slidins13s

I have a 91 240sx with a blacktop sr20det in it. I have been trying for the past few months to do research and fix my missing problem in my engine. The engine runs fine yet the idle usually bounces around between 1-2k rpms. when driving it pulls fine up to 3k rpms, at 3k with throttle floored it will just sit there and miss. But if you slowly accelerate to 4k rpms then it boosts all the way to redline just fine. My initial instinct was a boost leak because the missing happens right as the car tries to boost. But I have checked for boost and vacuum leaks several times. I have also
-replaced the fuel pump
-replaced the spark plugs
-gapped them to a few different gaps (.30 now)
-replaced the coil packs
-cleaned throttle body
-replaced MAF
-replaced throttle position sensor
-recirculated blow off valve

I have done so much research but can't seem to figure out my problem. Any help will be greatly appreciated.

Loufig

Coolant temp sensor

Dboyizmlg

Check for proper voltage on TPS sensor.

Also, new air filter.... This happens some times!

Banana_Cute

unplug TPS see if it runs any better. if it does. BAD TPS same goes witht he MAF..

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Loomis112

Could be a maf maf or tps. Are you running an afc at all??

slidins13s

I'll replace mine and see if it helps thanks.

slidins13s

I put a whole new tps in a month ago and made sure of proper voltage.

slidins13s

I have changed the maf and tps recently,

slidins13s

no afc, and I have changed the maf and tps and checked them also

ultimateirving

Can you describe how you checked for boost leaks?
Also how do the plugs look when you pull them out?

__________________
Z32 with lq4 swap
Desert Street Scene || Dssevents.com

slidins13s

I made a makeshift boost leak tester where I pump air into the turbo and listen for leaks. And the spark plugs have one black ring on the very bottom but other than that they are pretty clean.

slidins13s

But I should add that I put these new spark plugs in about two months ago and the ones that I took out were covered and nasty.

slidins13s

UPDATE: I noticed the wastegate actuator solenoid valve had a nipple not being used and my BOV vac line was going to the third nipple on the TB that people tell me not to use. So I ran the vacuum lines differently to see if it helped.

The person before me had it like this; BOV vac line running to third nipple on throttle body. and the waste gate vac line ran to the solenoids first nipple, the solenoid's middle nipple ran to the right nipple on the throttle body, and the solenoid's third nipple was not used. (in the middle of the vac line from the solenoid to the TB nipple was a tee off for my boost controller)

Now the way I redid the lines after much research; I blocked off the third nipple on the throttle body. Then I tee'd off the FPR vac hose that runs into the first TB nipple, That tee off runs to my BOV vac line. With the waste gate I ran the WG vac line into one nipple on the solenoid, with the nipple on the other side of the solenoid I ran it to the second vac nipple on the throttle body. then for the third solenoid nipple I ran to a tee with the vac line that went to the TB second nipple, AND in that line i tee'd off for the boost controller/ gauge.

Doing this made a huge difference. First gear boosts really well and all the way through, the rest of the gears now pull thoroughly the whole time but just don't seam to be giving their all with boost (even though the gauges read normal).
I'm hoping maybe I did something wrong and am on the verge of fixing it lol, any suggestions?

tom_sr20

what kind of engine harness do u have? a custom wiring specialty harness or a hacked out engine harness?

slidins13s

I'm pretty sure its the oem harness but its pretty hacked up and just thrown everywhere, The other day I recirculated my wastegate into my hotpipe and it made a WORLD of difference on my boosting. Its still the same problem but very minor compared to before I recirculated it.

slidins13s

Also I my SR has a hard time starting up but then after it starts it runs just fine (but very rich). Here is a video I took to show you guys what it does, I just thought maybe whatever it is, could be linked to my other problem. https://www.youtube.com/watch?v=Nx7y...ature=youtu.be

tom_sr20

youtube link not working

blkvrtswp

Why are you using the OEM boost solenoid? Remove it! That is step #1. It is useless.

slidins13s

Not OEM its a turbosmart boost solenoid, it's to turn up boost from my boost controller.

slidins13s

https://www.youtube.com/watch?v=Nx7yU6LywZg

this one should

tom_sr20

unplug maf sensor and start it. see if the hard starting goes away.

slidins13s

Unplugged it and I could hardly start the car, plugged it back in and it started back up.

tom_sr20

it should run on limp mode with the maf unplugged. mine starts and idles fine with it unplugged. I did happen to try it on a friend's s14 but it would do what u described. it will barely run.

slidins13s

I can start the car and then run it without the maf fine. But the car has a hard enough time starting as it is, I have to give it gas. So with the maf unplugged it was only harder.

slidins13s

Update: the only O2 sensor I have is my wideband and the wires are disconnected from the bunge in the down pipe. I am ordering an AEM uego so hopefully this will fix my problem as there is no O2 sensor at the moment.