99 TA suddenly runs crappy...bad gas??
07-27-2009, 01:22 PM
#1
99 TA suddenly runs crappy...bad gas?? So i've been breaking in my new clutch and my car has been driving perfectly for the first couple hundred miles on it. Last friday night it didn't start immediately when i turned the key and when I drove it the next day it took two turns to start and partial throttle acceleration was "choppy" and it felt like it was hesitating. It idles at 500 rpms and sometimes it dies if i don't keep the revs up. I bought gas at a citgo several towns over ($10 worth.. so about 4 gal) the day it didn't start immediately. The next day when it started driving really bad, I bought $20 of gas from a different citgo. I put in some dry gas and added about 5 gallons of sunoco gas and replaced the fuel filter since then. Its still acting the same.... what should I do???
07-27-2009, 02:03 PM
#2
Get a scan and see if the 02 sensors are switching properly. Gotta use a real OBDII scanner like the dealerships use though, the little orange won't show you anything but a code reference number.
And no, you will not get an SES light when they are failing, only when they actually fail.
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And no, you will not get an SES light when they are failing, only when they actually fail.
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07-27-2009, 06:12 PM
#3
i just got back from autozone. the car barely got there, i thought i was gonna have it towed. the codes its throwing are: PO171 and PO174. the description says: suspect fuel pressure or MAF sensor, O2 sensor defective, ignition misfire-repair or fuel injector problem.
I'm pretty sure my o2's are fine cuz i've seen them recently and there were no codes for them. I think the fuel pressure is ok because i recently put in a walbro 255 lph pump with a new sock and all high pressure fuel lines. I also put in new plugs this summer and the wires are still good. I also had my injectors pulled this summer and they are fine too. So i decided to clean the MAF cuz it was pretty dirty and it improved things slightly (as in i was able to get home) but its still running shitty when you give it gas. should i just replace the MAF?? is the MAF something that gets gradually worse or does it fail immediately?
I'm pretty sure my o2's are fine cuz i've seen them recently and there were no codes for them. I think the fuel pressure is ok because i recently put in a walbro 255 lph pump with a new sock and all high pressure fuel lines. I also put in new plugs this summer and the wires are still good. I also had my injectors pulled this summer and they are fine too. So i decided to clean the MAF cuz it was pretty dirty and it improved things slightly (as in i was able to get home) but its still running shitty when you give it gas. should i just replace the MAF?? is the MAF something that gets gradually worse or does it fail immediately?
07-27-2009, 06:48 PM
#4
You did not listen young grasshopper.
Those scanners are only good for reading codes. You need to see how the 02 sensors are switching in real time while you're sitting there idling.
You can buy a new MAF and put it on, if it doesn't help, return it and get your money back. But after the engine gets warmed up (I have heard 122*F or higher) the MAF does NOTHING anyway, not until you go WOT.
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Those scanners are only good for reading codes. You need to see how the 02 sensors are switching in real time while you're sitting there idling.
You can buy a new MAF and put it on, if it doesn't help, return it and get your money back. But after the engine gets warmed up (I have heard 122*F or higher) the MAF does NOTHING anyway, not until you go WOT.
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07-27-2009, 10:46 PM
#5
I know what you're saying but I wanted to find out what the codes were without paying money to some stealership. Could you please explain what the o2's would have to do with this? I'm pretty sure they arent bad because they're not throwing their own codes and i saw them recently when I removed them from the headers.
07-27-2009, 11:10 PM
#6
I know what you're saying but I wanted to find out what the codes were without paying money to some stealership. Could you please explain what the o2's would have to do with this? I'm pretty sure they arent bad because they're not throwing their own codes and i saw them recently when I removed them from the headers.
Only way to find out is with a real scanner.
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07-29-2009, 10:08 PM
#9
Is this an EGR equipped car? My LT1 ran like that when the EGR became choked up with carbon. Dealership scan revealed "engine misfire- bad tune". Mechanic says maybe new plugs, Optispark (big $) service manual item # 6 or 7 says EGR. I remove then clean it and it cured the problem permanently. Try easy, cheap stuff first.
07-30-2009, 03:25 PM
#12
i just called a dealership and they wanted $100 for it. **** that!
07-30-2009, 03:31 PM
#13
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changing the MAF would have been my last resort. those things usually don't just fail spontaneously unless the sensor appears to be tampered w/ or damaged as they are sensitive. but from the diagnosis that you provided all clues are pointing towards 02 sensors.
edit: try fixing the problem before taking it on a long drive again because the failure to rear A/F ratios at the 02s causes the engine to overheat . just keep an eye on the temp gauge.
edit: try fixing the problem before taking it on a long drive again because the failure to rear A/F ratios at the 02s causes the engine to overheat . just keep an eye on the temp gauge.
07-30-2009, 03:46 PM
#14
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Try spraying out your EGR and MAF with throttle body cleaner. Spray down your throttle body while you're at it. Don't let this stuff get anywhere else. Put rags under the TB or something when you spray it. It'll take off the coating on the harmonic balancer and isn't good for lots of other stuff.
Make sure you've got spark on all of your cylinders and that your wires are good. You can pull your plugs and check them if you want, but don't do that 'til later.
It could be an O2 sensor as well, but if the car does this all the time, hot or cold, then IMO it's less likely. But still possible.
If cleaning the MAF doesn't work, then unplug your MAF and try running the car. If it runs better, you have a bad MAF. If not, then the MAF is most likely good.
Make sure you've got spark on all of your cylinders and that your wires are good. You can pull your plugs and check them if you want, but don't do that 'til later.
It could be an O2 sensor as well, but if the car does this all the time, hot or cold, then IMO it's less likely. But still possible.
If cleaning the MAF doesn't work, then unplug your MAF and try running the car. If it runs better, you have a bad MAF. If not, then the MAF is most likely good.
07-30-2009, 05:43 PM
#15
Try spraying out your EGR and MAF with throttle body cleaner. Spray down your throttle body while you're at it. Don't let this stuff get anywhere else. Put rags under the TB or something when you spray it. It'll take off the coating on the harmonic balancer and isn't good for lots of other stuff.
Make sure you've got spark on all of your cylinders and that your wires are good. You can pull your plugs and check them if you want, but don't do that 'til later.
It could be an O2 sensor as well, but if the car does this all the time, hot or cold, then IMO it's less likely. But still possible.
If cleaning the MAF doesn't work, then unplug your MAF and try running the car. If it runs better, you have a bad MAF. If not, then the MAF is most likely good.
Make sure you've got spark on all of your cylinders and that your wires are good. You can pull your plugs and check them if you want, but don't do that 'til later.
It could be an O2 sensor as well, but if the car does this all the time, hot or cold, then IMO it's less likely. But still possible.
If cleaning the MAF doesn't work, then unplug your MAF and try running the car. If it runs better, you have a bad MAF. If not, then the MAF is most likely good.
08-01-2009, 12:17 PM
#19
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Start cheap and then work your way up. Check the plugs for cracks and check the wires. My car did the same thing your saying when my O2's went bad. I replaced them and it's been running fine ever since.
08-01-2009, 01:28 PM
#20
I got the same dam code, been try to fix last couple month, change out fuel filter, change out injector 0-ring, fuel pressusre regulator, the dam code still their. So i gave up. after I making the thread about " post your LT1 eninge " some one point it out, that my MAF is backward !!!!, so I clean it and install the right way, my check engine light is gone for the last 5 day lol. So clean your MAF and make sure the arrow on the maf <---- point like that.
