Sr20det hits wall after 3000 rpms.... MAF maybe?

[devlmaycry]

Ok I got a 95 240sx with a s13 redtop. When I got the car it ran fine then over the last month it started acting up (minus the rectified squeak in the rear). It's mostly stock minus the aem truboost, turboxs BOV atmospheric, and walboro 255 (if I remember right). When I first noticed the loss of power I suspected boost leak or plugs so I replaced the cheap hose clamps with t-bolts on the hotpipe and tightened all the other ones. Replaced the plugs and gapped them to .028. I ran great for about 3days... Then I noticed it loosing power again. Especially on the highway when I would go to pass It felt like it was pulling all the timing and wanted to back fire, but rarely would. No power at all. So, I retightened all the clamps. That didn't seem to help at all, but now anytime I get into any boost under full throttle it has zero power. Though it seems like when I let it down to less than 3/4 throttle I get more power out of it. Vacuum seems fine and runs from 16-22. The boost will drop a lb or 2 when it looses power, but I'm not sure if the loss of power ='s loss of boost or the other way around. Seems like everyday it loses a little more will to live... Argh. Oh, and I just preplaced the fuel filter no change.

Right now under full throttle it doesn't want to pull past 5000 rpms, you can feel it wanting to back fire and has no power. However, under 3/4 throttle with no boost it wil cruise right on up to redline and behave well.... At least "well" considering.

The car idles fine and drives fine under low throttle, but dogs down terribly any boost with more than 1/2 throttle. All the fluids look fine. Oils good, coolant it fine. Etc.

I'm just not real sure what it could be. I've read a alot of stuff saying maf, cas, tps, coolant temp, spark blowout, bad coil pak, or boost leak; pretty much anything and everything. I'm just trying to get a better idea of the most likely culperit before I spend all day trouble shooting things that aren't likely to be the problem.

So, anyone whose dealt with similar problems or with more knowledge than me in the sr20det field feel free to throw me a bone please.
Modified by devlmaycry at 3:33 AM 4/28/2009

[leesredgt]

Is your gas tank rust free?

My RB25 was doing the same thing.Turned out it was bad fuel.

[devlmaycry]

Hmmm.... I hadn't thought of that, but all of the stuff coming out of my filter looked good. Is there an easy way to check that?

[captainfalco]

Search how to clean a maf, I know you can't clean it with just any solvent. It is also pretty easy to check the coilpack harness for continuity. Your best bet would be to someone local with the same sr (redtop, blacktop) and swap mafs coilpacks, ecus etc..

[cody180sx]

you also can take a screw driver and hit it with the plastic end just tap it a couple of times see if that helps

[240sxblacksr20]

its your maf it happend to my car just clean it realy good

[devlmaycry]

Yeah, I'm going to try and clean it when I get a chance prob this weekend. I'll post if it helps/fixes it.

[devlmaycry]

Yeah started air assault school this week.... Retarded right now. I haven't had time to do anything to the car, but the rainy weather is either affecting it or, it's getting worse now anytime I give it ful throttle it runs like crap. However, I plan on cleaning the maf and replacing the plugs (again). Hopefully that will clear it up. Oh, and checking the tps, cas, and the other usual stuff.

[devlmaycry]

replaced the plugs like 2 weeks ago and it seemed to run fine for a few days... now it's acting up again... So, I put the timing light on it today.... It was off a few degrees, but even once I set it to 15 it still runs like crap after I get into the boost. I guess I'll just continue to replace plugs every 2 weeks until the problem solves itself...... I figure I'll check the tps voltage next. Then maybe the maf voltage once I find a DIY on how to do it.
Modified by devlmaycry at 7:47 PM 6/6/2009

[kouki munster]

Check your fuel pressure regulator.

[devlmaycry]

How do I check the FPR? Just the vacuum lines or is there specific procedure?

[kouki munster]

Get a gague and check your fuel pressure. At idle It should be 36 psi with the vac. line connected and 43 psi with it disconected. Look to see if any fuel comes out of the vac. nipple on the fpr, if so replace it. And lastly get a vac. pump and pull vac. on the fpr and watch the fuel pressure, as vac. increases fuel pressure should decrease.

If you haven't already it would be a good idea to download a fsm for the sr.

[hilux30]

It's not you MAF or the car wont run that much, it maybe the Fuel PR but sounds more likely your throttle positioning sensor is off, I mean in voltage and it will cause it to fall flat on it's face. Locate it, you will see it is adjustible, get a voltmeter, and with ignition on but engine off, ground the meter to a negative, the other wire connect it to the signal on the TPS. At idle it should be very close to .40 volts, and then open the throttle (engine off) and it should be at 4.01 volts or very close. Check it and see....

[hilux30]

with all that said, if your FPR is the original, you should replace it regardless....

[devlmaycry]

*RESOLVED* I think.... turns out the alternator was putting out an intermittent 30amps.... Instead of 90. So, I did the KA swap, and after day one and replacing the cheap autolite plugs with the ngk bkr6e it seems to be running the way it should. Weird how no juice going to the motor and plugs will make it run like crap. If I don't post after this then it's fixed.