Not sure if this makes any sense... My Cav had been running a little strange... It seemed like it was missing above 4500 RPM. Plus, occasionally, under light load, I could hear it "pinging" a little. So, I decided that I would try running Shell 91 Octane. After a few starts, It seems like the missing problem has gone away, and it doesn't seem to be pinging anymore. But, as I entered the on-ramp today, the check engine light came on. It has been on for several other starts and has stayed on. I have not had a chance to scan it with my scanner. I moved recently, and it is in storage.
Has any one else seen anything like this after running higher octane fuel? I am hoping that it is just an O2 sensor issue.
This is for my 2005 Cav. I have no mods on this car. It has 97,000 miles on it.
My GTP has two tables for high and low octane fuels. Is that the same for the Ecotec PCM's?
treb
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it sounds to me like an o2 problem. when my front o2 went bad my car did the same thing. sometimes higher octane gas isn't unleaded which can clog up o2 sensors.
BP wrote:it sounds to me like an o2 problem. when my front o2 went bad my car did the same thing. sometimes higher octane gas isn't unleaded which can clog up o2 sensors.
All gas sold in US consumer gas stations (anything from a pump on the street) is required to be unleaded. Unless you picked up some racing gas at a specialty shop or the track (110+ octane), then you're not using leaded gas.
Quote:
Has any one else seen anything like this after running higher octane fuel? I am hoping that it is just an O2 sensor issue.
This is for my 2005 Cav. I have no mods on this car. It has 97,000 miles on it.
My GTP has two tables for high and low octane fuels. Is that the same for the Ecotec PCM's?
The Eco has this as well, but it doesn't work on octane, thats a misunderstanding. Basically your car will learn from the low table to the high table based solely on knock. More knock means less advance, less knock means more advance. The car does not have an octane sensor. I'm willing to bet that the code that comes up says something about a purge problem, which indicates a loose gas cap most of the time.
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You know, I have heared about that gas cap issue over on the ClubGP forum before. I have left my gas cap completely off of the GTP and that code has never come up. It will be interesting to see if that makes any difference on the Cav. Funny thing is... It has a locking gas cap, and I don't have a key, so I try not to tightnen it too tight. I know, I know... It clicks. Maybe overtightening is all in my mind.
Might be awhile before I can get my tuner out of storage. Maybe I'll go after the codes the old fashion way, but in the meantime, I'll get a new gas cap.
Thanks for the advice guys!
treb
Need to find me a Quote...
i dont understand why you think the 91 octane had anything to do with it since you said the car was "missing" before you put in the 91.
Missing... Well, it's hard to explain it... It just did not seem to accelerate without a little hesitation above 4500... Like it was missing??? (Maybe wrong terminology.) The car sat in a lot for a while, and I had not put a full tank of gas into it yet, so I figured it was the cheapest route to go towards any type of trouble-shooting. It had a quarter tank of gas in it when I bought it, and I only put a couple of dollars of 87 Octane fuel into it. I figured that it needed some fuel that had an additive that would clean the carbon out a bit. Who knows, maybe there was some water in the tank??? BTW... The Check Engine light has gone out. I did not do a reset of the codes. As a matter of fact, I have not even looked to see what the code was. I did "tighten" the fuel cap a little more. I'll go back to using 87 Octane when I use up the Premium. I can't afford to run that premium gas in the car all the time.
Thanks,
treb
Need to find me a Quote...
You need to check the code without all this talk is useless.
FU Tuning
^Yep
Probably a misfire code or Emissions.
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My brothers car did that when he had it tuned but it was because he had a spike in his fuel map. Fixed the spike and it evened out.
-Chris
treborjm wrote:You know, I have heared about that gas cap issue over on the ClubGP forum before. I have left my gas cap completely off of the GTP and that code has never come up. It will be interesting to see if that makes any difference on the Cav. Funny thing is... It has a locking gas cap, and I don't have a key, so I try not to tightnen it too tight. I know, I know... It clicks. Maybe overtightening is all in my mind.
I would have to say your problem lies in here...its not that the lights on because you put different gas in it....it is on because you didnt tighten the cap when you were done...
The reason you might not have seen it is because perhaps you weren't driving the car in a similar fashion to the requirements for the self test of the evap system to initialize. Below is the drive cycle for your cars, you could try driving it, to see if the light will go off, stay on....whatever. I would really recomend you get the code read to see what it really is....
Performing a GM OBD-II Driving cycle:
Cold Start In order to be classified as a cold start the engine coolant temperature must be below 122°F (50°C) and within 11°F (6°C) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
Idle The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.
Accelerate Turn off the air conditioner and all the other loads and apply half throttle until 55mph (88km/hr) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
Hold Steady Speed Hold a steady speed of 55mph (88km/hr) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
Decelerate Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 20 mph (32km/hr). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
Accelerate Accelerate at 3/4 throttle until 55-60mph (88-96 km/hr). This will perform the same diagnostics as in step 3.
Hold Steady Speed Hold a steady speed of 55mph (88km/hr) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
Decelerate This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.
Locking gas caps are known to having caused problems with the EVAP. They dont seal right. I work at a shop and so many people switch to the locking gas caps and they set codes.
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