+ mph while under slight load/acceleration I will feel the car and the gas pedal shimmering around a bit. If I take my foot off the gas it goes away instantly. While this problem is happening i see the RPM's drop 2 hundred or so then the RPM gauge will shake while back and forth a tiny bit while i am driving the car and giving it slight gas. It almost feels as though it's misfiring but the PCM is not picking up any misfires.

My three guesses are: Vacuum leak, dirty maf sensor, or the TPS sensor. Also over a month ago I had changed the plugs. The problem didn't start right after I changed them but a couple weeks after. I don't think it would be the plugs but I haven't ruled it out just because it's the most recent thing that was done to the car.

I'm going on a road trip in less than 24 hours and my car is the only option. Any possibly help you could give would be much appreciated. Thanks for thinking.
 


that makes sense.. it doesn't happen when the engine is cool. when it's hot the problem is much more apparent. but when i hit the brake while it's happening it causes no change. <-- info i should have included before
 
i've put it in third and put it back into 4th just to get it to stop, did not notice it in 3rd gear at all. but i didn't do too much driving while in 3rd.
 
It shouldn't be trying to lockup TCC while going only 40mph but who knows.? Is your speedometer bouncing at all when it's doing this?
 


I guess it could be the TCC PWM. Sometimes a PCM reflash will take care of this. Is the PCM programming stock?
 
Shouldn't be going into lockup at 40mph? I believe and would have to check for this particular car etc, TCC lockup typically is programmed for around 35mph in third gear.

I'd be more apt to believe this is tune up related. Please tell us brand of wires, brand and model of plugs, if you've checked the coil pack towers for corrosion and or cleaned the TB/airfilter recently.

If you ever need to test if TCC has locked up. Keep your right foot steady on the throttle and gently press the brake with your left. You are aiming to turn on the brake light (pcm sees this) which unlocks the tcc and you should see a 200-500 jump in rpm. Letting off the brakes should allow it to relock.
 
yeah pcm is stock, i do have another one i could try out.

plugs are AL606 copper and wires are AC delco maybe? those could probably be changed by this point. air filter has not been cleaned in a little while. neither has throttle body. cleaned MAF this morning. before work as well as checked for vacuum leaks. didn't see corrosion but i'll take a coil pack off to look. don't know if cleaning the MAF helped yet, i don't think it did but i'll test it on my way to work. i'll retest the tcc unlock on the highway as well.
 


BillBoost37 said:
Shouldn't be going into lockup at 40mph? I believe and would have to check for this particular car etc, TCC lockup typically is programmed for around 35mph in third gear.

I'd be more apt to believe this is tune up related. Please tell us brand of wires, brand and model of plugs, if you've checked the coil pack towers for corrosion and or cleaned the TB/airfilter recently.

If you ever need to test if TCC has locked up. Keep your right foot steady on the throttle and gently press the brake with your left. You are aiming to turn on the brake light (pcm sees this) which unlocks the tcc and you should see a 200-500 jump in rpm. Letting off the brakes should allow it to relock.
Click to expand...

In drive the car should immediately unlock TCC at 40 mph under any acceleration, no? If just barely maintaining speed it shouldn't be "hunting" for lockup. This is when the PWM is working its hardest.

I challenge you again Bill! -------- I'll probably lose again but that's OK.

Watch, it's probably a vacuum leak, TPS or something stupid like that...DERP
 
it's locking and unlocking fine.. i've checked a million times. i cleaned the MAF sensor and it's been running fine.. i took it on a 200+ mile trip.. the shuddering feeling happened once and didn't last long (which is strange).. it does seem to be more of an issue when the temperature outside is warmer.. next warm day i'll really test it.. so it's running absolutely fine but i doubt it's fixed... so i will re-post soon.
 
That's why I'm thinking ignition.

Chuck...I'll have to screen shot a set of the tables for you to see what I'm talking about with TCC etc.
 
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