Fluctuating RPM below 3000rpm

So i'm having a problem where my RPMs are fluctuating, and also the car lurches when driving in the problem area as well.

 

Even at idle I cant hold my RPMs without them jumping +/- 300rpm

 

 

Just installed, new plugs, injectors, TGV deletes, turbo inlet but to no avail it didnt fix the problems.

 

Tuned with COBB Stage 1

 

No CEL

 

Tried cleaning MAF

 

Cleaned the Crank sensor and Camshaft sensors.

 

Could it be fuel pump??

 

I just spent a lot of money and its not fixed please help

tried unpluggin the MAP sensor and it didnt fix the problems.

 

Also took off the vacuum line for the FPR and it didnt change.

 

When I unplugged the MAP sensor I was still able to get readings on my AP for manifold absolute pressure???

Did you replace the manifold donut gaskets?

Yes I did.

Double-check that all hoses are correctly connected. Also check for cracks and other leaks. Spray brake cleaners on various points where a leak may exist.

 

The coil connectors are also known to lose their tension, which can cause occasional misfires.

 

Clean the throttle body if you haven't done that.

 

And check the MAP sensor and hoses to it as well.

 

Then do a data log, it may provide a lot more information to sift through. O2 sensors, MAF, temperature, manifold pressure, rpm etc.

 

Also check for pending fault codes.

all coil packs were fine when I changed plugs.

 

I cleaned the MAF and throttle body.

 

Am I able to data log with my AP?

Went for a little drive and heres my datalog

 

Should also mention car hits boost very quickly and pulls hard.

datalog10.csv

Front O2 sensor

Front O2 sensor

 

you can tell that just from the datalog??

DAM should be 1 at all times. JmP what are you seeing that screams front o2 sensor.

DAM should be 1 at all times. JmP what are you seeing that screams front o2 sensor.

 

What is DAM?

 

Also noticed the ground straps on the bottom of the engine were broken. ill replace those.

Front O2 failure can result in idle surging and dropping without setting a CEL. It's happened a number of times and it also effects a ton of other different things (obviously) in AFR and again, without any CEL. If you can find someone that has a known good one, change it out and see if it fixes it.

 

I had a bad front O2 that looked fine in all scanner information as well as data logs, and I changed it on a hunch because of STFT bouncing all over the place and that instantly fixed the idle as well as off idle acceleration and smoothness.

 

It's not a 100% fix all but it definitely warrants a look, especially since the lack of CEL upon failure doesn't point directly to it.

Ok well from my understanding on the Cobb Stages is based on mostly a stock setup. The TGV deletes are not stock any more and your going to need a specific tune for this car with them in play.

 

Go find a tuner and if the O2 sensor is old then it will warrent a replacment.

 

You have to look at all the vac lines and ensure they are not leaking... There are lots of threads on these subjects.

Ok well from my understanding on the Cobb Stages is based on mostly a stock setup. The TGV deletes are not stock any more and your going to need a specific tune for this car with them in play.

 

Go find a tuner and if the O2 sensor is old then it will warrent a replacment.

 

You have to look at all the vac lines and ensure they are not leaking... There are lots of threads on these subjects.

 

Local tuner and research shows that TGV deletes are fine without tune.

 

also I had this problem before the TGV deletes.

Front O2 failure can result in idle surging and dropping without setting a CEL. It's happened a number of times and it also effects a ton of other different things (obviously) in AFR and again, without any CEL. If you can find someone that has a known good one, change it out and see if it fixes it.

 

I had a bad front O2 that looked fine in all scanner information as well as data logs, and I changed it on a hunch because of STFT bouncing all over the place and that instantly fixed the idle as well as off idle acceleration and smoothness.

 

It's not a 100% fix all but it definitely warrants a look, especially since the lack of CEL upon failure doesn't point directly to it.

 

what is STFT?

 

Thanks for the info. ill fix the grounds and if it doesn't fix it ill replace the front 02

Ok good luck with that. Ground straps are a needed peice. Dynamic Advanced Multiplier from my understanding should be 1 otherwise there is a reson for it staying at .75 like a vacuum leak and the ECU is trying to reduce knock.

Ok good luck with that. Ground straps are a needed peice. Dynamic Advanced Multiplier from my understanding should be 1 otherwise there is a reson for it staying at .75 like a vacuum leak and the ECU is trying to reduce knock.

 

Opened up the map in AcessTuner Race and it shows the DAM set at 0.75 so I'm guessing its correct?

Went for another ride, was able to get some 3rd gear WOT going, and after warm up DAM went to 1

 

https://drive.google.com/file/d/0B7t77ONq8FF5bzhPelVabFFrTmM/edit?usp=sharing

Using some berrymans fuel system cleaner as a first step trying to solve similar issues. Going to replace plugs and check the PCV is operating as well. Could be none of theses but since I am pretty sure all my vac lines are solid I'm on the hunt for cleaner operation. Good to hear your back to 1... Did you find antsy vac leaks before hand?

Using some berrymans fuel system cleaner as a first step trying to solve similar issues. Going to replace plugs and check the PCV is operating as well. Could be none of theses but since I am pretty sure all my vac lines are solid I'm on the hunt for cleaner operation. Good to hear your back to 1... Did you find antsy vac leaks before hand?

 

Talked to a tuner and he doesn't like my O2 sensor readings so ive ordered a new one. At the same time ill be fixing the ground straps and hopefully this resolves the issue.

Seems like a good start.

STFT=Short term fuel trim=idle control and initial acceleration

Still have not yet received my front O2 Sensor so I have not replaced that.

 

Some reading tells me that the Rear O2 sensors on our cars can cause problems as well? I got a PO2097 Post cat too rich a couple times so I dataloged the rear sensor.

datalog13.csv

I hope you got a OEM front O2 sensor, my after market one lasted about 2 years. My rear O2 is aftermarket and its still fine.

Yes I have an OEM front o2 sensor that should be here tomorrow. Im waiting for a call back on either a bosch or denso rear o2 sensor.