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Discussion Starter · #1 ·
Ok, so to start this long post, let me say I’m new member here, any advice would be greatly appreciated cause I’ve been pulling my hair out over a week on the same problem over this damn car. I cannot afford a different car, cannot afford to take it to a shop, so I need to fix it. I have a 07 Cobalt 2.2l LS sedan and it had a LOT of issues, I took pretty much everything out all the way down to the head gasket, cleaned everything up, put new head gasket, all new coolant system (radiator, fan, all hoses, ECT, therm, water pump, all seals/gaskets replaced). On the head I replaced ALL the valves and keepers, reused the springs & retainers, rockers, lifters, replaced all the valve seals, lapped the valves, threw that together, put the head on, put new head bolts in. Then started the timing, whole new set (chains, sprockets, guides, bolts) everything lined up, tried to turn the engine by hand and it went around once and stopped. No movement. So I took it apart, had to buy another tensioner since they are one use now, and redid the timing. All marks lined up again, this time I turned the engine by hand and it went around multiple times so I figured good to go. Threw the new timing gasket and new cover/oil pump on, put new harmonic balancer & bolt and new tensioner, bolt & belt on, put new valve cover gasket & bolt grommets in new valve cover and put it on, wiped crud off outside of injectors with a shop towel and put them in, put new PCV hose on intake and slid intake on, put new OSS, MAF, MAP, and KNOCK sensors, reconnected battery and tried to start. Stalled for a couple seconds, then fired up loud like a 90s truck. Super loud and rough startup, and then in 5-10 seconds goes all the way down to normal revs, maybe a little under (500-600) then when I go to accelerate it stumbles as I accelerate, it will get to the speed eventually but won’t really go over 2500-3000 RPM the entire time unless I floor it but when I floor it something sounds like it’s gonna blow up. I’d really appreciate any advice, I don’t mind doing the work and don’t have the money for a shop anyways, I just need direction on where to look/what to do. Thanks in advance for all help and thanks for letting me join!
 

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That’s a lot of guessing
What did you find that was binding up on your first attempt?
What type of oil and how much did you put in?
Did you turn the engine over for a while with the starter without the plugs in to prime the new oil pump?
What type of diagnostic tools do you have?
And why did you pull the head in the first place? Out of grins, How many miles on the engine?
Please help me understand “fired up loud like a 90s truck”. What did you mean by that?

what did you do to the intake manifold and throttle body?
And what are the current codes? What were the codes before you started.
 

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Discussion Starter · #3 ·
Thank you for responding, and so first things first the first attempt at rotating engine by hand it went around the first time, then stopped as I tried to go around again, doing so very lightly as to try to not damage anything. And the second time it went around more than 10 times so I had figured that was good, considering the repair manual said go around twice to make sure. The oil I put in was STP high mileage, put in basically the whole jug, and when I checked it a few mins later it was perfect level, right under the max line. And when I attempted to start I had forgotten to plug my fuel pump relay back in so it went a few cranks without starting, hoping that primed the oil pump enough. I also should say wasn’t ‘brand’ new, came off a car with less than 2k miles on it. Still basically brand new when I put it on. I did put new crank seal in it cause that came with the timing cover gasket. As far as tools and diagnostic tools, I’m pretty lucky to have a pretty decent setup for just starting out, got a multimeter, good quality test light that does 6-48V, and have an INNOVA 5160 RS scanner. The thing that sucks here is I’m not getting any codes for what is currently happening. As for miles, it had 165k when I got it, I drove it to 178k and the timing chain skipped and destroyed that engine. Didn’t know what timing chain slap was back then 🤦🏻‍♂️ But thankfully was still just barely in warranty so they threw the current engine in it (that was at 175k when put in, and is now at around 182k - btw it’s out of warranty now). I pulled the head just because I needed to replace the head gasket, cause I was constantly loosing coolant and found out why, the coolant hole from the water pump was split right to cylinder 1. But fixed that, and as I said replaced ALL coolant system parts except the heater core itself (my heat/AC is ironically working just fine). I also replaced the valve seals while I had the head off, cause they were almost all shot, and I’m glad I pulled my valves cause all my exhaust valves were pitted and cracked along the faces, so all new intake and exhaust valves and keepers up top for them as well (and as I said I did clean up the bores and lap the new valves in till they all had a solid line around the faces). So by fired up like a 90s truck I mean the car used to start, fire up, and go right down to normal revs and idle pretty smoothly. Now what is happening is I turn the key, it cranks 2-3 times sounding like it’s gonna explode, then roars to life barely and stutters all the way down to normal revs, then drops slowly to lower than normal revs (500-600-my car usually ran good at 750-850 idle) and then whenever I try to accelerate it stumbles and seems like it is fighting me, like I’ll hold the pedal down and the RPMs will go up a little then immediately drop back to where it was originally. Another thing I should mention, the spark plugs in it before were copper NGK spark plugs, but in the manual it said it required iridium so I changed them to iridium plugs, don’t think that should be causing this if anything should help it run better I’d think, but just giving that info. And as far as mods, NADA. Zip. Literally only has a non-stock Sony megabass radio (came with it), EVERYTHING else is stock. Haven’t had any money to put into mods yet, been putting it all into parts and shop visits just to keep it alive. There were no codes before I started. After the first time trying to start a few times and it didn’t, I scanned, got P0230 fuel pump circuit, that reminded me about the relay, I replaced that and then it started up really roughly. Gave me a P0016 code cam sensor position not plausible, so I switched the cam sensor back to the old one and that went away, didn’t even clear it on my scanner. I’ve re scanned multiple times after driving I’ve taken it on the freeway and it does get it to 60 MPH (albeit slugging and stumbling the whole way up) but it will get there. So this is where I’m at, I’m thinking maybe I wiped a chunk of dirt or carbon into the fuel injectors or maybe the intake airbox resonator (the one under the right headlight) is misaligned. Do you happen to know if that thing is supposed to be connected some specific way? It literally just kind of went in the hole, and didn’t seem secured any way other than the screw holding it to the car itself, so I was wondering if it’s a vacuum system how does it vacuum if it’s not fully connected? There is a little piece of foam on the top of it, is that supposed to plug the gap between it and the upper airbox? Thanks again for taking the time, sorry I am long winded just like to make sure I get all the info out there to best give you an idea.
 

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Discussion Starter · #4 ·
Sorry, didn’t elaborate on the first time attempting to rotate by hand, I think it was the exhaust cam skipped a tooth when I went around the first time, cause I didn’t see/ hear any valves touching. And I still had intake manifold off so I didn’t see any damage to anything. I’m not entirely sure, I just know it didn’t go around more than once the first time I did the timing, and when I re-did it it went around and around multiple times so I had figured that was good. Both times all the marks were lined up with the sprockets so I’m not 100% sure why it stopped the first time, but I redid it just to be safe. Also, I do not have a compression gauge, but I’d assume since it was running decent before I started this stuff that the compression should be fine. I also have a fuel pressure gauge, but not 100% sure how to decipher it, I just used it to depressurize the system when I took the fuel rail off to get the head off.
 

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Discussion Starter · #5 ·
An update, I started messing with the live data on the scanner to try to narrow this down, and noticed my LTFT was pretty high, 7-as high as 13, then when I’d accelerate it would go down a little by little to almost 0 then when I’d let off immediately jump back to 7.. so I reset them by unplugging the battery for a half hour, turned the key with battery unplugged and key stuck in ignition to drain any residual power, and then rebolted battery on and started up and it started a little smoother. I’m not sure if this means I’m going the right direction, or if it was just a lucky start. I’m going to try a few more things in the morning, and I’ll be back for updates.
 

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Seems interesting. But what did you do to the intake manifold and throttle body?
This is important to one of your stated problem

and your scanner should be able to clear all of the engine codes without disconnecting the battery.

Now you might be able to do a cylinder balance test with your scanner.
During this test, the scanner will tell the ECM to shut off fuel to one injector and monitor the rpm drop. Then it will replete for the other 3 cylinders and give a report on the cylinder power balance.
This can also show a weak/ plugged injector or suspect cylinder.
 

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Discussion Starter · #7 ·
I can do that cylinder balance test, my scanner has that I just didn’t know how to do it so ok, I will try that. And weirdly enough the only thing I did to the intake manifold and TB was cleaned the TB (motor/sensor side up so nothing dripped in sensor) and cleaned a little oil out of the intake manifold that I saw when pulling it apart. Otherwise, just replaced it’s gaskets. Didn’t change/modify it in any way, it is still stock. The one thing I’m curious about with intake is if there is some specific way the under headlight resonator is supposed to attach to the airbox? Like is it supposed to be sealed where it connects to the upper one? Cause mine has a little piece of half ripped up foam up there, but I don’t remember if it was fully attached when I removed it, I don’t remember it being hard to remove. Attached a pic to show my engine bay, that top part of air manifold the one on top of throttle body still off and plugs & coils still off, but I figured that was a better view. Anything you want to see, anything else to try? I’m going to do the power balance test and see what that tells me.
Hood Motor vehicle Car Automotive design Automotive exterior
 

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Discussion Starter · #8 ·
Ok, did the power balance test, idk if I did it right but I didn’t get any report, I just had the ability to turn each injector on and off and then I watched the RPMs. Each one acted pretty uniform, it was idling around 800-850, then shut one off it would drop to 760-810, turn it back on it went right back past 800. So I’m not sure what this means, but that’s the info I got.
 

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The tip of the air inlet does not matter, after all there is a hole on the end of it, the foam just helps keep water out.
Timing chain tensioner is not single use, you just had to reset it.
Did you activate the new tensioner before rotating the engine or trying to start the engine? You have to push/hit the guide to release the locking mechanism on the tensioner. If not the chain would not have any tension on it and could have jumped.
If the engine bound up when trying to turn it over the first time, sounds like you had it mistimed. Leading me to think it may still be mistimed but only off one tooth and still running, I'm not sure if that would cause interference with engine parts or not, so only a guess.
If it is in time, a clogged or broken cat can cause power issues.
There are other things it can be, especially with all the work done and parts replaced.
 

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Discussion Starter · #11 ·
The tip of the air inlet does not matter, after all there is a hole on the end of it, the foam just helps keep water out.
Timing chain tensioner is not single use, you just had to reset it.
Did you activate the new tensioner before rotating the engine or trying to start the engine? You have to push/hit the guide to release the locking mechanism on the tensioner. If not the chain would not have any tension on it and could have jumped.
If the engine bound up when trying to turn it over the first time, sounds like you had it mistimed. Leading me to think it may still be mistimed but only off one tooth and still running, I'm not sure if that would cause interference with engine parts or not, so only a guess.
If it is in time, a clogged or broken cat can cause power issues.
There are other things it can be, especially with all the work done and parts replaced.
Thank you for your help, and so yes I did hit the tensioner with a long screwdriver put it right on the tensioner tip (over the chain and guide from inside of engine from top) and popped it with a hammer, and when i checked it the chain wouldn’t budge. So I figured it was done, but I guess I can’t say 100% for sure. The one thing I did that I’m curious if I wasn’t supposed to do was I put a very thin layer of thread sealer tape on the threads of tensioner (thinking to stop any leaking oil) but I haven’t seen anyone else do it so I’m wondering if that would cause any issues. And yea I’ve seen things now on how to reset the newer tensioners, but I didn’t know at the time and the one that came in my timing kit came with a paper that literally said one time use, could not be reset. Idk if that’s just for that specific one, or just planned obsolescence at its finest. But either way, I would think if it was mis timed it would throw a code, no? I’m not sure I’m really shooting in the dark here at this point. And when I used my scanner it said everything passed OBD2 wise except the EVAP yet, but that’s cause I can’t meet the conditions for the test. So what it’s doing now is just literally starting up rough, then goes down to idling somewhat normally, it will rev up to 2500 RPM in 1st & 2nd (0-20-40MPH) but once it hits 3rd gear/40MPH, it REFUSES to go over 2000RPM, it will start at 1k-1500RPM then while revving slowly accelerate to 2kRPM but then immediately drop back to 1kRPM and do that over and over, and if it has extra load (going uphill) it strains even more. It does seem like either air, fuel, or cat to me but I’m just not sure what to test from there. I’d think tho that if the CAT and FUEL OBD2 tests passed and my oxygen sensors were acting normally during live data that the cat and fuel systems are working, maybe not at full efficiency but enough to pass the test… I’m not sure tho, that’s why any advice and help is welcome. Thank you again. If you got any extra ideas shoot cause I’m grasping at anything at this point I really don’t want to take the damn timing apart again unless I’m FOR SURE that’s the issue.
 

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There is a good chance one of your cams are off by 1 tooth. Also, you should be aware of throttle position relearn, but it looks as if you’ve passed it since your idling at 600-800 rpm.

at this point, I would not worry about long term fuel trim until you drive it a bit and get the system running.
With the cylinder balance, we see the injectors and coils/plugs work at low speed…good.

not happy you turned the engine over and it locked up. This can very easily bend a valve. It it was an exhaust valve, less prone to pop up through the intake, making it more difficult to hear. A COMPRESSION test would tell it all BEFORE I would pull off the front of the engine to check the cam timing.
Now if your getting 25-35PSI fuel pressure, your good to go there, and we know the spark is working….the only thing left is internal timing or massive intake leak….with no error codes, that pretty much rules out intake leak.

still leaning on missed timing or poor compression (bent valve)
 
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