[COLOR="Blue"][B]BC Update[/B][/COLOR] P0303 - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
Problems and Service Talk about any mechanical problems you are having

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post #1 of 59 (permalink) Old 02-21-2018, 05:55 PM Thread Starter
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[COLOR="Blue"][B]BC Update[/B][/COLOR] P0303

BC update

I now have just over 125k miles on the BC update A stock 2008 LS. The mods include activating the cruise control, replacing the steering wheel to the SS stile with the extra buttons for cruise & radio controls.
Fe5 shocks & struts and a new Front 05 SS sway bar, Thanks to eBay and ZZ parts. New forged Al LCAs and the new intermediate steering shaft. That was a pita. Also installed new AC stock 41-103 iridium plugs and both O2 sensors (Denzo 234-4066 rear & 234-4668 front) air filter and sprayed the mass air flow sensor.
Changed the oil & filter using Mobile 1 5W-20 and replaced the original cabin air filter/ mushroom farm.
All this when EBay delivered the BC from Florida back to TX where it was originally titled
Since then I have changed the oil & filters once both engine and cabin.

After my second oil & filter change I had the P0303 code pop up within 500 miles. As a recall I played swap plugs, injectors and finally cleaned the MAss air flow sensor before the code cleared and provided another 5k miles.
Oil is now 70% and that P0303 is popping every 2nd or 3rd tank of fuel. Averaging 33-34mpg.

Now time to brake out the TechII and see if and how many misfires are actually happening
I checked an still have the original O2 sensors along with a new pair of Densos And that second set of Moog sway bar bushings. My miss order. I read you needed 2 and the listing said one per box so, I ordered 2 boxes and received 2 per box.
@$7.00 It was just the same to keep them as to pay shipping back.

Also its time for new tires. RF is showing the wear bars on the stock 195/R65 Toyos.
I still have a complete SS cobalt rear Axel with rotors, calibers, and the SS E-brake assembly and SS rear Coils.
Remember it is set up for 5 lug and I have the 08 LS 4 lug setup and still have the stock LS front coils.

So there you are enjoying running around @ 70 mph getting 32-34 mpg and enjoying the MP3s from the replaced front speakers.

Time to do a little PM deciding if stock 15 or new 16 or a set of SS 18 wheels and 4 new 5lug hubs or....
Work on my Geronimo. Still need to do some smoothing on its ruffled feathers.
Thogan3 likes this.

BC

Last edited by 1966tbird; 02-21-2018 at 06:46 PM.
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post #2 of 59 (permalink) Old 02-25-2018, 03:00 PM Thread Starter
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@Coby7
Looked today at RF tire. It’s pretty much gone. Wear bars are clearly showing. Both rear tires have very good tread.
LF tire is a good used tire.
Thinking on installing 5 Lug hubs and 18” SS wheels. This would force new front rotors also.
Now I have that SS rear with brakes. But still no proportioning valve and I have not installed or have the ABS.
So a little background on installing the ABS and how it is on the Cobalt. 2 front an 1 rear servos or all 4 wheels???
Or
Just getting 5 lug rotors and drums

18” tires ~$125 X 4
5 hubs ~ $40-$50 x 4

5 lug rotors & drums ~ $20 x 4

I still have one odd 15” steel wheel stock hubcap does not like.
Toyo 195/65 15 ~$75 ea

And I still enjoyed tooling around not the stock (as received) Tokyo’s.

BC

Last edited by 1966tbird; 02-25-2018 at 09:18 PM.
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post #3 of 59 (permalink) Old 02-26-2018, 10:37 AM
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ABS system uses sensors at all 4 wheels. The proportioning valve is not and absolute necessity if you don't have ABS. It's just that rotors bite a little better than drums and may take some getting used to. If you find the rear locks up too often then you will have to get one.

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post #4 of 59 (permalink) Old 03-06-2018, 07:23 PM Thread Starter
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Took the Tech II out today and pulled up the errors (P0300) and looked at the count.
Cylinder 1 -2
Cylinder 2 -5
Cylinder 3 -12,000
Cylinder 4 -4

Pulled up the misfire graph and misfires on cylinder 3 stop generating above about 1200RPM
No other errors
Fuel trim 0 to 2
Front O2 sensor moving up and down ~0 to ~.500
Rear not moving but about .700 - .850

Checked fuel injector and cylinder balance and all injectors and coils respond pretty much the same when I disable one.
Instant rpm drop then engine returns to ~ 90% prior RPM. On re-enabling, there is a sudden increase in RPM for ~3 sec then RPM returns to pre-test value. This is on the fuel injectors and coils. That is if I had indeed accessed the tests properly.

Base RPM command 550RPM engine speed 750RPM plus or minus 20 rpm
No other codes

So, I will play swap parts between cylinder 2&3, clean the mass air flow sensor and check the oil level. It’s been ~3,000 miles since oil change and oil at ~75% using Mobil1

On another note. I pulled up my radio info and logged radio 25775626 calibration 4
I do this in prep to install a Malibu radio UUI option. It’s a Panasonic with a USB port on the front on the lower Right corner & mini jack on lower left. If I would have thought about it, I might pick up the vicm (sp) with Bluetooth and the BlondStar mirror/mic. Not interested in BlondStar just the Bootooth for wife’s phone.

---------- Post added at 03:23 AM ---------- Previous post was at 03:18 AM ----------

Quote:
Originally Posted by Coby7 View Post
ABS system uses sensors at all 4 wheels. The proportioning valve is not and absolute necessity if you don't have ABS. It's just that rotors bite a little better than drums and may take some getting used to. If you find the rear locks up too often then you will have to get one.
4 sensors yes without a question. But, I have not checked, is there 3 hydro lines (LF,RF,R) or 4 lines. I do know of some ABS systems with 3 and others with 4.

BC
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post #5 of 59 (permalink) Old 03-07-2018, 06:57 AM
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Always 4 with T/C

Every minute spent angry is a happy minute lost for ever and ever!!!
Drives 2016 Cocoa Buick Encore 1.4L Turbo auto KL4CJDSB2GB652675
Drives 2016 Sunset Orange Trax LT1 1.4L Turbo auto 3GNCJPSB8GL142716

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post #6 of 59 (permalink) Old 03-08-2018, 05:46 AM Thread Starter
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Thanks @Coby7
Swapped plugs & coils between cylinders 2 & 3. No joy!
Still gendering misfires on cylinder 3...
Next I will try injector swap or ..... ?
Leaking injector o-ring or dirty injector? Will dirty throttle body cause just 1 cylinder misfire? Does not seem likely.
Leaking intake port/ bad gasket/o-ring?
Remember both O2 sensors new & I still have old ones & a new set.


Also looked and saw the 6 brake lines into the p valve telling me more amount the 4 wheel ABS.
By adding the 4 hubs with sensors I suspect I would need the body wiring to the 4 corners.
I would be surprised if they were there on a non ABS LS.
Connecting the ABS pump assembly should not be a large problem taking it from an ABS Cobalt & its p valve.

BC
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post #7 of 59 (permalink) Old 03-08-2018, 07:24 AM
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You may have a bit of carbon build-up on the exhaust valve causing it not to seat properly. You may be due for a good seafoam cleaning before you burn that valve. If you do a compression test and it shows up low on cylinder 3, then you'd know for sure but don't panic.

Doing the ABS swap is a project for sure, good luck.

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post #8 of 59 (permalink) Old 03-08-2018, 10:01 AM Thread Starter
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Ok
I could see that (sticky or leaking exhaust valve) can do a max pressure and differential/leak down test.

Just looked at TechII live misfire graph. No misfires over 1000 RPM. With engine at operating temp. At idle I am seeing cylinder 3 ramp up from zero to ~ 50 counts over 6-10 sec. then it drops straight down to zero for about 2 sec and then starts to ramp up again.
The max value of the graph does not look to be max value available.
Just a simple saw tooth graph with a 10% dead spot between the ramps.

Will try to do pressure test today.
Again this is @125,000 miles on engine

BC
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post #9 of 59 (permalink) Old 03-15-2018, 12:49 PM Thread Starter
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Swapped cylinders 2 & 3 fuel injectors and cleaned the MAF sensor. Let’s see if any change now. Last P0300 happened alter 130miles

I looks like the T-body has never been cleaned. I don’t think that is an issue though.
If this does not work, I will do the cylinder pressure diagnostics.

BC

Last edited by 1966tbird; 03-15-2018 at 12:52 PM.
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post #10 of 59 (permalink) Old 03-15-2018, 12:58 PM
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run some seafoam through the T-body. should clean it up pretty nice.
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