I have been working with a tuner via email trying to nail down my tune by sending him datalogs. I have been running max rich at idle on the driver side, and he has come to the conclusion that I have an issue either mechanically or with a sensor.

Here is what I know:
Brand new denso o2 sensors on both sides.
My fuel injectors are not leaking, I know this by pulling the fuel rail up and watching them for some time under normal fuel pressure.
Brand new spark plugs in all cylinders
Fuel pressure at simulated WOT is 42 psi. 36 psi at idle.
Engine seems to run fine so a misfire is not suspected

Here is what I'm not sure about:

My fuel pressure regulator vacuum line smells of gasoline. However, when trying to verify if it is leaking fuel past the diaphragm, I come up with nothing. Fuel pressure holds steady when the system is primed.

Occasionally when I go to start a new data log, Code 16 is tripped.
I will reset this code, and the engine will run without incident. This has happened only 2 or 3 times over the past few months, and I am unable to pinpoint when it happens as I do not have a working check engine light.

Datalog: FileSwap.com : post spark plug1.uni download free

Engine:
355 LT1, LT4 Hot Cam, 1.6 rr's, #30 SVO injectors, mild port work on heads, 52mm tb

I am out of ideas
Thanks

 

For those that can't see the datalog my lterm blm at idle are about 102 on the left and 139 on the right. I have switched my fuel injectors to the other side with no change.

I have played with my throttle screw and this only affects the left side blms making them read more rich, down to a 98. I have a factory ported tb out to 52mm.

Anyone have anything?

 

DTC 16 does not turn on the SES light.

 

Many people claim they get the best results with AC Delco or Delphi O2 sensors. I never tried anything else, so I don't know how true this is.

Something is screwed up - it's idling in Cell 4. Supposed to be in Cell 16. The stock programming will not let the BLM's drop below 108. Your tuner appears to have lowered the limit in an attempt to allow the PCM to lean it out. At the end of the log it goes into Cell 4 at idle, and now the BLM"s are 113L/124R.

It's using Cells 0, 1 and 2 for decel, it should be using Cell 17.

Idle is the only only place you have split BLM's - everywhere else its pulling fuel out on both sides, just not as much as on the left side at idle. Cell 6 is actually reversed, with
120L/115R.

Cell 15 is used in power enrichment mode, 128L/129R and the O2 readings are high 800's for the left side and low 900's for the right side. Looks like its not that far off when it defaults to Cell 15 (because it's pulling fuel otherwise).

Whatever your problem is, it's only in low load cells.

What happened at record #3259? The throttle is open 9%, the speed is 0, rpm drops like a rock, looks like it stalled as the throttle closed. Is that correct?

I'd ask the tuner why its idling in Cell 4 instead of 16, and why it's running decel in Cells 0 - 2, when it's supposed to be using Cell 17.

 

I forwarded the tuner what you said and he had this to say, "The tune cannot tell the PCM which fuel trim cells to use. I agree, 17 is the normal decel cell, 16 is normally idle".

So obviously there is something else causing my PCM to use those cells. What could this be?

Also he made note that my voltage is low across the board getting up to only 12.7 volts at wot. Could that be a source?

3259 I believe is me stalling the car in first gear.

Thank you for your reply

 

Don't know.. thought maybe he used a PE mode tune, allowing him to change A/F ratio at lower RPM/engine loads. But the bit flag does not indicate it's in PE mode when it's idling.

I've reviewed hundreds of data log for people over the last 10 years or so, and never saw one where it idled in anything other than Cell 16, unless the TPS voltage was over spec, and the PCM didn't know the throttle was closed. But your closed TPS voltage (0.57V) is fine.

Do you have U/D pullies? System voltage looks OK when you first start it, at ~13V. Then it just continues to fall off, to 11.x V. With an 800+RPM idle speed, the alternator should be able to handle the load at idle, unless you have the pullies or some large electrical load like a stereo. The system voltage reported by the PCM is often about 1V lower than the voltage measured at the battery.

Spark advance holds steady at idle at 29*. I guess they might have done that for the cam. Typically the stock programming is closer to 20* at idle.

What did your old spark plugs look like when you pulled them out? Any evidence of running either rich OR lean? Did left bank plugs appear the same as the right bank?

 

I do not have ud pullies.
I do however have a stereo system with 2 subwoofers and a 500w amp. I have a fared capacitor as well.

Here is a poor quality picture of the old spark plugs


Also, it may be possible that that datalog was a fluke..I don't know why, but I have not noticed it idling in 4 before or since then. Here is another datalog from a couple months earlier showing the same symptoms. I played with my TPS and IAC counts some since this was taken. Also, I switched my o2's since then.

FileSwap.com : 1883 1.uni download free

 

Still having problems with this.

Things I have done since last post without effect:
Readjusted my valves
Checked plug wires with an ohm meter
Replaced iac

My tuner also seemed lost on why it idles in 4.
He suggested perhaps my tps is bad.
Could the tps possibly still read accurately but still not relay proper information to the PCM?

Also, a thought occurred to me. I believe on the right side of the engine the intake manifold ports are slightly bigger than the heads, could this reversion cause my blms to behave this way?

 

Verify that you get the same volt readings on the TPS signal wire that the PCM is reporting for the TPS sensor. If the volts at the sensor are the same as the volts the PCM is reading, there is no problem. The only possible reason they might not read the same would be a problem with the signal wire or the ground (low reference) wire.

And in the log where its idling in Cell 4, the TPS voltage is 0.57. That is within the acceptable range for closed throttle.

If the vehicle is moving, you could have an issue, since the PCM requires the vehicle to be stationary to recognize that it is idling. I don't remember the MPH readings in the log, but it's something I would normally check.