Fueling issues: the "I've completely surrendered" edition

[MTBwrench]

I've been chasing some recent, really unsafe, fueling issues. I'm hoping possibly someone could chime in and perhaps help me mull this over. Many minds are better than one. I'm at a total and complete loss here.

 

Build Details: Fresh rebuild (250 miles in) with all new gaskets everywhere. I installed a VF52, TiAl 38mm wastegate, and ID1000 top feed conversion paired with Injector Dynamics' LGT fuel line kit. DW65c replaced in January, and I just installed a new new one today (used two o-rings). Fron O2 was also replaced with a brand new OEM sensor. More details can be found in my build thread (Search "DD Racewagon Build") Currently on a break in basemap from Boosted performance, with a few revisions to see if we can snag the issue.

 

Here's my issue: Its just running crappy, and randomly leans out. I'm also getting a ton of 1 to 3 count roughness in all 4 cylinders. I first noticed this upon first startup... AFR's were in the 12's and then steadily rose to 15-16 as the ECU learned idle. Cruising around, it leans out and bucks/misfires between 2500 and 3000rpm. Everywhere else it pretty much keeps 14.6-14.7AFR. I haven't been past 4000. Upon application of throttle it immediately leans, stalls, then returns to stoich and carried on with its day. Under boost, granted I've only done a few <10psi and no more than 4000rpm, it flatlines at 10.0 and stay there. AFR numbers correlate almost exactly between my front O2 and wideband O2.

 

In light of all of this, I rented a fuel pressure gauge. One odd thing I noticed, when I disconnected the feed line under the hood to splice in the gauge... almost no pressure came out, and maybe a shot glass worth of fuel. Definitely not the mess I usually get. Pressure read ~31psi at idle and rose to ~42psi with the reference line unplugged. Cruising around it floated between 30-40psi, and rose to ~50 with a few pounds of boost. From my research, this seems okay. I've replaced the fuel pump, filter, front O2, and put fresh gas in it. There has been zero improvement. All that's really left is an electrical issue, or the regulator. Seeing as it doesn't hesitate to start, and pressures were okay according to the fuel pressure gauge, I'm leaning away from that. Any ideas?

[m sprank]

Compression, timing, vacuum leak, MAF sensor, I can keep going with hypothesis.

[MTBwrench]

Compression, timing, vacuum leak, MAF sensor, I can keep going with hypothesis.

 

To answer your questions: I've done a boost leak test which revealed no leaks, and A/B trims are also pulling a minimal amount of fuel. Compression and timing I'm *assuming* are just fine seeing as I'm on a break in map and its a an OEM shortblock with freshly rebuilt heads. The MAF sensor is a different story. I've never replaced it... and I actually just pulled it out of my intake about an hour ago. It was COVERED in black soot... time to clean and oil my GrimmSpeed filter. I've also ordered a new MAF. I cleaned the existing one, and it seems to be smoother whilst cruising, but still bucks hard with application of throttle. I urge you to keep going with hypothesis!

 

I'm thinking the fuel pressure regulator could be a feasibly hypothesis as well, it just doesn't seem right that there's almost no pressure relief and nothing coming out of the supply line when I disconnect it. I used to get showered in fuel. Not opposed to getting an aftermarket regulator. My stock one has every bit of 215,000 miles on it.

 

I've attached some logs, for those curious enough to look.

Accel.csv

Idle.csv

[birkhoff]

MAF sensor covered in black soot?? There's a smoking gun. Or smoking something. If you are still running the stock airbox, get a new OEM filter (or any dry filter for that matter), clean the MAF sensor and the inside of the airbox and see where things go.

 

With the stock airbox/filter my MAF sensor looks clean after 20, 30, 40 K kilometres. I've only rinsed it twice in the time I've owned the car (6 years?) and it really didn't look like it needed it!

 

If MAF signal is faulty and not reacting when you open the throttle, then no wonder it goes lean. I suppose you could log the voltage from the sensor along with other parameters, but really, it shouldn't be getting visibly dirty anyway.

 

Added in edit: if you are getting misfires in all cylinders, that it a good thing, in a sense. The rest of us are chasing trouble isolated to one cylinder, which sounds better but experience is proving it to be a tougher nut. All cylinders means something global. Some kind of air or fuel metering problem. At least that is how I would interpret it.

[solidxsnake]

MAF definitely seems suspect. Even though you've already ordered a new one, I'd try cleaning the one you have as well. Also, I assume you know that the thermistor you see clearly when you remove the MAF sensor assembly is not the MAF sensor, but the IAT sensor instead. The only reason I mention it is that when you say it's covered in soot, I wonder how you can even see/tell that, as the actual MAF sensor wires are quite difficult to see, even with good lighting. I would think it's tough to visibly examine them and determine they were dirty. The IAT sensor, on the other hand, is very easy to see and will often get quite dirty.

[MTBwrench]

MAF sensor covered in black soot?? There's a smoking gun. Or smoking something. If you are still running the stock airbox, get a new OEM filter (or any dry filter for that matter), clean the MAF sensor and the inside of the airbox and see where things go.

 

With the stock airbox/filter my MAF sensor looks clean after 20, 30, 40 K kilometres. I've only rinsed it twice in the time I've owned the car (6 years?) and it really didn't look like it needed it!

 

If MAF signal is faulty and not reacting when you open the throttle, then no wonder it goes lean. I suppose you could log the voltage from the sensor along with other parameters, but really, it shouldn't be getting visibly dirty anyway.

 

Added in edit: if you are getting misfires in all cylinders, that it a good thing, in a sense. The rest of us are chasing trouble isolated to one cylinder, which sounds better but experience is proving it to be a tougher nut. All cylinders means something global. Some kind of air or fuel metering problem. At least that is how I would interpret it.

 

I found it weird that I was covered in anything in the first place... It never was when I had my OEM airbox. Currently I have a GrimmSpeed CAI installed, with the oiled filter, and it definitely needs a servicing. I might get their dryflow filter, to avoid getting oil on the MAF and causing that issue as well. I'm glad the issue is global as well... if it was one cylinder I'd be saying my prayers and checking compression. :rolleyes:

 

MAF definitely seems suspect. Even though you've already ordered a new one, I'd try cleaning the one you have as well. Also, I assume you know that the thermistor you see clearly when you remove the MAF sensor assembly is not the MAF sensor, but the IAT sensor instead. The only reason I mention it is that when you say it's covered in soot, I wonder how you can even see/tell that, as the actual MAF sensor wires are quite difficult to see, even with good lighting. I would think it's tough to visibly examine them and determine they were dirty. The IAT sensor, on the other hand, is very easy to see and will often get quite dirty.

 

Well, I'll clarify: looking at the MAF housing it was covered in a thick black coating. The thermistor had probably about 0.5mm of crud on it, and I could see the grime making its way up and into the MAF body. I'm almost 100% sure this is due to the oiled GrimmSpeed CAI filter, so I'll be getting a single use dryflow filter instead. At the tiime when I got in on the group buy for the intake, they didn't have the dryflow as an option yet.

 

I cleaned the hell out of the current one with MAF cleaner, and it made quite a difference! I'll report back when I get the new one installed on Monday. I'm still leaning towards getting an Aeromotive FPR and come type of inline fuel damper, just for good measure. The way I look at it, I have so much invested at this point it may be a bit of insurance.

[m sprank]

If the FPR is suspect there is nothing wrong with an OEM replacement. If going to an aftermarket, I prefer the non-adjustable type like Outfront or Radium (Bosch regulator).

 

Sounds like you are on to something with the MAF. One thing at a time so as not to get ahead of ourselves.

 

Your logs show little, too many parameters and there is no misfire. Your AF 1 learning is high (almost 8% which should be considered the max allowable). It could all be an advanced case of the "stumble/studder" with the new motor and base map combined with a MAF and possibly failing FPR. Where is your FPR manifold reference line plumbed from?

[StkmltS]

Wanna join my misfire club?

 

I'm interested in seeing what ends up being the problem.

 

Sent from inner space.

[MTBwrench]

If the FPR is suspect there is nothing wrong with an OEM replacement. If going to an aftermarket, I prefer the non-adjustable type like Outfront or Radium (Bosch regulator).

 

Sounds like you are on to something with the MAF. One thing at a time so as not to get ahead of ourselves.

 

Your logs show little, too many parameters and there is no misfire. Your AF 1 learning is high (almost 8% which should be considered the max allowable). It could all be an advanced case of the "stumble/studder" with the new motor and base map combined with a MAF and possibly failing FPR. Where is your FPR manifold reference line plumbed from?

 

I was only looking at aftermarket FPR's for two specific reasons:

 

(1) I was expecting they are higher quality/better performing

(2) I would love to totally eliminate the fuel stumble and my (admittedly very little) research has suggested an aftermarket FPR may help

 

However, you're not the first person to tell me OEM is fine, and don't bother with adjustable. Care to explain? I've never actually been able to find a concrete answer. Is it just a case of "blow your money on something better"? As for the logs, looking at them they seem to be the ones I took after I cleaned my MAF. I guess we can see the improvement! And thank you for reminding me to change my datalog parameters, they must've reset when I did a firmware update.

 

Wanna join my misfire club?

 

I'm interested in seeing what ends up being the problem.

 

Sent from inner space.

 

Unfortunately, it looks like I've bought myself a membership to the Misfire Club... Hopefully the fixes for both of our misfires are simple-ish!

[birkhoff]

 

. . . snip. . .

 

Well, I'll clarify: looking at the MAF housing it was covered in a thick black coating. The thermistor had probably about 0.5mm of crud on it, and I could see the grime making its way up and into the MAF body. I'm almost 100% sure this is due to the oiled GrimmSpeed CAI filter, so I'll be getting a single use dryflow filter instead. At the tiime when I got in on the group buy for the intake, they didn't have the dryflow as an option yet.

 

 

Um, do you still have the stock airbox and filter. Put it back until you solve this problem unless that means you have to change the tune. Probably does, now that I think of it. Can you revert?

 

Back in the day I ran a late '50s mercedes diesel that used an oil bath filter. I suppose that was the ultimate technology for filtration at the time, and the engineers ruled when the average joe was spending 2x annual income on a car designed to run half a million miles before major service. To me, it sounded very cool. What a pain though. The oil level was either too low, meaning poor air filtration, or too high, sending a fine mist of oil into the intake and all around the engine bay; almost sweating dirty oil. It seemed impossible to keep oil at the right level given the variety of driving conditions and engine RPM. And totally incompatible with a modern sensor equipped engine. Plus, if you had to pay someone to maintain the thing, it would break you.

 

Modern intake housings, much higher quality filters, and some hard questions to the engineers made oil bath filters obsolete for mercedes (my 1980's diesel has a HUGE paper filter that lasts a few years). To me, oiled filters in cars are a step backwards by some 50 years or so.

 

Oops, that sounds like flame bait. Put the old filter back if you can.

[NSFW]

Rich in boost sounds like a post-turbo air leak.

 

But crap on the MAF sensor sounds just plain bad... If you have the stock air box with a deleted resonator, the hole where the resonator was becomes a vacuum for road grime. The air filter should keep that grime away from the MAF sensor, but the MAF getting dirty suggests a problem with the air filter regardless.

 

Aftermarket FPR did nothing for my (intermittent, mild) cruise stumbles. Neither did a tee fitting with a foot+ of fuel hose. Not sure what's up with that.

[MTBwrench]

Um, do you still have the stock airbox and filter. Put it back until you solve this problem unless that means you have to change the tune. Probably does, now that I think of it. Can you revert?

 

Back in the day I ran a late '50s mercedes diesel that used an oil bath filter. I suppose that was the ultimate technology for filtration at the time, and the engineers ruled when the average joe was spending 2x annual income on a car designed to run half a million miles before major service. To me, it sounded very cool. What a pain though. The oil level was either too low, meaning poor air filtration, or too high, sending a fine mist of oil into the intake and all around the engine bay; almost sweating dirty oil. It seemed impossible to keep oil at the right level given the variety of driving conditions and engine RPM. And totally incompatible with a modern sensor equipped engine. Plus, if you had to pay someone to maintain the thing, it would break you.

 

Modern intake housings, much higher quality filters, and some hard questions to the engineers made oil bath filters obsolete for mercedes (my 1980's diesel has a HUGE paper filter that lasts a few years). To me, oiled filters in cars are a step backwards by some 50 years or so.

 

Oops, that sounds like flame bait. Put the old filter back if you can.

 

Can't revert the intake, neither do I want to. I ordered a dryflow (a.k.a.- paper) element for my GrimmSpeed CAI, gonw ill be oil issues! I always thought those old Mercedes diesels were super cool. That's crazy about the filter element though... another case of Germans being Bermans.

 

 

Rich in boost sounds like a post-turbo air leak.

 

But crap on the MAF sensor sounds just plain bad... If you have the stock air box with a deleted resonator, the hole where the resonator was becomes a vacuum for road grime. The air filter should keep that grime away from the MAF sensor, but the MAF getting dirty suggests a problem with the air filter regardless.

 

Aftermarket FPR did nothing for my (intermittent, mild) cruise stumbles. Neither did a tee fitting with a foot+ of fuel hose. Not sure what's up with that.

 

I got rid of the stock airbox a while ago. I wanted the whooshy noises! I'm 99% sure the fouled MAF is directly due to the filter which, as I said, will be replaced soon. The running full rich part might be a symptom of the base tune. I'm still breaking it in, and considering all my mods and the fact that it hasn't been on the dyno(yet), I'm sure it's crazily conservative. But, to the point you made: I've done a boost leak test and no leaks!

 

Granted I haven;t gotten into boost since and I don't really plan on it until I'm tuned.

[m sprank]

Adjustable FPR's tend to be out of adjustment when they come into my shop. Another possible issue from adjustment. If you dont need adjustable (and if its not a full race car you most likely dont) then spend your hard earned money elsewhere. A nice 3 bar non adjustable FPR works great.

 

Do you have a Learning View? It would help some to see AF 1 (A,B,C,D) learned fuel trims.

[MTBwrench]

New MAF is installed, and the wagon is 90% better! Most (but definitely not all) of the stumble is gone, very smooth under (low) boost, and idle is much cleaner. AF learnings are:

A: -4%

B: -1.6%

C:-3.1%

D: 0% (Doubt I've even gotten into this range yet)

 

However, it still bucks hard with rapid throttle angle increase (a.k.a. starting from a stop, or giving it gas after coasting for a second). The buck is usually caused by swinging rapidly from 12.0 to 17.0 and returning to stoich, all within far less than a second. It's usually accompanied by a misfire count of 1 or 2 in any cylinder. It'll also occasionally, as in it happened twice in 60 miles) lean out for zero apparent reason whilst cruising at low RPM under load.

 

I have a new FPR on the way, and if that doesn't fix it, then I'll bet it's the basemap. At this point the only thing not replaced in the fueling system is the pump housing, the damper, and the hard lines from the tank.... My tuner said the bucking is most likely a tune issue, I'm praying that it is, or that it's resolved by the new reg. Will check back with results when the reg comes in.

 

 

Adjustable FPR's tend to be out of adjustment when they come into my shop. Another possible issue from adjustment. If you dont need adjustable (and if its not a full race car you most likely dont) then spend your hard earned money elsewhere. A nice 3 bar non adjustable FPR works great.

 

Do you have a Learning View? It would help some to see AF 1 (A,B,C,D) learned fuel trims.

 

I completely understand that. For that exact reason I kind of narrowed it down to the radium regulator with a Bosch 3 bar cap, and the OEM regulator. I went with OEM to retain the fuel damper, as it's the only one left in my fuel system, and it was $60 cheaper. And no, I'm surely not racecar enough.

 

See above for my fuel trims. I have an locked AP tune, so no learning views for me.

[m sprank]

You can still pull an LV with a laptop and tactrix cable. If you dont have one, the AP can read them individually.

 

Your trims are fine. I have had more than a few base maps not run perfect. Especially with a fresh built motor. Go ahead and replace the FPR. Then it might be time to visit the tune.

[MTBwrench]

You can still pull an LV with a laptop and tactrix cable. If you dont have one, the AP can read them individually.

 

Your trims are fine. I have had more than a few base maps not run perfect. Especially with a fresh built motor. Go ahead and replace the FPR. Then it might be time to visit the tune.

 

Coming back to this. I still haven't gotten the FPR yet, as it's backordered. Hueberger told me it'll ship Wednesday.

 

The lean conditions have spread now... on cold start it runs really rich (12's) for the first few seconds, then leans out to 16's, and returns to stoich. It'll usually do that a few more times whilst warming up. No correlation to fuel pump duty either, as I had suspected it was caused by the pump switching from 100% to 33% after startup. It also leans out when starting from a stop, or coming toa stop. I'm beginning to suspect the FPR more, and the basemap magnifying it since well, it's a basemap!

[NSFW]

Have you tried replacing the pressure-reference hose that runs from the manifold to the FPR?

[MTBwrench]

Have you tried replacing the pressure-reference hose that runs from the manifold to the FPR?

 

Of course! All my vacuum line, breather hoses, inlet, TB hose. Really every bit of piping save for the coolant/breather crossovers and BPV hose has been replaced.

[NSFW]

Sounds like the FPR might be the last remaining bit of hardware to swap out. Rear O2 sensor could maybe be a factor, but probably isn't, I've only heard of that causing people to run consistently rich.

 

If you have a Tactrix cable (or a knockoff) try logging these:

 

RPM

MAF

Load (calculated)

throttle pedal angle

manifold relative pressure (2-byte)

primary open loop enrichment

open loop vs closed loop (I forgot what this parameter is called)

final fueling base

AF Correction #1

AFR - front O2 sensor or WBO2, doesn't matter since you say they agree

 

And post some 5-second logs showing some of the weirdness you've described.

 

It would be interesting to see if the AFR fluctuations correlate to changes in the fueling mode, or to boost, or to anything else. And it would be interesting if the Final Fueling Base parameter is moving around as much as the actual AFR (it probably isn't - it should stay pretty close to Primary Open Loop, +/- 0.5 or so).

[NSFW]

It might also be interesting to force the ECU to stay in open loop. That removes both O2 sensors from the fueling calculations, so if it solves the problem then that would point to one of the O2 sensors as the root cause.

 

http://www.romraider.com/forum/viewtopic.php?f=33&t=7897

[StkmltS]

I hit 500 miles today... did I beat you to it?

 

Sent from inner space.

[Max Capacity]

If your having issues on this Breakin base map. Put the known good map in.

 

I started my engine on the MAP that was in the car for years and worked well. Why add another variable ?

[MTBwrench]

Sounds like the FPR might be the last remaining bit of hardware to swap out. Rear O2 sensor could maybe be a factor, but probably isn't, I've only heard of that causing people to run consistently rich.

 

If you have a Tactrix cable (or a knockoff) try logging these:

 

RPM

MAF

Load (calculated)

throttle pedal angle

manifold relative pressure (2-byte)

primary open loop enrichment

open loop vs closed loop (I forgot what this parameter is called)

final fueling base

AF Correction #1

AFR - front O2 sensor or WBO2, doesn't matter since you say they agree

 

And post some 5-second logs showing some of the weirdness you've described.

 

It would be interesting to see if the AFR fluctuations correlate to changes in the fueling mode, or to boost, or to anything else. And it would be interesting if the Final Fueling Base parameter is moving around as much as the actual AFR (it probably isn't - it should stay pretty close to Primary Open Loop, +/- 0.5 or so).

 

I don't have a Tactrix cable, but I do have my AP hooked up, and I'm 90% sure I can get all of those logged. The final fueling base parameter though... pretty sure thats not in there. What I will say though, is that my AF correction directly correlates with all of this. I'll also mention this: now that I've got a fair amount of miles on it, and my catback is on again, the issues seem much improved albeit not gone.

 

 

I hit 500 miles today... did I beat you to it?

 

Sent from inner space.

 

Not even close. I'm currently at 790 miles.

 

If your having issues on this Breakin base map. Put the known good map in.

 

I started my engine on the MAP that was in the car for years and worked well. Why add another variable ?

 

I would, but a lot has changed from the last motor to this, different heads, different shortblock, different rails/lines/injectors. There's no way the last good map I had would work, and I definitely don't want to mess with that kind of stuff. Variables have been added because racecar!

 

My new FPR should ship today, hopefully I have it by Friday. I'll post back here when I get it swapped in and let the ECU relearn everything for a few miles.

[Max Capacity]

If the FPR doesn't do the trick. My next thought is, can you have a Tuner street tune the car.

[NSFW]

Given what he's describing I think there's a pretty good chance that would turn into having a tuner troubleshoot the car. Not sure if good investment.

 

"Final Fueling Base" is the name chosen by the RomRaider reverse-engineering guys, but Cobb probably does have the same parameter. It is the value from the fueling table plus all of the compensations. You can mostly think of it as AFR that the ECU is trying to achieve - that's not strictly accurate but it's close.

 

Anyway, if that parameter is moving around in ways that match your actual AFR then that would point to a problem with the tune rather than with something under the hood. And if that parameter is stable while your actual AFR wanders around a lot, then that would suggest that the tune is just fine but you've got a hardware problem of some kind.

 

In a steady cruise it will oscillate +/- 0.5 or so about once per second. That's just an emissions thing, don't worry about it, but if you see that oscillation then you've definitely found the right parameter.