Big Inch EFI Guru's - Tech Please!

EricLar80 · Jun 26, 2011

So, I have been working on getting my 393W conversion up and running (see THIS THREAD ). I have it all installed and finally got to start it for the last time last weekend.

Well, it started immediately (the good news), but it has a severely rough idle (the bad). I have put in a base tune using the Moates tuner; mainly adjusting for the displacement, MAF and injectors. It wouldn't be so concerning if it were just and idle issue, but it also has an intermittent loss in RPM if I bring it above idle. It does seem to smooth out above idle, but there is almost a shudder, and loss in rpm. It quickly recovers and does it again without a real steady pattern. It seems to affect both banks evenly, and at the same time.

So, in attempting to diagnose this issue, I have verified a few things:

fuel pressure is good while running
compression test when cold had all cylinders between 160 and 165psi
no vacuum leaks (only have the FPR and PCV attached, so that's easy to check) - also tried leaking a little mapp gas around the intake
vacuum guage shows the needle moving from about 15-18" of vacuum corresponding to the erratic idle, but also has a high frequency, low amplitude bounce overlaid on it (any thoughts?)
no KOEO codes as I have all the emissions stuff disabled through the tune
coolant is circulating properly, so temp should be good
all sensors hooked up that I can possibly think of
I retuned for the stock MAF just to see if the 73mm C&L cal I was using was incorrect (no difference)
pretty sure I purged any air from the fuel system/rails

One other odd thing I noticed - I happened to pull my upper intake off very shortly after shutting the motor off and noticed little puffs of smoke wafting from the lower intake - is this normal? Makes me think that the vales may not be seated right, but I am not sure. I don't hear any noise in the valvetrain. If it were the springs; I would only expect to see issues at higher rpms, right?

Starting to grasp for straws right now...

Any and all ideas are welcome.

Thanks,

Eric

lars · Jun 26, 2011

Sounds like you've looked at most of the basics. What about base timing? You can also use the timing light on each wire to confirm that the other cylinders are firing. Did you confirm a good spray pattern from the injectors before you installed them? Rather than a compression test, you could try a blow down test. That'll ID any valves that may not be seated.

dbevans2249 · Jun 26, 2011

What cam did you end up using? Is the lobe separation angle enough to keep EFI happy? Could the intake ports on the heads you chose have any effect on the idle?

EricLar80 · Jun 26, 2011

lars said:
Sounds like you've looked at most of the basics. What about base timing? You can also use the timing light on each wire to confirm that the other cylinders are firing. Did you confirm a good spray pattern from the injectors before you installed them? Rather than a compression test, you could try a blow down test. That'll ID any valves that may not be seated.

I set base timing initially, with the spout out, of course. I will take another look at that. Good idea to check each wire; I'll do that.

How can you confirm the spray pattern? The injectors are new, so I would hope they operational. I do have an extra rail, so I am willing to hack it if needed.

I went to HF to pick up a tester, but they couldn't find any of the 2 they had in the store. I'll pick one up at another location.

Decided to pick up another mass air sensor since they can cause any number of issues; no difference. I hate the shot in the dark method.

Thanks,

Eric

Broncobowsher · Jun 26, 2011

Since you can tune it for free, how about just blindly adding 5 and 10% extra and less fuel. Just see what happens? Yea, it may jack other parts of the tuel curve, but lest see if we can narrow this to a fuel issue or something else?

The puffs of smoke in the intake? I take it you pulled the upper intake and saw them in the runners? doubt it is valves. probably a cloud of fuel vapors.

More free ideas to check, does it do it with the Spout out or only when the computer has control of the timing? A trick is to start the engine, crank in about 25° of base timing without the Spout, see what it does. This gives you a fixed amount of advance that the computer can't mess with.

I have seen the dyno shop take the air filter off and put a couple feet of straight pipe before and after the MAF to make sure it isn't an air turbulance issue in the MAF.

Those are my initial free (or cheap) things to check. None of which is likely to fix anything, but should get you from the dark room into a dark hallway where there should be some light toward the end.

EricLar80 · Jun 26, 2011

dbevans2249 said:
What cam did you end up using? Is the lobe separation angle enough to keep EFI happy? Could the intake ports on the heads you chose have any effect on the idle?

I ended up getting this cam with these springs. The cam has a LSA of 114 degrees, which is supposed to be good per any cam selection guidelines I have read. It was also a cam specified by Comp that would work good in my application.

I'm sure the intakes can affect it, but I would expect it somewhat rectify with RPM, though; not have this intermittent loss of power as well.

Thanks,

Eric

EricLar80 · Jun 26, 2011

Broncobowsher said:
Since you can tune it for free, how about just blindly adding 5 and 10% extra and less fuel. Just see what happens? Yea, it may jack other parts of the tuel curve, but lest see if we can narrow this to a fuel issue or something else?

The puffs of smoke in the intake? I take it you pulled the upper intake and saw them in the runners? doubt it is valves. probably a cloud of fuel vapors.

More free ideas to check, does it do it with the Spout out or only when the computer has control of the timing? A trick is to start the engine, crank in about 25° of base timing without the Spout, see what it does. This gives you a fixed amount of advance that the computer can't mess with.

I have seen the dyno shop take the air filter off and put a couple feet of straight pipe before and after the MAF to make sure it isn't an air turbulance issue in the MAF.

Those are my initial free (or cheap) things to check. None of which is likely to fix anything, but should get you from the dark room into a dark hallway where there should be some light toward the end.

I will tune in the higher and lower MAF transfers and test that.

Hard to say what the smoke was; I kneeled in to get a whiff, and it smelt like lean-burnt exhaust (you know, the stuff that burns your eyes). I'll try to replicate it as I can get the intake off in about 3 minutes.

I have locked my advance in to 30 degrees using the computer; I can confirm the lock with my datalog. No benefit when doing it electronically . I can try doing that mechanically.

The intake tube setup is exactly (literally) what I ran with the 5.0L; and I had zero issues. The differences start with the throttle-body.

Thanks to all for the ideas. Keep them coming and I will continue to test 'em. I have to head to San Diego for work tonight, but I will get these tested tomorrow.

Eric

DirtDonk · Jun 26, 2011

At any given time, there are at least some valves open. So you can't always worry about the odd puff out of the manifold.
However, it does say that things may not be combusting as well as you'd like, which would certainly follow with your rough running.

What chassis wiring harness, and what engine wiring harness?
Did you verify you have voltage on Pin 3 of the TFI during START only? I think it's #3 anyway. Double check me on that.
Usually, it's only a problem when you try to reve the engine up, and yours sounds to be all the time. But it's one more thing to check.

I would certainly triple-check your firing order, as mentioned. That looks like a great cam choice to me, so unless you somehow managed to get it in 6° retarded or something, it should have a decent idle and rev easily.
It doesn't say, but I "assume" that it's an HO firing order, since it states it's a "replacement" cam for later EFI engines. I hate assuming, but it does kind of leave that info up in the air, with a couple of clues.

Oh, and what about valve adjustment? How did you perform the initial adjustment, and what type of locks/studs/rockers are you using?

Good luck.

Paul

EricLar80 · Jun 26, 2011

DirtDonk said:
At any given time, there are at least some valves open. So you can't always worry about the odd puff out of the manifold.
However, it does say that things may not be combusting as well as you'd like, which would certainly follow with your rough running.

What chassis wiring harness, and what engine wiring harness?
Did you verify you have voltage on Pin 3 of the TFI during START only? I think it's #3 anyway. Double check me on that.
Usually, it's only a problem when you try to reve the engine up, and yours sounds to be all the time. But it's one more thing to check.

I would certainly triple-check your firing order, as mentioned. That looks like a great cam choice to me, so unless you somehow managed to get it in 6° retarded or something, it should have a decent idle and rev easily.
It doesn't say, but I "assume" that it's an HO firing order, since it states it's a "replacement" cam for later EFI engines. I hate assuming, but it does kind of leave that info up in the air, with a couple of clues.

Oh, and what about valve adjustment? How did you perform the initial adjustment, and what type of locks/studs/rockers are you using?

Good luck.

Paul

I have the RJM harness. I was running it before the swap to the 393w without any issues. I double checked that the harness engine ground is in place too. I also double checked all the fuses.

I read thru that pin 3 issue the other day; I can confirm that, but never had an issue part 3500 rpm in the past.

I have the firing order as HO in both the program and on the dizzy.

I am really wishing I degreed the cam now. I put it in straight up, but who knows if it was ground incorrectly - something that has been haunting me. Is there a way to confirm the degree without removing the timing cover? Summit lists it as an 88-93 5.0L mustang replacement cam and the valve adjustments seem to align with that.

Eric

EricLar80 · Jun 26, 2011

Actually, two things I want to confirm:

The MSD distributor didn't have the #1 cylinder labeled on the dizzy anywhere. Surely that matters. I did some googling before stabbing and ended up using the magnet sensor in the dizzy (the one for the PIP) as the location for the #1 cylinder. It lines up well with one of the spark boot posts, and seems to be how the stock dizzy is lined up for the pictures I could find.

Can someone confirm on their stock dizzy that the marked #1 location is in line with the magnet pickup?
I adjusted the vales by moving the cylinder to TDC and adjusting both the intake and exhaust at the same time. Do I have too much overlap for this to be a good idea? I did this twice without any difference; maybe I should try the more traditional method? Anyone had any luck/difficulty with adjusting both at the same time?

Thanks,

Eric

DirtDonk · Jun 26, 2011

Although I always say to degree a cam, it's so unusual for one by a major manufacturer to be ground that far off as to be almost unheard of in normal circles. I've heard of it happening, but only third hand and never saw it.

But, now you've got me thinking about something else. Just for giggles, why don't you pull cylinders #1 and #3 spark plugs, and verify that the cam is the advertised firing order?
Yeah, that's probably even more unheard of, but hey, it's so quick-n-easy that I say do it anyway. Easy enough to find TDC on number 1, then rotate the crank clockwise with a finger over number 3 and see if it blows compression past your finger within that first 90 degrees of crank rotation. If it does, well at least you had some fun fooling around needlessly, but if it doesn't, then you've at least confirmed that the cam was either boxed or ground incorrectly.

Hope that's not it, but it would sure simplify things to at least KNOW something!

Paul

DirtDonk · Jun 26, 2011

As long as you were on TDC (of the compression stroke) for that cylinder, then the overlap shouldn't effect anything. AT TDC neither valve should be opening. I'm thinking that it'd have to be one whale of a radical cam for that method not to work.

Paul

DirtDonk · Jun 26, 2011

What are you using as your adjustment though? 1/2 turn past zero lash? A full turn? Something else?

Paul

EricLar80 · Jun 26, 2011

DirtDonk said:
What are you using as your adjustment though? 1/2 turn past zero lash? A full turn? Something else?

Paul

1/2 turn past zero lash. I just followed the dizzy position to keep track of where I was (compression stroke). I'll try and do it the other way I guess, just because it will bug me either if I don't. If it was over adjusted, I don't think I would be able to get any compression and start; under and unwound expect to hear noise, right? I have always adjusted the other way in the past, may as well do it this time too.

One point of interest, I have the 7/16 rocker studs, which have courser threads than the 3/8ths. Wouldn't think that would be enough to make a difference.

Eric

broncnaz · Jun 26, 2011

Cam selection should be fine and most cams are usually not that far off when there ground still wouldnt make a big differance in the way the EFI runs as with 114 lobe seperation the computer should handle it fine. If it was advanced or retarded it would only move the more band although actual igintion timing readings would also be affected but again shouldnt be more than a degree or 2. Puff of smoke in the intake no big deal its a fresh engine and while it may be tight nothing is broken in yet. probably just a little seepage from a valve thats slightly open and warm cylinders from the recently run engine.
I know you said you didnt have any vacuum leaks but not all vacuum leaks are dectectable externally if the leak is between the head and intake it can be leaking into the lifter valley.
Distributer oreinetation doesnt matter You can Stab it in where ever you want and wire it from that point. Also a little extra valve lash due to courser thread wont hurt anything. I doubt its enough to really make any differance at all. hydraulic lifters usually have about at least .200 travel I believe that with each full turn of the nut lash is reduced by aproximately .040. So at 1/2 turn your fine.
I would also think you would be throwing some codes if its not running correctly have you checked for codes yet? They may tell you something or at least give you a direction.

lars · Jun 26, 2011

Lots of good basic ideas so far, Eric.

May not be valve lash, since you got good compression. In any case, you probably don't have a valve held open.

Injector spray pattern is basically apply 12 volts and fuel pressure. If it's working, it'll be obvious.

Agree with the others, that cam is mild. As long as the lash is ok you are fine.

Sounds like you used a lot of the electronics from your 5.0. Did you use the sensors too? How about the TPS?

I know this is parts swapping, but since you have an aftermarket distributor, it might be a good idea to try a plain old boring stocker if you can get your hands on one, just to rule it out.

Oh yeah, codes?

DirtDonk · Jun 26, 2011

I've been thinking about it too, and how many different programs have you tried? Is it possible that you have a defective ECU? I think you said that it ran fine before though, is that correct?
You running an automatic or manual trans? Auto or manual ECU? Jumper position in Ryan's harness?

Is that hole in the front left corner of the lower intake where you have the ACT sensor?

Did you verify number 1 TDC was actually where the timing mark and the pointer meet up? So many combos,..

Are you using the harmonic damper that came with the 351? Stock flexplate too?
Hmm, did you remember to use a 28 oz imbalance flywheel/flexplate to match the 28 oz stock damper?

Paul

ren71 · Jun 27, 2011

My hunch would be a bad/incorrect tune with the moates. You've added an extra 30% in displacement in addition to whatever other upgrades you may have also done. If the moates is anything like the tweecer, it's sometimes a steep learning curve to get a correct base tune.

I'd also recheck your valve adjustments, it's easy to lose track whether you're in tdc during the compression stroke vs exhaust stroke.

Do you have a list of mods? Are heads, MAF, Injectors, TB etc. all bigger?

Smog pump, egr, delete?

EricLar80 · Jun 27, 2011

broncnaz said:
I would also think you would be throwing some codes if its not running correctly have you checked for codes yet? They may tell you something or at least give you a direction.

No codes. I disabled the smog equipment, so those don't even throw a code.

Thanks,

Eric

EricLar80 · Jun 27, 2011

lars said:
Sounds like you used a lot of the electronics from your 5.0. Did you use the sensors too? How about the TPS?
Oh yeah, codes?

I reused most of the sensors; the only ones I did not are the TPS and the IAC. I have verified that the TPS is linear and doesn't have any noise (via the datalogging).

lars said:
I know this is parts swapping, but since you have an aftermarket distributor, it might be a good idea to try a plain old boring stocker if you can get your hands on one, just to rule it out.

Oh yeah, codes?

This may be tricky, as you know of the dizzy issues with 351w - any tips for a TFI based dizzy for a 351w besides aftermarket?

No Codes, except for the 11.

Thanks,

Eric

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