Engine Bogging at 4k RPM
06-25-2009, 09:15 PM
#1
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Engine Bogging at 4k RPM Hey folks, I finally got my car back into running trim after a year and a half broken (Deployed to Iraq, so I couldn't fix it. ;.
And now it bogs down at 4k RPM when I go WOT. Though it only seems to do this in first or second gear. Anyone have any ideas? Also, my 'BRAKE' light on my dash is lit up. I went under the car and the e-brake doesn't seem stuck, my fluid levels are fine and the brakes work fine. The only thing is my e-brake handle feels a little loose, any ideas? Thanks in advance.
And now it bogs down at 4k RPM when I go WOT. Though it only seems to do this in first or second gear. Anyone have any ideas? Also, my 'BRAKE' light on my dash is lit up. I went under the car and the e-brake doesn't seem stuck, my fluid levels are fine and the brakes work fine. The only thing is my e-brake handle feels a little loose, any ideas? Thanks in advance. 
06-25-2009, 09:24 PM
#2
Bogging engines at mid to upper rpm's is usually an 02 sensor issue. Could be failing. Get a scan to see if they are switching properly. You will not get an SES light until it fails alot of the time.
It has to be a real OBDII scanner though, like the dealers use. Not just the kind that shows codes.
It has to be a real OBDII scanner though, like the dealers use. Not just the kind that shows codes.
06-26-2009, 01:33 PM
#3
In addition to an O2 problem, you could just have a dirty MAF. I'd try cleaning that first and see if it cures the bogging problem. A $5 can of MAF cleaner (you need special stuff) is a hell of a lot less expensive and time consuming vs. messing with your O2 sensors.
A lot of people have issues with their brake light due to the switch hooked up to the e-brake handle. You may want to check that out and make sure its working correctly.
A lot of people have issues with their brake light due to the switch hooked up to the e-brake handle. You may want to check that out and make sure its working correctly.
06-26-2009, 01:56 PM
#4
In addition to an O2 problem, you could just have a dirty MAF. I'd try cleaning that first and see if it cures the bogging problem. A $5 can of MAF cleaner (you need special stuff) is a hell of a lot less expensive and time consuming vs. messing with your O2 sensors.
A lot of people have issues with their brake light due to the switch hooked up to the e-brake handle. You may want to check that out and make sure its working correctly.
A lot of people have issues with their brake light due to the switch hooked up to the e-brake handle. You may want to check that out and make sure its working correctly.
06-27-2009, 08:34 AM
#5
There are some conditions where the MAF is ignored, but they logic is complex and most of the conditions do not occur under normal driving.
06-27-2009, 10:40 AM
#6
Bogging engines at mid to upper rpm's is usually an 02 sensor issue. Could be failing. Get a scan to see if they are switching properly. You will not get an SES light until it fails alot of the time.
It has to be a real OBDII scanner though, like the dealers use. Not just the kind that shows codes.
It has to be a real OBDII scanner though, like the dealers use. Not just the kind that shows codes.
Definitely sounds like it could be a MAF issue though, they can wreak havoc on driveability and performance if they are dirty or failing.
06-27-2009, 12:02 PM
#7
This is urban myth. The MAF is the best source of information for the PCM with regards to airflow and its used all of the time. (I've seen this written in a few other places and checked the factory service manual to confirm.) I've also had the MAF issue and was plagued by it at all temperatures.
There are some conditions where the MAF is ignored, but they logic is complex and most of the conditions do not occur under normal driving.
There are some conditions where the MAF is ignored, but they logic is complex and most of the conditions do not occur under normal driving.
I unplugged my MAF when the engine was cold. Started it up and it ran rough as hell while idling and warming up. All of a sudden (I'm assuming when it reached a certain temp, I was told it was 122*F)....and BAM...perfect idle. I then drove off and the car ran 100% perfectly. No sputtering, no misfires, no hesitation, no smoke, no loss of power.....it ran perfectly. I did one WOT run and it hesitated and ran rough. As soon I came off the throttle and drove normally it operated 100% perfect again till I got back home.
It proves, without any doubt, regardless of what any literature or tuner says or thinks.......that the MAF is not needed at all after its warm and if you drive in any way except WOT.
And I'm talking a good 1 hour drive all around Orlando....it was operating perfectly with ther MAF unplugged.
There's also one other thing I've learned by accident. All PCM's are not created equal. They do vary in how they operate.
.
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06-28-2009, 05:01 PM
#8
I don't know, I think I did the ultimate test on this one.
I unplugged my MAF when the engine was cold. Started it up and it ran rough as hell while idling and warming up. All of a sudden (I'm assuming when it reached a certain temp, I was told it was 122*F)....and BAM...perfect idle. I then drove off and the car ran 100% perfectly. No sputtering, no misfires, no hesitation, no smoke, no loss of power.....it ran perfectly. I did one WOT run and it hesitated and ran rough. As soon I came off the throttle and drove normally it operated 100% perfect again till I got back home.
It proves, without any doubt, regardless of what any literature or tuner says or thinks.......that the MAF is not needed at all after its warm and if you drive in any way except WOT.
And I'm talking a good 1 hour drive all around Orlando....it was operating perfectly with ther MAF unplugged.
There's also one other thing I've learned by accident. All PCM's are not created equal. They do vary in how they operate.
.
I unplugged my MAF when the engine was cold. Started it up and it ran rough as hell while idling and warming up. All of a sudden (I'm assuming when it reached a certain temp, I was told it was 122*F)....and BAM...perfect idle. I then drove off and the car ran 100% perfectly. No sputtering, no misfires, no hesitation, no smoke, no loss of power.....it ran perfectly. I did one WOT run and it hesitated and ran rough. As soon I came off the throttle and drove normally it operated 100% perfect again till I got back home.
It proves, without any doubt, regardless of what any literature or tuner says or thinks.......that the MAF is not needed at all after its warm and if you drive in any way except WOT.
And I'm talking a good 1 hour drive all around Orlando....it was operating perfectly with ther MAF unplugged.
There's also one other thing I've learned by accident. All PCM's are not created equal. They do vary in how they operate.
.
I've unplugged plenty of MAF's in diagnosis of an issue (MAF/Speed density systems only) and had the car run fine as well. However, the difference between having the MAF plugged in is "running fine" vs. running optimally. When you unplug the MAF, the PCM reverts to speed density and predetermined airflow tables. Its not that it doesn't need the MAF, its just that it can use other methods to determine airflow into the engine.
A good example if when Ford went from speed density to MAF on 5.0 Mustangs. It was a huge performance gain once you started modding, because simple bolt ons like intakes, exhausts, and throttle bodies resulted in big gains, whereas speed density resulted in little or no power gain because the PCM had no way to compensate for the incrased airflow, all it knew was the manifold pressure.
MAF allows for much more precise engine control in terms of power, emissions, and fuel economy. The PCM uses the MAF at all times, which is why it can wreak havoc on your driveability if it's starting toi report irrational values. Cars have been left stranded due to failed MAF sensors, especially on vehicles which use the MAF as the primary determinant for airflow as opposed to having a combination of MAF and MAP sensors, like our cars do.
06-28-2009, 06:11 PM
#9
I don't know, I think I did the ultimate test on this one.
I unplugged my MAF when the engine was cold. Started it up and it ran rough as hell while idling and warming up. All of a sudden (I'm assuming when it reached a certain temp, I was told it was 122*F)....and BAM...perfect idle. I then drove off and the car ran 100% perfectly. No sputtering, no misfires, no hesitation, no smoke, no loss of power.....it ran perfectly. I did one WOT run and it hesitated and ran rough. As soon I came off the throttle and drove normally it operated 100% perfect again till I got back home.
It proves, without any doubt, regardless of what any literature or tuner says or thinks.......that the MAF is not needed at all after its warm and if you drive in any way except WOT.
And I'm talking a good 1 hour drive all around Orlando....it was operating perfectly with ther MAF unplugged.
There's also one other thing I've learned by accident. All PCM's are not created equal. They do vary in how they operate.
.
I unplugged my MAF when the engine was cold. Started it up and it ran rough as hell while idling and warming up. All of a sudden (I'm assuming when it reached a certain temp, I was told it was 122*F)....and BAM...perfect idle. I then drove off and the car ran 100% perfectly. No sputtering, no misfires, no hesitation, no smoke, no loss of power.....it ran perfectly. I did one WOT run and it hesitated and ran rough. As soon I came off the throttle and drove normally it operated 100% perfect again till I got back home.
It proves, without any doubt, regardless of what any literature or tuner says or thinks.......that the MAF is not needed at all after its warm and if you drive in any way except WOT.
And I'm talking a good 1 hour drive all around Orlando....it was operating perfectly with ther MAF unplugged.
There's also one other thing I've learned by accident. All PCM's are not created equal. They do vary in how they operate.
.
The cold performance you saw when you unplugged your MAF was probably due to how EGR was interacting with your system while the PCM was making assumptions in the absence of the MAF.
