P0300 and pulling my hair out!

[haulinit]

I have been chasing my tail on this issue. The truck pops off when I kit the key then slows to a rough stumble of a idle after about 10 seconds or so it settles in and idles fine but with some missing. I have replaced or tested everything that I can think of still no dice. The truck started fine this morning when the temp was about 20F outside. I logged a start up, im out of ideas and starting to think this is a tune issue more then a part issue.

The thing that bugs me is once you get above 10% it stops missing and pulls hard, I have a log of running down the road if anybody wants to see it. Any ideas would be great as I'm out of ideas!

[WeathermanShawn]

Well, I certainly don't know your vehicle/OS as well as others..but a few questions...

I see you have a current DTC for EGR. Did the problems start after you disabled EGR?

Your LTFT's are pretty high (positive). That is equating to lean. Hard to know without an actual wideband, but thats a lot of +LTFT's for Idle.

How is the health/age of your O2 sensors? Any chance of a log with H02S11 and H02S21 logged?

Tune-wise, looks like you are running MAF-closed loop. You may just need to add some more MAF Airflow vs Frequency to correct those LTFT's.

Thats all I can see on a quick look. Good luck.

[haulinit]

I can log what ever you want me to log I'm very green in the tuning dept. The health or condition of my O2's is a ? I have not replaced them. No the DTC is from me not setting the mil's yet to reflect me blocking it off. I blocked the EGR off thinking it was stuck open and causing my missing condition. Thanks
for the help

[nevinsb]

It doesn't take much of a lean condition to cause misfiring. Did this issue start happening after tuning, the PCM swap, the cam swap?

[joecar]

Hi haulinit,

Remove the pids O2BIAS11/12 and add the pids HO2S11/21, MAP and MAF, and capture a new log.

How many miles on your O2 sensors...?
Does coolant level stay the same...?
Do you have any airleaks at/under the intake manifold...?
What is condition of spark plug and wires...?

+1 when did this start happening...?

[haulinit]

I have had the cam in for over two years with a Wheatley tuned black box, right before the PCM swap I was getting a high RPM miss above 4500 and WOT. If you didnt give it 100% throttle it wouldnt miss. Found out I had a bad injector replaced it and that took care of that miss. The truck started fine with the black box. After I switched to the 0411 it started having idle problems. The truck had 78,000 miles on it when I bought it, it now has 128,000 on it and I havent changed them. The coolant level stays the same ( I used the good fel-pro gaskets for the intake when I changed the cam). I checked for leaks and did not find any. New AC-Delco cap and rotor last night, plugs are about 1wk old. Tested the wires they were in good condition.

The start up issue started after the PCM swap. I will have to change the PIDs tonight and go relog.

[haulinit]

I was thinking if the truck was lean why would it start better when the temp was cold wouldnt that make it worse by making it leaner? Thinking out loud!

[WeathermanShawn]

When your car first starts it is utilizing B3605 (Commanded Fuel). The colder it is the richer your fueling will be at start-up.

The LTFT correction we were referencing is determined by B3802. The Idle LTFT's do not usually kick in until 60-70 C (PCM may reference Cold Idle Learning Fuel Cell).

You are 'lean' when you enter closed-loop. You PCM believes you need more fuel and is adding an additional 11% fuel with every pulse of the injector. Again, colder more oxygen is available for engine..you may be starting out rich enough to start, but once you hit closed-loop you are immediately lean. Thats why you really need to know the status of those two front narrowbands. If they are slow, not switching properly, or have a significant intake leak..you could chase the problems for a long time.

Hope that helps..:)

[haulinit]

I think I may have miss lead you a lil bit. The fueling does not have time to go to closed loop fueling it starts to stumble the second the idle comes off the initial start then becomes rough. The idle slowly comes up to desired idle and smooths out.

[WeathermanShawn]

No, I get it.

Your initial Idle prior to entering closed-loop is the problem (cold-Idle). I was just stating that the health and age of your O2's will determine how quickly and efficiently you can enter closed-loop. The LTFT's are stored. There is some interplay on LTFT's and start-up. So if you are lean yesterday, the PCM will be trying to add fuel even on start-up (as you enter closed-loop).

Its possible your VE Table may not be accurate. Do you have the ability to monitor or preferably log wideband AFR?

So, we are 'guessing' on this end that it is fueling-related. I was just suggesting to verify that your O2's were up to the task. We only have the LTFT's at this point to make and educated guess. Either way, fresh O2's are never a bad idea.

Good luck.

[haulinit]

Sorry I do not have a WB02 I'm going to get one when the budget allows. I will have to get under the truck and figure out if I have a three wire or four wire per cat 02's. Can't I run a emissions test with the scan tool to determine if they are functioning correctly?

Thanks guys you have been very helpful :cheers:

[WeathermanShawn]

No.

You need to know the amplitude and frequency of the O2's to determine if they are properly switching. They will normally switch 3-5 times per second. Poor performance will affect all phases of a closed-loop tune.

No shortcuts as far as I know. Some of Idle Tuning can be done by examining LTFT's, but guessing at fueling without a wideband will be just that...a guess.

Good luck in your endeavors!

[joecar]

Shawn is saying to log HO2S11 and HO2S21...

by looking at these wave forms using the fastest sample rate (keep pid channel count to 24 or less) will give an indication of the health of the O2 sensors (if they switch several times per second when hot, and a few other things);

there is an OBD-II test, but it requires you to trigger it by doing a so-called "Drive Cycle", but even then this test is a pass/fail test, it doesn't necessarily point to any O2 sensors that have slowed down.

[haulinit]

here is a log of idle with the requested pids. I changed the maf table by adding 10%, it help on warm idle restart but cold start in the morning will tell. Maybe you can tell by log if I need to change my 02's from the log. I would just like to say thanks for the help :cheers:

[WeathermanShawn]

Perhaps my first question would be why is your HO2S11 and HO2S21 the same? Those are two different banks..each should be reporting different values..:confused:.

So, looks like it took ~ 1:14 (min/sec) to go into closed-loop. Did it run immediately better after 1 minute, or did it take longer?

[haulinit]

It started to straighten out in about 30 seconds. Later in the log they read differently. My LTFT's are now showing negative I think I may have gone to far I modded the table by adding 10%. What would happen if I turned the min enable temp down to about 30*F in table B3802? Sorry for all the questions I still haven't wrapped my head around all of this! I did a search and couldnt find how to do a idle learn, any help pointing me in the right direction or does it apply to this?

[WeathermanShawn]

I never see the change in O2's mv..where does that happen?

Also, I don't see any LTFT's logged..:confused:.

I'm not sure what 10% change you made to the MAF. All the table, or just the Idle area?

I would not attempt to change the Closed-Loop Enable Temps. Yes, you could make them lower, but your narrowbands are very cold at those ECT's. They do not work well when cold, so I would just leave that Table alone.

I don't think an 'Idle Learn' is applicable at this point. If/when your fueling is determined to be correct..unless you changed the Idle Learn Parameters, it will 'learn' on its own.

Quite frankly, if your ride deteriorated after your swap, then I would look there for the answer. I am still confused why Bank 1 and Bank 2 would read the same. Any possibility the wiring of your O2's might have been inadvertently changed?

[Taz]

I agree with WeathermanShawn, by running and driving the vehicle for a while, you will have probably accomplished the OEM idle learn procedure.

For what it’s worth ….. anytime the PCM is disconnected from the battery, loses power, or is reprogrammed, the idle must be relearned.

PCM Idle Learn Procedure

1. Turn OFF the ignition
2. Restore the PCM battery feed
3. Turn OFF the A/C controls
4. Set the parking brake and block the wheels
5. Start the engine
6. Run until ECT is at least 176 F (80 C)
7. Shift transmission into Drive
8. Allow engine to idle for 5.0 minutes
9. Shift transmission into Park
10. Allow engine to idle for 5.0 minutes
11. Turn OFF the engine for at least 30 seconds


Regards,
Taz

[haulinit]

I'm sorry guys getting my logs confused the one where they read different are my log from running down the highway with the cruise on. I will post it later if anybody wants to see it. I added 10% to the entire MAF table. I will check the wiring again to make sure I don't have a wire out of place.

[joecar]

If those two pids are identical then either of these can be a possibility:
- shorted O2 signals,
- missing ground connection,
- bad PCM.

[haulinit]

If those two pids are identical then either of these can be a possibility:
- shorted O2 signals,
- missing ground connection,
- bad PCM.

OH dont say bad PCM that has crossed my mind! I would have to buy another liscense to reflash another 411 correct?

[joecar]

First try to eliminate all the other possible causes.

I pm'd Tech Support regarding licenses on a bad PCM.

[haulinit]

The 02 MV change in this log. This log was last night shortly after the reflash and about 20 minutes of driving. The truck is starting better, I'm going to drive it a couple more days then see what the trims look like. Thanks guys :cheers:

[WeathermanShawn]

Yes, it generally looks like your O2's are switching fairly normal. It looks a little spikier than mine, but maybe the exhaust and set-up creates a different pattern. It does look like they are switching 3-5 times per second, and the amplitude looks fairly good.

Odd that your Trims would go from +10% to -10% with a 10% MAF change. I would try to get them in the -2 to -4 range if at all possible.

See you still have that Misfire DTC. I'll have to look through my tune, but being cammed I may have desensitized my Misfire Parameters or DTC. Cammed cars throw them all the time.

So for now, it seems O.K.?

[joecar]

The O2S seem to be working ok.

[haulinit]

Shawn, I had my misfire desensitized in one of my tunes I may have to go back and change them again. Thanks Guys