Looking for ideas on test procedures - rough idle, blue smoke

3225 Views 29 Replies 5 Participants Last post by chris360, Jan 21, 2020

chris360

Discussion Starter · Jan 7, 2020

Been awhile since I worked on this 93 Altima, last year while getting it unstuck in the snow I had to rev it high many times while going back and forth in driveway.
It drove fine that day (I recall all of a sudden brakes felt softer but could be imagination) but next day it was hard to start and has a very bad idle every since...however it ran great when driving.

Back at troubleshooting and it has now developed quite a bit of blue-ish smoke, along with rough idle...can also smell rich fuel.

Things to note:
Using light on ECm I get no codes (55)
When I pull two of the plug wires I get no change in the idle.
It shows spark in all wires, new plugs, new cap, cleaned the oily area from optic lens (has leaked there always since buying car)
Used noid to make sure each injector was firing.
Seems to be higher than normal (to me anyway) pressure when I take oil cap off but really don't know.
I recall the non working cylinders (no change when pulling wires) seemed to change places when I relieved pressure on fuel rail last year...it was plug number 1 and three and then it was like plug one and two for example next time I checked.

Things I have in mind as "possibilities" that I want to test and rule out if possible:

IAC valve
PVC Valve
Vacuum leaks (will be making smoke test machine soon)
Maf sensor (cleaned it already)
EGR valve
Worn out fuel pump (has new fuel filter)
Faulty injectors (will ohm test or swap them to check for difference)

I really need to do any tests I can with the least amount of money and rule things out or add other potential things to check..and hopefully someone can help me with the order to do these in as far as most likely culprits.
I love this car and have a horrible bad back so any help will be greatly appreciated.

Thank you.

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chris360

Discussion Starter · #2 · Jan 8, 2020

Maybe this can help pinpoint the problem...it sure as heck woke me up...lol

Pulled spark plugs to check compression...but each time one was pulled I cranked motor over to see if any combustion came out before putting compression tester in place.

All was fine for the first two I checked..then when I got to the number one (closest to distributor) huge bursts of what I thought was water shot out..but nope..it was gas and it erupted in flames...I am awake now..lol

So is this a sure sign of internal engine problems like head gasket or stuck valves?..or could it be some sort of plugged fuel system?

I get no change on rough idle at all when I pull that plug (calling it number one) and the farthest plug on the other side..I have swapped injectors, plugs and wires with no change.

UhOh

· #3 · Jan 10, 2020

2 out of 4 cylinders no fire.
one of those two has raw fuel injected into it
blue smoke has always meant burning oil

I'm not much of a mechanical help here, but looking at the situation: regardless of how much you like it, a '93 is 27 yrs old, when it hits major mechanical problems it's time to move on. I'll have to face that with my '97 at some point, too.

my $ 0.02

amc49

· #4 · Jan 11, 2020

Heavily leaking injector? Driven long enough has killed cylinder walls to eat oil. Engine may be junk. Compression test to find out if it's worth working on. Cat likely dead too.

Reactions: 1

chris360

Discussion Starter · #5 · Jan 12, 2020

Been watching many videos while its so cold out and running tests when I get a break in the rain.

Here is what I found but need to figure out next steps.

There was a wide open injector due to bad O ring in the cylinder closest to distributor and first inline of fuel delivery.
I fixed that and had to drain the oil due to amount of gas that leaked into it (wow what a lot of smoke when I started it first time).

I now have only one dead cylinder which is the one closest to distributor but am out of things to test.

I have used a noid light = all good
Swapped plugs = no change
Swapped wires = no change
Swapped injectors = no change
Fuel pressure good and steady
New distributor cap = no change (didn't do rotor since I see good spark on that cylinder)
Compression on all cylinders pretty even (maybe 5 psi different) and all seem to give about ten more PSI with wide open throttle..compression right around 165-170 cold on all.

My only two thoughts now could be bad valve(s) or leaking intake gasket..sprayed carb cleaner all around gasket and got no change though.

Any thoughts on next steps? I have never dealt with valves before but top of motor says there are 16...thats all I know..lol

Thank you all.

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d0ugmac1

· #6 · Jan 13, 2020

How do you know it's a dead cylinder? Does engine run (it should, even on just 3)?

chris360

Discussion Starter · #7 · Jan 13, 2020

d0ugmac1 said:
How do you know it's a dead cylinder? Does engine run (it should, even on just 3)?

It does run, just idles poorly still and when I pull any plug wire or fuel injector connector off any other cylinder it really gets rough and will die. When I do the same to the cylinder in question I get zero change.

chris360

Discussion Starter · #8 · Jan 13, 2020

chris360 said:
It does run, just idles poorly still and when I pull any plug wire or fuel injector connector off any other cylinder it really gets rough and will die. When I do the same to the cylinder in question I get zero change.

Also it appears to smoke a bit when I leave the fuel injector for that cylinder plugged in...like it's getting the fuel but not firing it off perhaps? I am still in process of confirming that but got snowed in for awhile...err.

d0ugmac1

· #9 · Jan 13, 2020

I'm thinking at this point it's the ECU or harness/ground that's at fault...drive signal for cylinder #1 injector not behaving properly. You'll need a scope to see this for sure...even if it's slow on, or slow off...you may see fuel spray, but it might be way too much, or way too little to combust.

chris360

Discussion Starter · #10 · Jan 13, 2020

d0ugmac1 said:
I'm thinking at this point it's the ECU or harness/ground that's at fault...drive signal for cylinder #1 injector not behaving properly. You'll need a scope to see this for sure...even if it's slow on, or slow off...you may see fuel spray, but it might be way too much, or way too little to combust.

That is now on my "potential" list as well..thank you.

I do not have a scope though or would know what to do with one if I had one..lol
I do however have a different kind of scope...one of those inspection cams with a small LED light.

Could I use this camera to help determine anything by chance?

Again I don't know much about valves or pistons but what if one of those items were stuck?..would it run? would I have compression like I do depending on where it got stuck? etc?

Snow is still falling and there's about 5 inches here so all I have right now is a very very slow internet connection to keep me from going stir crazy..but still trying to youtube myself into more knowledge...lol

d0ugmac1

· #11 · Jan 13, 2020

I feel your pain...I hate when sh*t breaks in the wintertime...

Best I can suggest, is to try removing injectors (one known good, and the bad one) one at a time and watching them squirt into a jar while the engine cranks, and maybe film them on your camera for comparison after? If you are on your own this could be a potentially lethal setup (fuel, fire, ice...) so be smart, and at the very least have a few fire extinguishers around, or a handy shovel and pile of snow...

d0ugmac1

· #12 · Jan 13, 2020

If your inspection cam is small enough, you might try to get a pic of the condition of the valves inside the non-working cylinder....but I would say valve issues are an outlier at this point compared to harness troubles.

Maybe take a pic of the failing cylinder injector connector inside, and the back where the wires exit...and then yes...20min to upload them...I know...

Are you any good at wiring?

chris360

Discussion Starter · #13 · Jan 14, 2020

Trying to type with frozen fingers...ugh..lol

So I did the injector test (miserably cold) they all looked similar to each other on the piece of paper (sorry I didnt video this as I did it before reading your reply). I also swapped again for known working...its always this first cylinder that does nothing when plug wire or injector is unplugged.

UPDATE: I did notice there was no change in fuel pressure now when I unplug the fuel regulator vacuum line..if this is indeed the regulator at the end of the fuel rail.

Any chance that could cause an issue like this?

As for the inspection camera...I know this will sound soo newbie but where would I put the camera to inspect valves? In the spark plug hole I would see pistons right?..so would it be in the intake after I remove fuel rail and injectors? Or would it be to try and snake it through my valve cover via the oil cap? If valve cover..can I just remove that fairly easy without having to phone a friend?..lol Asking since the dead cylinder is on other side of oil cap.

As for wiring...I would be much better at if I didn't have such a bad bone spur on my top vertebrae..anything bent over for one minute or more causes the devil himself to come attack my upper back with his flaming lazer stick of pain...or something like that..lol He is already on his way this evening I am afraid so I need to go hide from him for awhile..lol.

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chris360

Discussion Starter · #14 · Jan 14, 2020

Been doing more reading / watching / learning while thawing out and read that brake booster vacuums can cause air leaks..air leaks can cause misfires etc.

I keep remembering that when this car first had this problem I noticed a fairly significant difference in the feel of the brakes...since I am used to them how they are now I really can't tell if its still happening or not but am still wondering if somehow this could be related.

This may sound like nonsense to someone with a clue... but wondering if there is a possibility that some vacuum from the brake booster has failed which is causing some EGR valve or something else to not operate properly which changes the air / fuel mixture enough to cause a non combustible gas mixture to form in just that one cylinder?

amc49

· #15 · Jan 14, 2020

Inspection camera is worthless if you truly have that much compression on all cylinders. No valve problems either. They would lower compression absolutely.

Fuel or ignition issue.

Reactions: 2

chris360

Discussion Starter · #16 · Jan 14, 2020

amc49 said:
Inspection camera is worthless if you truly have that much compression on all cylinders. No valve problems either. They would lower compression absolutely.

Fuel or ignition issue.

Thank you.

I am learning that even though I have spark it may not be enough spark I guess so will be looking into that..along with that fuel pressure regulator issue which will be here Thursday...just learned the secret of using a grounding probe when taking wires off so I can quit shocking myself so that's a plus..lol

d0ugmac1

· #17 · Jan 14, 2020

MMMMmmmm. Sparks.

d0ugmac1

· #18 · Jan 14, 2020

A vacuum issue wouldn't take out just the one cylinder..I'd park that line of thinking for now.

From above you seem to indicate that your #1 injector was spurting like a champ when you did the paper test?

Given that you're on a distributor system, I once had a rough idle problem on an old V8...turned out to be some carbon tracing on one of the plug cables...basically a phantom wire made up of basically soot that bled power away from the spark plug causing misfires. I've also seen plug wires with problems at the crimps (where the metal makes contact with the inner conductive core of the cable). If you have enough slack, are you able to swap spark cables between #1 and another cylinder of similar length?

amc49

· #19 · Jan 14, 2020

'A vacuum issue wouldn't take out just the one cylinder...'

Not so.........it can easily if say the leak is localized enough on one intake runner to mostly affect it only. Look on the problem intake runner for a fitting on it only or any other place that can leak mostly on that runner only. I've seen say intake runner valves that wear out the common shaft leak at one runner to do it. Usually the worst when the leak is well past any plenum or at a single intake runner gasket to the head. BTDT.

chris360

Discussion Starter · #20 · Jan 14, 2020

Just shoveled it out again due to five more inches of snow...so cold now I have to be done but I tried new plug wire again since it showed up and no change.

This time I watched fuel pressure closely since I know a bit more about how it works and there is ZERO change in the pressure when I rev it up..stays at about 32 psi...same still when I pull vacuum line off regulator, no change. Not sure if there should be change on this car but videos on others show it usually changes when either of those happen.

I will also be checking closer for some sort of individual line to that one section of intake..but from what I could see this time around it was just the EGR tube that may be involved on that section of intake or close by anyway. (hope that's the tube I am talking about anyway..but I am already a newb and being a frozen newb is even harder..lol)

Thank you all again...I hate being this stubborn but I do learn a lot that may help my future $200 cars stay running so there is that..lol

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