1993 240sx HB, engine start and sputtering issues

[hun240]

I'll start a month ago...the engine would bog a little at 3K rpm but if you accel or de-accell, it would be fine and then it would go back to normal operation. No big deal, I thought if was bad fuel or something so, I got some fuel injector cleaner , but the problem would come and go. Last two weeks, it would start to buck and buck hard, between 2K-4K rpm no matter what I did, then I could not get it to go over 4K rpm. So, I checked the O2 sensor and changed that, I found a crack in the rubber boot by the intake put a new one on that. Still did not work...then I changed out the fuel filter and fuel pump. It may start but once it's warmed up it dies. A friend came over to day...and we checked and exchanged his MAF for my, it did not work. Checked the EGR and the hoses...actually replaced one...still did not work. Checked the water temp. sensors, ok. And basically it wont start now...I think it's flooded, since it takes about a half an hour to start the engine but then it bogges down again after a minute if that. I have a feeling this is not an easy fix, any suggestions would help out greatly...thanks!

[s13sr20chris]

check valve timing check fuel pressureand make sure you dont have exhaust leaking through AIR system

[slipnfall]

Chris, FYI this is the same '93 that I posted about here:zerothread?id=151402

Also we left the AIV(you said AIR, I assume you mean AIV) intake hose disconnected throughout the testing... I noted no exhaust exiting this hose.

Cheers,Jamie

[hun240]

Just an update... put in a new temp sensor...and it didn't fix the problem....any suggestions would be greatly appreciated.Thanks!

[s13sr20chris]

(you said AIR, I assume you mean AIV)

hah, thats what i get for working on american cars all that day! brainfart!

[s13sr20chris]

well, i have seen a few things that have not been ruled out cause this sort of thing.

one would be the distributor. those things heat up and sometimes act funny.

still, im leaning more towards a fuel issue. do you have anyway to verify fuel pressure?

[slipnfall]

Chris,

Haha, no problem re: the brainfart.

I did remove the distrib cap and inspected it and the rotor. It was suprisingly *very* clean: no carbon dust, white arc markings, or scoring(from rotor not being on all the way). Spark plug wires looked fairly new, though I didn't ohm them out.

Worth mentioning: there was an error code for 'ignition signal', I think 14 from memory(I'll verify later). Occurance was twenty-two times. I assume this was a result of the stalling and/or no-starts.

I did not check the power transistor or coil, but assumed them to be good because we could get spark after it flooded. What are you thinking? Crank position sensor in the distrib?(that's the only thing really in there electronic-wise). I would expect a code for this though.

Other than picking up(buying) one, no we do not have a fuel pressure gauge.

Thanks for the help. 'slip

[s13sr20chris]

crank pos sensor...yeah, thats what i meant. i was not refering to the cap and rotor.

you could try a fuel volume test by seeing how much of a coke bottle you fill up with one key on cycle.

[slipnfall]

Would a clogged exhaust/cat cause these symptoms? Reason I ask is hun240 flogged(floored) it when it was about to stall: a black/grey-ish smoke started rolling out from the resonator, but none out the tail-pipe. We're going to disconnect the collector and see if it will stay running.

[slipnfall]

Scratch that, the exhaust wasn't the problem. I bought a fuel pressure gauge and we'll give it a shot today. I know what the pressure are at idle, w/wout the vac source, but what should we expect off idle? hun240 really has to flog it to keep it running. Basically we're just looking for excessive increase or decrease in pressure when it dies, correct?

I'll post back results tonight.

Regards,Jamie

[s13sr20chris]

34 running with hose connected and 43 disconnected

[slipnfall]

Chris, Thanks for keeping up: we only got 1/2 of the test done today, with the vac line still connected. I wanted to see what the fuel pressure did when it stalled out.

I don't remember exactly what it primed to, IIRC ~40psiPrime tapered down to 28psi after a few minutesAt normal idle, pressure sat at 40psi.Durring stall, pressure spiked to 44psi, then back to 40.After it stalled, pressure remained at 40, but fell settled to around 35psi

Reason we couldn't get the other 1/2 of the test is we couldn't get it started again! We cleared the fuel by pulling the fuel pump fuse, and I even pulled all the plugs and dried them! Worth noting is that all of the plugs were black, but replaced a month ago.

We are going to check fuel pressure w/out the vaccuum line tomorrow: I have a vac gauge hooked to that line to see what intake vacuum is also. A vac leak would cause the base fuel pressure to be elevated, correct? Have you seen a vac leak cause the engine to die out like this? Would it be better to use the vac pump to control the pressure regulator? Idle vacuum should be around 22hg => 34psi fuel pressure.

-Jamie

[tiger]

Have you thought about spark plug wires... shorts in them would cause that "jerking" you're talking about. That woudl throw an ignition signal code, wouldn't it?

[slipnfall]

Well, the car hasn't thrown any codes since we started messing with it, so those codes were 'left-overs'.

We tested the fuel pressure with the vac line disconnected/plugged: it was 46psi, with manifold vacuum at 12"hg... which is low...

So, to see if it was the low vacuum(and thus high fuel pressure) causing the car to stall, I hooke my vac pump up to the FPR. Started the car up, and gave about 25-30"hg of vacuum, enough to pull the fuel pressure down to 34psi... well the car still stumbled and died.

We did find a disconnected vac hose: was the atmospheric line for the AIV. The T it connected to was already capped off, so that really didn't fix anything.

Suggestions anyone?

[slipnfall]

bump for a friend

[s13sr20chris]

did you ever confirm that the car has good spark at the stall? maybe check ign timing during the stall. also, try moving distributor around while its stalling to try to revive it.

may want to check inj pulsewidth with a meter.

also, see if you can keep her running with maf unplugged.

[jamied311]

Im having the same exact problem now with my 91... Bump

[slipnfall]

Well I'm not sure how I would check spark *at* the stall, but right afterwards we checked... at least one plug had good spark. The problem is it only stays running for maybe 20seconds tops, so I'm really confined to what I can test(unless I had 6 arms and 4 eyes ) j/k

We did try(cold start) a working MAF, and I ohm'd the ground from the connector. Oddly enough, this '93 does *not* have a seperate ground wire/lug on the connector: it's all within the MAF harness. Was this a TSB or something on this car(?), because my '91 has one.

After thinking about it, the car isn't really flooding all that much on the stall... I mean, there isn't gas pouring out the collector(exhaust is still disconnected), and I only smell fuel when we try to re-start it. I was thinking it might be the cold start valve: once the reed inside moves just enough, it opens an air leak... it takes a *long* time to get it to start again, even after clearing fuel/drying plugs.

Thanks again,Jamie

[slipnfall]

Well Chris, things have gotten worse... not it won't even start. huh240 said he started it one day just to keep some juices running, it died, and just refused to start after that. I went over again to try and lend a hand with no luck.

We installed a spare distributor, making sure to properly time it: no good. I even checked the crank position sensor and the injectors by turning the distrib. by hand. Now I didn't verify that each had fuel dispensing, but I could hear them click, and eventually smelt gas. The plug wire from the coil was sparking durring this also.

Can plugs become so fouled they'll prevent it from starting? We're out of options here it seems... I even went down through the FSM for 'won't start or imposible to start durring normal conditions'. The only thing we didn't try was swapping ECM's, but because this has been a progressively worsening problem, I doubt that is it(ECM electronics tend to just go, not slowly get worse over a month)

Any ideas?Thx,Jamie

[slipnfall]

Re-bump... I'd really like to help this guy get his wife's car running! So we have verified fuel[pressure], spark, crank position sensor is working... the car doesn't even *try* to fire, so I don't think timing is an issue(I timed it correctly from the crank pulley though). Also won't attempt to start with throttle wide open(in case of flooding). So the only thing that's left is air, right? I still can't get confirmation if a vac leak will cause it to not start.

Thanks,Jamie

[hun240]

Yep, an update.... it started today...yes....it lasted for a minute or two and then died again. I was able to hold it to 3K before it went south... and then it would not start.

Just out of the blue, is there anyway to reset the ECU, other than taking the battery offline, am I way off?

BTW thanks for all the help!Paul

[slipnfall]

Hun240, Yes you can reset it either by pulling the battery overnight, or using the consult interface we had(car doesn't have to be running). This resets the self learned closed loop maps. You would want to do this for things like, modifying the intake(ie cold-air), or replacing any sensors like O2, MAF, CTS. Unfortunately[I'm pretty sure] it won't help your situation.

Here's a pic of where those two idle valves are. The one that is missing(that squar-ish hole) actually comprises of two valves: the idle adjustment screw, and the ECU-controlled valve. The ECU opens this valve up(by means of pulsing it) to compensate for things such as the air conditioner being on, etc. The valve that you do see installed, adjacent to it(10 o'clock), is the cold start reed valve: the electrical connector applies current to a bi-metal reed, which as it heats up, slowly closes off the airway, thus slowly lowering your idle as you warm up.

I have a lot more pics that would help with vacuum routing if you'de like, just shoot me an email.

I hope someone else can chime in to help you out, I know you really don't want to tear into those valves.

[slipnfall]

I just thought of something - I don't know if this will work or not, but maybe we can disconnect and plug the air feed line for that cold-start valve. I think it's the large 1/2" dia one off the intake tube. If the feed line is sealed, it would eliminate that valve possibly being stuck open and letting a ton of air into the intake.

Thoughts anyone?

[jznsx]

i had this same problem on my s13....it turns out the spark plug wires were all jacked up...i had them replaced and the car runs fine

[slipnfall]

What were the symptoms? Wouldn't stay running, or just run like crap? Hun240 I don't remember ohm'ing out the spark plug wires, but you know we did have spark on all four... IIRC the longest wire should have less than 30kohm of resistance: the others should decrease.

[hun240]

It would run for a 1-2min. even at 3K rpm and then just die...flood and then it won't start for a couple of days. I checked the wires awhile ago and they ranged from 7Kohms to 10.8Kohms. At first I thought no way, but then I read the manual and anything below 25Kohm should be acceptable. I thought good wire had less resistance than that? Thanks for the feedback,,,time to try some new wire...Laterz...

[slipnfall]

Your wires are fine - spark plug wires actually need a bit of reactance: they act as a capacitor, working with the inductance in the secondary coil to provide a 'punch' of power. aka a flyback power supply output configuration. Otherwise the energy from the coil would, for the sake of simplicity, drain away too quickly/easily and not facilitate good spark.

I don't think plugging that hose I mentioned above will work - it's also the supply for the idle-air screw. You could unplug the ECU-controlled one, but that won't tell you if it's physically leaking.

Another thing we might consider is the EGR valve - if it's leaking and allowing excess exhaust into the engine, it'll just choke and die... holding the throttle open might be giving it enough air to allow it to run for a bit. Unfortunately the only way to eliminate the EGR is to swap it with a working one. I know for a fact David has about a dozen of them at his 'backyard 240 parts haven'.