MGBRaceman

have a friend with a Nissan 200SX and he's been reporting a lack of power under load. Bogging after say 10% throttle. Not RPM based but load based. My first instinct was a faulty mass air flow sensor. We tested the sensor at 2.5 volts @ 4000 RPM. Helms reads 1.3 to 1.7V at idle, we had 1.6V, this is good, however, the helms recommends 4.0V at 4000 RPM. For those of you that are familiar with the SR20DE engine, is 2.5V @ 4000RPM and acceptable figure, or is this unit definately no good?

Pyrate

I was having the same trouble and I was thinking it was my MAF. Car would hesitate and shit from idle to a little bit of throttle. It did it a month ago for a day then stop and a month later did it again for day and now it's running fine. So does this problem for ur friend come and go?

MGBRaceman

It seems to be constant. I'm really thinking it's a maf because the problem doesn't exist at idle and the voltage is right where it is supposed to be at idle. But at higher RPM (under load) that's where the problem is.

uptownspeedstar

Dip the maf in rubbing alchohol.That fixed the maf on my mazda.

projsr20det

Could be a few other things as well, What type of plugs? Recent basic tune up?

Try to find the ground wire in the MAF harness, tap into it and ground onto the body\engine (do not cut the harness wire, just tap). Common issue with a Sr20.

Pyrate

Ok nevermind that's the total opposite then of what i'm talking about

mpg9999

A common problem on the earlier SR20 MAFS was a bad ground, however I dont think the B14 chasis had that problem. Its work checking anyways. If its bad just run a new ground wire to the IM.

2.5 volts at WOT sounds low. Are you in fact testing it at wot throttle under load, or just at idle? I hit a peak MAF voltage of about 4.4 depending on weather conditions. Other then that I'd just check the common tune up stuff like all your ignition components and maybe the fuel filter.

MGBRaceman

All ignition seems to be in good order, we will check the ground. The voltage check was done with the car in neutral as instructed in the helms, It was also not at wide open throttle, the helms instructed to check for voltage based on engine speed, not TPS. 4.0 volts and 4000 RPM

mpg9999

In nuetral at 4k I get about 2.3 volts. Your manual is wronge. No way you can get 4 volts at 4k under no load.

20psi 240sx

yeah the maf is more then likely not your problem. to me it sounds like someone changed the timing. Nissan's are almost imposible to accurately set the timing without a snapon tool or techtom mdm100. if you have a snapon tool, plug it in with the car at idle.
1. read the ign timing with the snapon tool....it may be anywhere from 9-20. for this example, lets say it says 13 degrees btdc.

2. hook up a timing light and read what the crank pulley says timing is. there are 6 noches on a sr20de pulley. the first on the left is -5, then 0,5,10,15,20.

3. if the timing light shows 13, just like the snopon tool..you are done. if not, make it say whatever the snapon says at the same time as the snapon says it. double check as the timing will move around alot. key here is to make it say the same as the tool.

4. if you use good gas, set it a couple degrees more advance, ie if snapon says 13, set with timing light to 15.

the biggest thing here is to FORGET that a sr20de should be at 15 at idle.
i think you should try this word for word and see if it fixes the problem. if you don't have a snapon tool, or your mechanic doesn't want to listen to instructions from a punk like me, i have a techtom mdm100 and know a ton about the sr20de. you could bring it to the shop for me to check it out.
Good luck!
Shaun