Very Choppy Idle

A

Akia Hawkins

Greenie N00B Member
Greenie Member
I have a 2008 MS3 and im having a wild issue. It has a very choppy idle which causes stalling most of the time, and it has started randomly losing all accelerator pedal, as in I goto give it gas and it does nothing. Then when you pull over itll stall because its struggling to idle, and wont start back for anywhere between justa few minutes to an hour. (when it has issues starting back i noticed in the AP, KOEO, HPFP has 0PSI. Im on a base map from Will @PDTuning, hes saying check for vaccum/boost leaks, verify coil packs are good, and check grounds. The car has been smoke tested with no luck, im sprayed every vacuum line with starter fluid hoping to notice a difference in idle, but no luck. the car has spark. i can unplug each coil pack individually and notice a difference in idle. The car does doesnt throw any codes until 1. It Stalls at idle, itll throw a P300 code or 2. It stalls after losing accelerator pedal, itll throw a p2122.

Now i have an idle log, just recently the car wont go above 3600-3800 RPMS, the last couple times i drove the car the KR was maxing out at 8.00 around 2000-3000RPMs, im wondering if anyone could see if anything in the datalog is obviously off. The Plugs are NGK6510 gapped to 0.027 per Wills request. im wondering if its a injector issue as the car has 155k miles on it, is there anyway to verify it being an injector issue? Ive always heard, knock could be a sign of an injector issue.

Thanks in advanced.
 

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Have you checked that the throttle body is operating correctly
 
Your vacuum at idle is quite low.

Either you have a leak somewhere (like a catch can drain in the open position or a bov/bpv leaking at idle) or you're down on compression significantly.

Vacuum at idle is typically around -10psi at sea level om a healthy motor with no boost/vacuum leaks. So unless you're at like 5000ft ASL, the low vacuum you have at idle is indicative of an issue. You're at about -4.5psi at idle

Your coolant Temps seem to be quite high and all over the place as well. Either air in the system or you have an issue with the thermostat, etc.
 
Sho said:
Your vacuum at idle is quite low.

Either you have a leak somewhere (like a catch can drain in the open position or a bov/bpv leaking at idle) or you're down on compression significantly.

Vacuum at idle is typically around -10psi at sea level om a healthy motor with no boost/vacuum leaks. So unless you're at like 5000ft ASL, the low vacuum you have at idle is indicative of an issue. You're at about -4.5psi at idle

Your coolant Temps seem to be quite high and all over the place as well. Either air in the system or you have an issue with the thermostat, etc.
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Compression test revealed all cylinders had between 175 and 190PSI. I know the vacuum is super low for what it should be. KOEO, vacuum reads -12.5, but i for the life of me cannot find a vacuum leak. So back to my original thought of a with clogged injectors or something of that sort?
 
What sho is saying is that you have a vacuum leak. Keep looking.
 
Key on engine off, should read almost 0psi. If you're at -12, then the info you gave PD regarding your map sensor is incorrect and he scaled it accordingly or the map sensor itself is bad
 
Sho said:
Key on engine off, should read almost 0psi. If you're at -12, then the info you gave PD regarding your map sensor is incorrect and he scaled it accordingly or the map sensor itself is bad
Click to expand...
I’ve had issues with MAP sensors, originally the car had a CS 3.5 bar map sensor which died, replaced it with a Bosch 3.5 bar w/pnp harness, the new sensor was DOA, had it warrantied and this data log is with the new 3.5 bar. He asked for pictures of the MAP sensors when I had the CS, go verify the calibration was correct, then asked for a picture of the Bosch sensor to verify it was actually a 3.5 bar to verify the calibration was correct.
 
You had issues with sensor...you still have issues with sensor. You need a friend with a verifiable sensor. Then tuner has the range of what ever sensor you use. Has to have correct span (low to high values in reference to vacuum/pressure) to do calculations...it's a very important data input to ECU. Here is key on engine off. Key on engine at cold idle. Yes the digital number is zero and the green pointer isn't sitting exactly at zero...this is just a simple example of what to expect. My zero is not perfect, it's a older analog separate sensor plumped on intake manifold nipple. Very important is full scale. Mine has a 0.1 psi error at 30.00 reference pressure. Zero while not perfect but then this is a old analog instrument calibrated for high boost. I only get one end of scale 20230731_192708.JPG 20230731_192652.JPG adjustment..
 
Cfoldone said:
You had issues with sensor...you still have issues with sensor. You need a friend with a verifiable sensor. Then tuner has the range of what ever sensor you use. Has to have correct span (low to high values in reference to vacuum/pressure) to do calculations...it's a very important data input to ECU. Here is key on engine off. Key on engine at cold idle. Yes the digital number is zero and the green pointer isn't sitting exactly at zero...this is just a simple example of what to expect. My zero is not perfect, it's an older analog separate sensor plumped on intake manifold nipple. Very important is full scale. Mine has a 0.1 psi error at 30.00 reference pressure. Zero while not perfect but then this is an old analog instrument calibrated for high boost. I only get one end of scale View attachment 25876 View attachment 25877 adjustment..
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Okay, great information! I’ll verify my KOEO value in the morning. If it’s actually 12.5 like I think I seen, is this just a calibration issue? Or is this a physical sensor/wiring issue?
 
Cfoldone said:
You had issues with sensor...you still have issues with sensor. You need a friend with a verifiable sensor. Then tuner has the range of what ever sensor you use. Has to have correct span (low to high values in reference to vacuum/pressure) to do calculations...it's a very important data input to ECU. Here is key on engine off. Key on engine at cold idle. Yes the digital number is zero and the green pointer isn't sitting exactly at zero...this is just a simple example of what to expect. My zero is not perfect, it's a older analog separate sensor plumped on intake manifold nipple. Very important is full scale. Mine has a 0.1 psi error at 30.00 reference pressure. Zero while not perfect but then this is a old analog instrument calibrated for high boost. I only get one end of scale View attachment 25876 View attachment 25877 adjustment..
Click to expand...
Okay, scratch what I said about -12.5, idk what monitor I glanced at when I seen that but KOEO, it bounces between -0.01 and -0.06
 

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That's ok. Normal digital noise. A crude but cheap and quick test. Pull sensor or if you have still your many "unknown good" ones. Connect to wiring harness use a appropriate hose on to sensor hot side---- what goes in engine air side... Suck and blow pressure with mouth. You will get diff values on AP. Remember max is 30 psi or the sensors max. No air hose!!
Then you know it's ok from sensor connector through ECU and reported correctly for AP to get values (might be wrong pressure value numbers) the question will be is programmed span correct for sensor + tuner values of sensor= actual pressure.
 
So
Cfoldone said:
That's ok. Normal digital noise. A crude but cheap and quick test. Pull sensor or if you have still your many "unknown good" ones. Connect to wiring harness use a appropriate hose on to sensor hot side---- what goes in engine air side... Suck and blow pressure with mouth. You will get diff values on AP. Remember max is 30 psi or the sensors max. No air hose!!
Then you know it's ok from sensor connector through ECU and reported correctly for AP to get values (might be wrong pressure value numbers) the question will be is programmed span correct for sensor + tuner values of sensor= actual pressure.
Click to expand...
if I do the blow throw a hose test and the sensor reads different PSI, that means the sensor/connector/harness are good, correct?

also I have a question on why the car won’t rev past 3800rpms? It sounds like it’s trying to build boost and 2stepping, but it instantly goes max lean 29.95.

How likely is it that the intake manifold gasket is bad? Causing my vacuum leak? Even though I’ve sprayed too and bottom of the manifold with starter fluid and nothing.
 
Unless you can apply a known amount of vacuum or pressure, it only means sensor is sending a signal and wiring to ECU is reading it. You still haven't proven if sensor type or tuner feedback on scaling values is correct.
Now that you are asking about rpm / fueling troubles...you had better look on forum and fill out the conditions of faults worksheet. The worksheet of faults, modifications (ALL) listed. Then a starting point for your needs can begin.
If the vehicle hasn't ran correctly from beginning, additional mods can compound faults. So painful but going back as far as possible to stock might be easier. Especially if you a refit OEM intake and map sensor. Just to see if running correctly then.
 
Cfoldone said:
Unless you can apply a known amount of vacuum or pressure, it only means sensor is sending a signal and wiring to ECU is reading it. You still haven't proven if sensor type or tuner feedback on scaling values is correct.
Now that you are asking about rpm / fueling troubles...you had better look on forum and fill out the conditions of faults worksheet. The worksheet of faults, modifications (ALL) listed. Then a starting point for your needs can begin.
If the vehicle hasn't ran correctly from beginning, additional mods can compound faults. So painful but going back as far as possible to stock might be easier. Especially if you a refit OEM intake and map sensor. Just to see if running correctly then.
Click to expand...
Year/Make/Model: 2008 Mazdaspeee3
Mileage: 155000
Location: Glasgow KY
Concern: Very Choppy Idle, High KR 2-3k RPMs, Low Vacuum at idle, hesitation during partial throttle.
DTC's: None
Modifications: Damon OCC, CS HPFP Internals, CS Cat Back, GFB BOV, JBR Intake, Bosch 3.5 BAR MAP, NGK6510s 0.027”
ECU/Tuning Software: AP V3
Tuner: Will Dawson @PD
Is the concern intermittent? No, Constant.
Can you duplicate the concern? Anytime it idles.
Recent Repairs: VVT job, Replaced plugs per tuners request, the car has had this issue since I’ve owned it, I bought it this way.
Correction:
 
Akia Hawkins said:
Year/Make/Model: 2008 Mazdaspeee3
Mileage: 155000
Location: Glasgow KY
Concern: Very Choppy Idle, High KR 2-3k RPMs, Low Vacuum at idle, hesitation during partial throttle.
DTC's: None
Modifications: Damon OCC, CS HPFP Internals, CS Cat Back, GFB BOV, JBR Intake, Bosch 3.5 BAR MAP, NGK6510s 0.027”
ECU/Tuning Software: AP V3
Tuner: Will Dawson @PD
Is the concern intermittent? No, Constant.
Can you duplicate the concern? Anytime it idles.
Recent Repairs: VVT job, Replaced plugs per tuners request, the car has had this issue since I’ve owned it, I bought it this way.
Correction:
Click to expand...
Update: idle issue ended up being a clogged EGR (stuck open) threw on a EGR delete and it’s doing great now.
 
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