Stumble at cruise only

[rob-2]

I had this issue. Turned out I just needed to flush the transmission. After the mechanic mentioned it could be the torque converter I remembered my mountain run a few seasons back and how the car never felt right afterwards. The ATF had broken down and the converter was having trouble. She feels back alive again now.

 

Interesting. I can only feel it with the TC locks up.

[kzr750r1]

Thats what I'm also thinking and have done one pan drop 4.75 quarts.... Going to do it again in 500 miles at next OCI.

The fist pan drop did make an improvement but I also changed plugs at the same time so YMMV.

[kzr750r1]

I'm on brand new plugs and still have the problem. I'm wonder how old your plugs would have to be to cause this problem?

 

For me it feels more like a misfire or very faint lugging.

Plugs were not that old. Possibly 28K on them and they didn't look bad. But changing them and the ATF seems to make a difference in drivability.

 

On another note the idle after the plug change has been so smooth it seems the motor is not running.

[LegacyLove88]

I'm no expert by any means, especially when it comes to transmissions and torque converters. Just trying to throw some ideas on what worked for my cruise and low speed hesitation. I did plugs as well, and it still persisted. I cleaned up all of my grounds thinking it might be a bad ground, but that didn't help much either. The flush worked like a charm though.

 

On the other hand, I'm pretty jealous you got your idle smoothed out, kzr. Good luck with your issue though.

[kzr750r1]

So your saying you had a full flush of all 12qt? To me it fgeels like the converter is slipping out of lockup more than a engine miss. But I'm also in the end of an Etune and it's confounding us whats going on.

[firehawk618]

I'm on brand new plugs and still have the problem. I'm wonder how old your plugs would have to be to cause this problem?

 

For me it feels more like a misfire or very faint lugging.

 

 

Exactly the same for me. I believe the reason us 5EAT guys only feel it after torque converter lockup is because that stops the torque converter from "masking" the chugging.

 

I have done plugs, pcv, front o2, smoke test for intake leaks, cleaned the MAF, BNR16, catless dp.

 

I have to say I just replaced the turbo tonight and it definitely feels a lot less pronounced........could just be a fluke as I haven't driven it too many miles yet.

 

What strikes me as odd is that when I log cylinder roughness I get 0's on all 4 cylinders. I was sure hoping to get a misfire on either one or all cylinders.

[rob-2]

Exactly the same for me. I believe the reason us 5EAT guys only feel it after torque converter lockup is because that stops the torque converter from "masking" the chugging.

 

I have done plugs, pcv, front o2, smoke test for intake leaks, cleaned the MAF, BNR16, catless dp.

 

I have to say I just replaced the turbo tonight and it definitely feels a lot less pronounced........could just be a fluke as I haven't driven it too many miles yet.

 

What strikes me as odd is that when I log cylinder roughness I get 0's on all 4 cylinders. I was sure hoping to get a misfire on either one or all cylinders.

 

Going to test my injectors this weekend. Get no roughness either. Haven't done turbo or o2

[firehawk618]

I can say this is my 2nd day after the turbo / dp swap. Car is SOOOO much smoother than before. It's still got a tiny TINY bit of it but I can really hardly feel it and that's because I'm so tuned into looking for the stumbling. I'm really hoping the ECU doesn't relearn itself into old bad habits.

 

I don't know if I already mentioned this but during my tear down and swap I didn't find a single bad vacuum line. I also did a smoke test after putting it all together and found no leaks. The smoke test was under almost no pressure though so if there's a small boost leak it wouldn't expose it.

 

So far the logs I've uploaded for review look ok.

 

I did also load in a Bren tune to get my new combo going but I really don't think that plays a part because stock, cobb stg1 both did the exact same thing.

 

I could be wrong though.

[rob-2]

I can say this is my 2nd day after the turbo / dp swap. Car is SOOOO much smoother than before. It's still got a tiny TINY bit of it but I can really hardly feel it and that's because I'm so tuned into looking for the stumbling. I'm really hoping the ECU doesn't relearn itself into old bad habits.

 

I don't know if I already mentioned this but during my tear down and swap I didn't find a single bad vacuum line. I also did a smoke test after putting it all together and found no leaks. The smoke test was under almost no pressure though so if there's a small boost leak it wouldn't expose it.

 

So far the logs I've uploaded for review look ok.

 

I did also load in a Bren tune to get my new combo going but I really don't think that plays a part because stock, cobb stg1 both did the exact same thing.

 

I could be wrong though.

 

Interestingly I've had it on both the stock tune and a stage 1 cobb tune.

[kzr750r1]

Could be right about the TC covering. I feel it may also be slipping out shooting up in RPM by 300 to 800 rpm and increasing the line pressure a bit.

 

Are you working with Bren on a etune?

 

Just received another revision from Dave and look forward to getting it on the road for a full gammit of conditions. I've been resetting the ECU each rev flash lately so it learns from scratch. Seems to help it settle in the learning faster so you can give a decent assesment. Hard describing whats going on in text. I can't use my hands to explain.

 

I'm having a hard time not blitzing the freeway at 80 and have to slow down to get real world driving impressions.... CHP must have received some funding in my area, they are out in force since just before the new year.

[firehawk618]

Interestingly I've had it on both the stock tune and a stage 1 cobb tune.

 

Yes I was really hoping the cobb OTS tune would clear it.

 

Could be right about the TC covering. I feel it may also be slipping out shooting up in RPM by 300 to 800 rpm and increasing the line pressure a bit.

 

Are you working with Bren on a etune?

 

 

My car you cannot see the rpm's change, only feel it ever so slightly and worse at times as you gradually roll into boost then it disappears once you're into boost a bit. Sorry no boost gauge so I can't tell you exactly when it smooths back out.

 

Yes working with Bren on an E Tune. So far I did the initial 3 logs for him. Idle, cruise around the block and WOT 2-3 run and he said it looked great. Asked me to do a pull in 3rd only to redline which I did and am waiting to hear back. So far the only thing I've loaded is his base tune.

[rob-2]

Yes I was really hoping the cobb OTS tune would clear it.

 

 

 

My car you cannot see the rpm's change, only feel it ever so slightly and worse at times as you gradually roll into boost then it disappears once you're into boost a bit. Sorry no boost gauge so I can't tell you exactly when it smooths back out.

 

Yes working with Bren on an E Tune. So far I did the initial 3 logs for him. Idle, cruise around the block and WOT 2-3 run and he said it looked great. Asked me to do a pull in 3rd only to redline which I did and am waiting to hear back. So far the only thing I've loaded is his base tune.

 

I asked my tuner to add a bit more fuel in the low boost areas. I don't like trying to keep 14:1 a/f. That still has the stumble.

[kzr750r1]

Guys if your 5eat is long in the tooth place some Lucas Transmission Fix in it and start saving for a rebuild. Stumble at cruse is dropping each time I drive it and shifts much better. Start using sport mode as much as possible. I'm hoping it settles the TCU some more and lasts a little while. More milking it for all it's worth with good and bad news all in a $13 bottle.

[rob-2]

Guys if your 5eat is long in the tooth place some Lucas Transmission Fix in it and start saving for a rebuild. Stumble at cruse is dropping each time I drive it and shifts much better. Start using sport mode as much as possible. I'm hoping it settles the TCU some more and lasts a little while. More milking it for all it's worth with good and bad news all in a $13 bottle.

 

What makes you think your tranny is going?

[kzr750r1]

Slipping, plain and simple. I'm feeling it applying a request for increased torque. There is nothing wrong with my intake and all other indications show I'm not having a tuning issue, have a long log to review tonight. In fact the better it runs the more I feel the slipping.

After this second pan drop plus adding the LTM it's staying locked up much better in all conditions. Not just where I was feeling slip before.

So for now its sport and manual mode as primary. D will only be used on the freeway no hills. If I'm hitting a hill on the freeway I'm shifting into 5th manual, all in hopes to keep the line pressure at the maximum, slipping to a minimum. I have run a lot of freeway miles in drive mode and unfortunately 5th are the clutch pack group that has suffered the most. Who knows the torque converter may be failing as well…

I would really like to place the valve body kit on this but will now probably do it as part of a rebuild. Having the grip back makes it a fun car to drive again.

But it will not last forever and will need to be addressed.

This transmission has been mistreated by some accounts here on the forum.

Early on I didn't flush the transmission the dealership claimed to have done it. I don't believe they did much more than a pan drop if at all. After 110K or so I began doing regular drops and swapped the filter. Done what I can. Now it's time to milk it for a little more milage.

I have learned more about this car than I should and now wish I jumped over here earlier. May have been a little more concerned about fluid drops on this transmission and so much more....

[fishbone]

Searching the forums for location of front O2 sensor and a DYI and came across this thread. There's so many different terms one can search for in regards to this issue that it seems I have missed pretty much all conversations on this

http://legacygt.com/forums/showthread.php/oscillating-cruise-control-219862.html

 

2005 LGT, auto, Stage 2 for many miles now, 110K miles.

Yesterday I used my cruise for the first time in a while and discovered that it feels as if I am oscillating the throttle pedal.

I glanced at the AP, injector duty cycle was steady, fuel pump duty same, AFR mostly same, didn't register any cylinder roughness. The throttle position would jump between 4% and 6 or 7.

None of this is happening under regular driving.

 

Any ideas? What else should I be checking?

It's been suggested to look at the A/F Learning 1 which I plan on doing.

I'm ashamed to admit I'm not sure which/where is the front O2 sensor.

[kzr750r1]

A/F sensor is at the collector before the up pipe. O2 is after the cat at the end of the tail pipe.

[fishbone]

Yep, found my answer in the meantime. On the manifold, can be accessed via pass side wheel by turning it right and undoing the plastic cover.

Are we talking about the same thing here as far as what may be faulty? The front or rear?

[kzr750r1]

I would do both at the same time.

[fishbone]

That would obviously be the safest route but at the same time I want to make sure I'm doing what needs to get done rather than throwing money at the problem.

I will see what I can find out via datalogging and report back. Wide ranges in A/F Learning 1 is what I have been told would be an indication of a flaky O2 sensor.

 

What I do not understand is why this is only happening while using cruise. It is so obvious it would be impossible to miss if I am duplicating cruise control conditions, meaning steady throttle on a straight road.

[kzr750r1]

Look at these like expensive light bulbs, if one is bad it's time to swap both. I've blown plenty of catalytic converters in my lifetime. Trying not to repeat these mistakes on this car.

[fishbone]

Point taken. If I narrow it down to being an oxygen sensor issue, I will replace both. It could still be something else, at least from what I am reading here.

[kzr750r1]

For sure. I was not considering my transmission as failing till I put the snake oil in and had a real positive result.

[fishbone]

Same sensor socket needed as the one used for the rear one, yes?

It would be beautiful if replacing an O2 sensor is what will take to clean the mystery/unexplained random knock I have been experiencing for a number of years now while in closed loop.

[kzr750r1]

I can't remember if they are the same size. I think they are.