93 SR20 idles rich, won't go past 3k under load

[easarcher]

I'm posting this for a buddy of mine, he recently blew his KA and decided to do an SR swap. It's a 93 model year motor (forgive me, I don't know much about S-chassis, i'm a Z guy). He did the whole swap himself. It idles pig rich, and will rev to redline in neutral, but under load it won't go past 3k RPM and spews black smoke (rich as FAWK.) He has tried multiple MAF sensors, some junkyard, some known good; no difference in how it runs. Does anyone have any ideas?

He says he has asked here before, and everyone just shouts "IT'S THE MAF!" I just wanted to clarify, having exhaustively tested by swapping on other MAFs and reading the voltages, that IT IS NOT THE MAF.

[ultimateirving]

Sounds like a bad maf, but with all his testing we can move on for now..
I am leaning towards bad vacuum leak. If hes not used to boosted engines then he needs to make a boost leak tester and pressurize the whole system starting at the turbo.

Does the car idle different with the maf disconnected? Because it should be different between connected/disconnected

[easarcher]

Yes, disconnecting the maf while the engine is running causes it to stall out.

[ultimateirving]

That's good. Some indicication that the maf is Functioning. Have you guys cHecked the Ecu for codes ?
Also what plugs is he using and what gap?

The fact that he is getting engine issues under 3k rpm using points to limp mode which means something is off. I would also advise him to pop off the valve cover verify the mechanical timing then have him get a timing light and confirm that it's all timed good

[easarcher]

We haven't checked the ECU for codes because he hasn't wired the consult port up yet. He's skittish about it because he's heard he can fry the ECU if done improperly. I have a timing light, i can check ignition timing for him soon.

[ultimateirving]

Does his Ecu have the diagnostic light? There is a way to check codes without consult. But I've never heard of anyone frying an Ecu. It's 3 wires to splice in super easy

[GabeS14]

he already covered MAF...
so now check
#1-Intercooler piping! check all conections/pipes and couplers, make sure they are all tight.. this happened to me 3 times.
wouldn't rev past 3k and sounded like a subaru.. also :
#2-bad coil pack causes the same symptoms.

all easy cheap fixes.

[ultimateirving]

he already covered MAF...
so now check
#1-Intercooler piping! check all conections/pipes and couplers, make sure they are all tight.. this happened to me 3 times.
wouldn't rev past 3k and sounded like a subaru.. also :
#2-bad coil pack causes the same symptoms.

all easy cheap fixes.

Ah yes I forgot
About the coilpack. Good thought

[easarcher]

I'm not sure if his ECU does or doesn't have a light. Do you know where code meanings can be found, in case it does? I will get him to check for boost leaks too.

[ultimateirving]

Google has a nice list of engine diagnostic codes and how to retrieve them

[easarcher]

Alright, cool. I'll get with him and see what happens.

[fliprayzin240sx]

If its not a bad MAF, did you guys double check the wiring?

As far as checking the ECU for code, its pretty simple. Get to the ECU, there should be a screw on the side of it. Turn the ign key to ON (dont start the car), turn the screw fully clockwise for a few seconds, then back counter clockwise. Should put it in diagnostic mode. There should be an LED bulb inside the ECU that you can see or look at the check engine light on the dash, they should be blinking. First digit of the code are the long blinks, short blinks are the 2nd digit. So if you have 3 long blinks, then 2 short ones, then its code 32. It wouldnt be uncommon in your situation to have multiple codes so have a pen ready. Look up online for Nissan diagnostic code to point you on what each code means.

[easarcher]

If its not a bad MAF, did you guys double check the wiring?



Yeah, we checked the voltages to the MAF, and it seems to be working fine. I need to get with my friend on one of his days off and read the codes, that's next up.

[Kioes]

It's not Coil Packs either as it will freely rev in N right?

Check the loom through the wheel well, if its frawyed at all it could be cutting on each other, which would make the MAF send messed up readings, (i know you've checked MAF , but we had a similiar problem with a mates Ceffy, MAF was fine but wiring was shorting in the well)

Other then that i'm pretty stumped myself.

Could you possibly get a video of it running and cutting out?

If it's running really rich is it dumping fuel to much?