SR problems, starting/idleing, tech. help?

[S13GG]

I have a 90 240sx w/SR blacktop motor.

I had a problem with my SR whereby when I used more than 30% throttle it would backfire (brrrrr-brrrrr-pop). This would only occur under load (not in nuetral). He was positive that was a turbo gasket.

Before I got a chance to change it theSR decided to die. It ran fine and the next day it wouldn't start. It would turn over and flood itself but not start. For 2 weeks I tried tracking down issues, ignitor/coils, fuel pump/injectors, plugs... Then this week it started, but when it did it sounded rough, like 2 cylinders (400rpm and shaking), so I opened the throttlebody a little and eventually it would return to its regular idle.

Its still having trouble starting. It turns over like it did for the 2 weeks it wouldn't start, but if it does catch and run on its own, it dosen't do so immediately or smoothly.

Help please

[NISTECH]

how does it accelerate once its started? if it feels like its lacking HP it may be a bad MAF , It could also be a poor connection at the coolant temp or a failing coolant temp. how is the base idle on it?

[S13GG]

Once i got it to catch (on all 4) the idle was normal, 1300rpm, kickdown to about 700-800rpm. I also tried another ECU thinking it may by the Access (Blitz) ECU's fault, with no notable difference.

The second time I started it, it started the same, 400rpm, add throttle, then it caught. It idled right after that, 800, but for some reason it jumped to 2800rpm (after a minute or two) and minor throttle body (open/close) adjustment didin't matter so I shut it off. It was still warm an this 2nd start.

I have another mafs, told its an SR, but has 4 pins, part # 22680-58A10, and a black rubber nipple covering a flathead adj. of some type. Of course I sold my SOHC MAFS to a friend about a week before for his SR.

Thanks again

[NISTECH]

to check your base idle you need to disconnect the tps and start it up, car has to be previously warmed up though. When you disconnect the TPS it take the computer controlled idle out of the loop. This is when you adjust the idle air screw.

[S13GG]

^ I'll do this in the morning.

I'll warm up the car, (hopefully it starts and dosent need to be coaxed), shut it off, disconect the TPS and start it. what exactly should the outcome be (what am I looking for) ie: irregular idle?

Use adjustment screw to set new idle speed at? I thought 700-800 rpms was the correct idle speed?

the coolant temp sensor is some where in the middle of the intake manifold? (SR20DET)

What MAFS did my buddy send me? anybody? 22680-58A10?

[NISTECH]

your looking for the car not to start or to have such a low base idle it will hardly run. this is whe you need to back the base idle screw out a bit. your correct the idel spec is 700-800 rpm for BASE idle not TARGET idle which is what the computer accomplishes. They are usualy around the same number but when your starting the car it starts with base idle and compensates to attain TARGET idle. During this time it may flod the car out.

I am thinking the coolant temp sensor on th 20 is in the same place as the 24.

I'll see what I can fond on your air flow number

[NISTECH]

well did an exhuative search of all nissans produced in the us and none of them match that number,which indicates is from a JDM car.

[180fan]

MAFS on the s13 sr = sohc mafs with just one less space on the end. Only 3 plugs on both, just the SR has space for a 4th wire.

Coolant temp sensor is on the intake manifold side towards where that part of the harness splits into a Y. That one plug that's got a metal bracket that's attached to the valve cover. Coolant temp sensor = 2 wire plug just above the throttle body.

With the TPS off, you're looking to set your idle around 750-850.

[S13GG]

DOH!, I forgot the instructions. I removed the TPS while it was idleing at 700-800rpm(warm), the idle rose to 2000rpm (over 1 minute) after I removed the plug. I took it for a spin around the block, and it was still backfiring (under more than 30% throttle), but when I would stop the idle would dip to 400rpm, and it would backfire, it didn't seem to want fuel. I got it home but it died and refused to start again.

I did unplug the MAFS while it was idling and the idle dipped a choked a little.

Tomorrow I plan on changing that leaky turbo gasket (as per my friends 1st problem diagnosis), doing a comp. test (have to get a new tester), and hooking up a boost gauge I recently aquired. I'll probably throw a new coolant sensor (out of an old KA) in tomorrow.

I will warm it and test BASE idle tomorrow.Yeah that MAFS is JDM.

[S13GG]

I changed the turbo gasket, and the car wouldn't start, an unrelated problem.

I took it to my local nissan dealer, and they took 1 look (5 mins) and asked me to get them a CAS, as they couldn't and mine had no cover, and the disc was a little bit deformed.

After they got it it took them 45mins to install it, and it runs good as it ever did, but sometimes while waitng at intetrsections (stopped/nuetral) the rpm's will bog/bounce from 500-800rpm (while warm), instead of its nice even 700-800rpm idle of before.

I will warm the engine tomorrow, and unplug the throttle pos. sensor, so that I can adjust my "base" idle.

thanks again for the help, any luck with the MAFS #?this thread may be deleted

[NISTECH]

no i did an exhuastive search and it doesnt show as a us part number, but 180 gave you an alternative.

Why would you think this thread would be deleted??