Deputy_Dangle

iTrader: (1)

Hi guys, I really doubt the issue I am having is PCM or tune related but because the car is ran in open loop\speed density I thought this may be the best place to ask for help.

Setup includes:
347ci ls1
TFS 225 heads 62cc
Fast 102\NW 102
TSP Torquer2 cam 232\234 112lsa
FIC 42# resized ls1 injectors
newer corvette style returnless fuel system
all the other bolt ons that go along with such a setup
manual trans car


The car is a 97 Corvette with the original 97 PCM, with the 2 bar SD OS, but ran with a 1 bar sensor. I converted over to the SD OS a few months ago and began to retune the car from scratch, after getting the VE finished and starting on dialing in the idle\TF\TC table the car suddenly became very lean out of the blue. I assumed the fuel original fuel pump had fail and without doing any real investigation into the issue, i replaced the pump with a Lingenfelter\Walbro 255 unit. This seemed to solve my issue. But ever since then I have been constantly working with the TF\TC table attempting to get the car to return to idle properly. Last weekend I added a good bit of air to the TC table and the car really seemed to like it, I made small adjustments from there as it kept making the car run return to idle better. But all together the car ran great. I got into the car Monday to run errands in to and the car would barley run. I thought it may have been because it hadn't warmed up and it can be finiky until it does so. On the way to town I noticed it was running very lean, although running well enough to drive around, but did sputter and skip when leaving stops. I doubt any of that is relevant but I mentioned it in the off chance the TC\TF table may somehow effect the VE.

The car currently runs 4-5 afr points leaner (16.5:1-18:1) than it did before at cruising and in slight acceleration conditions. It reads 20:1-23:1 at idle. I don't think the wideband is completely accurate at idle but I don't think it is off at higher engine speeds. It was recently re-calibrated and didn't begin reading so lean until the engine began running poorly. Also the engine does not seem to have a miss or skip. I also don't see any signs of it being an overly rich condition that would cause the wideband to read lean.

So far I have checked the following:

Fuel pressure- holds 70 psi without issue, I thought 70 psi was a little high but after talking with people with the same pump it seems to be average.

I checked for injector signal with noid lights, all was good.

Pulled all the plugs, all the plugs looks good and where all consistent with each other.

Checked all coils and wires, all seemed good.

All sensors seem to be operating properly via the VCM scanner (map, tps, iat, ect)

I am going to pull the intake later today and double check for vacuum leaks, but after that I will be out of Ideas.

I've also attached a few scans of the issue to see if anyone can see something I may have overlooked. I anyone needs a scan with different PID's let me know and I will get it done. I will also attach the tune.

Thanks for any help
-Clay

Deputy_Dangle

iTrader: (1)

I just finished removing and reinstalling the intake. I didn't find anything wrong. It didn't solve the issue either. I am out of ideas.

Deputy_Dangle

iTrader: (1)

Also, for whats its worth, it's not throwing any codes.

Deputy_Dangle

iTrader: (1)

I checked and cleaned all chassis grounds last night and also tried a new map sensor just for the hell of it. Still no luck.

Deputy_Dangle

iTrader: (1)

Today I swapped the coil packs and fuel filter just to rule those items out which had no effect on the car.

I then uploaded a tune with the OLFA table set to 1.5 (was 1.0 before hand) in the 176-212 zone, this should have commanded an AFR of 9.8. Once the engine reached operating temp the AFR fell to around 13.5 at idle and all the issues the car had been having cleared up (sputtering on accel, stalling with big throttle increases, ect) and the car revved freely and quickly.

I think that rules out a possible ignition, mechanical, or fuel system part failure, but maybe not a failure with the injector itself (think pulsewidth issues).

But I am still pretty baffled by the issue and don't know where to look next.

mrvedit

I'm only an amateur at looking at other people tunes, but let me get the conversation started...
First your VE table entries in the 800-1200 RPM columns seem very low. I have a much wilder cam (239/251) and have "42" at 50kPa/800RPM and "45" at 50kPa/1200RPM while your values are 30 and 34, which would result in an extremely lean idle.
With your cam, I would expect values higher than mine.
Therefore for starters, your VE table look much too lean in that area.

Next, I don't think my engine would even fire at an AFR of 20+. This make me wonder if your widebands are reading correctly. I run widebands and the stock O2 on both banks. I confirm that the stock O2 are around 500mV when the widebands read around 14.7. It is a useful "sanity" check.

Last, keep an eye on the air temperature sensor; heat soak can cause it to read a much higher temperature than the real air, causing a lean condition.

Deputy_Dangle

iTrader: (1)

Thanks for the reply.

I guess I've never really compared mt VE to anyone elses but what gets me is the car ran great on this exact tune for several months. With that VE it would idle very steady around 15-15.3 AFR. But I will try some higher numbers to see what happens. But even then, the car is lean through out the entire rpm range, not just idle.

I don't think the wideband is accurate at idle at all, be it because of its location in the header that keeps it from staying at temp or possibly from overlap in the cam, I have no idea. When i tuned the idle cells of the VE I used the bidirectional AFR control in the scanner and set it based on what worked best. Which at the time showed around 15-16 AFR. The idle itself is very very steady, even now.

As far as IAT's go, I actually have the hood off of the car currently to help combat that issue. Without the hood the iat stays very close to the ambient temp.

Deputy_Dangle

iTrader: (1)

MrVEdit, I played around with the VE in the 400-1200 columns. Basically, when I added fuel with the Scanner the car of coarse ran better, but never reached the AFR I was commanding to it run. I made a few changes to the VE so the commanded VE in the Scanner corresponded with what I was seeing on the wideband, I added about 15% to the 400-1200 columns. The car ran much better this way, around idle and off idle at least.

But the rest of the tune is still very lean, I the rest of the VE is off by say 10-15%, the there will be some cells that are in the upper 120 range, which can't be correct. It makes me question weather or not the VE is the core of my issue or not. After all, the car ran pretty good with this tune in it for the last few months and then suddenly went lean. I used the injector data that was supplied to me by FIC when I bought the injectors, so I don't think the data is incorrect, although I believe they are scaled at 58psi and I now know I have 70 psi. I would think that would make the car run more rich than lean though.

Here are two scans, the first (run9) was made the night before I started having any issues. The 2nd (lean run) was made the next after the issue began. Both are on the exact same tune to give you and idea far off the AFR is.

Deputy_Dangle

iTrader: (1)

I changed the IFR table to reflect the 70psi of furl pressure which made the car undrivable, which I expected. I then added a total of 30% to the VE which created some very high numbers, and it still ran too lean.


I SWEAR I WILL PAYPAL BEER MONEY TO WHO EVER HELPS ME FIGURE THIS OUT!!!!!!!!!

Darth_V8r

iTrader: (4)

Please don't be insulted by this question, but is the fuel filter plugged? Have you had the injectors cleaned? Sounds to me like a possible obstruction in the fuel system. If you already checked that stuff, politely disregard the questions

mrvedit

Why are you running 70 psi? Are your injectors way undersized? Your 70 psi partly explains why you engine would even start/idle with the very low values in the VE table.
Darth_V8r might be on the right path - it sounds like your injectors are not giving fuel as commanded and/or are not linear. Clogged filter or contamination would match your symptoms, especially it suddenly leaning out.

Deputy_Dangle

iTrader: (1)

I swapped the fuel filter out Saturday, although nothing seemed wrong with the filter that was on it. The injectors where cleaned\resized\flowtested by FIC back in March. I pulled them out and looked at the filter baskets when I pulled the intake Saturday and they appeared to be clean.

[QUOTE=;
Why are you running 70 psi? Are your injectors way undersized? Your 70 psi partly explains why you engine would even start/idle with the very low values in the VE table.
Darth_V8r might be on the right path - it sounds like your injectors are not giving fuel as commanded and/or are not linear. Clogged filter or contamination would match your symptoms, especially it suddenly leaning out.[/QUOTE]

I assume it has 70 PSI because the 255 pump outflows the oem filter\regulator combo. When I first realized it had 70psi of fuel pressure I did some searches on the issue and it seemed like a common occurrence with that pump and regulator.

Also, If I use the AFR control in the scanner to richen the tune (by around 2.5-3 AFR points), the issue mostly goes away. Which leads me to believe the problem is not mechanically related. I feel like the problem is somewhat tune related, but I don't know what could cause the tune to suddenly pull so much fuel. If the problem was fuel system related i would think the problem would persist as I riched the tune.

Does that make sense?

mrvedit

Everything you say makes sense, but not seeing an obvious problem/solution, I at least am kinda grasping for straws. At least to give you something to consider.
You are obviously a smart guy and have already considered the fuel pressure, fuel filter and contaminated injector issues.
You are correct that raising the pressure and not changing the IFR table should richen the mixture. The amount is the square root of the new pressure divided by the old pressure. So Square root of (70 / 58) = 1.099 for a 9.9% increase.

Deputy_Dangle

iTrader: (1)

That's neat, I didn't know that.
Do you feel like the issue is maybe a discrepancy in the IFR and\or the VE? I really think the lower VE columns may be off like you suggested based on the fact that upping them made the AFR control in the scanner more accurate.

Deputy_Dangle

iTrader: (1)

A buddy brought over his new Fast wideband setup tonight. I first installed the new WB in the same bank as my current WB to insure mine was reading correctly, and both WB's read the same. Then I installed the new WB in the opposite bank to see if the issue may be on one bank only but both banks were the same.

Im going to look more into the VE and IFR tables and see what happens.

mrvedit

Ok, I finally looked at your lean_run.hpl scanner file. Strangely my standard .cfg file showed more useful stuff, like the commanded AFR, than your .cfg file, but I rarely look at other people's file.
Anyway, the commanded AFR was at least correct, but what you get will depend upon the IFR table, the VE table, the engine size and a few "minor" modifiers. And of course the actual fuel pressure and the actual injector size. Since you say it once worked OK and suddenly went bad (lean), perhaps we should concentrate outside the tune.

Now back to "grasping for straws"...

First, are you measuring the actual fuel pressure at the fuel rail? If not, that might help. Personally I run a regulator with return line and pressure gauge. I check that gauge regularly and am thinking of installing a pressure sender and logging it, as it is critical.

Next, a single cylinder misfire will give you an extremely lean reading on the wideband O2. You might expect the opposite, but these sensors read the amount of "free/unused" O2 in the exhaust, and when you have a misfire, there is a lot for free/unused O2 going out the exhaust. I recall that I once forgot to plug in one spark plug wire and my O2 for that bank read 18! (Its great to have a wideband gauge on the dash for each bank.)

Do you know if you are getting the same lean condition on both banks?

Again, just some novice ideas from me.

eaglegoat

What this all sounds like is that it was tuned by someone who doesn't know what they are doing. The fuel pressure should have been verified prior to the engine firing the first time.

With that being said, I suspect the fuel pressure was even higher previously and has dropped now, resulting in a lean condition, which accounts for all your poor drivabilty indicators.

When you changed the injectors to reflect the pressure adjusted size you also needed make corresponding equivalent changes to the airflow tables. Hence, why it became undrivable.

JakeFusion

iTrader: (7)

Just as a reference point, my VE table is in the 30s in the 800 and 1200 cell around 70 kPa (where my cam idles). You really can't base a tune off how it looks compared to another. I have good injector data, good fuel pressure, and it has a rock solid idle. If I push it to 40+ in the VE table, idle goes to **** and it becomes a surging mess that dies.

Deputy_Dangle

iTrader: (1)

I know, The 97 PCM is soooooo slow I try to run the bare minimum in the scanner. Anymore than around 17 status bits and everything slows way down. But I agree that the issue is more than likely outside of the tune.

Yes, checked at the rail.

Plugs and wires have crossed my mind several times as the issue. I checked them sometime last week and they all looked good and where firing. I put a wideband in each bank last night and the two banks were consistent with each other. To me that rules out any type of single cylinder issue, but I am defiantly not all knowing.

YES!!! Very much so.

The FP was tested when the engine was first fired, back in March or so. But sometime around June the FP went out (or so I thought) and I replaced in with a Walbro 255. Being that seemed to solve the issue immediately,other than a few minor VE tweaks, I didn't feel the need to recheck the fuel pressure. Lesson learned there.

I hadn't considered that but that is a very good point.

I have that same issue.

Deputy_Dangle

iTrader: (1)

Last night I decreased the IFR by around 15% which made the tune a little rich but for the most part was in the ballpark. I made some small changes to the VE to get it in more inline. I drove the car and it seemed to have way to much air so I zero'd the TC table. The car ran probably the best it ever has, for the first time it didn't need a ton of air in the TC to return to idle properly.

If the tune is in fact the core of the issue, I still don't understand why it would suddenly require so much more fuel. Unless adding air to the TC like I was doing before would cause a lean issue. The current injector data in the tune is now incorrect which makes me wonder why the it works so much better than the correct data. Unless I somehow got a botched set of injectors.

I attached the tune after the IFR\VE change and a scan of that tune.