Komet

Hey All,

I failed my test drive pretty hard today, looking for some additional eyes on my datalog. According to the shop manual I need to check the everything. This is an L98 350 TPI that sat for 11 years, so far I have replaced:

-All intake manifold gaskets
-Injectors (Delphi 22lb/hr)
-Cap, Rotor, Plugs, Wires (OE spec AC Delco)
-Holley AFPR set to 47ish PSI
-Fuel filter
-EGR valve
-195F thermostat
-VATS bypassed via jumper cable on relay and VATS delete module to ECM.
-Negative battery terminal, cleaned several chassis / engine grounds.
-Battery is 1 year old

Scenario:

Starts hard when cold, takes ~5 sec of cranking. Has a slightly hunting idle that evens out as it warms up. Stumbles a little when the throttle is opened usually, but not always. ECM has basically 0 miles on it since battery disconnect. It has ran pretty good in the past, but it's inconsistent. Drove approx 1/8th mile at 20mph, put it into reverse, engine sputters and dies. I suspect the front brakes are grabby and putting additional resistance on the system. Has a real hard time getting started again, eventually does but is sluggish. Limped it back home, kinda chuggle / surgey and low on power. Does continue to idle. Temp gauge in car reads 240, other gauges are whacked out so I don't trust them. Car has a history of moderate-severe electrical issues. Datalog says the engine barely hit 190, hoses kinda felt hotter than that. Heard some bubbling from the radiator which would indicate 210+. Put 4ish gallons of 92 octane gas in 6 months ago, might have mixed with old gas I couldn't siphon out but it didn't seem like there was a lot in the tank. I can't imagine I've used it all during the test runs. It's yellowish but that could be the lucas fuel treatment. Smells ok. Gauge says about 1/2 - 5/8 full depending on the temperature. Said 3/4 when I first filled it. I can hear the fuel pump running, every time I check it I've always got full pressure, seems unlikely to be fuel delivery.

Got a bunch of codes thrown in the datalog and probably more than one concerning number, is anything egregious standing out to anyone? The engine idles up ~200rpm when I connect the logger, can't take it out of 10k resistor mode or it won't connect.

Note: I am using the A028-L98-LB9-1985-1988-9600.adx data stream file in ALDLDroid, I can't get the A059-L98-LB9-1989-9600.adx to connect using this program but I'm under the impression the data should be the same, but at a lower baud rate. Could be wrong. Was able to connect at high speed baud rate using some other program and a PC but I sorta blew up the motherboard on that PC with a magnet unintentionally.

Reddragon88gta

I am no expert by any means but your IAC counts spent a good amount of time at 160 which I believe is maxed out, the BLM are in single digits which makes no sense because as low as it goes is 108 for very rich but that may be the lower baud setting in ALDLdroid. Also it never enters closed loop.

I remember when I started using ALDLdroid I used A028 and the data was not as fast and it raised the rpm up as well. The data was much better on A059 IIRC

I would at least check out the IAC or give it a good cleaning. Wish I had more for you.

What codes are you throwing?

Komet

Log says it threw these:
14 Coolant High
25 MAT High
41 Cylinder Select
24 VSS
32 EGR
42 EST Monitor (Knock Sensor)
52 CAL-PACK
53 Battery Voltage High
55 ADU (ECU)

From my perspective, it looked like the ECM was trying to add fuel really hard and it wasn't working (clue #1). I went out today with the idea that I'll start looking for vacuum leaks. Didn't super make sense given how well it was running previously but it's easy and I've got a little propane torch deal. Cranked for 4-5 seconds, no fire. I noticed the fuel pump was making a high pitched whine (clue #2). Usually it sounds like it's pushing against the pressure, sort of a whurrrumm. This was more like whirreeeeet.

I had a big THIMK moment and put the fuel pressure gauge on. 10psi, does not increase with fuel pumpage (clue #3). She ain't got no gas in it. Went and got me 4 gallons and it's running strong again, 40psi at idle, fuel pump noise back to normal, no repro on the dying in reverse, first gear pedal all the way down chirped the tires, etc. So yeah, I guess that's a datalog of what it looks like when TPI runs out of fuel.

Super not a big fan of the whispy white smoke coming out from around cyl #7 but that's unrelated to this issue.

Propane didn't increase the idle speed though.

SbFormula

Why 47psi? Standard is 43.5psi That will enrich your AFR in PE/Open Loop/Cranking and throw off your BLM if on OEM .bin. Waste of fuel?

Reddragon88gta

I run about 47-48psi on my slightly modded L98 and have better performance and near perfect BLMs.Some cars respond to more or less fuel depending on each engine set up. Also keep in mind I run Bosch 3s which tend to run leaner so a little extra fuel helps at least in my experience. I also have a non stock tune.

Komet it sounds like you nailed it with the low fuel if adding fresh gas helped, still trouble codes or did it all get better?

a62belair

CTS issue?
Changing this cured my intermittent issues.
I have the Bosch 3's as well on my LB9.

SbFormula

Thanks for the explanation. I am aware of all that. I was asking Komet who appears to have a stock L98 on stock tune with Delphi injectors rated at 43.5psi. The OEM tune tends to run rich at WOT, so increasing fuel pressure won't help matter.

Keep in mind that perfect BLM can't be an illusion as they are an average of a large area in your VE/MAF tables. You can get "near perfect" BLM on average and have extreme Max/Min. Also slowing down the rate of update will help BLM averages. BLM are in my experience inaccurate (and useless) as they react after the fact. I tune on the INT alone and it gives me a more accurate VE. The INT is instant and covers smaller cells. My BLMs have been disabled. BLM can also throw off your open loop and WOT in certain cases.

I also have bosh3s. I have adjusted my tune accordingly for voltage and low BPW. They did not run leaner but rather richer as they were more responsive than stock. So interesting that yours run leaner (which I don't know how you measure that?).

Anyhow, I guess I am hacking this thread. So I'll keep quiet now

Komet

The install sheet that came with the Holley AFPR said to try setting the pressure to 47, so that's what I did. I set it to 47 with the vacuum line disconnected. With the line connected at an idle it's more like 40 psi and when I rev the engine by hand it sorta drops to 39? (Does that mean my pump is weak? Great.) I don't have any data to support whether or not this is a good choice as I haven't actually driven the car anywhere yet, but I will continue to get datalogs.

Feel free to hack my thread though, I like learning stuff and would eventually like to move on to upgrading / tuning my EFI.

SbFormula

Stock pump is good for 50psi if I remember (don't quote me lol). Definitely something wrong if at WOT you get on 39psi!! At Idle I get 32psi with AFPR adjusted at 43.5psi. I get 43.5psi at WOT. My 383 pulls lots of vacuum at idle though. I have a Walbro 255lph pump on stock fuel lines.

If you have an original fuel pump, I would definitely change it for prevention.

Reddragon88gta

My tuner, Tuned Performance, mentioned the Bosch 3s tended to run leaner than stock which I noticed when adjusting fuel pressure up my data went from a tad lean to just right. I noticed as well that INT was very close to 128 as well at the 47-48psi but I am far from an expert and appreciate the info about the importance of INT over BLMs.

You are correct that the stock tune is rich but I read the old TPIS articles about bumping pressure up and getting more power but the reliability of that info is dicey…the FPR is almost used to trick the ECM it appears but regardless it’s been useful with making small adjustments and I followed the instructions just like Komet. With my experimenting with fuel pressure my performance went down if I went below 43.5 and up when I went over that. I read some guys on here said they went faster with less fuel too. I don’t want to hijack the thread either but Komet seems cool with it and just wanted to share my experience. Once again it depends on each individual car and it’s mods

SbFormula

Interesting! Bumping the fuel pressure is basically adding fuel across the board without touching the tune. So at WOT, it could increase performance as it increases AFR. Like you say, it depends on each vehicle. My original LB9 was running mid 11 for AFR on stock tune at WOT. When I swapped for the Bosh3s, it was even richer including BLM. I had to pull some Voltage and low BPW usec adjustment in the tune. Had to adjust VE to get AFR at 12.6 average at WOT. Problem with increasing fuel pressure to gain performance at WOT is it affects start-up and Open Loop also. It could create rich condition at start-up. In certain case, too much fuel pressure can affect injectors opening at idle on low BPW. Bottom line, I'd rather keep the pressure at 43.5psi and tune VE at WOT with an AFR gauge and maybe dyno session (coming soon!). If I increase fuel pressure, it'll throw off all my start-up and open loop tuning. Another trick to add fuel across the board is to decrease injector flow rate in the tune without touching the fuel pressure. That will keep the injector opened a little longer.

BLM can vary greatly depending on air temperature, engine cycle: under 30 minute of operation, heat soak, etc. and also ethanol content (another complicated topic).

While we are at it, if one is not using a catalytic converter, they don't have to use closed loop and basically get rid of INT/BLM all together, tune with AFR gauge in open loop.