SR starts, doesn't run right (super rich, won't rev past 2500)

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Luke

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:help My sr swap is complete finally it starts fine and runs ok, but something's not right.

When it starts, the engine runs smooth but it's super rich. The first time i start it, it will run for a min or two, then studder and die. After that, it will run and idle fine at 800 and run forever but it runs so rich, there's fuel coming out the back of the exhaust. Sometimes when i rev, it will stumble, but quickly catch up and rev freely, then when i let go it will studder a little sometimes and then go back and idle. It won't rev past 2000-2500 rpms at all. Everyone tells me it's a bad MAFS or the wiring.

It will drive around as long as I don't give it any throttle. If it do it will buck and hesitate.

Info. you might be able to use to help me figure this out:- My gauges aren't installed but I connected my boost gauge and it reads -16 at idle- I've gone over my IC piping over and over and it's all tight. I doubt there's a leak. I installed my BOV last night, but before that, i had the hole on the hotpipe blocked, so i know that's not the problem.- I also unhooked each coilpack one at a time to make sure each cylinder is firing. Unplugging each coilpack had the same results, so I know they all should be firing.- Before the engine went in, I installed pregapped Denso iridium plugs, and I checked the timing by setting cylinder 1 to TDC and lined up the CAS. I didn't have to reset the CAS because when I pulled the valve cover, the CAS looked like the instructions I have to set the timing manually.- I checked over the wires I extended and they are fine. I don't know how to test my MAFS but I checked for continuity between the ground wire on the MAFS and the chassis and I got nothing(this has me thinking, how do i check the grounds?)- While I checked the MAFS wiring, i checked the o2 sensor wiring also.- My ECU is wired up but not mounted in the kick panel yet. Does that cause any problems? I took a ground wire from the ecu case to the chassis, because i thought the ECU may need to be grounded.- First I cleaned the SR MAFS, no luck. Then I picked up a used SOHC MAFS and wired that up correctly using the SOHC connector. That didn't work, last night i cleaned it, and tried again, no luck.

Does anyone know the procedure to check an S13 blacktop's ground connections, the TPS and the MAFS? I can't find anything at all by searching.Also, what's the procedure to reset the ECU? I disconnect the battery cable for a while hoping it does. How long would it stay in it's limp mode in this case? Until the problem goes away, or until the ecu is reset??

Any help would be greatly appreciated, i'm stuck on this.:help :help :confused:


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gtune4
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maf sensor probably. the computer limits the revs when this is malfunction to 2-2.5k. use a voltohmeter to check your gounds, and make sure all of your wires between the comp and sensor are legit. alcohol and a q-tip work well to clean the maf. be careful. the o2 sensor will act funny around 4000rpm!

Dugi
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yeah probably your MAF. When the problem is fixed your computer will correct itself.

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Hijacker
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check your computer for a code. the happened to a swap i was helping out on last week. It was simply a matter of cleaning the connectors, and reconnecting it. Heck, reseating the pin was probably the fix.

Luke

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tenkawa_akito wrote:check your computer for a code. the happened to a swap i was helping out on last week. It was simply a matter of cleaning the connectors, and reconnecting it. Heck, reseating the pin was probably the fix.
My ecu does'nt have an led for diagnostics. It's a blacktop and jeff @heavythrottle said there isn't diag. in the newer blacktops.

S13 King
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I'm having that EXACT same problem with mine. It started after my friend ran a mustang. Just quit out on us. We checked the MAF and it seems to run worse with it so we do think its the MAF or the wiring. I'm going to get that checked today. Maybe we can find the problem.

It won't hold idel, runs rich, and won't go past 2500k, on my boost gauge its saying that i'm pulling good vacume. I also checked the intercooler piping.

The motor I have is a Blacktop from a 94' 180sx

Let me know if you find out something.

Luke

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Ok, i'm picking up another SOHC MAFS today and i'm going to try and trace the wiring back for the 100th time.

S13 King
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ok, i'm taking mine to get the wiring checked on it. But I think its kinda odd that it would just do that. The car was running fine and then this,lol.

Keep in touch so we can figure this out.

meggala
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check your cooler piping there could be a leak there seen this b4jsut fully read your post check your intercooler could ahve a small crack also check if any vacum lines have split of come off. seems like air in getting in their to my untrained mind.if you have taken off the maf and there is no difference that could be the problem but I doubt itmeggala

S13 King
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i did that with mine and still nothing has changed. If they can't figure out what it is today then i'm going to take it to SGP in houston, TX. I heard they do good work

S13 King
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Just got back from the shop, thye had no clue, car runs worse then ever (i had to limp it home). I've got no choice but to tow it to light speed or SGP. Most likely Light Speed since they did the swap.

However I was thinking, maybe the ECU is fried or something?

Luke

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I got her running tonight. I knew it had to do with the MAFS, but it wasn't the MAFS itself at all. I followed the wiring for the MAFS back, and I found that one of those ziptie things that hold the harness to the chassis had cut into the MAFS wiring. The black wire and white wire were severed. I soldered them back together and she purrs like new. It makes me feel good to know that I did this whole swap with no mistakes. Some lazy japanese guy probably decided to pull on the harness to get those ziptie things out.

Thanks to everyone that helped!:greenboun

S13 King
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awesome man congrats on it. I traced the wiring back and still nothing. Tomorrow I'm going to limp it to the shop in houston to have them look at it. So......yea thats what i've gotta do. I'm thinking something is wrong with the ECU......

I'll keep ya posted.

Luke

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The way I found out it was my wiring was test with a multimeter. I tested the continuity (ohms) from the black wire on the MAFS connector to a ground, and I got nothing. Then I tried testing the voltage on the white wire, nothing. I did get voltage on teh black/white stripe wire because that wasn't cut. Try that out if you haven't already.

I was all mad that I had to unwrap alll the wiring to try and find where it was cut. Then I spent about 5 min. and I found it.

S13 King
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what are the OHM readings?a buddy and i are right now going over them. If you can PM or post asap. Thanks

Luke

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When you have good continuity, the ohms would get close to zero. If it's nothing, the ohm meter does nothing.

S13 King
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I knew it was probably something so simple. Well on the GReddy FMIC kit there is a pre mounted fflange for the BOV. The shop that did the install had just taped over it. Reason we didn't see it was cause the support rest against that side.

Well I had them compression test it, and leak down, check the harness for any other ghetto riggin and weld that premounted flange shut instead if putting tape over it,lol.

Now the car runs great, killin Z28's, GT Stangs, old Cobra Stangs, and any thing just about to step in my path,lol.


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