So, I've been trying to chase down this problem for a few weeks now but I haven't gotten any closer so I'm looking for a bit of help.

It all started randomly, I was driving down the interstate with cruise control on and she started bucking a little bit like it was loosing fuel/power so I take it off cruise and it's fine for the next few miles until I get towards my exit and as I'm going up the off ramp I put the clutch in to go down from 5th to 4th and there wasn't the normal slow rpm drop, it just hit zero, so I pull it into 4th and pop it back alive, thinking okay that was wierd, except, exact same thing happens all the way down to 1st and it dies completely.

As I'm sitting there waiting for some fuel, that's what it seemed like was wrong, I thought to myself, **** my fuel gauge must be busted now it's still over 1/4. I try it a few times and she sputters a bit but won't start so I let it sit. About a minute before fuel came I tried it, this is after about 20 minutes waiting, and she fires right up, fuel gets there, I shut down, fuel up and she doesn't start again. We wait some more, it fires up, and there's not an issue all the way to my destination or the ~25 mile drive home, but that was after sitting for a few hours.

Fast forward to about a three weeks ago, coming home from an ~75 mile drive she dies in the middle of a fairly busy road just a couple feet past a stoplight intersection, luckily. But, it did happen to act up about 10 miles before the but that was doing about 75mph and I just let it coast in gear for a bit and she would be fine. Not this time, tried downshifting to keep it alive but got nothing. Had to have my passenger and I push it into a parking lot off the road and we waited, mind you it was like ~90 degrees out that day. Anyways, I let her sit about 30 minutes, tried it and sputtered but wouldn't start, waited another 30, same thing, repeated this a couple more times, nothing. Luckily I had a tow strap in the car and knew somebody with a truck.

Now, just about a week ago, same as the first time. She dies while driving around but fires right over after sitting for about 15 minutes and doesn't have a problem for the couple mile drive straight home.

As I've said, I'm lost on what the issue could be my log looks fine, the tune hasn't been adjusted in a few months. She was driving fine for months, with a slight vacuum leak, before this just happened out of the blue.

I would attach the datalog from that third time, but it and the tune even zipped are over the size limit. It was a long drive before it happened.

 

sounds like your fuel pump is going out. when it acts up test fuel pressure. also when it acts up check spark. if you have only one you know where to start looking.

 

Damn, I really hope not, that 3rd gen fuel pump is only about year and a half old with only about 12k miles on it. I did notice though that sometimes when I'm fully on it my AFR will drop to about 11ish and come right back up, faster than you can blink, as I'm climbing through 1st usually around 4-5k, but it does not show in the log that I can see.

 

It does sound to me like your fuel pump dropping out too. When did you last change your fuel filter? It could be a blocked orpartially blocked fuel filter...

 

A fuel pressure gauge would be a good first step.

Depending on your MS version you may have spare analog inputs to which you can connect a pressure sensor for datalogging.

Oh, as for the datalogs, they are just text files. Load up in Excel or even Notepad, then chop out all the extra rows before the interesting part starts.

 

Fuel filter was replaced at the same time.

Any recommendations on a decent fuel pressure setup? I'm running Ms3x so I should have a few spare inputs lol.

I'll try to examine the log file in excel when I get home and hopefully I can trim it down to the right spot, just wish megalog had the option to trim them built in.

 

I was having another look through the logfile and for some reason I thought maybe my FPR? Would that cause this kind of issue?

Anyways, here's the log, dramatically trimmed from 12.1mb to 1.17mb btw, and tune and hopefully somebody smarter than me can help figure this out.

 

Sigh, I can't open either of those files. It's not you, it's some weird issue with my laptop that happens whenever I download an MSQ or log file. It corrupts and turns into a binary file for some reason. I've not figured it out since it only happens on downloads.

Can you post an image of MegaLogViewer showing the log data from the time the car stalls?

If not, I'll try to remember to take a look on Monday when I'm at work.

 

Here ya go.

 

Something electrical is very, very wrong. Do you see how every signal goes completely nuts just before the car dies? That to me means a major electrical problem. Such as a bad ground, or a loose battery cable, or something like the alternator injecting a mess of noise into the system.

Without stepping through the log, that's my best guess.

 

I honestly don't see how it goes nuts. I see me downshifting to try and keep it alive and in turn map/ve1, rpm, and afr (fuel cut) all go up. Pw and duty cycle drop until it's back out of fuel cut. And clt drops about 2 degrees during fuel cut/decel which would also be normal right?

I mean, that all seems just normal to me. I also might be getting my hands on a fuel pressure tester kit some time soon so I can see idle pressure and static flow, but that's about it. I've been thinking that even though the log shows that PW and duty cycle kick back in, I don't think it necessarily means that anything is flowing right? Just what the calculated values should be, just like the fuel flow gauge in TS?

 

Okay, so following the FSM test procedure on 4a-66, I got 40, 34 with slight stuttering, and 40 psi each. Keep in mind this is on an FD pump, so I don't know if things would change? Also, where does that leave me? I'm leaning towards fuel pump, but could crappy stock fuel pump wiring or something electrical do this as well? I know it says to check the main relay and wiring harness, but if the relay was bad, wouldn't that mean 0psi, and I'm assuming the wiring harness would mean just the fuel pump wirring, correct?

 

I've rewired my pump and went from 10.7v to 12.3v with key on engine off, and I get 13.8v with car running, but I still get the same pressure readings except without the stuttering.

I had it running in the driveway for a while and it still wants to die, it leans out to about 16ish while just idling. I haven't grabbed that log to look though.

Does this help me in any way determine if it is the pump or not?

 

I was browsing through a couple threads and ran across the mention of the in tank hose deteriorating and the sock collapsing so I pulled the pump to check and snapped a few pics. It seems fine to me but a second or third set of eyes never hurt right?

 

I interpreted the wild oscillation as massive electrical noise, not you trying to keep the car going.

That pump looks fine.

I'll do my best to have a look at the MSQ when I can to see if there is something obvious.

Right now I don't have an explanation except that if it begins gradually leaning out, it generally points to fuel pump issues.

 

Well, I noticed the fallacy in my pressure testing method, I didn't block off past the gauge so I went to test it this morning and got ~94psi but all other readings were the same.

Also, I was just letting it idle in the driveway because it has just sat since last time and she started acting up so I grabbed my phone and took a quick vid of the pressure gauge when it happened next, which took a while so I trimmed the vid down. If you watch you can see pressure starts dropping before the engine starts slowing. Also, the car was fully warmed up and the log file and the gauges in TS didn't really show much other than MAP, PW, VE, and AFR skyrocket then return to normal.

 

I can't see the vid, says it's private - but going off what you're saying, I still stand by my first suggestion. Fuel pump issue or fuel filter blocked. Fuel filters are cheap, replace it. Worth a shot. If it keeps happening then you know it's a fuel pump or wiring issue to the fuel pump.

 

I didn't realize I had set it to private. Should work now. I've got a filter coming from the local O'rielly, gotta wait till Tuesday for it to get here.

 

Then there's your problem. Fuel pressure either by a failing pump, bad wiring, or clogged filter.

One of the reasons I decided to include a fuel pressure sensor in my Cosmo build. Actually I'm going to add oil pressure as well.

 

Well, I've redone the wiring, got a new pump in transit, and I'm grabbing a new filter in the morning. Hopefully I can finally have the 7 as a dd again, reliably. Here soon I hope to sell off most of this s5 engine and intake I have sitting around and run a new fuel line setup. I'm thinking -4 or -6, whatever is closer to stock hard line size, and Rising RPM rails just so I can squeeze an Aeromotive FPR in and get some nice looking AN fittings and SS hose.

 

Well, got the new pump and filter in. Still dies while driving, though not as abruptly. It started and idled fine in the driveway, took it out for a test drive and I was going through first and my afr gauge was all over the place and slowly started doing it in higher gears over ~3k rpm with less and less throttle input and lower and lower rpms. Eventually, it was a gradually leaned out to my MTX-L gauge's max of 22.4 and she just stopped. Still a bunch of lost sync 11 and 17 and I noticed while cranking in the log it shows almost 16k rpm in a couple spots and flashes between cranking and not down at the bottom of TunerStudio.

 

In what condition is the relay which controls the fuel pump? If you run it, can you feel it getting hot? Maybe pop off the cover and check the contacts for melting. Same with the wire terminals.

Also check the main power feed to the MegaSquirt, fuse panel, etc.

The 16,000 RPM blips indicate sync loss with the cat. May be a consequence of misfires, but during cranking indicates a weak CAS signal or noise (possibly from a bad electrical feed or ground).

There is something heating up and failing, it looks like.

 

Well, my starter decided to finally give up on me. I'm thinking that's why I got the 16k spikes as it slowed to non-existent rpms.

I guess this means I'll have to wait until I get another starter to continue testing. I'm currently re-examining my MS3x to DIYPNP BOB soldering, and haven't seen any issues. Just to clarify though, the shield for the cas is grounded in the MS right? So it shouldn't need to be connected to the BOB?

 

A faulty starter would definitely cause RPM spikes during cranking.

Correct, the CAS shield should only be grounded at one end, typically the ECU end.

 

Well, new starter is nice and I noticed a very slight fuel leak, didn't quite tighten the clamp on the filter all the way so it was leaking under pressure but has been fixed. Still dying though. It'll rev just fine when she's first started, after coolant temp is up of course, but after driving a bit to test, during which she started acting up, she struggles to rev above 3k unless I give it a lot of throttle and it leans out and pops and sputters around 6k and up. I'm gonna have to agree with something heating up and failing. I know wiring could do it after heatsoaking, but what else could it be? I know a sensor could possibly do this as well, but which do you think would do this?