Compression Waveform

Darren Mechanic Wisconsin Posted   Latest   Edited  
Discussion
Driveability
2008 Saturn Astra XE 1.8L (1 2H0) 4-spd (AF17)
P0101 — Mass or Volume Air Flow Sensor "A" Circuit Range/Performance

maf is fine, engine has breathing problem, any thoughts on compression waveform, suspect valve timing, I may decide to do cam / crank waveform if needed.

0
Dean Owner
New York
Dean Default
   

I am chasing the same code on the same car. Does your car run ok? Does it set lean codes or rich codes? Can you provide more info?

0
Default Ð Awarded
Darren Mechanic
Wisconsin
Darren Default
 

Runs lean . No fuel mix codes yet. Runs super lean at idle.

0
Default Ð Awarded
Stuart Owner/Technician
United Kingdom
Stuart Default
 

Looks like the inlet is late in opening and there is quite a bit of turbulence on the exhaust closing and inlet opening periods as well. Valve timing is defo worth a check and are all cylinders the same ? Does it have an EGR Valve?..

0
Default Ð Awarded
Darren Mechanic
Wisconsin
Darren Default
 

No egr

0
Default Ð Awarded
John Instructor
Pennsylvania
John Default
 

Agree Stuart. The intake cam timing is retarded, the first thought from there is where does the PCM want it to be at that point in time?

0
Default Ð Awarded
Jeff Diagnostician
California
Jeff Default
 

Can you upload the raw pico file ?

+1
Default Ð Awarded
Bob Owner/Technician
Massachusetts
Bob Default
   

Darren, We could better help you out if you could post some more test data such as fuel trims at idle, cruise and under load. Also, the freeze frame data would be helpful to see under what operating conditions is the code setting. A VE test would be helpful also. This code can set for many reasons. Vacuum leaks, heavy deposits in the throttle body, intake restrictions, sensors out of spec etc…

+2
Default Ð Awarded
Keith Diagnostician
North Carolina
Keith Default
 

Looks like possible exhaust event closing early. There is a noticeable rise in exhaust pressure at end of event. Cam crank correlation would be a good choice.

0
Default Ð Awarded
Nicholas Diagnostician
New York
Nicholas Default
 

Hi, did you check exhaust back pressure?

0
Default Ð Awarded
Justin Mobile Technician
Utah
Justin Default
 

I don’t see any backpressure issues in the capture.

0
Default Ð Awarded
Keith Diagnostician
North Carolina
Keith Default
 

Doesn’t appear to have a exhaust back pressure issue. Hovers around 0psi on evo. Just sudden rise at the end of exhaust timing. Makes me wonder about valve timing.

0
Default Ð Awarded
Eri Technician
New York
Eri Default
 

As stated by Stuart intake valve seems be a bit late possibly

0
Default Ð Awarded
John Instructor
Pennsylvania
John Default
   

The intake cam timing is late in this capture, that is evident by both the pressure rise at the end of the exhaust stroke which needs all of the valves closed to occur and how long it takes the cylinder to go into a vacuum after TDC (E-I). Grabbing a CMP/CKP capture before teardown would be a good idea. Overlap the compression waveform with the CKP and the CMP captures.

0
Default Ð Awarded
Bob Owner/Technician
Massachusetts
Bob Default
 

John, I would agree with your assessment of the pressure waveform capture, I'm just a little curious how we got from a P0101 to an in cylinder test. It may turn out to be a mechanical issue but it would be nice to see the data that supported going to an in cylinder pressure test in the first place.

+1
Default Ð Awarded
John Instructor
Pennsylvania
John Default
 

Isn't the engines ability to pump air part of "the basics"? A P0101 is easily divided into two categories, low calculated engine load with fuel trim correction and low calculated engine load without fuel trim correction. From there it's all fundamentals, it's just the way that we measure them today that appears exotic.

0
Default Ð Awarded
Justin Mobile Technician
Utah
Justin Default
 

I just posted a basic example tonight.

0
Default Ð Awarded
Bob Owner/Technician
Massachusetts
Bob Default
 

Sure it is, but wouldn't you be looking at some scan data before diving into in cylinder testing? Don't get me wrong, I love my pressure transducers but I usually have gathered some other data that will lead me to using the transducer. It's not the first test I'm going to do. I was just hoping the OP could post some supporting data for going in cylinder.

+1
Default Ð Awarded
John Instructor
Pennsylvania
John Default
 

He didn't post data but he started off with "maf is fine, engine has breathing problem" which while he didn't specifically share the data strongly suggests that he had already investigated that angle.

+1
Default Ð Awarded
Richard Technician
Virginia
Richard Default
 

You don’t have any data posted so I will give you results I just had on a 08 Saturn 3.5. I was asked to go to another shop and program a new ECU . After I was done, the car had a number of drive ability issues. Later , I was asked for some assistance in diagnosing it. I found voltage drops on ground wires for the MAF , TCM , ECM and the trans range selector​.​It ended up being a

0
Default Ð Awarded
Keith Diagnostician
North Carolina
Keith Default
 

He has a performance problem at MAF. My suspicion is that it’s extremely out of range. It looks like the cam timing is off. No real way to know that without a little more info (known good waveform, cam crank correlation). This would certainly cause this issue. Should be able to see it with absolute load as well. In fact I’m sure he would. Any way hope he resolves it soon.

0
Default Ð Awarded
Eric Owner/Technician
Wisconsin
Eric Default
 

I would really like to see the actual Pico file if you could upload it please.

0
Default Ð Awarded
Darren Mechanic
Wisconsin
Darren Default
 

I will try.

0
Default Ð Awarded
Simon Diagnostician
New Zealand
Simon Default
 

As stated by some of the replies above, the original PSDATA file would be needed to analyze the data efficiently. However, if the in-cylinder trace is taken at idle, the compression pressure is high, I usually see about 70-90 psi at idle. Also, the compression cone is uneven, note the intake side (vacuum) is higher than the exhaust side. But, as I said, I would need the PSDATA file to be

0
Default Ð Awarded
Caleb Technician
Indiana
Caleb Default
 

Looks a like very retarded intake cam timing. What is the manifold vaccum at idle with VVT solenoids unplugged assuming it has VVT?

0
Default Ð Awarded
Orlando Technician
Ontario
Orlando Default
 

Any updates?

0
Default Ð Awarded
Darren Mechanic
Wisconsin
Darren Default
 

Customer took vehicle.

0
Default Ð Awarded