Just running weird
Thread Starter
Teching In
Joined: Oct 2009
Posts: 29
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From: Whittier CA
Just running weird Hey guys I have an 01 SS with almost 80k miles and here is the deal. Few months ago it started running a little rough at idle then check engine light came on ended up being an EGR valve. I replaced both and ran great for a few weeks. Started running a little rough again no check engine light or codes so I changed all the plugs with NGK iridium's again ran great for a few weeks. Next I install the SLP cold air intake and I cleaned the throttle body and MAS. It ran excellent, I was actually getting 22mpg with 91 octane around town. Now its running rough again at idle and its down to 16mpg. The only thing I can think of is get the PCM tuned or get a tuner. Any help would be great.
Unplug the MAF while its idling, if nothing changes while it crapped out without throwin a code, it does happen sometimes. I have been chasing a issue on mine for 2 weeks now & thinking this is my problem as well. Testing the theory today by swapping MAF's. I unplugged mine last night & no change to idle, it should have stubmled if it was working properly.
Thread Starter
Teching In
Joined: Oct 2009
Posts: 29
Likes: 0
From: Whittier CA
It wouldn't surprise me if the MAS is bad, the previous owner of the car had it in backwards. I'll try that out when I get back in town. I was also thinking of running sea foam through my car, the guy I bought the car from didn't put the best gas in it.
Last edited by p8ntballkid090; Apr 21, 2011 at 09:59 PM. Reason: i cant spell
Unplugging the MAF AFTER the engine is at operating temp won't tell you anything. The way to check the MAF is to unplug it when the engine is dead cold and start it up......if it acts totally wacked then the MAF is good. The MAF is only "in play" when the engine is cold and when you go WOT.
You guys both may have a failing 02 sensor(s). They can fail for months without giving a code or SES light. Normal symptoms are ...loss of MPG because it causes the engine to run very rich, down on power and rough running.
Need a scan with a OBDII scanner while the engine is idling to see if they are failing.
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You guys both may have a failing 02 sensor(s). They can fail for months without giving a code or SES light. Normal symptoms are ...loss of MPG because it causes the engine to run very rich, down on power and rough running.
Need a scan with a OBDII scanner while the engine is idling to see if they are failing.
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Really, cause mine will do the same thing weather its warm or cold if you unplug it while its running & I have brand new 13111 O2 sensors. If its plugged in it wants to die in either situation & runs like crap. With it unplugged its got ***** & runs smooth with a steady idle.
Really, cause mine will do the same thing weather its warm or cold if you unplug it while its running & I have brand new 13111 O2 sensors. If its plugged in it wants to die in either situation & runs like crap. With it unplugged its got ***** & runs smooth with a steady idle.
Well, I was told by a tuner that after the coolant temp reaches 122*F the MAF is turned off completely by the PCM.....and it will not come back into play until you go WOT.
So if you are up to operating temp.....unplugging the MAF or leaving it plugged in will have zero effect AT IDLE or anything except WOT.
If your engine is dead cold and you start it while the MAF is unplugged......it should have a very different effect than if you leave it plugged at cold start. The 02 sensors don't handle fueling when the engine is cold.
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Thread Starter
Teching In
Joined: Oct 2009
Posts: 29
Likes: 0
From: Whittier CA
Is there a way to test the MAS and O2 sensors to see if the are going bad, like test them with a volt meter? MAS and O2 sensors aren't cheap and Id like to only replace wants going bad but if its killing MPGs and making my car run bad, my suspension upgrade will just have to wait.
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Is there a way to test the MAS and O2 sensors to see if the are going bad, like test them with a volt meter? MAS and O2 sensors aren't cheap and Id like to only replace wants going bad but if its killing MPGs and making my car run bad, my suspension upgrade will just have to wait.
I'm sure there's a way to see if the MAF is getting power and you can also check to see if the PCM is sending it a signal. You'll have to ask the tuners in the DIAGNOSTICS section for that info.
But you can check the MAF by unplugging it when the engine is COLD. If it does not idle properly or how it always does, you have a MAF problem or something electrical with it is bad.
Or....go to a parts store and buy a new stock MAF, put it on and see if your problems go away. If they don't, clean it real good and take it back. Just tell them you cannot get that MAF to fit because someone modded your piping sizes and you NEVER got it installed at all. It works, they MUST take it back. I've done that with TPS, IAC, MAF, IAT and other parts....works every time.
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Verdad Gallardo Well, I was told by a tuner that after the coolant temp reaches 122*F the MAF is turned off completely by the PCM.....and it will not come back into play until you go WOT.
So if you are up to operating temp.....unplugging the MAF or leaving it plugged in will have zero effect AT IDLE or anything except WOT.
If your engine is dead cold and you start it while the MAF is unplugged......it should have a very different effect than if you leave it plugged at cold start. The 02 sensors don't handle fueling when the engine is cold.
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So if you are up to operating temp.....unplugging the MAF or leaving it plugged in will have zero effect AT IDLE or anything except WOT.
If your engine is dead cold and you start it while the MAF is unplugged......it should have a very different effect than if you leave it plugged at cold start. The 02 sensors don't handle fueling when the engine is cold.
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And again, it doesnt matter if my car is up to temp or not. If the MAF is plugged in its running like crap & wants to die. Doesnt matter if you start it cold or plug it in while its at operating temp idling. If there is a MAF plugged in it doesnt want to run. I have tried 3 different MAF's now & same exact result.
This Friday my car goes in for a SD tune & I'm done with the stupid MAF forever at that point. Causes more problem once it starts giving issues than its worth.
