How to diagnose and resolve engine issues using Durametric.

[jb92563]

Thanks for the words of encouragement XCELLR8.

Its nice having the tools (Durametric) but if you dont know how to interpret the data your not getting maximum bang out of it.

I bought a couple cigars last evening for my DIY smoke machine for vacuum leak detection. That should be amusing and of course a video will follow with the results.

I'll be getting a Fuel pressure gauge this evening and have read how to measure flow rate....so many liters per minute although I forget the exact number but will document it here when I do the test. (No codes yet)

update- I discoved that Autozone Loans equipment, no charge, so I brought home a nice expensive fuel pressure test gauge for my weekend pressure test...nice surprise.

The car is at 74K miles so replacing a few parts was due anyway so it wasn't unexpected. However the failed AOS precipitated this issue which I find rather odd, so I am expecting to see some vacuum leaks in that area and would make a lot of sense.

Not really expecting a fuel pressure issue but since its easy to check I might as well do it.

I did read something about the Fuel injector rail port where the pressure guage would connect to and wondered if a new washer was necessary when replacing the cap? I read that its a Schroeder valve ?

[JFP in PA]

Originally Posted by jb92563

Thanks for the words of encouragement XCELLR8.

Its nice having the tools (Durametric) but if you dont know how to interpret the data your not getting maximum bang out of it.

I bought a couple cigars last evening for my DIY smoke machine for vacuum leak detection. That should be amusing and of course a video will follow with the results.

I'll be getting a Fuel pressure gauge this evening and have read how to measure flow rate....so many liters per minute although I forget the exact number but will document it here when I do the test. (No codes yet)

The car is at 74K miles so replacing a few parts was due anyway so it wasn't unexpected. However the failed AOS precipitated this issue which I find rather odd, so I am expecting to see some vacuum leaks in that area and would make a lot of sense.

Not really expecting a fuel pressure issue but since its easy to check I might as well do it.

I did read something about the Fuel injector rail port where the pressure guage would connect to and wondered if a new washer was necessary when replacing the cap? I read that its a Schroeder valve ?

It is a metric Schrader valve, and the cap with washer is supposed to be replaced each time, but you can usually get away with taking it off once or twice before it starts to leak. Caps are cheap.

[jb92563]

Fuel pressure is good at idle 45 psi vs spec 47 psi
Beyond idle 57 psi vs 55 psi spec

I measured fuel flow at 3 locations.

just before fuel filter 1650 ml per 30 second s.
at fuel rail schreader valve 350 ml per 30 sec
At fuel return 825ml per 30 sec vs spec 850ml per 30

I also did the smoke testing and found no vacuum leaks except a very minor one at the intake variable length intake tuning flap bearing. Its in the second intake manifold crossover.

Smoke Tester config that worked: Old paint can with a scrap rag soaked in baby oil, crumpled up and lit on fire. Air compressor line into can at 3-5 psi and a line out near the top of the can.
Turn on air compressor, light the rag on fire and close the paint can lid. I also threw the cigar in there for good measure since the cigar only method did not work for me.
It then produce lots of smoke for a couple minutes before you have to relight it. I had to relight a couple times to be fully satisfied that the system was completely smoked through.
I put a plastic bag around the air filter and reinstalled it to effectively seal the intake system. I removed the MAF since you don't want to foul it with smoke residue and I used the MAF opening to introduce the smoke till it exited the oil cap, which I then closed and looked for smoke leaks.
Then I did the test again but this time with the smoke being injected at the oil fill until exiting the MAF opening and then I sealed the MAF opening and checked for leaks.

So no Vacuum leaks is the verdict on that.

The test drive did not exhibit the hesitation this time but seems to run a bit milder with less aggressive more normal acceleration than previous test drives.

Perhaps the computer is relearning and fine tuning the curves?

I wonder what the odds are that the DME computer is having issues or gone bad?
Do those fail often?

[jb92563]

The last Test drive and fiddling introduced new codes P1128, P1130,MAF code, fuel relay. Probably due to my fuel pressure tests as I pulled the fuel pump relay and cranked the engine over to release all residual fuel pressure before doing the fuel flow and pressure tests.

I'll reset all the codes by disconnecting the battery, redo the throttle adaptation and start with a clean slate to see what materializes now that it seems to be running somewhat better.

While I was under the car I did notice some burnt oil residue on the pre Cat O2 sensors on both sides. It looks like it was from the AOS failure as it was not there prior to the event.

My car did pass about 2 quarts of oil during the AOS failure so I'm thinking it could have fouled the O2 sensors and plugged catalytic converters but I am not seeing any codes to indicate that either have failed.

The Durametric trace that I got from the O2 sensors this weekend to see what was going on made little sense as the lines were wandering everywhere.

I was looking for a sine wave on the pre cat sensors and a nearly straight line on the post cat Sensors but got a little bit of everything all mixed together.

It made me think that perhaps I was not getting enough samples per second from the Durametric to see the proper wave form.

I think I need to pull the precat sensors next to inspect them and use my inspection scope to look inside the cats to see if I can see whats going on.

The front side of the exhaust manifold cats look good, no heavy deposits.

[jb92563]

Update.

I replaced the pre CAT O2 sensors and there is no improvement.

I looked inside the CATs with an inspection camera while replacing the O2 sensors and the CATs did not look fouled or damaged in any way.
I also looked at the pistons when replacing the spark plugs and could not make out clearly or understand what I was looking at but it sortof
looked like heavy deposits and the cratered surface of the moon.
Unfortunately the camera would not fit down the spark plug hole so I'm skeptical of what I thought I saw.
Anyone have a reference of what a ~70K mile piston would look like?

I have ruled out:
- Fuel Filter (Replaced)
- Fuel Pressure (Tested OK)
- Fuel Flow (Tested OK)
- Pre CAT O2 sensors (Replaced)
- Air Leaks (Smoke Tested)
- AOS (Replaced)
- Spark Plugs (Replaced)
- Oil cap seal (Replaced)
- Gas cap (Replaced)

I'm still getting the codes 1128, 1130 consistently and sometimes 0507

All the symptoms still point back to the MAF since when I disconnect it the car idles and seems to run normal, although I have not road tested it without MAF.

I returned my new MAF to Pelican and will try another one to see if somehow I got a bad one.

I pray its the MAF because I'm running out of ideas of what it could be.

I considered a bad or intermittent ground or dirty connection but the hesitation happens consistently so a loose connection would be more random I would think.

I had also considered removing the new AOS and reinstalling just in case the port to the engine block is somehow obstructed or to see if the bellows has a tear, although I would have thought that would show up with the smoke test.

[jb92563]

Update

Got the replacement MAF sensor from Pelican but attempting to start the car revealed a dead battery showing 10.9 volts, not enough to start the car.

Once a lead acid battery has died there is usually little chance of it being reliable after that so I simply replaced it without trying to revive it.

With the new MAF in place the same issues are still present. However the P1128 and P1130 codes have not come back.

and the RKAT is up around 4.5 which makes me think perhaps there might be an air leak after all.

[Graph place holder]

Wandering Idle, and a random hesitation.
Only codes P0507, P1571 and P0102 now.

However with the car idling in the driveway for some time while I'm looking at various Durametric parameters being graphed
the idle suddenly goes back to normal and the car seems not to exhibit any symptoms anymore.

I take it for a test drive and everything is back to normal.

I shut down, then start up again and its still fine.

WTF ????

Perhaps a bad ground like Wawa suggested?

Maybe those little random FRA spikes are indicating a wiring problem.

I hate these kind of problems, a pain to debug, and if you don't find the issue you can never really trust it to be reliable.

I'll have to start wiggling wires to see if that might be the issue.