1990 240sx KE24E: troubleshooting a (hopefully not) dead car

[Arrow]

::EDIT READ THIS:::PROBLEM SOLVED - bad distributor rotor::Just to save you guys time I summed up my most recent stuff in my last post so if you don't want this crazy long read go there please - this stuff just explains my troubleshooting process and the like. thanks for your help::/EDIT::

Hey guys, I figure that I am going to start a new thread since in my last one I eliminated the master cylinder and brake booster from the equation (to the best of my knowledge at least). So here's what's up:

It started yesturday... I had been driving for nearly 45 minutes when the car stalled out on a hill. It took 3 tries to get it going and once it was going the car had serious issues.First the car was shaking / hesitating considerably any time that I touched the gas.Second I started smelling oilThird I was hearing back firing coming from the front of the car (most likely out of the intake)Fourth when I parked the car and lifted the hood there was a whitish / bluish smoke coming from the back of the engine by the firewall (seemed to come from the back of the throttle body / intake) - also the smell of burned oil or something was strong...Fifth the car idles fine - right under 1000 rpm (which it's been doing for years), but any throttle results in the car to seemingly bog down.

Here is what I have done so far: I checked the spark plugs (actually only checked #2 and #3) but they were perfectly clean with no residue of oil or carbon build up what so ever. In checking the spark plugs I broke one of the plug wires (they are at least 4 to 5 years old and seemed that the one that broke was dry rotted a bit). So I bought some replacement plugs (no change in engine operation).

I have heard that a problem with the ground could cause hesitation - especially considering that the car idles fine. Another thing that I heard was the MAF could be another problem that might show similar engine problems.

To my knowledge (and previous searching) the MAF problems are seemingly more related to engine idle, so I'm not sure if this is the problem - inless it is a grounding issue w/ the MAF)

Grounding might very well be an issue that I will need to check into - just trying to get some people's advise before I dig into this thing as I will not be able to work on my car until next week...

I'm thinking the due to the smell of oil, the rings might have went - but do the rings normally go out so suddenly causing this type of operation? The car will drive... just not very well...

I don't think that it is the headgasket (but it could be) due to the smoke not being steam and that the car idles fine...

So basically I am very confused and frustrated... I have a spare engine back at home (150 miles away) and will probably look into rebuilding it asap... I am probably going to attempt to get the car taken to a shop here in Raleigh next week sometime to get a leak down test performed on it (hopefully this will tell me more about the condition of my engine)

Thanks again for all of your help and insight guys!

Modified by Arrow at 1:14 PM 4/24/2006

Modified by Arrow at 5:45 PM 4/25/2006
Modified by Arrow at 5:11 PM 5/9/2006

[rogoman]

OK, you've replaced all the spark plugs, now replace the ignition wires since they seem to be dry rotted. Also replace the distributor cap/rotor.

Do a compression test on all the cylinders and check the ignition timing.

Let us know what the results are.

[NISTECH]

Did you check all the plugs? is your V/C gasket leaking at the back? Plugs were clean,doubt its rings. Sounds more like you have an airflow issue, either the meter is bad or you have a loose intake tube at the throttle body allowing unmetered air in.

[Arrow]

alright here is the best update that I can come up w/ until around monday...

I did not check all of the plugs (my own fault and frustration...) I checked #2 and #3 though - clean. I replaced the wires (b/c I broke one that was dry rotted). And yes, my valve cover gasket leaks at the back (and along the side where the plugs are).

I found that if I slowly increased the throttle (and I mean very slowly) there seemed to be minimal problems (at least no problems until around 3k rpm - then minimal problems). But if I gave it gas any faster huge hesitation issues across the board.

After calming down and thinking logically about everything I have thought of a few things that could be doing this:fuel pump (never replaced)?fuel filter (replaced about 4 years ago)?bad injector (3 are pretty new - under 4 yrs - but one looks like it's still factory)? but I'm not sure if one injector could cause this much hesitation...PCV?Clogged Catalytic?

Thanks for everything and sorry for the long read.

::EDIT:: I don't think that there are any air leaks in the intake... I say this b/c I replaced all of the intake plumbing besides the plastic tube that goes over the radiator a few years ago. And when I was getting unmetered air in, it caused my plugs to get fouled fast and the symptoms were slightly different (it would not rev past a certain rpm no matter what). Now granted it could be the MAF... I did do the weak connector check... though the boot is dry rotted, when I shook the wires I didn't see any change, but that could be b/c the MAF is bad - not sure.
Modified by Arrow at 12:49 PM 4/13/2006

[Arrow]

what would be a way for me to check my MAF besides getting a hold of a known working one and switching them?

[BlackHat]

I had a slightly similar problem right after I removed my EGR system. I didn't get a good seal on the intake manifold and the car acted like it was coughing to death. It also lost a lot of power to that also. I never saw any smoke, but maybe the egr pipe busted? It's in the back of the engine... Maybe something to check out...

[Arrow]

I've got another question that hopefully can get answered before I go mess with my car tomorrow: is there a failsafe map in the ecu that would take over if I unplugged the MAF? I ask this b/c I'm suspecting my MAF to be the problem and I want to know if I would be able to disconnect it and the car would still run by using say the input of the TPS instead of the reading from the MAF (since the MAF might be giving really bad readings).

Thanks for all of your help guys!

[Arrow]

hey guys, I just spent some time working on and with my car and I've got a few statements / questions...

First, the smell that I noticed and thought was oil is either no longer present or I never was smelling oil... it smells like gas - hence the car is running rich. but not so rich that the exhaust is black or dark.

Second, I was messing with the MAF and came to a few observations:One, moving the connector hard (i.e. pulling it one direction w/ some decent force) caused the engine to stall out when idling.

Two, when I unplugged the MAF the car would rev better w/ little to no hesitation except for a few things: one the car would not rev past 3500 (could be a failsafe or something) and two if I lightly pressed the gas the idle did drop and wanted to stall... but the car would generally rev a lot better up to 3500 then would not go higher.

Three was that w/ the MAF plugged in the car would rev up to 6k+ rpm nearly at the same speed that it had before I noticed problems, but there was hesitation. There was also a lot more backfiring (through the exhaust) then w/o it being plugged in.

Four, after plugging in and unplugging the MAF it seemed to run a little better when the MAF was plugged in... Possible bad connections? I looked at them and they didn't seem too bad, attempted to clean them up and nothing changed - though I didn't use any contact cleaner or whatever... just a wire brush - which isn't too good at cleaning inside the connector.

So it seems like there could be a problem with my MAF... just not sure where to start. Should I replace the MAF and see if that solves it? I know that I should go and make sure that the connections are cleaned as good as possible though.

Also I was hearing a slight whistle when the car idled... It was definately coming from the intake area. Almost seemed to be coming from the PCV valve (or close to it). Everything seemed to be connected and hooked up fine... I'll have to spend a little more time looking into that though. Is it possible that a loose vaccum line or the like could cause the hesitation that I encounter even though it nearly goes away when the MAF is unplugged (aside from the 3500 rpm limit and the problem w/ just tapping the accelerator or slowly pressing it)??

Thanks again for all of your help guys!

[Arrow]

Ok guys, I've made some progress... minimal as it is, but I wanted to post up a status report and hopefully get some feedback.

I went out and bought a new (remanufactured OEM) MAF the other day and installed it. The first thing that I noticed is that my idle immediately dropped from around 1k to 700 (which is where it should be). That seemed to be a good start... but the car was running terrible - it even had idle issues where before it had none. I even put the old MAF on and had the same issues but w/ a higher idle.

So I checked my plugs - all 4 were really fouled with carbon - no oil though. I figured that since I probably had been messing w/ my car trying to find out what was wrong and messing w/ the MAF before replacing it (probably close to an hour of idling / revving) that the car might have fouled the plugs from running rich (since when I fist had problems the plugs were clean). So I bought new plugs and hopefully today or tomorrow I can put them in and see how things go.

So my question is: does it sound likely that the plugs could have gotten fouled that fast due to me messing w/ a bad MAF or does it sound like something else?

And I'm also going to investigate the whistling sound... seems like I have a vaccum leak near or at my pcv valve.

Thanks again!

[Arrow]

Alright, I've got another update:

I replaced the MAF w/ a remanufactured one and replaced the spark plugs since they were badly carbon coated- seemed to help out a decent bit but I still have some issues...

One is that I have some serious hesitation when I slightly depress the gas petal, but if I depress it more than around 1/3 or so there is no hesitation. And by the time the car warmed up and after a few high revs (high being near 6k) - the plugs got coated in carbon again! I noticed this when I couldn't rev past 5.5k when a few minutes before I could do it easily. I also noticed that the car had more problems starting after it had warmed up - it started fine but the idle was low and it wanted to stall until I gave it some gas and then it levelled out.

So I pulled the plugs and cleaned them w/ a wire brush (for some reason it didn't get them extremely clean - they looked tarnished) and saw that the brake booster vaccum line that I had previously attempted to remove to check for fluid had a loose clamp (on the end near the intake). So I tightened that and put the plugs back in. Started the car and no real improvement, still didn't want to rev past 5.5k and had the low throttle stalling issues.

Any help would be greatly appreciated!

P.S. would it be beneficial to put a link to this thread in say the 240 gen chat or the tech chat to get more responses? thanks

[NISTECH]

Check your coolant temp connections, make sure they are clean and tight. check your fuel pressure between the filter and rail while the car is running. If to high check for vaccum to the regulator at idle. If present you may have a bad fule pressure regulator. Do a fuel pressure leak down test. try to determine if you have a leaking injector.

The carboned up plugs seem to lead to a excessive fuel issue in the chambers.If af meter is not the cause then the next logical steps is to check the temp sensor for reading too cold, then to do the fuel pressure checks. You should also have a high 1200-1800 rpm cold start. If it is trying to idle at 700-800 you have a problem with the cold start idle control valve or too much fuel entering the chambers. This too would lead to carboned plugs.

The hard warm start up really says coolant temp sensor connection to me. [2wire red or yellow connector at front of intake]

[Arrow]

I know that the boot over the coolant temp sensor is dry rotted and that when I wiggle the wires at idle the car bogs and wants to stall... So I will hopefully get some time today or tomorrow to check the connector (I had been leaving it alone b/c I didn't want to spend the time to work on it - looks like it might have bit me in the butt).

I have never seen my car idle off of a cold start at 1200 - 1800 (by cold start I'm referring to engine at ambient temp - which at times has been below freezing and other times - like yesterday - at 85+)

How easy is it to do a fuel pressure leak down test? and I think that I do have a bad injector (#4 b/c it's the original factory one and I have 181k on the engine) but could one injector cause all cylinders to run rich? Also how expensive is a fuel pressure gauge? and would I need any additional lines to tap it into the existing lines? And any suggestion as to how I could check for vaccum on the regulator at idle? Or might it just be best for me to get it to a shop and see if they can fix it - but since I'm on a budget it might be best for me to fix it anyway (I have just under 2 weeks to get it working before I have to go home from school - and I would like to have my car running by then)

Thanks again for all of your help!
Modified by Arrow at 12:49 PM 4/26/2006

[NISTECH]

I know that the boot over the coolant temp sensor is dry rotted and that when I wiggle the wires at idle the car bogs and wants to stall... So I will hopefully get some time today or tomorrow to check the connector (I had been leaving it alone b/c I didn't want to spend the time to work on it - looks like it might have bit me in the butt).Modified by Arrow at 12:49 PM 4/26/2006

Right now this is all you need to worry about as this is likely a major part of your problem.Clean the terminals ,possibly replace the coolant temp sensor connector by soildering on a new one. Ask for a head temp subharness for an 87 300z at your local dealer. Cut the yellow connector off the endleaving enough of a pig tail. soilder it to the harness on your car. Clean the terminals in the coolant temp sensor with some battery cleaner or baking soda and water mix. Then plug her in and see if she works.

I have never seen my car idle off of a cold start at 1200 - 1800 (by cold start I'm referring to engine at ambient temp - which at times has been below freezing and other times - like yesterday - at 85+)

How easy is it to do a fuel pressure leak down test? and I think that I do have a bad injector (#4 b/c it's the original factory one and I have 181k on the engine) but could one injector cause all cylinders to run rich? Also how expensive is a fuel pressure gauge? and would I need any additional lines to tap it into the existing lines? And any suggestion as to how I could check for vaccum on the regulator at idle? Or might it just be best for me to get it to a shop and see if they can fix it - but since I'm on a budget it might be best for me to fix it anyway (I have just under 2 weeks to get it working before I have to go home from school - and I would like to have my car running by then)

Thanks again for all of your help!

Modified by Arrow at 12:49 PM 4/26/2006

Do not even worry about doing any of this at this point.

[Arrow]

One more question as I wait until after class tomorrow to get some work done on my car: would a faulty connection or bad coolant temp sensor cause the bogging that I have only when I lightly depress the gas? seems like it would effect the car no matter how much the petal is pressed...

inless it is just dropping in a lot of fuel to it when I press the gas and inless I press it hard there isn't enough air to mix w/ the fuel... (just thinking to myself on this)

[NISTECH]

When you give it gas the sensors tell the ecm to dump more fuel ,since its allready almost flooding the cyl's the extra fuel with slight air increase wants to make it stall.

[Arrow]

One more quick question: could a faulty O2 sensor contribute to the car running rich? I have suspected my O2 sensor to be bad since it is the one from the factory (and w/ 181k it seems like it would have gone) - so I previously bought a new sensor and have it sitting in the car b/c I was intending on seafoaming the engine before installing it... but that was last summer and I didn't get to it - darn procrastination.

Might be that I've had a few things that piled up and having one more part / connection go made the whole car come to a halt...Thanks again so much for your help and I really hope that I can find a solution to this within the next week...

[NISTECH]

Since you have the O2 you might as well put it in. But fix your coolant temp sensor problem first. I dont feel the O2 is the source of your problem though.

[Arrow]

Alright I went and pulled my plugs and here are some pics... mind you these were new plugs and w/in minutes they got that black... I just wanted to show a comparison and see if anyone might know what could cause fouling that fast... I know that my car was running rich but yet there wasn't black smoke coming out so I'm stumped... though there might have been a vaccum leak - now should be fixed.

plug on the right has been vigorously cleaned (took a while w/ a wire brush and part cleaner)



Why do I see a broken link image? selecting view image takes me to my gallery though...

Anyway, I also went and cleaned out many of my connectors - MAF, CTS, and every injector plug.... 2 injectors and the CTS were TERRIBLE! I also put some adhesive sealant on the MAF and CTS (the back wire connections) just to prevent water from getting in and corroding and also to help stabilize the wires so that they don't move around

But b/c the sealant hadn't cured yet I didn't want to fire up the car b/c I feared conducting across the sealant - I don't know why just did... that and I still had my plugs to clean... and I was 15 minutes away from my dorm and dinner was coming up soon too lol

[NISTECH]

I think it was that corrosion in the coolant temp sensor telling the ecm the engine was much colder then it really was.

Fixed your image btw. When you are veiwing your image in your gallery. right click in the picture and veiw properties. Copy the URL shown and paste it in your thread with the IMG tags.

[Arrow]

AWESOME! thanks for fixing my image! do you think that it could be running rich enough to foul the plugs that fast and yet not have black smoke coming out? thanks again I should have final results posted on everything mid-day tomorrow

[NISTECH]

it is unusual your not seeing black smog with the plugs fouling that fast. but yes a CTS can definitly cause a quick foul of plugs like that. The old Z31 and U11 max were notorious for that. Newer models were not as common on specific models but rather line wide.

[Arrow]

well, I fired up the car a few minutes ago...

Everything seemed to be going well too - had a high idle (1200) (upon start of a cold engine = good), the car didn't want to die w/ just a touch of the throttle = great...

now the interesting part - the car didn't want to rev up much above 3k or I started feeling bogging and some backfire... then after it warmed up it would rev fine but the car was hesitating and bogging when a little throttle was applied (just like before)

So my assumption is either that there is something else wrong or that the CTS is indeed bad and cleaning the connections only helped minimally for a cold start...

In conclusion I'm going to buy a CTS from autozone for $25 and replace it... see if it works then post back

[tinaslynn]

Replacing my CTS made a huge difference in my car... surprisingly..

actually didnt troubleshoot it, just went ahead and bought it when I got the TPS and some other odds and ends... When I went to take the connector off the CTS, it broke completely in half... then I prayed I was pulling the right sensor lol... it had corroded so bad that the connector was just brittle and snapped off with hardly an effort. Made a big difference for me as well as a new TPS... was having intermittent problems prior. Car runs like a different car now...

Good luck.. keep posting your solutions/problems.. I'm actually learning alot from this post lolT

[NISTECH]

it also helps to slightly bend the female terminal in a bit in the connector to get a better bite on the coolant tmep sensor. The lacking throttle response may be another issue.

[Arrow]

well, I got fed up w/ my car and took it to a mechanic... I think that the only thing left to be wrong was the TPS... b/c I bought a new CTS and it had no effect on the car... but I didn't want to buy a $50 TPS to find that it still didn't fix my problems... so I figured paying a shop $100 for me to stop chasing my tail in circles couldn't hurt... now I'll find out what's wrong tomorrow afternoon...

I'm hoping and praying that the fix won't cost more than $100 to $150... less would be great too

[tinaslynn]

Ouch.. I spent $24 on the TPS and like $22 on the cts at car quest (but I know the manager and get the manager's special lol).

Let us know what happens next... *crossing fingers for you*

[Arrow]

yeah... As of today the mechanics ruled out a bad ECU, and the engine itself (did a compression test and it had 175 across the board)...

So basically they are saying that it is probably something small and simple (electrical problem) and it's just a matter of finding it... and I sure hope that it doesn't get expensive... much over $150 or $200 and I might have to say something (depending on the cost of the part and possible labor involved to repair)

[Arrow]

well, I found out earlier today that the mechanic thinks that it is my distributer (timing was perfect)...Apparently the spark is fine and strong at idle, but as soon as the car gets revved the spark weakens... So he's getting a used one that he knows works to try in it in the morning - and hopefully my problems will be solved...

NISTECH - does it sound feasable that a weak distributer could be causing the symptoms that I've been having? thanks again!

[NISTECH]

it deffinitly could be if the pick up is breaking down. Its good he is only testing a known good one rather then selling you a distributor only to find out thats not it. It sounds like he is unsure so he is trying different things. I am sure he is not using a DSO or he would be able to say for sure if thats it or not. Alot of shops dont have DSO's including dealers or if they do most of the techs in the shop dont know how to use it. That tool when used properly can show you exactly what the ECM sees, something you cant do with a voltmeter. If you have a graph of what the signal should look like you can easily see if its not right with the DSO. This gives you the ability to be 100% certian that this part is failing before ever putting a new part on. However there is a learning curve using a tool like that.

[Arrow]

Thanks! I should be talking with him today and hopefully I will know more... the distributer that he did get brought in was the wrong one for my car (apparently there were two types made for the SOHC's? probably makes sense - hitachi and mitsubishi) so he told me that he had access to another one... hopefully everything works out well