Today my friend (I think his name is HolyShiznit on this board)tried to start his car (just got done with all the intercooler piping and downpipe), he has a ka24de with sr 370cc injectors, a z32 mafs, and an s-afc 2. There is a weird idle problem though, when we start it up the idle surges up to like 1600 rpms and then drops back down to almost 100rpms, it does this surging a number of times before it just dies. I can keep my foot on the throttle and hold it at 2000 rpms, and if I let the rpms drop very slowly it will idle just like stock. It does this no matter what settings we have on the s-afc, so im thinking it could be something else... anybody have any ideas?
(my buddy got called into work so that is why I am posting this and not him)
s-afc + z32mafs + 370cc idle problems
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Redline240
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- Car: 95 240sx
I don't know if this will help at all, but it doesn't hurt to add...this happens on a lot of 240's and can usually be fixed with a little throttle body cleaner, or carb cleaner...just buy a can, disconect the vaccum line between the brake master cylinder and the engine and start spraying it in with the engine running...have someone on the throttle to keep it from stalling...fixed my problem, might not fix yours...but i love stating the obvious! Its been mentioned about a million times on here...
Redline
Redline
Possibly has the afc set to corretc for dec air function. Also--check the maf wires how they were soldered. Sometimes a little fiddling with wired can make the ecu cranky if theya rent done totally right. I hate hearing that its giving your boy trouble, but I know that i bought my ecu used, and when i installed it--the tool before me had screwed with the settings and had the dec air function turned way up and caused my car to run like a it had the hugest lumpiest cam EVAR.
I hope I helped. Also--check the voltage. Its supposed to be 5 in 5 out on the stock maf--but there are guys that have ot run it on a 1 in 8 out or a 1 in 6 out--some use 2 in 6 out.Keep playing with it. It shouldnt hurt anything while you are figuring it out. You knwo what though--i just thought of something.This is exactly how my car was when i blew the head gasket. I was sold a set of bad sr injectors. The tool screwed me when he knew they were bad injectors, and it caused me to run way too lean and blew the head gasket. My car would do exactly what you are describing. Rev to like 2k then fall and either stumble at 100 rpms or die. It sputtered alot of smoke and crap though. As long as you arent sputerring crap, you are probably ok. What all did he mess with whil installing this stuff? Id say go back and retrace everything to make sure it was all done right.
I hope I helped. Also--check the voltage. Its supposed to be 5 in 5 out on the stock maf--but there are guys that have ot run it on a 1 in 8 out or a 1 in 6 out--some use 2 in 6 out.Keep playing with it. It shouldnt hurt anything while you are figuring it out. You knwo what though--i just thought of something.This is exactly how my car was when i blew the head gasket. I was sold a set of bad sr injectors. The tool screwed me when he knew they were bad injectors, and it caused me to run way too lean and blew the head gasket. My car would do exactly what you are describing. Rev to like 2k then fall and either stumble at 100 rpms or die. It sputtered alot of smoke and crap though. As long as you arent sputerring crap, you are probably ok. What all did he mess with whil installing this stuff? Id say go back and retrace everything to make sure it was all done right.
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Structure240sx
- Posts: 5615
- Joined: Sun Oct 06, 2002 5:04 pm
u have the maf grounded to the chassis right? i had to play with the hot wire sensor settings for a little while to get mine running right. luckily i had a wideband. i know he wanted to jsut get it running to get to a dyno 90miles away. i say jsut buy the wideband which will be much cheaper in the long run.
best way i think to go about getting it running right is set the low map 1000rpms at -27% sicne thats what the sr injectors are suppose to be. then jsut play with the maf settings until it idles decent. this should be good enough although the car will seem to idle great at 12:1 air fuel ratio sometimes richer, better than running lean tho. my car's idle usually on dec. air will surge like you said. its running lean in this case according to my wideband.
best way i think to go about getting it running right is set the low map 1000rpms at -27% sicne thats what the sr injectors are suppose to be. then jsut play with the maf settings until it idles decent. this should be good enough although the car will seem to idle great at 12:1 air fuel ratio sometimes richer, better than running lean tho. my car's idle usually on dec. air will surge like you said. its running lean in this case according to my wideband.
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HolyShiznit
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well, got it running and idling fine (I think they figured out it was something with the dec. air function), but today on the dyno it took a big crap. everything was going smoothly until all of the sudden it started running insanely rich, brought it back down to idle, idles fine still and with good a/f ratios, but step on the gas at all and a/f ratios take a dive to 8-9:1 and the car sputters and backfires. after much frustration trying to figure out whats wrong, we unplugged the maf all together and it ran exactly the same as with it plugged in, so we are thinking the maf is toasted (why i have no idea). so now his car is sitting up in portland not running, anything like this ever happen to anyone (the insanely rich condition)?
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Structure240sx
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HolyShiznit
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MikeMurphy
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the car was running/working just perfectly while it was on the dyno. he had it tuned up to about 4-5k rpms perfectly when all of the sudden it went super rich, he dropped the car down to idle to take out some fuel up top, next time he stepped on the gas it had the problem described above, where it was running perfectly not more than a few seconds ago. nothing we did after this made any difference in the a/f ratios, it was always extremely rich if you open the throttle at all.
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HolyShiznit
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MikeMurphy wrote:was everything working properly when you had everything on but the z32 MAFS? Did you try it or did you install everything at once?
What Rob said and the Z32 maf was from a very trusted friend's 300zx TT. I don't know why the MAF would break or if it did break but I am going back up to the dyno tomorrow with my stock injectors, 2 Z32 MAF's, and my stock maf. At this point I just want it to run.
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C-Kwik
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Is the check engine light on? I'd also check for any codes stored in the ECU.
A sensor of some sort may be malfunctioning. I had a break in a wire for my coolant temp sensor and this seemed to cause my ECU to go into some kind of a safe mode. It ran well for the first couple of minutes, but then it would run way rich. I think what might have been happening was that the ECU was running a safe program that somehow ignored the MAF reading. Which meant that it was providing fuel for 270 cc injectors. It ran fine except at idle where it wanted to die unless I slowly brought down the RPM's. And it was shooting flames out of the exhaust.
A sensor of some sort may be malfunctioning. I had a break in a wire for my coolant temp sensor and this seemed to cause my ECU to go into some kind of a safe mode. It ran well for the first couple of minutes, but then it would run way rich. I think what might have been happening was that the ECU was running a safe program that somehow ignored the MAF reading. Which meant that it was providing fuel for 270 cc injectors. It ran fine except at idle where it wanted to die unless I slowly brought down the RPM's. And it was shooting flames out of the exhaust.