Wild, intermittent sputtering and bucking
 

I would double check your engine grounds, have you changed the fuel filter recently, is the fuel pump getting loud, besides welding the air pipe what does the rest of the exhaust consist of? The fact that the issue is intermittent leads me to believe it is a sensor, ground, or fuel issue. If the issue were constant I would be more prone to consider vacuum

What was the condition and what was your history with this car before the modding began?
Honestly, faced with such a cornucopia of issues, I'd strip the engine down to the keg and start from scratch.
You'd have to do that to free the aux ports up, which is the first order of business anyway.

I just replaced the fuel filter, literally. I can't hear the fuel pump run and the previous owner had installed a gauge which reads 30-35 PSI at idle and a little more with revs.

I've had the car for 2 months and have treated it like a rotary for those months. I'm not sure why these problems are just popping up now. I will be taking the intake off to free the ports and check things out, I was just wondering if anyone had been here before.

Is there any way to lean the car out? It almost feels like it's choking on fuel, even under 3800 RPMs

As long as you run the stock ECU no, you can't tune the fuel delivery...or anything else for that matter.
Part of the engine strip I recommended before would be having the injectors serviced -at @$100, the most expensive single item, the rest, gaskets, seals, vac/fuel hose, sensors, figure another $100-150.
If you're lucky, the OMP lines will remain intact.

It's a daunting task because there is so much stuff layered on top of the engine.
Just taking it apart is likely to cause damage if the vacuum hoses or electrical are original and brittle (be especially careful with the vac solenoids).

It's the only way though and once done, should make your future life much simpler.

Will do.

I'm also going to replace the engine and transmission mounts with solid ones I have. I'll do those today.

Having the injectors serviced (the primaries I assume) is just a solvent clean, right? And I know I need the intake manifold gaskets, both to the engine and between the upper and lower manifolds. Every hose on the car looks quite recent and nothing is close to being brittle, but what lines would I be looking at?

I've also heard the main engine ground is near the intake manifold as well so I'll check that out for sure.

I'm also gonna set the gas pedal down and readjust the TPS because the idle is bugging me. I'll check for dead spots in the TPS too.

I have to say, the car pulls very well even with the aux ports unplugged. I'm excited to have them working. Speaking of which, there was an alleged rebuild on the engine 30k km ago. Could the ports be stuck from the owner being too easy during the break in period? The VDI is perfectly fine and I can move it by hand.... but I'm guessing that's due to its placement. I appreciate your patience, I'm still learning.

Thanks a lot for your help!

Edit: my car uses an ECU made by Blue Streak Electronics in 2006. I'm guessing it's made to OEM specs or even remanned by them, but it would be nice if it could be reflashed..

Why the hell do that?
If you can't afford real mounts, I suppose solid mounts are better than nothing but your setup is not capable of stressing OEM bushings and you'll be introducing NVH for no good reason.

No.
Read what Whichhunter says about it.
Do all four injectors at the same time.

There are actually a couple of grounds on the engine- one goes to the long mounting bolt for the starter, and another is a couple of ring connectors that bolt into the top of the keg. There's another on the hard vacuum spider that bolts to the dynamic chamber flange (very close to the IAT sensor and the throttle cable). These are all interconnected (not the starter motor one though) and go to a fitting on the firewall right next to the wiper motor.

Not sure what "set the gas pedal down" means but you can disconnect the cable altogether to adjust the TPS and idle and when you're done, reconnecting the cable should not affect anything.
The Magic 8 Ball says:"Highly Unlikely".
The actual port sleeves are aluminum and it's possible they are sticking but it's equally as likely that the actuating rods in the LIM are the problem. These are two piece steel rods, joined in the center with a spring (so be careful when trying to pull them out and be aware there's a seal you'll need to replace) and they fit into a rather long bronze bearing in the LIM.
Soaking the sleeves in Purple Power will remove and carbon/gunk.
The rods and LIM bearing you'll have to deal with as best you can.

Never heard of them but that means nothing, I'm sure more experienced folk have.

Ok, thanks for the info!

I have poly bushings in the front suspension-are solid mounts still a bad idea? I do enjoy the vibrations of the current shot tranny mounts so I'm sure it won't be too ridiculous of a switch. I suppose delrin would have been the smarter choice but I'm just trying to minimize drive train and engine movement while driving hard.

It was worded poorly but by set the gas pedal down, I meant to free some slack in it, because I read another post where a different member found that he could close the throttle by hand more at idle and this was the cause of that (and incidentally his erratic idle).

What seal do I need to replace that you mentioned was related to the rods? Is there a thread you could point me towards that covers the gaskets and seals I should grab before starting? If not I'll look at the service manual once I get home.

I would definitely chase those grounds first.

This is the actuator rod seal.
@AdrianD2...
You can't really "check the grounds first" because some of them are buried below all the intake manifolding and there's a lot of disassembly required simply to expose them. By the time you get down to the grounds, you're already committed to some replacement parts (mainly gaskets) and the other stuff I recommended (like vac/fuel hose) will never be easier to do...so why not do it?

Obviously, much depends on the condition of the engine but I'd figure on about $250 for parts (including injector service) and maybe two days of work (because you WILL run into something unexpected).
Because you'll be draining off some coolant (or else just letting the thermowax hoses overflow), it's also the perfect time to replace the water pump and rad/heater/thermowax hoses and belts.

The point of this seemingly excessive approach is to nip problems in the bud and save on future labor and diagnostic time. The two most common recommendations when someone has a problem are "Vacuum leak" and "Bad grounds!" and I've basically eliminated those possibilities.
As for the cooling advice...antifreeze has gotten somewhat pricey and bleeding the system can be a PITA, so why not just do it all and be done?

Clokker I do agree with you. I'm still new to the FC and have only owned mine for 2 months, preparing motor for reinstallation. If reaching these grounds is improbably without removing the manifold parts then I would definitely consider doing a little refresh of the areas of service.

However, since they cannot be reached without removal of some parts, then tackling other easier problems, like vacuum leaks, is probably a better idea.

Half the vacuum system is buried below the manifolds as well though.
Practically speaking, checking the vacuum and checking the grounds are the same thing.

Great info, guys.

Vacuum leaks are the first things I checked for. I couldn't find any on the air box, throttle body, or around the intake manifold, but I didn't realize that there were yet more leak-prone places under the manifold.

I'll try to find out what else I'd need to replace other than the two manifold gaskets before I tear it down. The problem is still intermittent, pretty much 50% of the time it will happen and it tends to happen all in one driving session rather than every second red light.

I would recommend getting back to your 5th-6th ports & getting that situation un-stuck & working properly or just removed. I might Speculate that the bucking and sputterring might be the result of back-pressure pulsing through the intake manifold when the VDI valve opens because the aux ports are stuck with one partially open & the other closed.

The other issues that could arise from this are Fubared fuel mixtures from non-functional aux ports & functioning secondary fuel injectors with no-where to go but backwards through the manifold.

If you're worried about grounding issues, add some of your own known good ones from the alternator to the intake manifold to the firewall... but that's just me...

Don't forget that the Altitude Pressure Sensor vacuum line has a restrictor pill in it that needs to be transplanted if you replace the Vac-lines. The ECU will act really Stupid if you leave this do-dad out of the line or fail to hook it back up.

I'm an idiot so I use black permetex on my old intake gaskets...

Otherwise, excessive un-burned lube-oil might foul the O2 sensor or maybe the Cat Temperature Overheat Sensor for a non existent Cat puts the ECU into idiot mode... I don't know anything about it, but I'm trying to make other guesses that "Could Be Helpful".

Some pics from a recent engine install, show you what you're getting into:
Attachment 609556

http://img.photobucket.com/albums/v78/clocker/Swap7.jpg

Attachment 609557

That's basically your vacuum/fuel spider in place (although I've made some detail changes, yours will look similar). Layered on top of this is the engine harness and it's all covered by the exten manifold.

The main engine grounds bolt to a boss on top of the center iron, right in the middle (almost) of this Medusa's nest, so you can see that "checking the grounds" is no trivial task.

I'm sure that will look a little more inviting when it's in person! (I hope)

Thanks for the pics! (we use the same oil filters, I see)

I just got hit in a parking lot on the prettiest part of the car, the rear quarter panel. I don't have very good luck. Hopefully it won't be written off or anything, because I'd like to take care of this soon.

Ramses, that's a good idea. I did just replace the 02 sensor, but I noticed that the one in there before was ceramic (or something, it was white) and the one I replaced it with was metal. Seeing as how it comes before the cat, though, I'm not sure if it's sensing anything there. Maybe the premix I've been using fouled it.

Ouch, quarter panel damage is the worst, I hope it works out for you.
My first shell had myriad dings/dents but I could comfortably live with them because I reasoned they were all bolt-on panels and if they really bothered me, I could replace them.
Then the rear quarter got scraped, that fantasy ended and I ultimately reshelled the car.

If you continue with the engine work...
-Get a new thermosensor. It's <$10 at Rock Auto and the only way the ECU knows coolant temp, so it's important.
-Get a big jar of dialectric grease and use it liberally on every connector you find.

From what I understood, the O2 sensor is really pretty stupid & rarely comes into play until a cruising mode is entered & open-loop processing starts to alternate between lean & rich to cycle the different Cat functions... & then there's the over-temp condition as well... All that goes on with the split-air pipe to the O2 Cat & also air injected into the exhaust diffusers in the rotor housings. It's no wonder that things might act screwy when you change the conditions.

You said you "welded" the split-air pipe?!? I'm not sure if the pressure build-up in the mangled air-system is going to mess with everything else... Suppose the Split-air pressure is now being added to the exhaust air diffusers & back-firing/detonating due to too much Port Air & an over-rich mixture?

You might "Un-weld" the split-air pipe & port it to the silenced dump line coming from the Air Control Valve on the Lower Intake Manifold. Most people end up ditching the factory air-emissions system completely, removing the ACV & air-pump & using blocking plates & fabing up a small electric air pump for the Aux Ports & VDI.

Believe it or not, I started out here with a plugged up Cat problem all those years ago... I Feel Your Pain... Sorry to Hear about the Parking Lot Inci-Dent... That Sux :( My boo-boos were self-inflicted long ago...

Uummm, what are "different cat functions"?
My understanding is that the split air pipe feeds air to the cat primarily during cold start to help light the cat off and begin functioning sooner (lower emissions) but that's about it- the rest of the time the airpump is either diverted to the exhaust ports or dumped overboard (all the while supplying the aux port/VDI actuators, too).

During all this though, the cat just does what a cat does...there are no different modes or functions involved.

Thanks, guys. :( It is the kind of unfixable where it'll never look right to me, even if it's "fixed" (i.e. pull and fill, yuck)

But, like Clokker, I picked up a car that had dinged panels, telling myself they could be replaced. Well, dammit, now the only piece that can't be has been hit. It was the only flawless piece, too!

Ramses, I think you might be on to something with the exhaust port idea. I wasn't sure if that's where the excess air is cycled, but seeing as how it's not able to push anything to the cat, that may be what's happening. It would also explain the 5500 RPM thing, as running rich + exhaust diffusers + advanced timing probably equals no power. Is it alright to just remove the pipe entirely and let the thing blow into the engine bay to test this theory?

clokker, maybe it is unable to dump enough air when it can't send any through the air pipe. My exhaust note definitely sounds different sometimes, and yes it is loud enough for me to tell, so it does sound like it could be related.

There are 3 different parts to the "Cat" system... the High Temp Reactor in the Header, & 2 different types of metal catalysts. 1 type tackles the Hydro-carbons & the other processes Nitrogen Compounds. These 2 different metals need to cycle between excess O2 & excess Nitrogen to recycle the catalyst to keep the exchange process going. The cycle is altered by changing the O2 injection amounts & locations & the altering of the AFR from Lean to Rich.

I didn't invent the thing... Look Here: https://en.wikipedia.org/wiki/Catalytic_converter ;)

I'm on my second shell as well... Use this opportunity to learn... Then get a good one to do correctly in a few years... I inherited my Dad's bottom of the barrel 4-lug SE & kept it running for 10 years, but it wasn't worth saving when an Excellent Shape GTU was had for a measly $1500.

I was over-whelmed for quite a while before I was really comfortable working on a Rotary... Even Now... My Brain still Melts occassionally.

I would guess that the un-welded split-air tube can just be left open in the engine bay. I'd try & get the aux ports freed up and the actuators re-installed... One aux port partially open might be bad news when the VDI opens and cause the Bucking Problem. The "Playing Cards" in the fan could be the extra O2 in the exhaust Port Air.

FB's had 'em but FC's do not have a thermal reactor in the manifold.

I could be wrong about the Thermal Reactor in the Header... I was under the impression that the earlier models only had a thermal reactor because of leaded gasoline, which kills the Catalysts.

The Thermal Reactor/Header was kept and the 2 extra Catalytic components were added when non-leaded fuel was mandated... The NA Header is Designed to Hold the Heat in a concentrated area to burn up the extra fuel & lube with the exhaust port air that is added... there's nothing fancy about it.

I remember Factory Cat Replacements were several thousand dollars back in 2002... It was excessive, but the alternatives were not really very simple or effective for me & started a Journey down a Road to Ruin & a School of Hard Knocks. Welcome to the Party. If you need your Nits-Picked then put on a Flame-suit & Pony-up an Opinion.

79 had reactor/ 80 cat