Vader, I did try unplugging the MAF but it didn't appear to make a difference. I do believe this is to be a software issue.

bjankuski, excuse my ignorance but it looks like I'm displaying all the fields available. I guessing this is because of my ADX definition file? I downloaded the one from TunerPro (12227165_160.ads) which had to be converted to an ADX file. I did locate another (1227165_6E.adx) elsewhere that I've not tried yet. Am I correct in thinking that the available values are dependent on the definition file and can't be added in TunerPro once the def is loaded?

Adding the datalog for the 6E file: https://datazap.me/u/ta76/88corvette...&data=47-50-53

A lot more info but I don't see a AFR field, maybe I need to find the correct ADX file?

 

Adx file could use some work. Missing signals. O2 doesn't follow the integrator, but integrator behavior looks somewhat reasonable. O2 signal very lean. Rich/Lean flag also showing lean which fits with the O2 behavior. Short to ground, or bad O2 sensor. Can't see BLM, but integrator should continue climbing to force a rich mixture. Strange. Custom tune could be a hack-job with limited fuel trim authority.

Injector pw running around 2 ms, so it shouldn't be that lean even with standard size injectors (22-23 lb/hr). Fuel pressure? Fuel quality? Assumed to be ok, but both potential sources of error.

Try replacing the O2 sensor. I like the heated 4-wire AC-Delco O2 sensor. Significant air in exhaust due to misfiring cylinders is also a possibility.

Chicken and egg situation:

https://datazap.me/u/ta76/88corvette...2541-4545-6008

rpm/load/spark advance variation is driving rpm/load/spark advance oscillation. Need to stabilize the spark advance for the idle rpm/load region in the tune in order to prevent spark advance variation from exciting the oscillation and at least eliminate one variable.

 

What are the cam specs? This might make it harder to cold start tune the combo. TPIS/AFR195 heads?

 

https://datazap.me/u/ta76/88corvette...mark=6077-6131

Upon a closer look into the integrator, the saw-tooth action suggests that the integrator is being reset as the BLM cell changes in response to varying rpm and airflow. The repeating integrator reset (to 128) is likely preventing the blm from increasing sufficiently in each cell as the cells toggle, but still doesn't rule out a bad O2 sensor. This fuel trim behavior could also be contributing to the surge and lean O2 readings. Would be nice to see the BLM and BLM cell data to really see what is going on there.

I've posted an adx file recently that should help. Shouldn't be too hard to find if you search for it.

You can open and display the existing xdl file with a new adx and export to csv again. The xdl file should contain the entire datastream independent of the adx, so you don't need to recreate the event in order to see additional data that is missing in your adx or missing in the csv export.

Update/Correction: Disregard the above, I didn't see it before, but the BLM and BLM cell data is there:

https://datazap.me/u/ta76/88corvette...6077-6131-6170

BLM starts out at 150 and reaches the maximum of 160 (adding as much fuel as possible) but still lean O2. Integrator behavior still a bit strange, not sure what is causing the repeating reset which is keeping the integrator from continuing upward. Initial BLM cell toggling between 1 and 0 and resultant BLM toggling between 128 and 150 is a contributing factor to the surge, so there is a lot going on here.

Suggestion: Drive it (if possible) and collect more data to see the fuel trim behavior in the other cells at increased flow and rpm. I want to see if the ecm can ever provide enough enrichment to swing the O2 rich.

Check the fuel pressure. Can you identify the injectors? Maf flow is also a bit low for the conditions. Maf calibration/sensor quality unknown. Need to get into the bin and see what you really have there. Get a programmer and read the file from the memcal/eprom. Likely a hack job.

 

Thanks again tequilaboy, It does run fine once warmed up (although the throttle seems sensitive), I'll get a file driving it. Do you think it could be the cam as KSA Aaron suggested? I think the cam is on the mild side but I will get the specs and post. Also, I did talk with PCMs4Less, they seemed pretty confident he could provide a PROM specific to my mods. Unless it has been changed the PROM in the car was purchased from TPIS to work with the heads/intake/cam/exhaust setup.

KSA Aaron - I'm not sure on the heads, I've yet to figure out which version I have.

 

Hello TA76!

You are getting a lot of good information here. I have learned from just reading the posts.

Oxygen sensors were designed to be used for 24 months or 50k miles before automatically being replaced. The early Non-heated sensors are only really reliable when they are fresh. The sensor take a couple minutes to warm up top 600* (F) and then it starts making it's signal that oscillates between Lean and Rich very quickly. The average should be about .450 Mv. An older O2 does not make as strong a signal and it starts to lag which is even worse for the ECM. As they age and start to fail the O2's generally go towards the rich side to prevent damage to your engine. The Oxygen sensor is one of the MOST important sensors in your EFI system and yet it is also very cheap and easy to replace (most of the time). A new O2 will increase your vehicle's mileage and performance back to where the GM engineers designed it to.

Switching to a "Heated O2" would be a good thing for most C4's. It helps the O2 warm up even faster than the exhaust does it. The only down side is you need a good source of power for the heater and this will require new wires to make the circuit work. The later heated style O2's are able to reduce emission even more!

If you have a real MAF sensor go out and buy some special cleaner made just for MAF sensor cleaning. The sensor wires are 1/10th of a mm, very tiny and fragile wires. They need to have the crud burned off or cleaned off. In normal operation the "Burn Off" relay would try and heat the wire until it is glowing and clean again. A faulty MAF sensor can really affect the drive ability of a Corvette.

 

Thanks ctm! I have cleaned the MAF, not wanting to just throw parts at it but it might make sense to replace a cheap O2.

 

Datalog from a drive today (post warm up). Hopefully I can get a new O2 sensor tomorrow. About a 4-5 mile drive down the interstate, started out briskly then settled into a steady pace until I exited, then a small burst of throttle before stopping the recording. I did notice that the temp on the dash was about 5 degrees cooler and what was reading on the laptop.

https://datazap.me/u/ta76/88corvette...?log=0&data=50

 

https://datazap.me/u/ta76/88corvette...-1071-3008-797

New O2 sensor won't hurt, but won't solve anything. Your O2 sensor is cycling and functional with no apparent delay.

The tune itself is generally lean with BLM ranging between 144(cell 15 WOT) mid-150s (cell 10 cruise), and 160 (cell 0 and 1 idle region). Cell 0 and cell 10 are important since they feed the SAM cells and determine what the fuel trims will be initialized to on the next ign cycle. This is why you see BLM values of 150 while still in open loop.

Needs significantly more fuel everywhere in order to bring the fuel trims down towards 128 (no fuel correction). Injector settings/offsets are suspect. MAF responds to tps as expected.

Conservative spark advance (~30 degrees at WOT). Its knocking a bit and pulling around 7-8 degrees based upon comparison of spark relative to tdc and (spark relative to reference pulse + 5.98 degree initial offset). Knock retard scaling cannot be trusted.

https://datazap.me/u/ta76/88corvette...55-159-161-136

Increase the fuel pressure by 16-20 psi (if you can) to target about 60 psi without vacuum in order to richen things up globally as a first step (assuming that you have an adjustable regulator). This will increase the injector flow rate by around 4 lb/hr. Unfortunately no way to solve all of your issues without proper tuning.

 

Heavy throttle looks safely rich, but its not really making any power, but should have a bit more rpm: https://datazap.me/u/ta76/88corvette...97-168-155-157

Might want to actually open the throttle fully and keep it open to about 5500 rpm next time around.

 

Thanks again TB, sounds like I replacing the existing PROM might be the way to go. Think I should go ahead and bite the bullet on that?

 

I think it would be prudent to get a programmer and read the existing bin file from the current prom to see what you have now.

When tuning a car, I like to start with the car's original bin and go from there rather than try and force some generic one-size-fits-all base tune on everybody. In some cases, it may make sense to upgrade to a newer mask/bin which is a popular approach, but this almost never makes sense for 4+3 cars due to different hardware, ratios, gear switches or lack thereof, on/off switch wiring and control strategy differences from year to year.

When dealing with an existing off the shelf or custom tune, there may be something there that is worth retaining, or it may be complete garbage. The only way to know is to read the bin and compare it against the stock equivalent that it was based upon to decide if it is worth using as a base for further tuning, or to throw it out and start from scratch.

Once you have a programmer, you can use it to program an eprom by yourself whether or not you choose to tune yourself, or rely upon a tuner provided bin. Nobody wants to bother sending programmed eproms via snail mail anymore, but somebody may still be willing to do so.

Once upon a time, I sent a programmer to my customers with the condition that it be returned. With the low cost of programming equipment, this method is no longer worth the trouble.

As far as I'm concerned, programming and data acquisition equipment is a must have for anyone running a modified efi car. An ostrich or emulator is a nice thing to have also.

 

I wanted to do a quick followup on this. I engaged TPIS to help me on the tune and gave them all the info I had on the car. I received the new PROM in the mail yesterday, installed it in the car last night and fired the ol'girl up this morning. WOW! What a difference! Idle issue gone! Throttle response much better, the car feels even stronger and smoother. However, I am getting a Service Engine light and a noticeable miss-fire when driving in OPEN loop. That seems to get better once the car goes into CLOSED loop but it is still there. Will pull codes later today and see what that tells me. If I can get that issue nailed down I will be one happy Corvette owner!

Edit-Got the codes, throwing codes 13 & 14 now. Looking these up it seems that is my O2 sensor and Coolant Temp Sensor are bad? Find it kind of odd since the old chip wasn't throwing any codes, then again it had issues for sure.

 

Clear the codes and try logging data to capture the codes being set. Try and get an electronic copy of the new bin from TPIS, or at least a text export to see what has been changed.

Both the O2 and coolant temperature sensors were working fine in the previous logs.

Code 13 suggests an open circuit or weak O2 sensor. O2 sensor voltage between 0.35 and 0.55 volts for > 15 seconds.

Code 14 is high coolant temperature ( > 130 °C).

Perhaps a connection issue with the new prom and/or adapter. Strange.

 

Data log from a quick trip around the block this morning, car was misfiring like crazy with any acceleration. It is raining here so I couldn't get to crazy with the throttle. Any thoughts? Sending this to TPIS as well. The SES light did come right back on (after clearing last night). Would sure appreciate if one of you guys (ctm or tb) could give it a look and tell me your thoughts. Its a bit bewildering to me but I did order a book one of you recommended in another thread so hoping to school up on this system. Edit-Just checked the codes manually via the flashing SES light and 13 and 14 are still being thrown but I don't see them on the log?

https://datazap.me/u/ta76/88corvette...20-21-50-53-70

Adding log #2, car was in CLOSED loop mode, major bog or fuel cutoff near the start of the log when I pulled out on the main road and gave it some gas.
https://datazap.me/u/ta76/closedloop...?log=0&data=50

 

Strange that the SES lamp and blink codes don't match the logged data.

No time to get into details now, but the prom id that is shown (66) is common to both the old and new logs. Are you sure that they changed anything and are you sure that you're actually running on the new Prom?

At first glance, behavior including fuel trims looks very similar between the old and new. I suspect that you are still running on the old prom or the old one is the same as the new one, or they were just too lazy to update the prom id, or the adx is displaying the wrong data. Should be 2 bytes so value of 66 looks strange also.

Did they send you a complete memcal, or an adapter with new eeprom installed. Post a picture of both of your memcals and/or eeprom adapter if you can. Confused.

Updated: Disregard since these comments were based on review of same old data so they are out of context.

 

This is the old one I removed, the new one looked totally different. It had these pins on the side that required me to somewhat slide it into the case then seat the unit. I'll see if I can find a photo without removing the ECM again. Thx!

 

Did you plug the old memcal onto the side pins as shown:

http://support.moates.net/wp-content...nd-memcal1.jpg

Not sure what really happens without the memcal plugged in, but I think you lose the limp home mode fueling (resistor packs).

 

Well I feel like a dope, no I didn't do that. But I have now and the shitty idle is back. Do you think it needs a stock PROM plugged in the side instead of the old TPIS unit?

Edit-Doing a little reading, I feel my issue is still the old TPIS PROM. Specifically the resistor packs on it as the old PROM should be bypassed, but still running Cold Starts off it? I think if I can find a stock 88 4+3 PROM it might fix my issues. Am I on the right track? If so, any idea where I could get a stock PROM?

 

As I understand it, the resistor packs only provide a method for limp home fueling in the event that the prom has completely failed. This is not the case in your situation since the code on the prom is running. The prom contains both calibration data (parameters) and assembly code.

I'm not convinced that TPIS changed anything significant (or anything at all) on the new prom. I would request an electronic copy of the bin file, a change log, or a text export of the bin file to see something to document what has been changed. Otherwise, best bet is to get a programmer and read, save and compare the bin files from both proms yourself.

I don't think a stock memcal or stock prom is the answer, but always a good idea to compare any custom bin file against the stock bin that it was likely based upon in order to see what (tuning) changes have been made.

Your stock bin was likely ABTR (same as mine). I should have some old copies of my original, and other copies that were downloaded from gearhead efi and various other file share sources over the years. Let me do some digging and I will post a copy of a stock ABTR bin.

I believe this is my original: