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Hey guys,
Coming back home today, my CEL came on. Autozone did a scan and it came up as P1175 (fuel injectors, upstream O2 sensor...My mileage is pretty dismal (18 city 21 highway) It also stumbles on acceleration. It idles fine and upon start up it fires right up. I've tried injector cleaners and even sea foam to try to fix the mileage and acceleration with no luck. The symptoms have been going on for a while, but it's the first time the CEL light came on. Where would be a good place to start? I have a fuel pressure gauge, but never used it. Where does this thing get hooked up, and what pressure should I be looking at? Forgot to add, plugs and fuel filter were changed this past fall. It's a 2006 Cobalt 2.4.
Thanks,
Jason
Last edited by WICobaltSS; 01-18-2017 at 02:23 PM.
I can't seem to P1175 as a typical DTC for cobalts. I see P1174
There are few parts I would look into
#1 Replace both 02 sensors, especially if they have lots of miles on them. 100k is a pretty good limit for them. Only us ACDelco parts
#2 Your catalytic converter could be clogged
#3 One or more of your injectors has failed. You should see misfires on that cylinder or you may be able to view the exhaust manifold with a heat gun to see what's not firing.
It's not too dificult to replace the 02 sensors. The injectors should be replaced as a set of 4 if possible.
Make sure you are telling us the right code.
Here are your replacement injectors. It takes roughly an hour for install on these. https://goo.gl/TDG0yi
I can't figure out which 02 sensor to get still looking But only buy ACdelco 02 sensors. Get from the dealer if you have to.
Thanks for your help. What I'll probably do first is check for vacuum leaks. I have a pressure gauge that I can hook up to the upstream O2 port, but I need to fabricate a connector, in order to check for exhaust restriction. If that checks good, I'll probably change out the O2 sensors and then injectors. I read somewhere that installing new injectors requires a re-flash? I also read there was a TSB on certain 2.4 models were installed with faulty injectors?
I guess with 120,000 miles on the odometer, this was due. I bought the car in August of 2015 and it was getting damn near 30 MPG highway.
#08-06-04-001B: Check Engine Light On, DTCs P0171, P0300, P1174 Set (Perform Injector Test, Replace Injectors and Reprogram ECM, If Necessary) - (Apr 21, 2009)
Subject: Check Engine Light On, DTCs P0171, P0300, P1174 Set (Perform Injector Test, Replace Injectors and Reprogram ECM, if Necessary)
Models: 2006-2007 Chevrolet Cobalt, HHR
2006 Pontiac Pursuit (Canada)
2007 Pontiac G5, G6
2006-2007 Saturn ION
with 2.4L Engine (VIN B, P - RPO LE5)
Condition
Some customers may comment on the check engine light being illuminated.
A scan tool may reveal DTC P0171, P0300 or P1174 set as current or in history.
Cause
This condition may be caused by the plugging of one or more of the injector director plate orifices which results in a lean condition.
Correction
Important: This condition cannot be corrected by cleaning the injector(s).
Important: For Chevrolet and Pontiac vehicles, reprogramming must be done using the remote method.
For Saturn vehicles, reprogramming must be done using the pass-through method.
Follow the published diagnostics in SI for any DTC recorded.
Perform an injector balance test using the Active Fuel Injector Tester (AFIT), CH-47976. Refer to the Fuel Injector Diagnosis (w/CH47976) procedure in SI. If any injector is identified as having a lean condition, replace all four injectors with the revised injectors. After installing the new injectors, reprogram the ECM with updated calibration files using the TIS2WEB Service Programming System (SPS) application. There are two calibration part numbers that are valid for "Engine Operation". Select the part number with the description that reads for vehicles with second design injector. The injector has a dark blue overmold color for this repair.
Important: The fuel injectors must be replaced and the new calibration files must be installed to ensure a complete repair. Failure to perform both repairs will result in the customer returning with the same condition.
If a vehicle returns with the same condition after having this repair performed, the technician should first verify that the complete repair was performed before continuing with SI diagnostics.
Thanks for the info Umrdyldo!
Well today I got the upstream O2 sensor off and hooked a pressure gauge to the port. didn't find any restriction as the gauge stayed at zero. I'll likely replace the O2 sensors as the upstream looked pretty worn. Plus at 120,000 miles, probably wouldn't hurt. I also pulled the coil packs and plugs and noticed a pool of oil in the first two ports. I'm guessing (actually hoping) a valve cover leak? So I pulled the cover and took some pics. Even with the oil in the ports, the coils seemed to run fine as there was no rough idle. No coolant visible so I'm just hoping I need to change the gaskets to cure the oil. As for the P1174, first O2 sensors then injectors.
Any thoughts?
It depends where the oil was. If it was on top of the plug it is likely the gasket on the spark plug or around the valve cover leaking down into the cylinder. I have this problem on one cylinder.
If the oil was on the tip of the plug you have a different issue. Could be bad cylinder or blow by from a failed PCV.
I have never pulled my valve cover but yours looks awfully gross. Looks like baked on oil which screams infrequent oil changes..
Oil was definitely coming form the top. One hole had a little, the one next to it had a bit. Ordered a new gasket. As for the oil changes, I would guess one or both the owners before me are to blame. I'm pretty religious when it comes to oil changes.
Thanks for your help
So I replaced the 02 sensors, and had the injectors cleaned, but still getting about 19-20 MPG. I removed the K&N Typhoon SRI and replaced it with the stock air box. I also sprayed around any possible places to check for vacuum leaks. I guess my next plan of action is to do a fuel pressure test and vacuum test. Is there anything I'm missing? The car seems to run fine, but the mileage is where I'm at a loss.
What is the ideal fuel pressure, and where is the best spot to do a vacuum test? Last time I hooked up a T fitting between the intake and the evap solenoid, which caused the gauge to jump around. Is the solenoid valve causing this? I never dealt with this type of thing, so any help in troubleshooting is GREATLY appreciated.
Thanks.
One thing I forgot to add. Have you looked at your intake valves yet?
If they haven't cleaned then you could get several miles per gallon more. I have cleaned mine twice and consistently get 2-3 more mpg every couple years from cleaning.
I would assume because you are running rich that an air leak or vacuum leak is not likely.
Hi Umrdyldo,
Thanks for the reply. Since I've owned the car (about a year and a half now) I have not seen the intake valves. How do you clean yours? I've seen several you tube videos of guys cleaning their engines with the seafoam through the vacuum technique, but never done it myself.
Hi Umrdyldo,
Thanks for the reply. Since I've owned the car (about a year and a half now) I have not seen the intake valves. How do you clean yours? I've seen several you tube videos of guys cleaning their engines with the seafoam through the vacuum technique, but never done it myself.
Firstly, Seafoam doesn't work. The intake valve crud is just too hard to dissolve quickly.
At 120k miles, if the valves have never been cleaned, then they are most likely really bad. You should feel misfires in your seat during cold start up.
I personally switch to using GM Top End Cleaner and soaking the valves for about and hour and then breaking the gunk free with a pick or screwdriver. It will seem like a daughting job the first time you do it, but if you take your time and maybe get a friend to help it's really not that bad. My first time took 8-10 hrs. Next time it took me 4-5 hrs.
The other nice thing about cleaning your intake valves is that it allows you to replace the PCV valve that is located inside the intake manifold.
Firstly, Seafoam doesn't work. The intake valve crud is just too hard to dissolve quickly.
At 120k miles, if the valves have never been cleaned, then they are most likely really bad. You should feel misfires in your seat during cold start up.
I personally switch to using GM Top End Cleaner and soaking the valves for about and hour and then breaking the gunk free with a pick or screwdriver. It will seem like a daughting job the first time you do it, but if you take your time and maybe get a friend to help it's really not that bad. My first time took 8-10 hrs. Next time it took me 4-5 hrs.
The other nice thing about cleaning your intake valves is that it allows you to replace the PCV valve that is located inside the intake manifold.
this would be great advice if the OP has an ss turbo, he doesnt though, he has a 2.4l. the lnf valve crud problem is because it has direct injection. valve crud is not a big issue on other cobalts because there is fuel flowing through the ports that keeps the valves fairly clean.
this would be great advice if the OP has an ss turbo, he doesnt though, he has a 2.4l. the lnf valve crud problem is because it has direct injection. valve crud is not a big issue on other cobalts because there is fuel flowing through the ports that keeps the valves fairly clean.
**** I don't remember seeing that in the original post. Sorry OP don't even read my latest posts.
So back to a 2.4 L Running rich.
The original code still points to a bad injector most likely. I didn't see where you said you replaced them.
Lol! No worries. I did change the O2 sensors, and the code hasn't popped up yet. I'll likely change the injectors in the near future. Couldn't hurt. I think a compression/leak down test will be in order. umrdyldo had me thinking about the caked on oil on the valve cover. I take good care of my 'Balt, but who knows about the previous owner.
THanks for your help guys!
Lol! No worries. I did change the O2 sensors, and the code hasn't popped up yet. I'll likely change the injectors in the near future. Couldn't hurt. I think a compression/leak down test will be in order. umrdyldo had me thinking about the caked on oil on the valve cover. I take good care of my 'Balt, but who knows about the previous owner.
THanks for your help guys!
Good, hope the 02 sensor fixed it all. Have seen a lot of posts of them failing after 100k miles.
Well, so far so good. I went to Fondulac yesterday (about an 80 mile round trip) and no light. However, upon arriving home I got out and noticed an odd smell. Looked under the car and there was a pool of tranny fluid underneath! @#!! Turns out that the tranny cooler line sprung a leak. Tranny fluid had bathed the engine. So I limped the car into the garage while feeling the tranny starting to slip. When I went to work later (in my daughters car) I back tracked to see how far the leak had gone. Fortunately it started about 8 blocks away and not Fondulac! I'm only hoping I didn't do any damage to the transmission (it's an automatic) My plans now are to replace the cooler line along with the injectors, and some suspension items. So the 'Balt will be sitting for a while. Dammit.
01-18-2017, 02:09 PM
