Starting problem

[InsanityInc]

I have a 1991 240SX SE hatchback.

It starts fine, but if you don't give it any gas, the revs keep dropping and it dies a second later. However, if you hit the pedal and rev it up to about 1600 or higher for a second, then let off, it works fine. Also, if I set the idle higher, it doesn't do it (but it causes the timing to go all wacky, so I can't leave it like that). Once you get it started, though, it idles pretty well. However, if it's not warmed up, every time you push in the clutch to come to a stop, the idle drops to about 400, then comes back up to 700. After it's warm, it stops doing that, though.

Occasionally, the car will throw code 32 (EGR function) and code 34 (knock sensor). It always seems to throw them together.

I guess it might be a vacuum leak, but since you pretty much have to remove the intake manifold to really check most of the lines, it's not exactly something that I can just tear apart in a day. Is there a way to check if you have a vacuum leak at the canister or something?

Or if anyone else has any ideas, I'm all ears. I've replaced the following parts:

Coolant Temperature SensorO2 sensorFuel PumpFuel Filter

(I've replaced a lot more than that, but nothing I can think of that's specific to this problem)

[tonkajuris]

I have the same problem. My car will not idle at startup. It works fine after having warmed up. However if the car gets really warm it decides to idle high. Kinda backwards. I have also replaced O2 Sensor and Fuel Filter. I am getting fuel at engine crank with pinch test. I don't know where the IACV air regulator is. Could someone post pic of KA24E engine. I have also unplugged connectors and reattached.

Any help would be appreciated. Thanks in advance

[MikeW]

I have similar problem on a 89 Nissan 240SX and I am having a time trying to figure out why it wont start. when it does finally start it acts like it has too much fuel for a short time. After that extra fuel burns off - then Whether your at idle or driving down the road the car runs fine no spit or sputter at all, runs and purrs like a kitten – until you come to a stop and just touch the gas pedal then it dies or stutters like it is going to and if it dies then wont start? The gas pedal can be depressed very slowly and it will stutter for a 1/10 of a sec then continue to run like normal. I hear the electric fuel pump and have sprayed carburetor/injector cleaner into the housing and no luck. Its almost like it is not receiving fire at first?Can you advise what electrical or fuel system related part I need to look for?

[s13sr20chris]

you all sound like you have a rich condition. thats kind of a guess but there you have it. check for voltage drop across the maf ground and try wiggling coolant temp sensor connector and maf connector. if you replaced the temp sensor be sure to replace the connector as well. there is a pigtail harness you can get.

[InsanityInc]

I'm pretty sure the coolant sensor is working correctly, because it's never given any strange readings, it's very consistent. Also, I pulled my plugs the other day, and none of them are black or smell like gas, so I doubt it's running rich.

Could it have something to do with the battery or ignition coil?

One other thing I did notice one day is that it happened one time at night when I had my headlights up, and I noticed the headlights kind of flickered and got much dimmer when it tried to die (dropped below 400 rpms or so), but as soon as I hit the gas to bring them back up, the headlights got brighter as well.

[s13sr20chris]

the coolant temp sensor that the ecm uses for fuel control is different than the thermal transmitter that the gauge uses. they are right next to each other though.

prob not the batt or ign coil(i dont think so anyway).

ok what happened was your car started dieing and the alt was spinning slower. when old alts spin slow they have trouble putting out 14 volts so lights will dim. they really have that prob more when under a high current demand. have you tried the basic inspection procedure? check timing, idle, and tps adjustment.

[InsanityInc]

I've timed it numerous times, and changed the idle numerous times as well. However, the timing seems to just randomly change, and drags the idle along for the ride. I replaced both timing chains, so that's not the problem.

I haven't done a tps adjustment, as I have no idea how to do it.

[s13sr20chris]

ok, to adjust the tps you need a set of feeler gauges and a dvom. if you have that i will dig up the procedure for your vehicle. is the egr valve staying open? you can check that by pulling off the valve and running the car with something else just blocking the holes(like a rag).

[InsanityInc]

I don't think the EGR is staying open, it just doesn't work right, since I had problems with my NOx levels when I had to get it smogged. I currently have the vacuum line that goes to the BPT valve capped off and connected to nothing, so neither the BPT or EGR is getting any vacuum. Doesn't seem to stick, either.

I have some feeler gauges, and I'm not sure what a dvom is? Do you mean DC voltage meter? I have one of those, too, if that's the case.

[s13sr20chris]

ok, let me try to remember to bring home the bulletin on adjusting tps with feeler gauges. its the updated method that works much better than the old consult method.

[InsanityInc]

alright, thanks.

[180fan]

InsanityInc, how are you checking your timing? The motor should be warm, with the TPS unplugged before you pull out the timing light, it should be quite consistant once the motor's warm and the idle adjusted to 800 rpm.

Checking the vac can be easy with a vac gauge. Got one at my local Kragens for ~30 bucks. That might be something to have a look at for the problem.

Check out the EGR by pushing up on the little saucer portion of the car. If the behavior doesn't change, you've got a stuck EGR. If it stumbles and nearly dies then your EGR's fine.

Have you tried switching your MAFS? My SR had a idle issue where at a cold start it would start and then go dead, next start it might do the same but might keep going and if it did keep going, the rpm would oscillate. If your MAFS is shot then it'll cause some weird problems. So that might be worth checking out.

[s13sr20chris]

ok got the bulletin. i forgot the s13 has the old style tps. does not apply.

[InsanityInc]

Quote »ok got the bulletin. i forgot the s13 has the old style tps. does not apply.[/quote]So... um.. what's the old way, then?

I have the FSM, is it somewhere in there?

Quote »InsanityInc, how are you checking your timing? The motor should be warm, with the TPS unplugged before you pull out the timing light, it should be quite consistant once the motor's warm and the idle adjusted to 800 rpm.[/quote]Yes, it is consistent when I'm timing it (usually). I followed the procedure in the FSM. However, occasionally when i'm timing it, the timing will suddenly jump like 5 or 6 degrees for a few seconds, and then come back. Also, sometimes when I start it up and go to drive it, I can tell the timing is totally wacked out. It runs badly, and the idle changes to much higher than what it was. Other times, it's fine.

Quote »Checking the vac can be easy with a vac gauge. Got one at my local Kragens for ~30 bucks. That might be something to have a look at for the problem.[/quote]But where should I test it at, and what should it read?

Quote »Check out the EGR by pushing up on the little saucer portion of the car. If the behavior doesn't change, you've got a stuck EGR. If it stumbles and nearly dies then your EGR's fine.[/quote]It tries to die. I tested that when I first started getting the EGR function light.

Quote »Have you tried switching your MAFS? My SR had a idle issue where at a cold start it would start and then go dead, next start it might do the same but might keep going and if it did keep going, the rpm would oscillate. If your MAFS is shot then it'll cause some weird problems. So that might be worth checking out. [/quote]Well, I think I'd be having more problems if that were the case. Sometimes it runs absolutely fine, other times it runs like crap (and the timing is usually to blame).

I'm not sure if I mentioned it, but the knock sensor ECU code gets thrown every once in a while, but I don't know if that means the knock sensor is being triggered, or if there's just something wrong with the circuit? Assuming it's being triggered, that might be what's causing the timing to change.

[s13sr20chris]

ok, im being retarded. just go by the fsm. the bulletin was released due to obd2 issues. the knock sensor should not be causing those probs. the code is prob due to a bad sensor and the ecm is prob ignoring it.

[InsanityInc]

Another problem I have that might be related:

If I turn on the parking lights, the idle drops by about 100 rpms, and stays there. If I turn on my headlights as well, it drops by a total of 200 rpms, which makes it rather hard to keep alive.

Could it be that the alternator just isn't putting out enough power? Also, the car runs oddly if you apply full throttle. You accelerate, then the acceleration drops off for a second, then comes back, then drops off, then comes back... it's wierd.

[180fan]

Yeah could very well be your alternator not pumping enough juice. When your car's running, what's the voltage that's across your battery? It should be from 12 to 14.4 volts. Also is your alternator belt tightened?

The vac tester, just tee off the vac line from your fuel pressure regulator. That'll give you the best vac. signal. Most gauges have the color coded thing on the side from what I've seen. Ha ha ha. You're good between 20-25 in-Hg.

Might just want to check over the knock sensor or just replace it. At least that way it gets rubbed off the list as possible culprits. The measure for a good knock sensor should be 10megaohms. If it ain't to spec, get a new one and make sure you don't drop it or give it hard knocks when putting it in.

[s13sr20chris]

thats a typical(though rather extreme case) of old alternators(jap make). they just loose their juice. its also fairly typical of japaneese cars to loose the ability to adjust idle relative to electrical load over time.

[gogg]

InsanityInc-- I am having similer if not the exact same problems as you are (maybe not as extreme), please let me know if and when you discover something, you can reach me on AIM at lanb135 and email at [email protected] I'd like to get mine and his problem resolved.

[InsanityInc]

Alright, I tested the vacuum at the fuel pressure regulator, and here's what I found:

At idle: 23 in Hg

When I apply throttle (even extremely light throttle), the vacuum drops by about 6 in Hg or so, then starts going up again.

Does this mean I have a vacuum leak?

[s13sr20chris]

nope thats good.

[InsanityInc]

Ok, well, I'm thinking it's the TPS then. I used the instructions in the FSM and tested it. The harness is fine, but at no throttle, the TPS has 8.72k ohms of resistance, while at WOT it has 1.72k ohms of resistance. The FSM says it should have 2k ohms at none and 10k at WOT. So, I'm guessing somebody managed to not only install it without an adjustment, but somehow installed it UPSIDE DOWN.

Yeah, that might be a slight problem.

[InsanityInc]

well, I haven't had a chance to actually turn it around or anything yet, since it's very, very hard to get to.

I managed to undo the bolts and turn it as far as it would go, to make it higher when it idled, and the car seemed to kind of run better, but the engine looks like it was shaking a whole lot more, and it still died when it started.

I think i'm going to buy a new TPS and install it...

[InsanityInc]

Well, turns out the FSM just tells you to measure the wrong terminals. Yay.

It was still off, and adjusting it to the correct setting fixed all acceleration-related shakiness/jerking that the car had, but it still dies when I start it. I'm guessing it has to be the IACV or the Alternator (I know the alternator is having issues anyway...)

[s13sr20chris]

do you have to jump it? have you tried just bumping up your base idle?

[InsanityInc]

No, I just have to rev it a little bit when I start it, then it's mostly fine. The idle is a bit sketchy sometimes, though. The revs will drop and the car gets really shaky for a second, then they come back up and it stops shaking. Still have the problem of dropping idle under electrical load, and when the brake booster is working. If I bump the idle really high, it'll start fine (like 900+), but the timing seems to do all kinds of wierd stuff if I leave it that high.

I cleaned out the IACV very thoroughly, and it didn't really seem to have much of an effect on the problem.

[s13sr20chris]

the timing acts up? like what, does it jump around? if so that is normal.

[InsanityInc]

somehow got double posted...?

[InsanityInc]

The timing will just shift, and it'll run really badly. You can feel it just lose power hard, and it starts to idle really bad, and you'll check the timing, and it'll be 5+ degrees off, steadily.

[s13sr20chris]

when you are doing it is the tps unplugged?