Rx7 Running Lean
 

Hello Everyone,

I picked up my FD two months ago and all has been great. I daily drive a B7 S4, however that air ride manifold in that broke this week leaving me unable to use the air ride and having to daily the rx7.

This week I have noticed a few issues. I can't narrow the diagnosis down but who knows, maybe (or probably) there are more issues than one. Let me know what you think.

Symptoms:
When it runs great it runs great! Boosts 10 psi, no boost creep, A/F around high 10s low 11s in WOT, it feels like it should.
Running rough: A/F Stays 13 and above, WOT, Idle, everything. It won't boost higher than 8 psi, RPMs bounce while driving sometimes, the throttle cable also feels stiffer. Never a CEL.

I tested the TPS and it was slightly off, hadnt had time to adjust it but it was only slightly. I was not sure if it was that, a failing fuel pump, misfiring, or who knows what.

I purchased the FD through a member here and mods are simple.
Turbo back exhaust
SMIC
Stock fueling/ECU

The build thread was here: https://www.rx7club.com/build-thread...build-1070041/

Thanks for your help!

Prob not a bad idea to replace and or send out the stock injectors to be cleaned and flow tested and possibly rebuilt or replaced.
I would also replace the stock fuel pulsation dampener. It's a known failure point that with age will fail and will turn the car into a "Car-BQ".

The fuel filter is a likely culprit when you see a lean condition from a basically stock car. It's possible also that the age of the cars you could be getting some corrosion in the tank or fuel is gumming up inside the lines/pump/injectors etc.

It's not out of the question you are having 1 or more of these issues but it's maintinence for a near 25 year old car that's infrequently driven.

Let us know what you find.

Mike

I never ran into this..
It could be that one of the rack solenoids is failing, though I test them individually as good. Maybe a connector came loose?
Fuel injectors were just cleaned and flow tested.
Fuel filter or pump aren't out of the question as I didn't touch those.
Good luck! Whatever it is should be pretty simple.

were the solenoids tested hot?

best to change the fuel filter if it hasn't been changed, but is probably not the problem

were the actuators tested?

are you pulling good vacuum?

you may want to upgrade to a PFC w/o the cat

Solenoids were tested cold and hot. On top of that I only used ones that worked with as low as 9v.

Actuators were tested as well.

Car pulled ~18 inches of vacuum when I had it.

The viton check valves I got through daleclark did leak by slowly. It's possible they could be causing the problem as well.

Solenoids and check valves won't be the problem unless the fuel pressure solenoid is acting up. Most likely the fuel pump is getting hot and causing an issue.

Wow great responses thank you all very much. I will start with the fuel filter and work my way up. Now that the snow is on the ground I won't be doing much testing but once I find something I will keep you all posted!

edit: I was planning on getting a PFC but 1 month after the FD purchase I found out I will be a Dad so things will be moving a bit slower than previously anticipated. I will be vinyl wrapping the car in the spring as well and I am on the hunt for a JDM transmission as the 5th gear grind is pretty bad at times. Couple that with a new clutch, man things add up faster than they do on my Audi.

Just to update the thread in case someone ends up having the same symptoms...

Today I changed the fuel filter and sway bar end links. I did not get to put a significant amount of miles on it but it seems one of those fixed the issue, my guess is it was the sway bar end links :lol: . The fuel filter was more of a pain than I would have expected but it is good insurance even if it is not the fix. I will know more shortly as I continue to drive it but so far results look promising.


I also replaced the lower temp thermostat with a factory unit for now. It never got to temp which cold motor, cold oil to the turbos can create an issue with the seals, and I never had heat to even defrost the windows. When it gets warmer out I may switch back. I now have a little air in the line cooling system so any suggestions besides a full flush would be great.

I also found a small crack in the black hard plastic host that is on top of the motor to the SMIC (I'm not sure of the name). I used some jb weld to cover up the hairline and so far so good but I will replace it.

Next plans are to replace the oil cooler line and clean up the motor. On the lift today I found a TON of oil residue, so bad I couldn't pin point the source. It was everywhere but the PO informed me of the cooler line so I will start there.

Coilvers came in, the vinyl wrap came in, ordered my projector kit, wheels, and stage 2 clutch. Lots of work ahead!

Show us a pic of the crack. These cars came with an air separation tank for the cooling system but they were plastic from the factory and are a major failure point.
Some delete it but the best solution is to upgrade it to an aluminum one and it will remove the air on its own. Otherwise you will have to burp the system yourself.

The AST was replaced with a metal unit. I only think there is air in there because I can hear a noise on the otherside of the firewall. I don't know how to describe it other than air bubbling when the heat isn't on. However my temp gauge doesn't move and I did everything I could to remove any bubbles that were in there. Maybe its a normal sound, I don't even know.

I don't have a pic of the crack, but it was below this jb weld. It was a hairline crack, barely anything but looked like it was from overtightening of the hose clamp

Attachment 614982

That looks like the pipe that connects to the Y-pipe. The Y-pipe is a known failure point and was upgraded in 1996. It's sold under the name Efini Y-pipe. It's metal instead of plastic. You should upgrade to the metal parts for sure.

It cracked on my 1st FD that was stock twins. Didn't know what the issue was until it was pulled apart for a single turbo out of frustration in 2001.

Thanks for the tip! I will have to add that to the list haha. I am looking for a line to draw in the sand that I do not cross however I seem to find justification for everything so far.

I always have a budget but the car dictates what it needs. The gray plastics in the 93 cars were upgraded in 94 to the black plastics. They are supposed to be less prone to crack butt at this point 25 years later you are lucky they lasted this long. I would consider these types of things maintinence items. Also 93 was the first model year and it had some teething issues. 96 they upgraded that Y pipe that had already shown itself to be a failure point. It was sold on all 96+ RX-7's moving forward. Of course here in the USA we stopped getting the car in 95.

I hear ya on the drawing the line in the sand. That's all well and good on a car with no problems. If you reached your limit with the car and it's still not 100% then the line in the sand becomes a For Sale advertisement as it won't ever stop bleeding you.

I never question maintenance, never have on any of my other money hungry cars and toys. It's the other parts I question more

Glad to hear the fuel filter fixed the problem! The car got a lot of maintenance from me, but there always seems to be more with these cars.

About the bubbling noise! I did some reading and it sounds like it can have to do with the mixing valve in the heater core or something like that. I'd look into that.

You're right, the maintenance you have done is actually what made me purchase it. You looked into things that I wouldn't have thought of which was nice. It is getting dropped off to get the clutch done this week actually so I am pretty excited.

I will definitely look into the mixing valve!

Accelerator feels stiff.

Hmmn, only time I have had this is when a tech has knocked my accelerator cable out of the throttle body pulley groove by twiddling the throttle shaft by hand (I guess to check that it has a return spring). It leaves the throttle cable end still in place on the pulley, but not working well.

Check that.

I sure will thanks!

well damn.. bad news. The issue is still there. I took it for a ride tonight and was having the same issues. Also, I get to the shop and start leaking coolant randomly, not cool. What level should my ASt be at when cool/slightly warm?

Good news is my wheels fit. once i get the coilovers on I will post some pics.

Leaking where exactly? At the overflow on the front passenger side by the headlight?

Did you add more coolant to the system after replacing the thermostat? You could have just overfilled the system and it was being relieved. Everything coolant hose is brand new

That is exactly what I was thinking. What should the level be at when the car is cool? I have never asked so many simple questions before :lol: The AST is about half full and the overflow looks to be below L currently.

The car failed emissions today as I expected. To my surprise they failed it for idling way too right, not while driving. My AFRs are around 11-12.5 at idle and they said it leans out under load a bit. Besides a PFC is there any way to fix that?

Too rich at idle = ACV or airpump.

Wires cut to install JDM Power FC into USDM FD

16-pin connector
---------------------
3J blue-green EGR SW (Calif)

26-pin connector
---------------------
4F black-red SPLIT AIR BYPASS SOL VALVE
4O blue-yellow EGR SOL VALVE
4P brown-yellow AWS SOL VALVE

So you can see it will fail smog unless you get all those 4 functions working with a USDM ECU or find a way to fake them or fake the smog tech out.

Ah okay. Guess I will be purchasing a PFC in the near future.