Rough running

[Billy Mild]

Originally Posted by Paul Workman

Gotcha.

The cross-counts...I'll have to do some more research/comparison. But, zero and 1 are waaaay low - ordinarily. I can't rule out a test equipment data error (yet). I'll have to get back to ya on that.

The extension I got at Harbor Freight, believe it or not. But, I've seen them on ebay and AutoZone's site (once) too.

Can the MT 2500 be "que'd" so that it can capture events in a time frame? My datalogger will do that and is how I was able to zero in on the the intermittent cause by seeing the "before and after" data when the problem occurred.

Are we having fun yet???

MT2500 does have a datalogger option that has a printer and you can capture "movie". I don't have manuals so it just is me poking around. I don't have the printer either.

Might be time to get ALDL droid and do some datalogging.

[Billy Mild]

I'm still waiting for my Bluetooth adapter for OBDI to do some true datalogging.

In the mean time I did some messing with the car. I swapped out the computer with an NOS example and went for a 45 minute drive. It seemed to run just fine. This could mean a few things.
1. The car only acts badly when its over 95 degrees out
2. The tune is off when its hot outside
3. The ECU is bad
4. Its something else all together

I was still getting weird BLM and INT numbers from my scanner when driving. Rarely was it close to 128 for BLM.

I decided to take a look at my spark plugs. Here are the pictures of my spark plugs. The plugs have 5000 miles on them. The gap was .045(which is not correct) and look to have some white powder on them. They are not black and sooty which is what I would expect from how the car has been running.







After swapping out the plugs I went back to my ECU and went for a drive. It seemed to run fine except occasionally would stumble around the transition from before and after the secondaries would start opening. For example, coasting around 2700 rpm to a stop then mashing the throttle would cause a hiccup, or when going slow and stabbing the throttle it seemed to hiccup.

I am going to drive the car to work tomorrow and see how it does. If its bucking or not smooth then I will swap out the ECU again to see if that clears it up.

[Billy Mild]

Today the Vette seemed to run okay. It did die on my after coasting on an off ramp from the highway. I will still rolling so I pop started it.

Tomorrow is supposed to be hotter, maybe it will act up.

Could a bad IAC cause running issues below 3000 rpm?

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[Paul Workman]

Originally Posted by Billy Mild

Today the Vette seemed to run okay. It did die on my after coasting on an off ramp from the highway. I will still rolling so I pop started it.

Tomorrow is supposed to be hotter, maybe it will act up.

Could a bad IAC cause running issues below 3000 rpm?

Sent from my Nexus 6 using ZR-1 Net Registry mobile app

A couple of things are bugging me about your results:

The IAC counts...What are they?
The one BLM numbers...128 is nominal, WHAT IS THE OTHER BLM #s??
O2 counts: What ARE they - left and right?

In my experience, the FA mix has to be pig rich before it will stumble (misfire) like I think you're describing. The plug(s) would be either wet and smell of gasoline, or sooty black so as spark would be bridging through the carbon, rather than jump the gap. AND! Such a rich FA would result in hard starting, and once it does start, you'd be getting black soot blowing out of one or both exhausts. Whte-ish indicates LEAN, and lean will cause misfire (stumbling) w/o the black smoke! What say you?

BLM #s, or high IAC counts, don't necessarily mean either sensor is bad. But, rather the ECM's response to CLOSED LOOP readings that are out of whack, and it trying to compensate and correct it will result in sensor readings that are outside of the window.

LOW 02 cross-counts = a lazy sensor, and if O2 average voltage is LOW (lean) or high (rich) you can expect the injector dwell time to be opposite - the ECM trying to correct the AF ratio. (The kicker is that it may not throw a code - due to the nature of the problem (being randomly intermittent).

Divide and eliminate.For giggles, SWAP THE O2 positions (left one to the right, and visa-versa) and see if the BLM #s "swap sides". And, see if the O2 counts follow the O2 swap.

Gotta run...got a friend's sick 81 (C3) in the driveway, and he's here now to work on it.

[Billy Mild]

The BLM numbers under WOT will be 128 on both sides. Sometimes under cruising the right side will be 116 BLM and the left side will be 126 BLM. What truly affects the BLM numbers?

The highest I have seen crosscounts is 4 or 5. Usually its around 0 or 1.

Today the temperature got up to 101 degrees. The car ran great all day. Occasionally when coasting to a stop right after pushing the clutch in the car would idle really low sub 500. It recovered everytime today, unlike yesterday where the engine died.

I will swap the O2 sensors maybe on Sunday.

[Paul Workman]

Originally Posted by Billy Mild

The BLM numbers under WOT will be 128 on both sides. Sometimes under cruising the right side will be 116 BLM and the left side will be 126 BLM. What truly affects the BLM numbers?

The highest I have seen crosscounts is 4 or 5. Usually its around 0 or 1.

Today the temperature got up to 101 degrees. The car ran great all day. Occasionally when coasting to a stop right after pushing the clutch in the car would idle really low sub 500. It recovered everytime today, unlike yesterday where the engine died.

I will swap the O2 sensors maybe on Sunday.

The Block Learn Memory (BLM) #s are indicative of the AF mix, long term. 128 is nominal and should be w/in (some say) ± 10 or better (i.e., ±5) in closed loop.

It isn't possible to say THAT is your problem, BUT it very well COULD be. It needs to be addresses - made right - before continuing.

#1 cause of (lean) in CL is the O2 sensors. And, low or zero cross-counts indicate a "lazy" or non-functioning O2 sensor. That will typically be reflected in BLM #s, IF there isn't multiple faults (i.e., something else adding to the overall symptoms!). Let's fix one thing at a time, and see what we have left after that.

Your BLM discrepancy in C/L is what I would expect if one O2's cross counts was low as 1. Cross counts as low as that is indicative of a lazy/dysfunctional O2 sensor; is why trading places with the O2s is one way to see if it the sensor, or perhaps something else. My guess is if the low counts follow that sensor, you can plan on replacing one - if not both sensors. Let's try swapping sides and see what happens to cross-counts, and after a short trip around the block a few times, see what the left/right BLMs are. (Might want to erase the BLMs by first disconnecting the battery for a minute before going for a drive so they can "reset". Then see what changed, if anything.)

Gotta run!

[Billy Mild]

Would unplugging all the plugs to the ECU be enough or do I need to unhook the battery for 10 minutes to completely clear it?

The car has been running just fine the last few days in the extreme. Its like she is back in action now. I'm guessing the larger gap of the old plugs(5000 miles old) and the extreme heat were causing some misfires.

I will reset the ECU later this weekend along with swapping the O2 sensors side to side.

[Paul Workman]

Just unhook the positive cable from the battery for a minute. That will reset amy cades as well, clean slate!

[LGAFF]

have you checked your MAT sensor?

[Billy Mild]

Originally Posted by LGAFF

have you checked your MAT sensor?

I have not. After the plug swap it seemed to run better. The car overall today seemed to run pretty good.

I still notice when coasting that it has a slight backfire and burble that I don't think should be there.

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