Engine surges while in overdrive while doing consistent speed

dla442

Original poster
Member
Mar 31, 2012
249
grand rapids, mi
Question? I have an 05 TB with 126k. Evrything is maintained to factory intervals. When we drive the TB on the freeway and are going a consistant speed and the trans is in overdrive, we can feel the engine or trans surging. Its like it is gently going up and down in rpms where you can hear it and barely see it on the tach but the TB does not increase or decrease speed. Its a droning sound wahhhh wahhhhh wahhh etc but is for sure an engine or trans causing the engine to do it. No bearings as i checked for wheel play and they do not move(amazing for 126k and never gone bad yet). No engine lights or codes. Has new plugs. Also when it starts up in colder weather, you can hear some crazy noise in the trans, almost like the fluid is being forced somewhere and then everything is great. Can a bad pump or trans parts cause this surging? I know this is so general in nature but i think the surging issues will relate to the start up noise. I have not noticed any loss of power, just the erratic surge and sometimes on acceleration is not a responsive when edal pushed and then its says "oh" and speeds up after the fact of gas pedal being pushed. Almost like a delayed reaction for the accelerator. The throttle body is regularly cleaned.

thanx in advance
 

christo829

Member
Dec 7, 2011
497
Fairfax, Virginia
Does that "startup noise" occur right when you start the truck, or after you put it in gear?

How quickly does it go away? Within a minute, after the truck warms up, after X miles, or...?

I had a 98 Lumina that started surging at speed, similar to what you're describing, and it was
the fuel pump. Not saying that's what's causing your issue, but something to keep an eye on.

How are the fluid levels? Any leaks, like in the trans oil cooling pipes or anything?

Good Luck!

Chris
 

bfairweath

Member
Oct 20, 2013
95
Neenah, WI
Yes, O2 sensors wear out. I think most people are going to tell you to replace them at 100k regardless if there is a code or not. I would only replace the primary sensor (upstream of the cat). The downstream sensor has no effect on how the engine runs. It only measures the performance of the cat.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
1) I would also suspect the TCC lockup clutch not staying engaged. Taking a mechanic for a ride with their Tech II or similar high end tool can see what's happening inside the tranny.

2) The upstream O2 sensor is hanging out in the raw exhaust stream, and after 100K, they really get coated with crud like a too-old spark plug. What happens is easily visible if you're looking at the raw sensor data. Instead of wiggling up and down from 200mv to 800 mV (or so, these numbers aren't precise) at once or twice a second, the sensor gets sluggish and only moves once a second or less, because the crud coating slows down the exhaust gases getting to the active area on the sensor. Sooner or later, the PCM will throw a code about the sluggishness, but way before that, the sensor data is not accurately telling the PCM what the combustion efficiency is, and you might end up wasting fuel as the PCM guesses. Waiting to get a code, and not changing the sensor at 100K along with the plugs, is misplaced frugality, as I'm fond of saying.
 

dla442

Original poster
Member
Mar 31, 2012
249
grand rapids, mi
thanks roadie...i know i should replace it but not into replacing parts just because..this part though make sense to replace as i dont think the gas mileage is great..on hwy the driver display says average of 14mpg and thats a 1k miles after it was reset. this could be my surging effect? the fan clutch may also be making my start up noise..not sure. i was able to stop the fan from spinning with a hot engine using a rag as a buffer. it made a bunch of noise that continued until i gassed the throttle then gradually the noise went away. it was 32 degress out with the hot engine when i did this. i will have someone with a tech 2 test it out while its driving. I hate the thought of a tc going bad....ug. the TB as been such a great car for us with only routine maintenance much of which I do myself. I will replace the O2 sensor(upstream). When the engine is cold should the fan be spinning and if clutch is bad how can i tell if it is functioning property especially when earlier it was a hot engine when i stopped it?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
dla442 said:
When the engine is cold should the fan be spinning and if clutch is bad how can i tell if it is functioning property especially when earlier it was a hot engine when i stopped it?
When the engine is cold, the fan clutch will be set to low engagement, but there is ALWAYS a tiny residual friction in the internal guts and in the seals, so it has a natural tedency to spin with low torque. Enough torque you should be able to stop it with a rag. It will not get commanded to high engagement torque until the coolant temp is above 240, at which point a bad clutch will set a code. You can't stop a fan spinning at high engagement torque.

If yours makes an internal noise when you hold it I'd be looking to replace it.

I think people expect the fan to sit still while the engine turns, and that can never happen because the residual friction of the seals will always overcome air friction trying to keep it still.
 

dfc739

Member
Jul 29, 2012
170
Des Moines, IA
the roadie said:
1) I would also suspect the TCC lockup clutch not staying engaged. Taking a mechanic for a ride with their Tech II or similar high end tool can see what's happening inside the tranny.

2) The upstream O2 sensor is hanging out in the raw exhaust stream, and after 100K, they really get coated with crud like a too-old spark plug. What happens is easily visible if you're looking at the raw sensor data. Instead of wiggling up and down from 200mv to 800 mV (or so, these numbers aren't precise) at once or twice a second, the sensor gets sluggish and only moves once a second or less, because the crud coating slows down the exhaust gases getting to the active area on the sensor. Sooner or later, the PCM will throw a code about the sluggishness, but way before that, the sensor data is not accurately telling the PCM what the combustion efficiency is, and you might end up wasting fuel as the PCM guesses. Waiting to get a code, and not changing the sensor at 100K along with the plugs, is misplaced frugality, as I'm fond of saying.

Another way to test the TCC lockup is to get it to highway speed and while it's "surging" in and out of lockup gently hold the brake. Give it enough gas to keep going a steady speed buy just apply a little bit of brake. The TCC will not lock up when the brake is applied. If the vehicle stops "surging" during this, look into getting the isolator valve to eliminate the PWM.
 

dla442

Original poster
Member
Mar 31, 2012
249
grand rapids, mi
dfc739 said:
Another way to test the TCC lockup is to get it to highway speed and while it's "surging" in and out of lockup gently hold the brake. Give it enough gas to keep going a steady speed buy just apply a little bit of brake. The TCC will not lock up when the brake is applied. If the vehicle stops "surging" during this, look into getting the isolator valve to eliminate the PWM.

what is an isolator valve and PWM?
 

gmcman

Member
Dec 12, 2011
4,656
Have you checked the trans fluid? Level ground, hot trans, engine idling.

When you dropped the pan last, did you reinstall a deep pan filter? (required)
 

dla442

Original poster
Member
Mar 31, 2012
249
grand rapids, mi
Fluid should be fine, but I'll check it. Reference my pan, I put the same filter type as what came out of it according to looking at it. That was almost 50k ago.
 

C-ya

Member
Aug 24, 2012
1,098
dla442 said:
what is an isolator valve and PWM?

This thread will give some info on this. http://gmtnation.com/f79/removed-pwm-control-tcc-7304/ You can search for torque converter lockup valve (that's what I used) and get more/better threads on it that may suit your desired path forward better than the one I linked.

The torque converter lockup is controlled by a valve in the transmission and it is controlled by a PWM (pulse width modulated) signal. There is a fault code associated with this if it gets bad enough, but sometimes (as in your case mayhap??) there is no code, but you can feel what is going on.
 

dla442

Original poster
Member
Mar 31, 2012
249
grand rapids, mi
Will be bring tb to a mechanic with a tech 2 to get to the bottom of the surging..could be fuel pressure, tic or something else. So I'll fork over a fee for the correct diagnosis and will post the results
 

Hatchet

Member
Nov 21, 2011
2,405
Mine started doing something similar. What mine appears to be doing is once it goes into 4th gear it drops back to 3rd and then back to 4th. Like it can't make up its mind what gear to stay in. The RPMs flux only maybe 200 rpm but it is noticeable. Is that what is happening?
 

seanpooh

Member
Jan 24, 2012
461
Same here with the surging when in OD. Hasn't happened in about 2 weeks though. It's on and off. I ordered the Sonnax Shift kit along with the Super Hold 2nd and 4th Servos and a new check plate to pretty much beef up the tranny as much as I can along with solving the common problems.

The Sonnax also eliminates the PWM which solves the slipping in OD which happens in all gears from what I understand... Once I have it installed, you guys are surely first to know.
 

Boostking

Member
Mar 10, 2015
3
I have an 06 trailblazer ls 4.2RWD with 116000. I bout if a cpl weeks ago everything was fine for the first couple day. It started an RPM flutter/surge between 50mph-70mph. The RPM were fluttering up and down by about 500. If I got into the gas it when away and if I let out it went away. Only seems to do it on slow acceleration. Things I have done (new plugs acdelco, cleaned TB, ran seafoam threw the fuel, check trans fluid cherry red and smelled fine,oil fresh as well,new mass air flow) yes I reset the pcm after all was changed and cleaned. The other morning I backed out of the drive and went to drive and it stalled and died fired right back up and was fine for the rest of the day. Still had the stutter/flutter/surge which ever you want to call it. Everything I have read is point to the torque converter and that this will fix the problem. Does this sound right to you guys http://www.ebay.com/itm/4L60E-4L65E-1996-2006-1870-P1870-CODE-BUSTER-COMBO-KIT-Corvette-Servo-Kit-Book-/270874884435?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item3f1166b953
 

kkeo211

Member
Apr 14, 2014
87
Hatchet said:
Mine started doing something similar. What mine appears to be doing is once it goes into 4th gear it drops back to 3rd and then back to 4th. Like it can't make up its mind what gear to stay in. The RPMs flux only maybe 200 rpm but it is noticeable. Is that what is happening?
Mine did the same thing last year. Like it was hunting for gears at 45mph plus speeds. It turned out that I was low on transmission fluid. I found out that over time, the bolts that held my transmission pan in place had come loosened a little bit and transmission fluid leaked out over time. I decided to go ahead and drop the pan, put in a new filter and changed transmission fluid. I have not seen this issue ever since.
 

Hatchet

Member
Nov 21, 2011
2,405
kkeo211 said:
Mine did the same thing last year. Like it was hunting for gears at 45mph plus speeds. It turned out that I was low on transmission fluid. I found out that over time, the bolts that held my transmission pan in place had come loosened a little bit and transmission fluid leaked out over time. I decided to go ahead and drop the pan, put in a new filter and changed transmission fluid. I have not seen this issue ever since.
I forgot about this thread. I believe my issue was a bad torque convertor. I lost all gears on high way and found out it was a blown fluid pump in the trans. Didn't replace the torque convertor and a few months later it happened again. This time I knew it was the torque convertor and replaced it.
 

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