KA DE running horribly inconsistent....

Post by **rsmithdrift** » Tue May 06, 2008 2:17 pm

OK, so here's the problem, when I start my car in the morning, it usually idles for about 30 seconds, then floods out and takes 5 or 6 tries to start it again. Once started it misses and hesitates and won't rev beyond idle no matter how hard I hit the gas. Actually hitting the gas seems to make it worse.... for about 30 seconds then suddenly goes back to normal. Seems fine till I put it in gear, it runs properly till I let the clutch all the way out, once the engine is under load it then floods out again and won't accelerate AT ALL, for about 30 seconds, then it surges and hesitates its way to 3k rpm. It runs fine over 3k rpm. This process repeats for every gear for the first few minutes of driving.

Once warm, it will run perfectly about 25% of the time. The rest of the time it will either run one of two ways.... 1. It will not idle (stalls, and if you keep it from stalling it misses constantly and smokes), and make LOTS of power and is very sensitive to throttle, (like the throttle does nothing till 25% then the car SURGES forward) almost like the gas pedal is an on/off switch, either full acceleration or none. Also the car smells VERY lean when it runs like this. 2.the other way it'll screw up is the way mentioned before where it will idle fine, but when you hit the gas it INSTANTLY starts missing and surging and stumbling and hesitating it's way slowly to 3k rpm, then it runs perfect from 3k to redline.... Also when it's stumbling and missing the more gas you give it the more is stumbles and misses.

Ok, so here's what I've changed chasing this grimlin... Fuel filter, plugs, wires, cap, rotor, o2 sensor, MAF, and CTS

I took it to a shop about a month ago to get this fixed and he said it was running extremely lean and the MAF was causing the problems, he said my old MAF tested fine, but it runs signifcantly better with the one that's on it now, which also tests fine, and is from a 240 parts car. He also added an extra ground wire to the MAF wiring harness to help it and it ran ok for a few days, then when I went on a 300 mile trip that week it started screwing up again and went right back to it's old screwed up ways. The guy at the shop said I'd have to get a air/fuel controller to fix the problem....

What strikes me as odd is that it ran perfect up untill 4 months ago, and it started doing this all of a sudden. And every now and then it'll run perfect for a whole day... then it goes right back to screwing around again for no reason at all. And when it changes from running perfect to running snappy to running horribly, it's like somebody threw a switch. It's not gradual at all, its like one second it's fine the next it wont run.

So I want to open this "issue" to the experienced NICO members opinions to see WTF is wrong with this car. Cause I'm at my whit's end and I can't afford to keep throwing money at it and not fixing the problem.

In short HELP!!
Modified by rsmithdrift at 12:56 AM 5/8/2008

Post by **voodoochild** » Wed May 07, 2008 7:30 am

HI I have a 92 240sx coupe that i bought about a month ago. It ran fine, until one day i started having almost the exact same problem as you and I have been unable to fix it.. so i am very interested in hearing what the good people of nico have to say about it

Post by **nismopu** » Wed May 07, 2008 9:32 pm

sounds like it could be the connector to your MAF itself. Make sure all the contacts are clean and that your MAF is secure.

Post by **sideways24d** » Fri May 09, 2008 12:53 pm

Sounds like ignition to me. Spark on all cylinders? it sounds like your running too rich. Do check MAF and O2

Post by **rsmithdrift** » Fri May 09, 2008 2:03 pm

Well, the connection is nice and shiny, and when I use a nail to make the prongs tighter it makes it run rich and flood out 100% of the time.

And I know it's not ignition because EVERYTHING is new, coil, cap, rotor, wires, plugs and it sparks on all cylinders and when it misses it's random.

But I think I made a breakthrough today... I was dangerously low on gas when I got home last night and it was to the point of loosing fuel preassure and when I got up this morning the car ran PERFECT for the whole 5 minute drive to the gas station. That's a first. And sure enough after putting $20 in the tank it immidiately went back to flooding out and bogging horribly. Could my fuel preassure regulator be screwing up and letting in too much fuel???

Post by **LayNLow240** » Mon May 12, 2008 7:00 pm

When is the last tiem you replaced your fuel filter? Its cheap, go grab a Z32 one if you haven't replaced it in the past 15K-30K miles. Another thing that comes to mind is possibly a clogged fuel pump sock, or maybe some corroded wires in your fuel pump. Its worth a look.Edit: I missed the part where you said you replaced the fuel filter. But do check the pump sock and make sure its still on, and intact. Also check the wires going to the pump.And if you can, check fuel pressure and see what its at. I think its supposed to be at about 43 psi.
Modified by LayNLow240 at 5:34 PM 5/13/2008

Post by **rsmithdrift** » Tue May 13, 2008 1:33 pm

How do I check the pump sock??? Isn't the only way to look inside the tank to take out the fuel pump??

Post by **LayNLow240** » Tue May 13, 2008 2:35 pm

Yeah, its not hard. Its under the access cover in the trunk. Gotta pull the carpet up and youll see a plate on the right side. Thats it. Four 10mm(i think) bolts, then the actual tank is below that.

Post by **rsmithdrift** » Fri Jan 16, 2009 7:27 pm

I know it's a resurection but the car still has this problem. It's consistent now atleast.

It ALWAYS runs pig rich blowing black smoke and making ok power and getting 14mpg with the airflow meter that shop put on it. Because that airflow meter reads 10v at idle. It should be 1.2v That's WAY too rich.

With the stock/factory airflow meter (the one it came with that the shop replaced (I still have it)) it runs worse. It cuts out if you give the car more than 1/4 throttle. It will gain revs and behave normally untill 1/4 throttle, then if you go above that limit or to full throttle it cuts out completely, bogs, the engine note changes dramatically, and the revs drop to 1200-1800rpm where it bounces and misses on all 4 cylinders randomly. When you let back off the throttle it'll actually jump up in rpm momentarily accompanied by a MASSIVE backfire. Obviously the car runs extremely lean with this airflow meter. It reads 1.2v at idle. Which is perfect.

So I have conclusively determined it is not the airflow meter that is wrong with the car, but instead, it is something else causing a severe lean condition upon throttle application, that the shop fixed by installing a broken airflow meter. It either has lots of unmetered air, or not enough fuel. I have checked the vacumn system and intake with a fine tooth comb and not found any problems or air leaks.

I checked the fuel pump, it's fine. All the other sensors read perfect voltage/ohms. The injectors all work but I have no way of testing if they are pulsing properly, and considering they've had diesel pumped through them I'm kinda weary of them. But I don't wanna replace them for no reason.

Is it possible that the injectors or the fuel preassure regulator are so clogged from diesel oil that it's making the car run lean like that??

Post by **spank044** » Fri Jan 16, 2009 8:08 pm

Diesel fuel? Why was there diesel in the car? The fuel is controlled by the maf. It is the most likely thing that would cause that problem. I suggest getting new fuel system components if they all had diesel in them. Inside the maf is an element and if that element is damaged then it could give good readings one day and **** another. I have a known working maf that came off my 92 DE if you want it for 20 shipped. When you pull your plugs, are they soaking wet or covered with little deposits?

Post by **rsmithdrift** » Fri Jan 16, 2009 9:15 pm

spank044 wrote:Diesel fuel? Why was there diesel in the car? The fuel is controlled by the maf. It is the most likely thing that would cause that problem. I suggest getting new fuel system components if they all had diesel in them. Inside the maf is an element and if that element is damaged then it could give good readings one day and **** another. I have a known working maf that came off my 92 DE if you want it for 20 shipped. When you pull your plugs, are they soaking wet or covered with little deposits?

Idiot friend put it in thinking it was regular gas (was in a red gas can)

I have 3 known working MAF's along with that broken one that show's 10v. All the good ones show 1.2v at idle and all make the car run EXACTLY the same. It's not the MAF

Pulled the plugs a week ago and cleaned them. They were solid soot. Black completely (from running rich on the 10v MAF) You should see how much black soot comes out the exhaust running on that bad 10v MAF... If the cars running in the garage it'll choke you out.

With any of the good maf's the car doesn't smoke AT ALL and idle's perfect, and idk what the plugs would look like. You just can't hit the gas.

I know when you give the car gas the maf reading goes from 1.2v to 2.5v is the highest I've ever seen it get up too. Which makes sense cause that was WOT 4k rpm. And considering a 5v max at 250whp that's about right. All the good ones read the same with throttle application. The bad one reads 10v at idle and goes to 12.5v at WOT.

I only replaced fuel filter and spark plugs afterwards. And LOTS of fuel system cleaner. It was a year and a half ago and it ran perfect before hand, started this crap ever since. Keeps getting worse too. that's what's odd.

Post by **spank044** » Fri Jan 16, 2009 9:42 pm

If you are positive the maf is good then you need new injectors. It won't matter how much cleaner you put in because the damage is done. Gasoline fuel injector are more delicate than diesel injectors. Diesel injectors are steel for a reason, diesel is corrosive and probably damaged the injector. In my opinion change them. They are fairly cheap.

Post by **rsmithdrift** » Fri Jan 16, 2009 10:23 pm

spank044 wrote:If you are positive the maf is good then you need new injectors. It won't matter how much cleaner you put in because the damage is done. Gasoline fuel injector are more delicate than diesel injectors. Diesel injectors are steel for a reason, diesel is corrosive and probably damaged the injector. In my opinion change them. They are fairly cheap.

Never thought of that.... I've wanted to get new injectors/new fuel rail ever since it happened, but I can't afford new injectors and the junk yards never have them, and it does act JUST like when my Z had MAF issues. And I didn't want to get new stock injectors when my ultimate plan is turbo. But it'd cost less getting a new set for a few months instead of getting 14mpg. It's rediculous.

But it just makes sense doesn't it?? Is their ANY way of testing how those injectors are performing?

Post by **spank044** » Sun Jan 18, 2009 8:48 am

Noid lights will tell you if you get power to the injctors and a company can do a flow test for you. Put a WTB ad in the classifieds, people are always upgrading.