Hesitation going into boost, gone when full boost hits
 

I would like to start this off by informing everyone that I am all new to the FD world and rotaries as well.

Mods:
Full 3" Exhaust, Non-Seq setup(pretty sure atleast?), 99 spec twins, PFC, stock everything else.

Back Story: Picked up the car about a month ago, everything was fine. Discovered the FPD was leaky, so I replaced that along with the plugs and wires, oil change, gear oil, etc. Original plugs I pulled where all heat range 9, I replaced with all stock plugs. Afterwards this problem occurred

Issue: The car hesitates and misses when going into boost, once I hit full boost the breaking up/hesitation/missing is gone. No idea what is going on here.

Things I have tried: Not much yet, checked for vac leaks by taking some brake cleaner and carb cleaner to the lines... nothing. Today after work I am going to pick up 2 more bur9eq plugs to see if this helps the situation. TBH I have no idea what it can be at this point and pretty much need guidance for information you all would need to help troubleshoot this.

Anything you need to know, please ask and I will try to respond to the best of my ability.
And to all those who post thank you in advance for your time and thoughts!
-Steve

well i dont know if this will help but im having somewhat similar problems.....and i think I might have figured it out. Sounds crazy but here is what i think is my problem:
so i noticed that i would try to go fast but wouldnt go as fast as I think it should be....but my rpms were moving pretty quick and my boost was only reading about 3 psi.........didnt add up
so i noticed recently that after a few seconds giving it some gas that my rpms would revv and then drop back about 1000 rpms or so and then slowly start going up again.......which made me think my clutch is slipping (yeah i know, i should notice a slipping clutch pretty easy huh, he he)
so im thinking that once i give it gas my rpms move but my car really isnt grabbing.....which would make sense that i barely read any boost until it finally catches gear. its like revving up the car in neutral (rpms move but no boost) i barely noticed because my streets are small and have not much room to drive it too fast to really test it.

i hope this makes sense. i dont know if this is anything you are experiencing but just in case. good luck!

well I went through again with some brake clean, seems I still have some vacuum leaks. Its kinda hard to pinpoint exactly what lines they are though. Tomorrow I am going to go through it and replace them all with the spare vacuum lines I have laying around as a temp fix.

drakujr thanks for the words, seems to be two different issues! however good luck trying to get yours fixed!

The twin turbo system can be a nightmare if the previous owner(s) put zero effort into keeping it running correctly, and most don't.

The best advice I can give is:
a) Do a search on the colored vac hose diagram. Download it, blow it up big, laminate it.
b) Do a search for Dale Clarks guide on vac hose replacement. Important point: use GOOD silcone hose.
c) do a search on Dgeesamans solenoid/actuator test writeup

There is no shortcut. Go through and replace every vac hose, test every solenoid, actuator, check valve (better yet replace stock valves with Dale Clarks viton ones), vac and pressure chambers. Test the Y-pipe, check every coupler. make sure you don't have vac leaks as well from bad gaskets.

It's a lot of work, but it's less work and frustration trying to chase and fix individual problems.

Thanks for the advice! I have already found the vac hose diagram, my hose piping doesnt seem to match up to any or maybe I just need to study the diagrams a bit more. I have read through the vac hose replacement guide and plan on getting some good silcone hose when money permits(holiday season :/), my buddy works at a toyota dealership/shop so hes gunna steal me some vac lines for the time being. So tonight I plan on going through and atleast replacing all of my vac lines and see if they remedies/helps the situation.

Would the old carb cleaner/brake cleaner trick work to find vac leaks at the y-pipe/couplers and gasket areas as well?

Also an update, When the motor is cold it seems to idle, rev fine, no missing no breaking up not shit. Once it gets up to temp it starts to stumble when going into throttle. So this is definitely making me believe it is a vac line fked up issue, my thought behind this is that since the motor is cold, as well as everything else(including the vac lines) they are shrunk down a bit. Once the motor is warmed up and the vac lines are taking some heat they expand and open up a bit, either they are cracked some where or not holding on well. Is my thought on this correct?

Thank again for all the advice guys!

If you check out dgeesaman's solenoid test writeup you will see it is recommended to test the solenoids both cold and hot. They can work ok until they're heated up and then have problems after they warm up.

There's no substitute for going through and checking the whole system on an unknown car since things could be hooked up wrong, found broken with a good visual, one way valves plugged in backwards, etc.

You just have to go slow and make sure you don't induce more problems into the mix.

Another good resource is : http://www.autosportracetech.com/RX-...leshooting.htm

Thanks for the link and again for the advice! Ill give it a good read later when I get home from work. The only crappy part about this situation is that recently my wife had to give up her car to her parents due to some issue with other family memebers. So the FD is the only car we have between the two of us! shitty situation and bad timing has seemed to occur! haha

If he's non sequential, solenoids are not an issue because they have been eliminated. You can quickly tell if it's non sequential because the vacuum chamber underneath the front of the UIM will be gone. The car needs a boost leak tester to pressurize the system using an air compressor. Fighter's garage sold one but you can make your own out of PVC parts. This one for a 300zx Twin Turbo would probably also work:

www.boostpro.net/prodtester.html , 300zx "dual pop" . basically you plug the intake for one turbo and then pressurize the other one using a tire valve fitting or a regular air compressor male fitting.

there could also be tuning issues at work, but without datalogs from the computer it's hard to say.

I still have 2 of the solenoids under the rack. If I provide some pictures would you be able to help me determine if it is configured to be Non Sequential? I only say I think it is due to the amount of block off plates it has on it. I have a 12 gallon compressor, will this be sufficient to do the test? also is their any sort of additive or what not I can use to visually see any vacuum leaks?
On a side note, I honestly feel like Im pulling the UIM atleast once a day(not really but it seems like it)
Thanks again everyone!

Ah I missed the non seq part. I don't really get the whole non-seq twins thing, but at least that will simplifiy troubleshooting for you.

boost/ missing problems
 

SDelong- welcome to the world of FD's- cars with complicated boost control systems that sometimes did not work well when new, now the car is over 15 years old, wires and sensors are cooked from years of high under-hood temperatures and previous owners have modified stuff and not left a good record of what they did. Yet FD owners are hooked, like loving a woman who gives them only trouble. Hope you get the car running better. I live in the same general area of VA (can hear artillary range at Quantico) and we are SOL on a FD specialist, unless you want to take it to Malloy Mazda in Woodbridge.

post a pic of the engine bay

Sorry about dropping off the face of the planet for the past few days. however here is an update!

I guess that means we should become the FD Specialists in the area then! haha

Ive gone through the vacuum lines with a diagram and replaced them with new vac lines(not silicone, rubber just to check if its the issue) and nothing, It seems I have a simplified seq setup. This is really mind boggling as it only hesitates, not want to boost, nearly dies at idle when the engine is completely warmed up. I really have no idea what to do at this point and starting to get very fustrated. Also, I know it is going to end up being something very very stupid, like a missing vac line. I would find it compeltely coincidental that something else failed as I replaced the FPD... Im thinking I assembled something wrong. So with that being said, anyone in the NoVA area want to come by this weekend and lend me a hand getting down on this? case of beer on me! Thanks for all the input guys!

Went to go dig around the engine bay today after work and what do I find you ask! Well, on the UIM, that little black solenoid/valve closest to the firewall, What I believe to be the Idle Control Valve? has a snipped wire.... seems from me taking the uim off and back on its plug decided it didnt want to jive anymore. so with that being said does anyone know what I can use as a replacement plug or how to depin the original plug to fix it as its broken right at the connector? Again thanks for the help everyone

Just a quick update for all those following, went to take a few pictures for CrispyRX7 and decided to "set" the idle screw. I set it to idle a little high and took the car out for a little bit(was easy on her due to the rain) to warm her up, got up to operating temp, low idle at operating temp... gone... odd I think but I only believe this to be a temporary fix as I believe the ACTUAL issue is the idle solenoid control(ISC/IAC/Black thing on UIM closest to the firewall near TB?)
Thanks,
Steve

that may be the problem does it sound like its trying to catch itself after you rev it up or does it straight die. either way id take carb cleaner and a tooth brush and clean out you throttle body behind the blades and take your idle control solenoid off and spray it out as well since they attract allot of carbon. this will generally help smooth the idle out.

only read your post OP. full exhaust and 99 twins + no tune = bad things happen

I rev it up, rpms fall, drops to 400ish and acts like it wants to die. All dependent on how far warmed up the motor is. I need to replace the connector on the ISC, so when I go to do that Ill start to clean them all off.

Right now Im trying to get it back to good running order before attempting to get it tuned. Kinda pointless to get tuned if its not even running right :/ Gunna try a few more things to get the hesitation fixed and if that doesnt work, I will see if PFS will take my car in to get it sorted out!

FINAL UPDATE, Finally fixed this ish.... funny story though.... vacuum lines that I had already checked seemed to be the culprit. its so hard to notice/see tears in silicones, moral of the story that I have learned, just replace all them fuckers in one fell swoop!
Thanks for all the advice from everyone! car is on the road running perfect!

I just stumbled upon this thread. Good to hear the car is running right!

Now get that little hussy in for a tune!! Lol