Blacktop ECU with Redtop O2 sensor? Or maybe plugs?

[Quigs]

I have a 94-98 Blacktop SR with an E5 ECU.
Stock with the basic bolt-ons:
-T25
-FMIC
-HKS SSQV (not recirculated)
-3" downpipe back exhaust
-Walbro 255
-running NGK Iridium plugs, heat range 7 I believe

However, I am using a redtop turbo elbow with the skinny O2 sensor, because when I was doing the swap my blacktop elbow was missing a stud. Instead of replacing it, I used the extra redtop elbow I had laying around.

I was running extremely rich, but my narrowband A/F gauge was showing lean. So, I bought a new redtop O2 sensor and the car started running much better, with the A/F gauge reading more accurately. I know that narrowband O2's aren't very accurate at all the begin with, but now the lights more accurately go with what I feel the car is doing as opposed to staying lean all the time.

Now, about 3 weeks later, I am running extremely rich again under boost, and it is breaking up like crazy and throwing out some black smoke. I am currently running about 11 PSI on the T25. I understand that there is a slight difference between the fuel maps of the redtop and blacktop ECUs, hence the different O2 sensors. Since I am using a redtop O2 sensor with a blacktop ECU, could this be my reason for running rich? I do have a fat O2 sensor that came with the motor (so I'm not entirely sure how well it works) but I would have to get a new elbow if this is the cause of my problem.

Also, I don't know much about the relationship between Air/Fuel, so do sparkplugs make a difference in these regards? The last time I was breaking up was because of my plugs, so I regapped to about .028 (if I am recalling correctly), but have read that SR's should run a gap of about .035. Would this change anything?

Recap:
I'm running rich. Could this be affected by using a redtop O2 with a blacktop ECU?
Do sparkplugs affect Air/Fuel at all?

Sorry for the long post, but I figure more info is better than less. Thanks in advance for any help, and please let me know if there is anything else I need to include.

[SoSideways]

When you're running under boost, your ECU shouldn't be reading from the O2 sensor, as it should just take in the info from the MAF and run the fuel map corresponding to the volume of air measured at the MAF.

The O2 sensor is only really used during idling and cruising situations.

If I were you, I'd check for boost leaks.

Check all the intercooler couplings and vacuum lines, make sure nothing is leaking.

To diagnose your problem, you're probably going to go through a few sets of plugs, so if you don't want to waste your Iridiums at $35 a pop, go get yourself some NGK copper plugs. They're like $7 for a pack of 4. BKR7E for heat range 7. Gap them to .028" and go from there.

Oh, lastly, did you check your timing?

[Quigs]

No, I have not checked timing. I've always kind of pushed that to the back of my mind only because the factory tape is still covering the CAS bolt and doesn't seem to have been tampered with. I am aware that there are many other things to affect timing, I just haven't wanted to mess with it until I rule some other things out.

[SoSideways]

No, I have not checked timing. I've always kind of pushed that to the back of my mind only because the factory tape is still covering the CAS bolt and doesn't seem to have been tampered with. I am aware that there are many other things to affect timing, I just haven't wanted to mess with it until I rule some other things out.

Ok well, I think you need to try to pull some codes from the ECU to see if there are malfunctioning sensors at play here, or if it's something mechanical.

That process alone should help eliminate a lot of the possibilities and help narrow down the cause.

I believe you said you didn't have the LED on the ECU, and thus wanted to use a 62 ECU to pull some codes?

You do know that if you did your wiring correctly, that you could pull the code from the E5 ECU straight off of your gauge cluster, right?

As long as you have wired the CEL (check engine light) correctly, you should see the CEL blinking in short and long blinks, just like the LED on the ECU itself like on the 62 ECUs.

[Quigs]

No, I did not know this. However, I am not entirely sure if the wiring is right...the guide I used when doing the wiring was very basic and there are some wires coming off the ECU that are not being used. It's definitely worth a shot though. Any idea where I could find more information on doing this? Like what wires I need connected in order for my check engine light to work? Thanks for all the help!

[SoSideways]

Well, I used a few references to wire my harness up.

1 being the 91 KA FSM, as I used that as my reference when I did all the chassis side of the wiring, and I found some red top pin out on the web, and also used some other people's cars as references for the black top O2 sensor wiring.

IIRC, the red wire coming out of the ECU into the dash plug behind the glove box on the engine chassis side is the wire for the CEL light.

Don't quote me on that one, but I think it's the red wire.

Pretty much just match the color of the wires on the dash plug, as most of them match up 100%.

[Quigs]

Okay, I'll take a look at my wiring hopefully sometime this week. If everything checks out, then all I do is turn the diagnostic screw on the ECU and the CEL will flash like the LED on the ECU does on the other ECUs?

[SoSideways]

Okay, I'll take a look at my wiring hopefully sometime this week. If everything checks out, then all I do is turn the diagnostic screw on the ECU and the CEL will flash like the LED on the ECU does on the other ECUs?

Yes, your CEL will flash the exact same way the LED on the ECU will flash, if everything were wired up correctly, and it is not hard to wire them up correctly :)

While you're down there, you might as well wire up the Consult port too :) I did mine, IIRC it's just matching wiring colors.

Take a look at the 91 240sx FSM's wiring section for more details.

[fliprayzin240sx]

I still vote boost leak. It sounds like a typical boost leak issue. Pressurize the system and see if you have a leak somewhere. Im willing to bet you got a few...

PS: DO NOT PRESSURIZE THE SYSTEM WITH THE ENGINE RUNNING!!! (figured Id throw that in there before we do a repeat of the SRT-4 forum).

[Quigs]

Car was running fine this afternoon. I just replaced all my couplers/fixed all my leaks last month so I'm going to be pissed if I have another one.

But, it seemed to be running great today, so I don't know. I'll take a look at it this week before I make the trip to GT Live. Gotta do some brake work too :(

Thanks for the help guys.

[fliprayzin240sx]

If you dont find a boost leak, double check your timing. Get a timing gun and check it. If not, put the engine in TDC and lift the valve cover. The 2 red dots on the CAS should be close to lined up. Ive seen an SR that had its CAS timing 180 off. Still boggled my mind how the hell this thing even ran.

If that still dont do it, my next advice would be the ECU water temp sensor fucking up. But thats only if the car runs okay when the engine is cold, then starts running like crap when the engine starts warming up. ECU cant tell the engine temp so its dumping extra fuel into the cylinder.

[Quigs]

I have a timing gun, and so I'll take a look at it tomorrow or Friday if I can find the time.

It is possible I have a temp problem somewhere, my water temp gauge was doing funny things tonight. I'll look into that one tomorrow, but I think it may be unrelated. Car ran fine again tonight, so until it happens again, there's really not much more I can do haha.

[SoSideways]

I have a timing gun, and so I'll take a look at it tomorrow or Friday if I can find the time.

It is possible I have a temp problem somewhere, my water temp gauge was doing funny things tonight. I'll look into that one tomorrow, but I think it may be unrelated. Car ran fine again tonight, so until it happens again, there's really not much more I can do haha.

Is your temp gauge an aftermarket one?

If you're talking about the stock one, forget about it. It's pretty much useless.

The only temp sensor you need to worry about is the one that sends signal to the ECU.

The S14 SR FSM has directions for how to test it out to make sure it's still within working condition.

[Quigs]

Haha, sorry I should have been more specific...it is an aftermarket water temp gauge. It's been a little higher than usual. I usually run at about 80*C but lately it's been creeping up to about 89*C. I know this isn't a significant difference, but when it has been running VERY consistently at 80*C for the past 5 months, I begin to question why it could be different now haha.

I have all the FSM's so I'll be able to take a look at them. Thanks for all the info, you guys have been a great help.