Fuel trim readings

46addict

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So I popped off the passenger side valve cover (the richer side of the two) to look for scored cam lobes or a broken follower. What I found was a cam phaser reluctor wheel off kilter. Can this be the cause of all this? I'm hoping it is so I can get new phasers and move forward with tuning.
 

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702GT

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So I popped off the passenger side valve cover (the richer side of the two) to look for scored cam lobes or a broken follower. What I found was a cam phaser reluctor wheel off kilter. Can this be the cause of all this? I'm hoping it is so I can get new phasers and move forward with tuning.

I'm sorry, off kilter? Are you meaning out of whack? The phaser looks fine from that angle. I don't see anything wrong with it. Spring tab and spring look good. That's all I can tell from that shot.

If there was a problem with the phaser you'd have CEL's or more severe mechanical problems. Probably noise too. There are already small imbalances in cam angle between the 2 cam shafts naturally. These small differences may contribute to a fraction of a percent of fuel trim issues. I doubt even a faulty phaser would contribute to a 10-15% fuel trim imbalance.

I'm still leaning hard on O2 sensors but if you've swapped them from bank to bank and saw no difference, it sounds like they aren't malfunctioning or reading improperly.

Have you pulled the injectors yet? I know you intended to replace the O-rings, which is a great idea (make sure you grease the O-rings on install, like vasoline) but it wouldn't hurt to order the rebuild kit for them. The kit will give you new top/bottom O-rings and new internal screens. There's great youtube videos on how to clean out the injectors, and then test their resistance and make sure they're within spec. Sticky or leaky injectors can definitely affect fuel trims, also one or 2 injectors with bad electrical resistance won't function properly either and skew fuel trims. Being that your O2's are reading one side definitely richer than the other side, a great easy test would to be swap all 8 injectors from bank to bank like that O2's. So the 4 from bank 1, swap to bank 2 and vice versa. Then fire the car up and see if the fuel trims jumped banks. If they do, bingo man.
 

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Thanks for staying with me and responding. My tuner thought something is wrong with the cam so I went looking for valvetrain problems. I guess I can rule that out. This car is showing no codes and I don't hear the phaser knock.

I also had a feeling I had one or more injectors stuck open so I installed 8 new ones of the same brand/flow rating and the problem remained. So the only thing left is o2 sensors. At this point I have nothing to lose so I'll replace them and hope it fixes the problem. If not then there must be a mystery vacuum leak or exhaust leak somewhere ahead of the upstream o2s.
 

702GT

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An exhaust leak that close to the head, enough to affect fuel trims, would be audible. Wouldn't be able to miss it. Vacuum leak that screws with one bank over the other isolated it to injector O-ring or intake manifold gasket, on the side that runs lean.

Here's one for the datalog; are the fuel trims unbalanced at idle, 1500rpm cruise, 2500rpm cruise, and 3500rpm cruise? (Reason: the different rpm ranges will cause the cams to actuate and at low load "cruise" will have the cams retard cam angle. At idle, the overlap and already minimal fuel requirements will naturally cause a lean condition. NA cams overlap by default which causes fresh air to flow into the exhaust before the exhaust valve shuts. Just curious what the consistency is at given rpm ranges and loads. I'd love to read those logs.)

Also, can you tuner cut you an open loop tune just so you can eliminate mechanical as being a possible cause? Open loop tunes, even at idle, ignore the O2's and command the ECU to provide exactly what the tune tables call for. (Reason: While an open loop tune ignores the O2's for fuel trims, the O2's ~should~ still report their readings. If the car still shows an imbalance while in open loop, then for sure there's a vac leak or other mechanical issue at play.)
 

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Yes, the imbalance exists at idle and does not change with rpm. I would think the fuel trims would level off with more rpm if it was a vacuum leak but that's not the case.

As for the open loop tune, see the 10/8/17 log. The trims are off base but you can see here they are matching from side to side. I didn't specifically ask for open loop but I'm guessing this is it, because he changed something afterwards and I was put back at square one (10/10/17 file). Both files were with the car revving or idling in neutral. The 9/14/17 file is a light load log.
 

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Dino Dino Bambino

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I pulled both front o2 sensors to swap them from side to side and noticed bank 1 (the rich side) was darker than the other. Imagine that. Switching them had no effect on STFTs.

Check the wiring to those O2 sensors and make sure it isn't either pinched/shorted out somewhere, or burnt by the header primaries.
 

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The pumps I have were bought used and seller said they had 15k miles. The sock and everything else looked good but maybe there is debris stuck in mine. Was your sock visibly dark?

Yes, it was dark all over the outside of the sock. Easy to clean though. But I still have this flaky crap floating around the bottom of the tank.
 

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702GT was right the whole time. I had a bad o2 sensor. I replaced the one that was black (probably from one or more injectors stuck open) and ran it. At cold start there was an imbalance but once coolant temp got to 160 both sides were dead on. I guess I'll order a few of these to go in the spare parts bin.

Fuel pump was also replaced with a Walbro 405 and I'll report back with any duty cycle changes.
 

Heaten m90

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Was it on the passenger side? And was it doing it in open loop? I was going to guess o2 sensor as well but looks like im 2 late
 

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Fuel pump was also replaced with a Walbro 405 and I'll report back with any duty cycle changes.

The Walbro 405 is reporting a 20% drop in DC at idle (went from .25-.26 to .15) which is good news. One of the GT500 pumps I bought must have been bad. No more used parts for me. Fuel pressure stays at 39psi like clockwork and we will see if it holds at WOT. However I'm not at that point yet because it's still being tuned.

The tuner I have been working with says the airflow levels in the tune had to be cut down to below stock levels for the car to run decent and because of that the car will never make the power I'm hoping to make. So I went to Lito and paid him to tune and to get a second opinion. He is saying the o2 sensors are stuck rich and the PCM is not doing anything to correct. I no longer have a fuel trim imbalance but the car is stuck in open loop and refuses to go closed because of the PCM not applying the right corrections. Lito suggested I try a different set of injectors and to bypass the MAFia if possible. I've been told by two different tuners now that MAFias are known to have issues. In the meantime I am trying out the set of 39lb injectors per Lito, to troubleshoot. I have no need for bigger injectors anyway since I'm on stock internals. I will pony up for some FIC 630s when the need comes.

I can't even sell the car like this because now it doesn't run and I feel like there is a simple fix I am overlooking so I'm going to keep at it. The engine held good vacuum when it ran and was reliable even if it was painfully slow (99mph traps). Stay tuned.
 
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rickf

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Gothca, But can't you use a stock MAF since you are not using the blower? Seems like one more piece to go wrong if it is not really needed.
 

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The blower is still installed. I installed a different blower pulley, injectors, and a pump and tried to retune the car. Then these issues surfaced.
 

702GT

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The MAFia is indeed a bandaide. I had one on my car, but I wasn't going terribly far out of the stock MAF's voltage range. If exceeding 550whp, I would suggest a SCT MAF or similar for your power goals. The further you extend the stock MAF range the more inconsistent the MAF curve becomes. The MAFia will work fine for WOT input, but because you're condensing the MAF voltage range it will have a harder time in closed loop. I used to have a MAF table that showed what I meant, but I can't find it. My MAFia was on one of the lower settings, I can't remember if the dial was 1-5 or 1-10. I think I was on setting 1 or 2. Gave me plenty of MAF range up to 9psi and 488whp (my highest dyno when we were playing with the MBC/wastegate on e85).

Also what injectors are you using? You seem to be having a lot of fueling issues. If the O2's are pegged rich and the PCM can't compensate either the tuner isn't inputing data for the correct injectors or the injectors are having a mechanical/electrical issue. Would be worth pulling the MAF and seeing if it needs to be cleaned as well, prochargers are notorious for spitting blower oil down the charge piping. Were you using the MAFia prior to these recent upgrades and did you have issues with it then? I understand Lito's reasoning of bypassing the MAFia, he wants a pure signal for closed loop to eliminate the MAFia and see how the car responds.
 

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I had mine on setting 2 as well but after Lito looked at the logs he said to go to #3. I have a wastegated setup as well. 3.40" pulley with a 10lb wastegate spring on a P1SC. It's a silly setup for a <700hp car but I did it to reach peak boost a bit earlier so I'm not having to rev to the moon.

I am using new Deka 60lb injectors. The blower is leaking from the bottom of the case but the charge pipes are still dry. I have also tried a different MAF from the parts bin with the same results. From what I understand, putting the MAFia on setting 0 is the same as bypassing it, and that should rule out MAFia problems unless there is a problem with the wiring. Doing this didn't help. So I may need to get a MAF extension wire to connect the pigtail from the current MAF sensor location to rule out wiring problems.

Between the six files Lito sent me, the most recent one left me with a car that doesn't want to start. I doubt it is a tune problem and I'm pretty sure it's mechanical.
 
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rickf

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What happens if you unplug the MAF? It should default to a baseline setting and run like crap but it will eliminate the MAFia. It should also give the readings that Lito is looking for.
 

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Unplugging the MAF still did not let me start the car. Lito sent me a revision but by this point the car had fouled two sets of spark plugs and a pair of front o2 sensors. On the new set of plugs, new o2 sensors, and Lito's revision, the car fired right up but then the MAF counts were way high.

We narrowed it down to a faulty MAFia. I let the car idle on settings 1, 2, and 3 and the MAF counts stayed at 375-400 on all three settings so I ordered an HPX MAF. This particular MAF was rebadged by VMP and they called it VMP 5000. The coating on the plastic body was too thick to slide into the MAF slot so I had to file off some material. I hated having to do that but now the car runs better than ever before. Just a few fine tweaks from Lito and I'll be good to go.
 

702GT

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Unplugging the MAF still did not let me start the car. Lito sent me a revision but by this point the car had fouled two sets of spark plugs and a pair of front o2 sensors. On the new set of plugs, new o2 sensors, and Lito's revision, the car fired right up but then the MAF counts were way high.

We narrowed it down to a faulty MAFia. I let the car idle on settings 1, 2, and 3 and the MAF counts stayed at 375-400 on all three settings so I ordered an HPX MAF. This particular MAF was rebadged by VMP and they called it VMP 5000. The coating on the plastic body was too thick to slide into the MAF slot so I had to file off some material. I hated having to do that but now the car runs better than ever before. Just a few fine tweaks from Lito and I'll be good to go.

Great news! Keep your eye on that HPX MAF for a while and make sure it stays legit. Had a buddy have some bad dealings with VMP over their MAF's, had one DOA and another start malfunctioning few thousand miles down the road. Finally told VMP to stick it where the sun don't shine and bought a SCT MAF, never looked back. VMP's had great reviews overall, dunno if my friend got stuck with a bitchy rep or they're just proud of their MAF's, but the customer service was a bit of a nightmare on that issue.
 

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