johnu

Hi all
I have some engine smoke issues with my 1987 automatic.
155,000 kms on the car

T2 sensor and O2 sensor are new. No cats, with xpipe.

When the car is cold, there is black smoke and a hunting idle for 30-60sec after start.

Also when the car sits for a long period there is blue smoke on start, as well as under heavy acceleration.

Compression test today shows around 180psi at each cyl except #3 is hovering around 170psi. I added a shot of oil to the cylinder and the reading was then 210psi.

Any ideas??
Car runs great otherwise. I have all the parts for an intake refresh which I am hoping to do this summer.

Thanks
John

depami

Your blue smoke symptoms are often leaking valve seals.

Your black smoke issue could be leaky injector(s).

OTR18WHEELER

What type of oil is in it now?
I've read that syn oil tends to be ABLE to absorb and seep in areas where conventional oil won't.
Oil can pool in the bottom of the throttle body, and then get sucked through the intake.
I suggest changing to a better brand 20w50 for the warmer seasons.

johnu

Mobile 1 15w50 synthetic

FredR

Putting some oil in the bore will temporarily increase the ring seal. Sounds as though you might just to need to blow the crap out of the motor or flush with something like Swepco 502 to clean it up.

Presumably you carried out the compression test with a warm motor and the throttle plate fully open.

My motor typically makes 185 psig on a compression test and does so on every cylinder. I doubt the one on 170 is a problem but good if you can eliminate it from the equation.

Motors running on synthetics seems to consume a bit more oil than the dino variety. What you are probably seeing is a mix of the crappy breather system plus some wear. As Denny says If the motor still has the original valve seals in it then they are probably as hard as nails. The usual sign of that is blowing smoke after off throttle engine braking and then gassing it though.

The black smoke is obviously excess fuel -just a question of why- could be several reasons- have you had your injectors u/s cleaned and calibration checked? From my experience they tend to screw up the spray pattern and/or pass too little fuel but anything is possible if they are sticking or not sealing correctly. bottom line you need to know your injectors are functioning correctly.

If the temp 2 sensor is not working correctly that can also do strange things.

Rgds

Fred

johnu

Thanks for the input.
Valve seals are original.
I have not cleaned the injectors yet. That will be part of my intake refresh.
I figured maybe a slightly worn ring in the 170psi cylinder when the oil sent the psi so much higher. It is within 6% of my average reading so i guess i am not too concerned about it.
Test was done with engine warm. Throttle plate wasnt wide open. Does it make a substantial difference?

FredR

You are trying to compress air- if a full charge of air cannot get into the cylinder you are not likely to compress it as much. To be fair, I am not sure how far open the throttle should be to avoid problems but the easiest [and most consistent] way is ram it full open. Try it with the throttle fully closed and see what happens to your compression readings!

I doubt you will have one worn ring- you could have some localised damage but more likely it is a bit of crap on a valve seat on ring land. If you can try a leak down test - that can probably tell you whether "the problem" is in the piston or the valves.

Redo your compression test with the throttle plate fullly open and report back with the results. I reckon there is a fair chance you will see 185 psig or so across the board but make sure you blow the oil out of the cylinder you plonked it in by running the motor first.

What is your oil consumption?

Rgds

Fred

johnu

Thanks Fred
I only drive about 2000km in the summer then store it for winter. I do an oil change each fall, so i havent been having to add oil at all.

FredR

Sounds to me as though you need to get onto the F1 circuit at Montreal and give the thing a bloody good thrashing for a couple of hours [after checking/cleaning the injectors]. If you are not using a noticeable amount of oil in 2000km then you are just not working the motor- understandable with those SOB's in the funny hats who always get their man!

Run some Swepco 502 in your oil before you change it- better if you can give it a bit of a thrash at the same time. Indeed sounds as though it might be better to add it at the start of your summer season!

Pulling the injectors is not a big job [getting them out of the base can be a bit of a tug] and the cleaning/checking is well worth it if it has has not been done previously- trust me on that one.

Of course it is a good time to do this when the manifold is off - I have seen dirty injectors costing close to 10% reduction in power delivery on some cylinders in my environment- maybe different where you are.

Rgds

Fred

Imo000

Come over to my house and I'll have a quick look at it. Also, might want to try some high mileage oil to see if it swells up the valve guide seals and stops the blue smoke. A good "Italian tune-up" might help clear things out too.

johnu

Thanks for the offer!
I think I will thrash the hell out of her, do the intake refresh with cleaned injectors and have another look at it then. I will post the results...at the rate I work though, it could be a while!

I also want to replace my motor mounts. Should I do this before, after or in conjunction with the intake refresh?

thanks
John

JBGold07

My black smoke was due to MAF failure

johnu

I was wondering about that possibility

JBGold07

Also now thinking about it. My car had been put in storage with over 9ltrs of oil in it and had sucked oil into the intake. Was a pool of it below the MAF. May explain a bit of blue smoke. Fairly common in searches for my intake, not sure for '87's