Surging Idle/Stall on start up

[GreenF350]

Allright, let's get all the important info out of the way...

I am working on a 1996 240sx with a KA24DE engine and auto trans. for a friend of mine. Basically, he was told $1400 to fix his timing chain rattle. (I think we all know that only took about $2 worth of sealant to get rid of that problem.) Aside from that, it had a jerking/miss issue when driven and a surging idle. I think it is that surge that is causing it to die right after it starts unless you give it some trottle for a few seconds. Here is the history....

Pulled it apart and removed the upper timing chain guides (the one on top and the one on the driver's side) That took care of the rattle. Went to pull codes on it and it wouldn't power up my scan tool so I chased that down to a blown fuse. (Not sure why it was blown, but it hasn't popped again yet) Pulled the codes and got a P0100 "MAF Sensor Circuit Fault" and a P1445 which as far as I can tell is an EVAP sytem code. I have checked out everything under the hood for the EVAP system (to include pulling the vaccum lines and plugging them to see if it would help the idle along with the checks listed in my manual) and couldn't find any problems. I do plan on getting into the charcoal canister and the purge valve on it in the next few days. Then I went ahead and gave it a tune up for good measure (Cap, Rotor, plugs) That seemed to help a bit, but nothing significant at idle, it did however get rid of the miss while driving. Today I went out and started it up and tapped on the MAF sensor (Seen that as a "test" in a few other posts.) and the car started sputtering and died, but I haven't been able to duplicate that since that one time. Took it out and cleaned it up because $7 is a lot cheaper than the $230 for a new one and still no change and I haven't got the MAF code back since the first time I checked and cleared the codes.

So, here are my questions unless someone knows exactly what is wrong.

Is it worth buying a new MAF when I can't be 100% sure that this one is bad?

Could the P1445 Code cause idle issues and what else am I missing that I should check for this code?

Any other ideas are welcome, I'm not familiar with Nissan 240's and what problems are common with them. Thanks for the help and sorry it is so long, but figured the more info the better.-Aaron

[sx moneypit]

The evap problem is not going to affect your idle.The fact that when you tapped on the MAF sensor and it acted up is a pretty good indication that it is bad unless you have a problem with the connector.When i first got my car it had about the same symptoms as the car you are working on.I bought a sensor from the junkyard and it cost me about 75$.

[GreenF350]

Well, It sounds like that is most likely the problem. I doubt I will be able to find one in a junkyard around here (they just don't have any 240's in them) so I guess I will search the internet or just go buy a new one. Hopefully that will fix it. Thanks for the input.-Aaron

[sx moneypit]

Try the classifieds on this site,i am sure some one can help you out.

[allenms240]

Crc maf cleaner?

[nismoracingsx]

He already tried cleaning it...read teh post .

You did check your throttle body/ iacv for dirt/buildup, correct? If your car is stumbling at start UNTIL you give it gas, I would guess its getting choked idling..

An evap code that tripped could have just been the gas cap and it was stored on the ecu. Was it a hard or a soft code??

As for the MAF code. I don't know whether you have been driving the car a lot since clearing the code, doesn't it take 2 or 3 failures of a specific criteria to trip a troubleshooting code? Maybe you just haven't duplicated the proper engine conditions to get it trip.

Do you know any else with a 240 by any chance? You could always try swapping your MAF with theirs to see if the result is the same.

GL

[GreenF350]

I was wondering about the Idle Air Control Valve, but I went out and messed with it again this morning and was able to duplicate it stalling when tapping on the MAF sensor a few times and decided that was good enough for me to go ahead and bite the bullet. I ended up ordering a brand new (Well, remanufactured) one today. It seems to be at least a semi common problem for them to go bad, so I figured why get another one that may go out sooner than later...Not to mention, even if I spend $500 to get it running good again he will be stoked to have his car back for WAY less than $1400. I was actually wondering if I hadn't driven it enough to set the MAF code again, it currently has expired tags on it so I have just been driving around my neighborhood, about 35mph or less. The EVAP code is a hard code and if I clear it and then start the car it will be back almost instantly, but does take a bit to become a hard code. We'll see what this new MAF sensor does and go from there. I thought about finding someone else with a 240, but honestly I am a diesel/American muscle guy, so that really limits my options here. I work with a guy with a 240 but his is an S13. Anyway....I know it sucks searching and then not finding the solution or the end of the story so I will make it a point to post up my findings/experience as I keep working on it. Thanks for the help and ideas.-Aaron

[sx moneypit]

Good deal keep us posted!

[GreenF350]

Ok, I finally got the new MAF from the parts store and put it in. The jerking/missing when driving appears to be gone (hard to say though since it was an intermittent problem). One problem down, one more "big" one still to go. I want to get this thing to run/drive as perfect as possible before I give it back.

It is still doing the idle surge thing and also when warm if it is started without putting your foot on the gas a bit it will rev up to about 1200RPM and then as it returns to idle it can't catch itself fast enough (or so it appears) and dies out. If you give it some throttle for a few seconds and then let off the gas it will idle ok except the RPM repetetively cycles between about 1100-1000rpm to about 600-700rpm. Other than the above problems it seems to run and drive just fine.

I'm out messing around with it right now and I have double checked timing and ohmed out the idle switch in the TPS. What's next? I am ALMOST at a loss. I am wondering if it is a dirty/faulty Idle Air Valve. What do all you guys that have a little more experience with these cars think?

-Aaron

[sx moneypit]

Clean the IAC valve and while your at make sure and clean the throttle body.Also i don't know what brand of part you bought ,but some of those reman. air flow meters have given me problems in the past.I had to put 3 of them on my wife's 300zx before i got a good one. On customer's cars i try to get them to buy Nissan air flow meters instead of off brand. I will be checking this thread early Monday morning .Good luck!

[GreenF350]

Thanks again for all the help. I couldn't really get to the IAC Valve so I sprayed a bunch of carb cleaner down the tube from the intake hose. That took care of the surging idle. Sprayed out the throttle body and looked in there with a flashlight and man was it dirty. Got some Sea Foam and ran it in the PCV line and got a LOT of the intake cleaned out. I am sure it still isn't perfect, but leaps and bounds above what it was. Now that it is running "good" it seems to have uncovered or developed a new problem. When it is sitting at idle, usually with no load (in park or neutral) it has a light, intermittent miss. It only happens about every 5-10 seconds and will maybe do it twice in a row. It's not bad, but enough to drop 50-100rpm for a second. No stalling and it drives good. If it's in neutral/park and I give it just any amount of throttle the intermittent miss seems to go away, I do however think I will occasionally get it while driving around if cruising at a steady speed. Hard to tell because it is pretty subtle. It really seems like an ignition problem, but I checked for spark at each spark plug wire while it is running and it still seems to get a spark when it "skips".

I sure wish I had bought the scan tool software for my computer that does datalogging when I had a bit more cash, I think that would help out a lot right about now. I just had to have the bigger turbo for my truck though.

-Aaron

[GreenF350]

Ok, scratch the above post. I think I finally got it all squared away. I drove it today for awhile and I think everything is good to go. I suspect that there was still a bit of Sea Foam in the intake that was causing the miss. Once again I appreciate all the help. I love the internet. So here is the final score...

Removed timing chain guides to fix the rattle.....check

Replaced MAF sensor to stop the stalling/jerking.....check

Cleaned IAC Valve to fix the surging idle/stalling at startup.....check

Everything I set out to fix seems to be 100%. Now just an oil change and I will give it back to the owner.

-Aaron

[sx moneypit]

Glad you got it taken care of,glad to help!

[bassboy3313]

Hey GreenF350. I am wondering if you had any pictures of the tubes and lines where you sprayed the carb cleaner and where you put the sea foam in? My s13 is having the same exact problem with the whole surging idle/stall on start up. My car was swapped with a ka24de, just not sure if its an s13 or s14 ka24de and if they are any different.

I sent you an email as well, just in case you get there before here. I would appreciate the help. Thanks.