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Discussion Starter #1
Hello all,
I have read multiple threads in this forum about my issue. I'm hoping you guys can give the solution I'm looking for. I have a 2009 Cobalt LT1, 2.2 Ecotec, Automatic. 72,000 miles. No warranty. My car surges or pulses at steady speeds, usually between 30-45mph. The rpm jumps up and down between 200-400rpm. I'm hoping there are some out there who have had the problem corrected and can tell me what I need to have done. This is my daily transportation to work, 80 mile roundtrip. I don't have a lot of extra money to throw at chasing the problem. Please tell me what fixed your problem. Thank you.
 

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There have been quite a few people with the same problem that seem to have been fixed differently. When mine did that it was still covered under warranty but they replaced my tcm over 2 years ago now and it has been perfectly fine ever since
 

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Kinda of sounds like your torque converter is starving. Have you verified your transmission fluid level?
 

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Did you follow this procedure?

Start the engine and allow the engine to idle until the transmission fluid temperature has reached at least 105degF. Depress the brake pedal and move the shift lever through the gear ranges, pausing a few seconds in each range. Return the shift lever to the PARK range.

Remove the fluid vent cap. (red cap on drivers side top of trans)
Raise the vehicle on a hoist(or support on jackstands)
. The vehicle must be level, with the engine running and the shift lever in the PARK range.

Remove the transmission oil level control plug(its a small usually 10mm hex bolt on the right/passenger side of trans, below and in front of the right hand axle.)

Check the fluid level. The fluid level should be even with the bottom of the threaded plug hole.

Add DEXRON®III (or better) automatic transmission fluid in increments of 0.5 L (0.5 qt) until the fluid drains from the plug hole.
 

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Yes. I did just as your post stated. I had today off. So I took the car to 4 different shops. 2 Tranny shops and two trusted mechanics. I explained my problem, and I got 4 different opinions as to what the cause could be. No one thinks its the tcc solenoid. So, wasted time today, wasted gas and I'm still no closer to solving. I guess I will drop the pan and change the fluid and filter, and see if maybe that helps. One tranny shop said to add Lube Guard(10 oz.) and see iff that helped. It made it worse.
 

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If anyone is still following this post, I've gotten nowhere with this issue. I took my Cobalt to a very reputable transmission shop this past Friday. He kept the car for two days and had another knowledgeable mechanic look into it. Both are ASE certified and have 70 years experience between them. They could find nothing. Took it to the Chevy dealership. They drove it and checked the ECM and TCM. Could find nothing. The mechanic told me that he has seen this in other models and that doing a fuel injector clean and top cylinder clean with new plugs would make it better. I did a top end clean with Seafoam, replaced the plugs with OE plugs and rather than clean the injectors, I've ordered new OE injectors. So far nothing has helped. Hoping injectors do it.
To recap: I've changed the oil and filter, new air filter, new fuel filter, new AC Delco plugs, top cylinder clean. Had a tranny shop run diagnostics on tranny and engine, and I am waiting on injectors.
 

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The dealership had my car for like 2 weeks before they fixed it when mine was doing this, they didn't even have a loaner car for me haha
 

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New fuel injectors installed. No changes. Fuel pump starting to fail???????

---------- Post added at 06:17 PM ---------- Previous post was at 05:45 PM ----------

I read the whole thread you suggested. It seems like there is no solid solution. Very frustrating.
 

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Discussion Starter #13
dropped transmission pan and changed filter. Fluid looked good. Pan was clean inside, with minimal residue. Bottom of transmission looked clean also.

---------- Post added at 09:41 PM ---------- Previous post was at 09:40 PM ----------

Thinking of adding Lucas transmission fix to the fluid. Opinions?
 

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Went to the dealership today. They duplicated my problems. Reset the idle, relearned the crankshaft position and reset the shift adapts. I've only driven 12 miles but the surging is gone. Hopefully this will be long-term.
 

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Update on your cobalt

How is your cobalt performing now? I'm having similar issues and today the check engine light came on...
 
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