Rx7ADK

iTrader: (4)

1993 manual FD stock sequential twins.
just can't figure out issue I'm having. I will try to give all the details I can think of.

Mods: HKS RS twin intakes, hks downpipe, aftermarket muffler (some Australian manuf.), rats nest deleted, air pump deleted.

Engine is backfiring bad, stumbling at touch of throttle, bucking bad if I try to drive. Idles rough. No CEL and don't know how to tell if I'm in limp mode.

Sidenotes: removed rats nest for sequential setup, but I never used any resistors on unplugged solenoids (don't even know what that means, lol). I also distinctly remember hearing a quiet pop sound as I took a propane torch to burn carbon off the spark plugs. Maybe ceramic cracked? Would that be a big issue? I have tried disconnecting battery, depressing brake for 30 seconds, then restarting car but have same issues.

Maybe issue is spark? If plugs aren't burning enough fuel then it will create bad backfiring as more fuel is in exhaust and stumbling etc as it's probably just flooding engine.

Things I've thought of that I have yet to do.
1) change plugs
2) quadruple check for vacuum leaks
3) find out if block off plates are necessary
4) 330ohm .5watt resistor needed in unplugged solenoids (rats nest removal) maybe?
5) TPS adjustment?

Any ideas?

FührerTüner

iTrader: (5)

Do #5 first.

Also change your plugs. Its easy enough...

Rx7ADK

iTrader: (4)

Thanks for the reply. I've read a lot of success threads from TPS adjustments. I didn't put that as #1 only because this engine ran perfectly fine a week ago. Now it's pooh since I have changed a few things

misterstyx69

iTrader: (142)

are the plugs hooked up in correct sequence?..to right coil position?

Rx7ADK

iTrader: (4)

Leading is lower 7eq plug. Trailing is top with ngk 9eq plugs. The plug wires all reach to pretty much one plug so I can't imagine any of them are swapped.

misterstyx69

iTrader: (142)

Just a tid-bit of info:it's the trailing plug wires that would be looked at..if anything.
The leading coil wires fire at the same time anyways,so you can have them mixed up and the car would still fire the leadings as normal.

TomU

iTrader: (11)

Stock ECU?

Sgtblue

iTrader: (16)

^My thoughts exactly.
If you're on the stock ECU you're in limp mode. And it will stay that way. You can NOT remove emissions and whatever else "rats nest deleted" means without a standalone ECU. And I'll help you out a little more...YES, BLOCKOFF PLATES ARE NECESSARY.

Rx7ADK

iTrader: (4)

Yes stock ECU. I wish I had found a thread of the 50 I read on rats removal that explained the necessity for a standalone. That bites. You would think that limp mode would throw a CEL or something too. Also, if I'm in limp mode, shouldn't I be able to disconnect battery, depress brake for 30seconds, reconnect battery, then not be in limp mode right off the bat? I'm just trying to get her running, not going for HP numbers. Maybe I should put all the vacuum hoses and solenoids back on.

Also, I have now got my car stuck in a neighborhood that's a mile or so away from the house, lol. I happen to have a spare ECU lying around. If I connect that ECU up will it get me home?

Rx7ADK

iTrader: (4)

Yah, I'm on stock ECU, simplified sequential rats nest removal performed, and didn't buy banzai block off plates. This thread (pretty knowledgeable guy I think) says stock ECU is ok with emissions removed and stock main cat (just will have a junky idle).
https://www.rx7club.com/3rd-generati...o-i-do-886474/

How can I most easily remedy this issue without reinstalling all the rats nest and without spending $500 on a standalone that I don't want?

Rx7ADK

iTrader: (4)

Ok I have pulled the codes using the described method on the forum. All 4 of them to my knowledge are directly related to my following simplified sequential diagram of removing b,c,d, and g solenoids.

28 Solenoid Valve (EGR) - open or short circuit
31 Secondary Air Bypass Valve - open or short circuit
32 Secondary Air Switching Valve - open or short circuit
50 double throttle

So....based on researching the forums, you can keep the stock ECU and main cat and not have the air pump installed and have the rats nest removal (following the simplified sequential diagram on forum).

Assuming that's true, what's my better option? Should I buy resistors for those 4 solenoids I unplugged or should I just put all the rats nest vacuum hoses and solenoids junk back in (air pump stays gone though, don't have one anymore)

Now I have direction. Can anyone on here help guide me of the pros/cons/possibilities of these ideas? I am coming up with 3 possible ideas:
1) put rats nest back in.
2) put resistors in all spots where solenoids were removed (no clue how to do that)
3) buy a Apexi PowerFC plug it in and go, essentially throwing a grand or 600 (used) down drain. Lol


Here Is the simplified sequential diagram I followed.

Sgtblue

iTrader: (16)

I would have recommended you leave well-enough alone until you could buy a standalone. But you 'committed' when you removed all the emissions. Yes, I read your other thread in the 3rd gen. section too. Adding resistors (even if you were able) is a bandaid at this point. Since you're now committed, no longer have an airpump and don't understand how to add the resistors it seems your only two options if you want the car to run decently again is to put the car back together as it was (used air pumps won't cost much more than shipping), or get that standalone. And getting a PFC is NOT throwing money "down the drain". Properly installed it all but eliminates 3 grand hesitation and will allow tuning to accommodate performance modifications down the road. You still need block-off plates installed (be careful not to over-torque the bolts when installing). And ideally you need an idler pulley to replace the pulley you removed with the airpump. It's that pulley that maintains sufficient contact with the waterpump so it doesn't slip. And over-sized (underdriven) pulleys are also a bandaid IMO.

I left my AP on the engine for a few months after deleting emissions during a rebuild for a coolant seal (old picture)...



I ended up going with a Garfinkle idler to replace the AP. They're a little hard to come by now, but Pineapple Racing also makes a version...







Not trying to be harsh, but maybe a good lesson for others that there are almost always unintended consequences from modifying these cars. Some more significant than others. Good luck.

Sgtblue

iTrader: (16)

I recommend Banzai for block off plates. They're what I used. Good fit, no complaints...
FD3s RX-7 Block Off Plates

You can also get the Pineapple idler pulley thru Banzai too... PR FD Idler Pulley Kit (93+ RX-7)

Rx7ADK

iTrader: (4)

Thanks guys for all the advice.
That Garfinkle piece is nice! Sorry if I sounded rude regarding the PFC upgrade. I was just saying that For my long term purposes it would nit be money spent wisely.

I bought the car as a roller because I always wanted a rotary fd and keep my Ls swapped fd. The engine I bought had no air pump when I bought it and had the greddy pulley kit in its place so that's that. I figured since engine was out ad easy to work on in that state that it would be a good idea to get rid of the emissions vacuum lines etc.
I see that the four emissions solenoids simply need to stay disconnected and loop a 330ohm .5watt resistor in place. That seems simple, but I'm just confused at the necessity for block off plates. For instance, the double throttle isn't doing anything and isn't causing an issue if nipple is capped and butterflies are securely wired open. As for the main cat air supply hardline, other than cleaning things up I don't understand why that had to be removed either.

Are Those 4 CEL codes putting me into "limp mode"? If not, then all this (adding resistors for stock ECU), though necessary, isn't even my problem. I also plan on re-routing my feed fuel line filter because, well, that's obvious. Haha.

TomU

iTrader: (11)

You don't need block off plates if there's no leaks. Simpler than tying back the double throttle is to remove the throttle blades.

You can try the resisters, but I would think the stock ECU is tuned to work as a system and when you mess with the system, it won't be tuned (even with resisters). If you can't afford a used PFC, you may want to look for a modified stock ECU. These used to be popular before PFC came into play, talking about Pettit and I think REA might have made one. They usually go for less than $300 if you can find one (think most have gone the way of PFC tho).

Rx7ADK

iTrader: (4)

Update: installed resistors on all 4 solenoid harnesses and that removed all 4 CEL codes that were being thrown. I was getting the same symptoms though.
(crank crank, start, backfire, stumble, die.....crank crank, start, feather/pulse the gas lightly, backfire, pulse throttle to hold Rpm's high enough to run enginefor a few seconds, stumble stumble, die. Any time I push the throttle heavy down at all, immediate die)

I also hooked up a spare ECU I have, didn't help.

I had a dirty fuel tank, so I thought maybe my fuel filter was bad, so I relocated fuel filter, replaced fuel filter, same problem (although fuel pressure is more steady now)

Maybe spark plugs are fouled or the injectors are clogged?
Any ideas guys?

Rx7ADK

iTrader: (4)

VIDEO UPDATE.
Replaced spark plugs and getting good spark. Here is a picture of a brand new plug after a few attempts at running the car (maybe 4 minutes total running). The old plugs were not wet when pulled them (so I do not think flooding is an issue whatsoever)



VIDEO 2: ran for a full minute here stabbing throttle repeatedly, then it died.

And here is a temporary clear fuel filter I installed just to keep track of the cleanliness of the fuel. This is from fuel sitting in this filter for the past few weeks and as you can see, even though I made attempts to clean the tank as good as I could without breaking out the baffles, this is what new fuel ends up looking like right now.

FührerTüner

iTrader: (5)

Seems to me like you could be running on 1 rotor. Also seems like you have a lack of fuel

Id check fuel pressure and injectors.

Rx7ADK

iTrader: (4)

Thanks for your input. Both rotors were showing 85-95 compression on all faces that I could tell, and both leading plugs look the same as the plug picture above so I would think I'm running both rotors.
In line fuel pressure gauge is showing approx 34psi at idle. Pressure got a little better after filter replacement, but it isn't the issue. I think the nasty fuel got past the fuel filter and gummed up the injectors.

Anyone else?

FührerTüner

iTrader: (5)

Timing?

Also i think if you dont clear those codes, youre gonna be stuck in Limp Mode.

Have ur injectors cleaned and flow tested.

Rx7ADK

iTrader: (4)

I'm on stock ECU. Nothing I have done should throw it out of timing. Also, codes are all cleared already.

Sgtblue

iTrader: (16)

It's seems to be running just fine on both rotors and nothing to suggest a timing issue to me. I agree, it seems to be a fuel issue. Without reading back through all your posts, you have drained the old gas? Checked the fuel pump sock? Changed the OEM filter? Maybe dump some serious system cleaner (BG etc.) Have you checked the Factory Service Manual for fuel pressure specs? Just thinking out loud.

Rx7ADK

iTrader: (4)

When I got te car, it was a rolling chassis with a 1/4 tank full of 10 year old gas. Lots of rust in tank and the bottom of tank was varnish. Without removing baffles I did the best I could to clean it. The varnish is disintegrating now with fresh fuel in it (fuel is dark colored at te clear-view filter and that is probably clogging things up.


Sgtblue, You just gave me a great idea.....I think. What if I remove fuel line at the firewall and dump some sea foam in there (couple ounces worth at least) then fire the car up? That should clear it up no? If it does then I know for certain it's injectors sticking or clogged. From there, I'll have to just buy a new tank or something and get the injectors serviced.

TomU

iTrader: (11)

If your fuel system is gunked up, you have a choice. You clean the entire system, or work the gunk through the system.

Cleaning means taking the tank out and thoroughly cleaning it, replacing the filter and sock, and sending out the injectors for servicing. Probably should replace all your fuel hoses if they are original while your at it.

Working the gunk through means changing your filter and sock periodically as they will get gunked up, but eventually will get cleaner as the gunk gets worked out. Same goes for the injectors, you will probably need to send them out for servicing a couple of times.

My rec would be to entirely clean the system. You may even be able to clean the tank w/o removing it by flushing it real good with the drain plug removed. If you use any non-combustible liquid to clean it, you'll need to make sure that's out and dry before you put clean gas back into it.

Sgtblue

iTrader: (16)

What about OEM fuel filter?

Personally I'd just run some BG44K system cleaner thru the whole thing and continue to drive it conservatively (little or no boost) around the neighborhood to see if things improve.