[TurboTodd]

93 lx coupe 2.3t swapped.  all stock engine except ranger cam (Daily driver).

when cold, at the onset of boost (0 vac 0 boost, but pressure slightly climbing), I can feel a pretty good surge.  It does not feel like an ignition miss-not at all.  Like it's either going rich or lean.  As it warms up, it is less pronounced.  At full operating temp, I don't feel much of it at all.  Almost seems to be in OL only? ECU goes in to CL, but once I notice it in CL, it still surges.  Once at full operating temp-driving for approx 20-30 minutes (from work to home), again I don't notice it as much.

Pulled codes this morning after I drove to work.  81, 83, and 42 all CM.  25 and 34 KOER.  I do not have EGR.  42 is a rich code which I  have had before and posted about.  I seem to have fixed the major  issue there-boost leaks, in that previous post.  I don't remember if I cleared the codes or not, though, in my haste of getting it back going.

I'm thinking either an injector, or VAM issue.  I don't have a way to look at vam voltage while driving, only at idle and it seems to be ok at idle. 

Ideas?

[TurboRay]

.
You said "all stock except Ranger cam" ~ BUT.......I see "Stinger FMIC" in your sig. FMIC's and their related plumbing are often the cause of surging/trailer-hitching, Todd. If it's not too much work, perhaps you could try temporarily reinstalling the factory pipe/hose between the compressor outlet and the TB, to see if that cures the prob?

Unfortunately, if it does, I don't recall what others have done to fix the prob (something having to do with the VAM?). Maybe someone will chime in with "the cure".  <shrug>

[TurboTodd]

.
You said "all stock except Ranger cam" ~ BUT.......I see "Stinger FMIC" in your sig. FMIC's and their related plumbing are often the cause of surging/trailer-hitching, Todd. If it's not too much work, perhaps you could try temporarily reinstalling the factory pipe/hose between the compressor outlet and the TB, to see if that cures the prob?

Unfortunately, if it does, I don't recall what others have done to fix the prob (something having to do with the VAM?). Maybe someone will chime in with "the cure".  <shrug>

Did that this evening.  Didn't seem to help any.  I didn't feel like it was trailer hitching, more of a very slight misfire as I am accelerating, as the intake pressure crosses 0 into positive pressure.  I wish I knew a better way to explain it.  I do get the trailer hitching from time to time if I am coming OFF of the throttle from boost back to vacuum, so I'm familiar with that.  Unfortunately there is no cure for that aside from going standalone/SD which I am not gonna do right away.

[Hemi]

Has it always been like this with the current build, or the behavior just started recently?

[Howard]

Are you using any type of blow-off/bypass valve?

[TurboTodd]

Well...the short version of a very long story

Car SAT in a body shop for a year.  In that time it just sat, nothing was done to it.  I got it back, paid another shop to finish it.  Took a month.  That was January 2022 when I got it back.  I reassembled the car/finished it up in Feb and began driving it again after selling my 2019 Ecoboost back to the dealer.

After reassembling (installing the IC, tubing, etc) I initially had a very rich running engine  with a CEL and code 42, in which I found a couple loose IC clamps when doing a boost pressure test (10 psi found it).  Tightened the clamps, cleared the codes (pull the jumper while in self-test) and it has been fine, for roughly a month.  The other day it began running poorly as stated in the original post.  Just started doing it.  I changed plugs the day before, perhaps it has some bearing?  Autolite 104 if it makes any difference, exactly the same as came out of it.  Gapped .035.  Idles good. Start getting into boost it starts running kind of poorly.  Almost as if the timing is retarding, or the engine is going intermittently rich. 

Today I drove it to work.  Perfect all the way (30 min drive mixed highway, freeway, and city).  On lunch, I felt it acting up a little, no CEL at all.  Sat from noon:30 til 5:00, jumped in to go home, and it started running like poo the minute I was getting into traffic.  Soon as I am at 5+ psi, it clears right up and runs normally.  At steady cruise from 1500-2200 rpm, it was bucking, almost like trailer hitching but not quite.  My other car does this, but it is untuned, entirely too much ignition timing and for some stupid reason the RH side of the motor (v8) is leaner than the left side....anyway, I ain't going there right now with that car.  Jumped on the freeway, ran it on up to 70 and it ran all the way home.  I got off the freeway and sat there at a light.  Idles ok, though I can tell it's richer than it should be based on the idle quality.  Drove on home, another 10 minutes at 45-55 mph, pulled in the drive, it ran almost perfect.

yes it has a BOV, recirculated back to between the vam and turbo.  I plugged it for giggles and it changed nothing.  I also did a pressure test again this evening and could not find a boost leak anywhere (manifold, head, not even the throttle shaft seals).  I believe it to be sealed up good. 

Pulled codes while it was still warm, 81, 83 continuous, then 42 in memory.  Have not seen a CEL.  Also for giggles I cleared everything again, then drove down to the local dollar general then back.  Never in boost.  Maybe 7 minutes round trip.  Code 42 stored again in memory.

So, I then tested the TPS, all good there.  Sweep is nice and smooth.  0.84 at idle and 4.7 or so at full throttle.  Then, decided since I have the DVOM out, let's look at the VAM.  Just with the key on engine off, vam in my hand but still plugged into the harness, I manually shoved the door open slowly.  For the first 1/8 inch or so of opening the door, there was no reaction from the DVOM.  Then as I kept pushing the door open, it finally started to increase the voltage.  At one point, I want to say around 0.4V, there was a slight hiccup as the door was opening, the voltage did not climb-it did fall back about 0.05v, but then began to climb back again.  I ran it through several sweeps from fully closed to fully open and it did the same each time at roughly the same spot.  I seem to remember on my SVO, the first part of opening the vane, it was dead the same as this one but I do not remember a dead spot or "hiccup"; but it's only been ~20 years since I owned that car and I'm sure I've forgotten much since.

Went to do a fuel pressure test and I can't find the adapter that goes on the rail.  Always something.

Did not pull the upper intake off to look down it's throats for a leaky injector.  Ran out of motivation for the night after working all day.

So I have a couple possibilities, in my opinion.  VAM issue, and possible injector issue.  These are stock 35lb brown tops that I bought here a number of years ago.  Is there a such thing as remans?  AFAIK, they have been NLA for decades?  I think a reman VAM is still available though isnt it?

I wanted to add that the engine vacuum at idle is 20"/hg, coasting down a hill in DFSO it runs up to about 23-24". I haven't noticed it being any higher or lower since I've owned the car with this engine, so I don't "think" there is a major mechanical issue?

[TurboTodd]

Dug into it

Replaced the VAM since the original had a couple dead spots in the sweep of the door.  Not much change, if any.  Pulled injectors and put in another set that I had laying around.  No change at all that I can tell.  Tried a different known-good BAP, nadda.  Tried known-good distributor, nope.  10 deg initial without the spout. 

the only issues I can find are that the oil cap leaks when you're hard on the throttle (blowby??) and  I did find that the turbine elbow bolts were a little loose but I cranked them tight and haven't noticed anything different, other than it sounds a little different when spooling now-more of a howl than a whistle at first, overall quieter. 

Still haven't been able to check fuel pressure BUT if it were high, you'd think that a hot start would show a rich running condition at idle before it goes into CL, and I'm just not seeing that.

Maybe try plug wires?  I don't have another set to try but I ran into an issue before with wires that was weird.  These are Motorcraft wires, have maybe 20,000 miles on them.

It "almost" feels as if timing is retarding which made me think of the wires.  It does not however feel like a complete misfire like a normal failing plug wire would do.

[TurboRay]

You mentioned BAP, so I gotta ask.......you don't have a manifold reference hose connected to it, do you (you shouldn't)?

For even more "giggles" try swapping to a different (new or used) dist rotor. Sometimes they develop an intermittent "leak" between the center contact and the shaft beneath. While the cap is off, make sure there's no "carbon tracking" between the pins (or.....just replace it). Also, close the plug gap to about .025. I don't suppose you've got a spare coil "laying around"? 

If you can't find your Schrader-valve adapter to check f/pres......you can ghetto-check it with a <gasp> tire-pres gauge. The pressure should be around 40-ish (39 precisely) with the engine OFF, after cycling the key on and off a few times (leave it "on" for about 2-3 secs each time you cycle it).  <shrug>

[TurboTodd]

no, bap is open to atmosphere.

tried rotor-->no change.
tried cap--> no change.
dunno if i have a coil; well maybe I do--on the v8 car.

TPS was acting weird this morning, wouldn't return to "idle", kept hanging at .85-ish volts (snap it and it'd finally run back to about .83 and idle would settle down).  Maybe part of the problem?  Tps sweep is linear.

[TurboTodd]

Pretty sure it's fixed.

TPS had no effect as I suspected. But I had it and figured it's worth a try.

PLUG WIRE(S).

I went to the parts stash (you turboford'ers have one of those dont you???) looking for my other coil, and found a new set of Motorcraft plug wires that I apparently didn't use at one point, and tossed them on. Runs perfect now. OR, as well as a 30+ year old car is going to run.

These wires didn't have 20,000 miles on 'em. But I am understanding that TF's are hard on ignition components, so?