SR20DET Running Lean/ Limp Mode?

[BroDude240]

Hello Zilvia!

I drive a 1989 S13 Hatch and I swapped S13 Blacktop SR20DET into it about five months ago. When I say I, I mean I had a shop that specializes in Nissan's and swaps do it for me. Since I got my car back, it hasn't run right for more than two weeks.

When I first got the car back, it would die out when I would put it into neutral. After diving it for a couple more hours it started sputtering. I took the car back the next day and they found out that the engine timing was off 15 degrees. They sent me off with re-adjusted timing, new spark plugs and new oil. A week later while cruising down the road, the pedal seemed to give out, my A/F Ratio goes 10:1 and the car starts sputtering/ misfiring like crazy. When I got home and turned the car off, the ECU made a short buzzing noise (Limp Mode?). I called the shop and they told me to drive the car back. I went to start it and it ran fine. I called them back and told them what happened and they told me to wait until it acted up again, then bring it to the shop. Sure enough it happened again. Same symptoms and all. When the car got there, it suddenly started running fine again (go figure). They ended up wiggling the harness, did a boost leak check and still couldn't re-create the issue. They gave me another fresh oil change, new plugs and sent me on my way. I'm sure you can all guess what happened a couple days later. Since the place is about 45 minutes from my house, I wasn't to keen on driving my car all the way back there on a misfire so I had them send a tow truck. They picked it up and when it got there, it started up fine. They performed another boost leak check and still nothing. Sent me on my way again. The last time I brought it there, they finally got to witness the issue first hand. They did another boost leak test and nothing. They ended up unplugging my ECU, plugging his ECU in and got it to run fine. He came to the conclusion that I had a bad ECU. I was a little skeptical because wouldn't plugging someone else's ECU always work because it hasn't detected the problem yet? Wouldn't it have to be in the car for a few days to truly determine if that's the problem?

Since then I've given up on taking it back there seeing as it happened again a week later. I've taken to the internet to research similar problems. From what I've read, it could be a bad MAF sensor, vacuum lines, bad ECU, a vent to atmosphere BOV, an exhaust leak or an O2 sensor.

I've started to test these things little by little and here's where I stand so far: The next time the car went into "limp mode" I pulled the MAF and got the car to idle better. Right then I figured that was obviously the problem so I went ahead and ordered another new, used OEM SR20DET Blacktop MAF. Plugged the new MAF in and the problem dissapeared for about two weeks (the longest it's ever gone without going into "limp") then after an hour drive home from a friends, BAM it happens again. Same symptoms as always (10:1, misfire, black smoke then eventually dying when put into neutral). When I pulled the code off the ECU it was telling me the it was the MAF again. I tested the wires going into the MAF and had a ground, 12V constant and the reference voltage. What are the chances of having TWO bad MAFs?

This whole time I've had the car back it has also been running extremely lean according to my AEM A/F gauge. I get 18 or --- at idle, 15.6-16.2 while cruising and 11.5 at WOT. I thought maybe the car running lean is casing the ECU to limp. I checked for exhaust leaks and found that my ISIS screamer pipe had exhaust coming out at idle which, according to a tech at my work, means my wastegate is stuck open and could be causing the bad A/F ratio. When I called the shop who did the swap they said that my A/F is normal for a stock SR20 with no tune and that the exhaust coming out the screamer is also normal because the pipe doesn't have a valve, it's just open all the time.

Not knowing a whole lot about cars (I'm learning lol) I'm feeling extremely conflicted with whose opinion to trust. That's why I've turned to Zilvia for some advice before I start throwing more money I don't have into parts that don't need to be replaced. The shop told me to start with replacing the ECU and then see if that solves it. Any help is EXTREMELY appreciated. I'm completely stumped.

Also to note at idle my oil pressure gauge reads about 9PSI and flashes at me.

Here is the parts I currently have on my car if it helps diagnosis this: All parts were purchased brand new minus the motor and MAF

S13 SR20DET Blacktop (stock internals)
Stock MAF
Stock E5 ECU
Stock Turbo (Running 7 Lbs)
Srock Wastegate
GodSpeed Intercooler Kit
Mishimoto Radiator w/ New Mishimoto Fans
Greddy FV BOV
ISIS Screamer Pipe
ISIS 3" Downpipe
ISIS 3" Test Pipe
Apexi 3" Hi-Flo Exhaust
Steel Braided Lines here and there
AEM A/F Ratio Gauge
Glow Shift Oil Pressure Gauge
Warlbo 255 Fuel Pump
Wiring Specialties Tucked Wiring Harness

That's all I can think of for now. Please help me out guys. I'm completely stumped.

[Kingtal0n]

I had this exact problem with a wiring specialties harness. One of the pins that contacted the coilpack output (At the ecu plug) was only making contact sometimes. We tracked it down by individually twisting each coilpack output wire until the symptom appeared.

To fix it, at least temporarily, I shoved some bits of wire into the plug to make the contact patch "larger".

otherwise, it does sound like an ECU related issue. If you cannot cause the problem by twisting and pulling the wiring harness around, you should try a new ecu. Always keep a spare 62/E5 handy. heck, even I have one, and I dont even have an s13 sr20 anymore.



Here is some food for thought,
The wideband is telling you more than you realize. If a coilpack output failed, the wideband would read lean, it would pick up the oxygen leftover (unreacted) by the misfire.
So, misfires cause lean readings- yours is a rich reading? You need to describe the problem better. If the engine "sounds like it is missing" but the wideband is reading rich, again that points back to the ecu/maf/leaks....


Another possibility is that your "BOV" is getting stuck open and leaking to the atmosphere. That would also cause this same problem. Try plugging the BOV with a sock or tape or something to eliminate it as a possibility.

[BroDude240]

I had this exact problem with a wiring specialties harness. One of the pins that contacted the coilpack output (At the ecu plug) was only making contact sometimes. We tracked it down by individually twisting each coilpack output wire until the symptom appeared.

To fix it, at least temporarily, I shoved some bits of wire into the plug to make the contact patch "larger".

otherwise, it does sound like an ECU related issue. If you cannot cause the problem by twisting and pulling the wiring harness around, you should try a new ecu. Always keep a spare 62/E5 handy. heck, even I have one, and I dont even have an s13 sr20 anymore.



Here is some food for thought,
The wideband is telling you more than you realize. If a coilpack output failed, the wideband would read lean, it would pick up the oxygen leftover (unreacted) by the misfire.
So, misfires cause lean readings- yours is a rich reading? You need to describe the problem better. If the engine "sounds like it is missing" but the wideband is reading rich, again that points back to the ecu/maf/leaks....


Another possibility is that your "BOV" is getting stuck open and leaking to the atmosphere. That would also cause this same problem. Try plugging the BOV with a sock or tape or something to eliminate it as a possibility.

I failed to mention when I ordered the harness, I ordered the wrong MAF connector (Z32) and the wrong injector connector (Bosh, EV1) so the guy's at the shop had to cut those and put the correct ones in. The injector ports have already been replaced twice and don't have any excessive resistance. Same with the MAF connector.

Good point. I guess it sounds like it's misfiring but it is running 10:1. It sounds like I have a heavy cam but my idle is fine. The ECU shows a solid red light and buzzes when the car is turned off. When you try to drive the car, it sputters hard over 2,500 RPS unless you floor it. After running like that for a few minutes it will die when put into neutral. I have a video on my phone but no way to upload here. This problem occurs at completely random times.

I'll give the BOV thing a shot tomorrow.

Is my A/F ratio fine like they say it is or am I running a risk driving it like that? Could an ECU cause a bad A/F ratio?

Thank you for the reply by the way.

[Kingtal0n]

do not drive the car like that. Running excessively rich is not good for an engine.

It sounds like you need to run it on another computer to verify that is the problem, why not buy/barrow one from the shop that has the spare they tried? did their computer make the same noise? I've never heard an ECU make noise before. Did you look at the little knob to make sure its not turned (with a screwdriver you can turn the CEL knob on the ECU)

this is how your engine is fueled:
maf voltage -> ecu -> injector on-time


As you can see, there is little to it (maf voltage & ECU). Given that your problem is intermittent, that pseudo rules out injector O-rings, but not so much a sticking regulator (fuel pressure may rise to 100+psi if that is a good pump), things of that nature. It does point to a "boost" leak, but one that large should not be intermittent (unless it is the BOV related which I mentioned) which comes back to maf voltage related (notice how boost leak leads to maf voltage related).

after considering what I said about the O-rings and regulator, that only leaves the maf voltage, and ECU, with a "maf voltage problem" being the less likely of the two.

[sil14zenki]

9psi oil pressure seems low to me...just sayin