Hot start stalling and low voltage

[Darius]

Hey fellas,

I'm not having any luck here so I am looking to you for some ideas and remedies. My RB25 has been acting up once it gets up to operating temp. Here's a link to the Youtube video of it idling.
http://www.youtube.com/watch?v=8rallMGZiQ4

Here's the writeup I wrote in the description section of the video:
"Troubleshooting what appears to be several things. First, it was running good all summer on the same tune. Raced a guy and the next morning the exhaust pulse sounded different.

No knock, good oil pressure, reloaded the tune, good battery, alternator and grounds everywhere, no change. Drove it more and now it cold starts fine but stalls on hot starts if it even starts in the first place.

So I replaced the IACV and that seems to have helped with the stalling after heating up, but I haven't redone the idle learning yet either so it idles artificially high. The Supra TT Denso fuel pump pulls 10.4A all day, so that seems about normal. I swapped out each LS2 coil pack and no change. I tested fuel pressure tonight (in video) and it is 35-37 psi which is low but increases with boost. I'm focusing on the fuel pressure regulator there as it probably needs to be upgraded to an adjustable unit.

The voltage dropping to 13.7V concerns me because it has never dropped below 14.0V for as long as I've had the car. And it is intermittant and only when the car is hot. After the video I restarted the car and the voltage was at 14.0 with both fans on. It might have dipped to 13.9V by the time I turned it off, but this just shows how inconsistent it is.

The fans each pull 15 amps, the fuel pump 10A, and coil packs 2A. The previous alternator was 1yr old and it also did the same thing as the one that is a week old. I doubt I got two failed alternators. Next I'll try to run separate battery voltage signal wires because I'm thinking the alternator isn't receiving accurate voltage readings so it knows when to bump up the voltage.

I'm really looking for help here guys. Any ideas are welcome...just don't say "it needs a grounding kit" "

Sorry for the lengthy read, but I feel like I have tried everything and am at my wits end.

[LeD ippen]

Is it missing firing or anything else. the symptoms you describe sounds like coolant temperature sensor (Ecu one) or the Camshaft position sensor. i leaning towards the cas because usually things like cas or crankshaft when they get hot the car does not want to start no more and stall at times. this happens a lot on gm car with the crank sensor and hondas with distrubitors (crank sensor inside distributer). hope this helps good luck.

[Darius]

The CAS definitely gets too hot to touch sitting behind the radiator. And it is randomly missing infrequently but not under load and not while driving, only while idling. Odd I know. While driving, it acts totally normal except the AFRs are high and widely variable. Off throttle, it wants to bog down and stall.

I can try out a new coolant temp sensor too. That isn't a big deal.

[gawdzilla]

maf going bad?

[Darius]

I don't think so. It allows me to pull hard well above 3000 rpms and doesn't studder or hesitate at all. The driveability of the car while cruising or accelerating is so good that you'd never know there was something wrong unless you had the gauges telling you so.

[240z4u]

Your long winded explanation became boring to me about half way through, so Ill make a suggestion based on skimming;

Is your narrowband 02 sensor taking a poop? It is only used in some parts of the map on the PFC for closed loop operation, part of it being at idle.

You have beotchworks injectors? Wonder if one of those things is hanging up. Are you seeing richness when it dies or lean? What about when you are attempting to start it?

Keep it real.

[Darius]

OOOh don't get short with me pancakes!

I do not run with O2 feedback on in the PFC. Does the PFC still use the narrowband for idling regardless if O2 feedback is on or off?

Yep I have Deatschwerks injectors and I can feel all of them firing. The AFR is between 14-17.0 and varies widely between that range. I can't see what the AFR is when I start it because the wideband unit goes into "warming mode" whe I turn the key to start.

[Darius]

Checked the ECU coolant temp harness and found that the wiring was discontinuous from the plug to the ECU on the purple wire (pin 28). The blue wire (pin 30) looked good. It also looked like the connection to the DIF fan controller for temp signal got hot.

And after further inspection my coolant temp sensor is shot. I'm hoping the DIF fan controller didn't receive any damage...or cause it.

[eh?]

I was gonna say check your data logs. Do you have a datalogit?

[Darius]

This gets weirder every time I work on it. eh?- I don't have any recent logs with it stumbling. I have previous tuning logs that show the voltage staying constant at 14.0 all the way to redline.

Here's what I found last night. I replaced my coolant temp sensor and was testing the harness to make sure it was good after I repaired it. Following the FSM, it says to turn the key ON and check pin 1 (PU) vs ground and it should show 5V power. CHECK!

Turn the key OFF and check pin 2 (B/L) to ground. CHECK!

Plug in the coolant temp sensor and check the voltage at pin 28 (PU) at the ECU with the key ON. NOPE! No voltage.

So I start testing continuity and there is NOT continuity between the PU wire at the coolant temp sensor plug and pin 28 at the ECU. Yet, my PFC hand controller is registering a temperature of 27*C. What the hell is going on here? Also, I probed around the ECU plug and found that several other pins have continuity to the coolant temp sensor plug. I'm assuming this is internal to the ECU and is a common power supply to some sensors??

[Darius]

I keep updating this in hope that someone will come across it and know what is wrong with this thing LOL

I replaced the FPR <edit> and coolant temp sensor tonight and it started up cold just fine, typical. After I got to my destination, I figured it wouldn't start because it would be a hot start. So I test started it when I arrived; it started up like it should without hesitation. After I let it sit for a couple hours while I ate dinner and had a couple beers, I went to leave thinking my problem was resolved with the new FPR, the little bastard started acting up again and it took three long runs with the starter for it to finally turn over and idle. When it finally started, it fell on its face and I had to restart it again. Finally I kept the idle speed up to prevent it from dying and drove home. No issues on the highway, typical.

[LeD ippen]

how is the a/f? maybe o2

[Darius]

The AFR was consistently lean prior to replacing the FPR. Now it is consistently rich. I need to do the idle re-learn and reload my tune to get back to normal and see if it goes back to being lean. I have also been wondering about the stock O2 sensor being faulty and giving me crappy idle learning. I replaced it with the original swap 5 years ago, but it may have failed. That would also coincide with why this started happening after a couple of hard race pulls. The logging, however, shows my O2 sensor fairly consistant at 0.8V showing that I'm running rich, which matches my wideband too. I'm not counting it out, that's for sure.

My next step is to perform the idle relearn, reload my tune except the idle cells, and re-evaluate the symptoms from there. I think I've changed too much to make any further assumptions until I get AFRs back to where they were.

[240z4u]

You think your breathalyzer interlock could be causing this problem?

[240z4u]

^ Kidding of course, the wiring for that would not cause hot starting problems.

[eh?]

Neeed to see logs.
Have you checked for Vacuum leaks? Hows the fuel pressure when it occurs?
Don't see how the stock o2 would make a difference since you said o2 feedback is off.

[Darius]

I logged on my way into work today and nothing seems to be out of the ordinary. I compared it to my last log in May and can't find any real discrepancies. I haven't pressure tested the system since this spring, so I should do that to be sure there aren't any leaks.

I do have O2 feedback turned off, but I wasn't sure if there was some weird function in the PFC that still utilized the O2 sensor for idling or something like that.

Evan, they don't give a breathalyzer interlock for your 7th DUI, only for 3-6. They upgrade you to the ankle bracelet with automatic alcohol detection just like Lindsay Lohan has. I'm wondering if that could give off an electromagnetic field which could be throwing off my MAF signal.

[240z4u]

Evan, they don't give a breathalyzer interlock for your 7th DUI, only for 3-6. They upgrade you to the ankle bracelet with automatic alcohol detection just like Lindsay Lohan has. I'm wondering if that could give off an electromagnetic field which could be throwing off my MAF signal.

Well done sir.

[Darius]

Update:

I reinitialized the PFC and tried to do the idle learning process. I say tried because the car stayed at AFRs of 10.8 and 10.9 the entire time. My garage wreeked of rich exhaust even with the door completely open. While it was going through the idle relearn, the fuel pressure was 45 psi with the vacuum line attached. I'm picking up a new narrow band O2 sensor today because I can't see any other part malfunctioning to the point that it would cause the PFC to not adjust the fuel mixture at idle so the AFRs were in the 14's. If anyone has opinions otherwise, please let me know because if this doesn't work I'm running out of ideas.

[USMCgetsome]

i'm gonna say the maf is killing you. Are you watching the sensor voltages?

[Darius]

I am going to try to calibrate the wideband sensor tomorrow night to see if it is out of whack. It initializes fine and idles like normal but the wideband says it is really rich. If it was idling at 10.9, it would be stumbling pretty bad. I'll update you tomorrow. And I'll check my MAF voltage logs too, but I think it is good because I can drive it just fine and it doesn't break up or cut out at 3000 rpm or anything like that.

[Darius]

I calibrated the wideband and there were no changes to the readout. I ordered a new sensor tonight. This sucks!!

[Darius]

I've been considering the possibility of an exhaust leak, but most of what I read on the internet shows the AFR's running leaner and not richer. Does anyone have similar experience with that? I'm trying to prepare for if the new WB sensor responds with the same reading as the first WB sensor. I'm fresh out of ideas after that.

[240z4u]

Have you checked for chafed wiring anywhere? It still could be a maf problem.

[Darius]

I reloaded my old fuel map to get it running halfway decent except I left the idle cells intact. I drove it around quite a bit tonight and the AFRs are rich under idle conditions. They are also slightly rich through the rest of the map that I reloaded but I attribute that to running slightly higher fuel pressure than the stock FPR was creating (45 psi at idle vs. 40 psi or less).

I'm still at a loss for why the ECU is calibrating the idle at 10.9 and not leaning it out. I'll pull the MAF off and clean it just to be sure it isn't a problem. I will also check my logs to see what its output voltage is compared to what it was when it was running fine.

[Darius]

I checked my datalogs and the MAF is reading the same voltage at idle as it did 6 months ago when it was running strong and tuned (1.23V). I haven't cleaned it yet, but don't see a real need.

So I thought the wideband sensor had taken a crap and bought a new one. The new one reads the EXACT same as the old one so I must have a fuel injection related problem. One thought is that I have a leaky injector. They all tick when the car is running so I don't think one is sticking open. It will be obvious when I pull the spark plugs if either situation is the case. I really hope it is just the injectors. Deatschwerks please don't fail me now. The Midcoast Road Rally is next Saturday and I CAN'T have the car be out of commission that day. I suppose I can run the car as-is because it runs smooth, doesn't bog down, doesn't miss, etc. You'd never know something was wrong with it unless you could see the wideband and smell the exhaust at idle. It doesn't smoke at idle but it definitely smells rich. It smokes a little on the highway under load because of the richness, but those are the only symptomes. However, I want to be able to lean it out and increase the boost before the rally.

A second thought is that my PFC is not calibrating itself properly or it is not controlling the injectors properly for whatever reason. That would majorly suck if something was wrong with the PFC.

Third idea, mayyyybe CAS??? But that tested out according to the procedure in the FSM.

[240z4u]

I keep a spare cas at home, if you want to try it you are welcome. Seems unlikely though.

[Darius]

This gets weirder every time I work on it. I swear to god this thing got shipped from Japan with The Grudge.

I pulled the plugs last night after letting it idle for a little. ALL of them were damp with fuel not just one or two. So WTF is going on with my PFC? Why won't it trim the fuel back during the idle-learn process? I'm manually doing it now because I don't want it to guzzle gas while it idles, but it surges when I do that.

I've double checked my fuel injector scaling values and they are all good with the flow test results that Deatschwerks sent along with them. I'm beginning to think that the PFC is not recognizing that it needs to trim fuel for some reason. So weird...

[Darius]

Update (again): I took the car out yesterday and tuned the mystery problem out of showing symptoms. The idle surges up and down intermittantly, but I can live with that.

I also tweaked the boost ramp setting that I had dumbed down due to traction issues. I forgot about it and had since bought drag radials and never changed it back. Increased that setting almost 50% and the car becomes an entirely different animal. Fun with tuning!

[DeatschWerks]

That's good. Still humming along?