1981 Datsun 280ZX GL


#1

I am the original owner of a 1981 Datsun 280ZX GL. It has never been overhauled, but mechanics have said it doesn’t need it. The car recently had a tune up, but it hasn’t help the problem. It runs very well and then about the seventh stop (for lights, etc) it starts running very rough and bulching out white smoke. It then doesn’t have much power. It has always started immediately until this started and now it struggles sometimes. All rubber hoses and air/flow meter boot have been replaced.

Please help me identify the problem. I would love to keep the car. I drive it to work most of the time, but can’t depend on it now.

Thank you.

Marilyn Misenhimer


#2

How many miles? Does the smoke smell like antifreeze or oil? Does the antifreeze have any oil in it? How does the oil look? How do the plugs look? You should have the compression checked on all cylinders, and also have a leak-down test.


#3

White smoke is often, but not always, a sign of a head gasket breach and burning anti-freeze.
If the shop did a tune-up as an attempt to cure this problem I think they’re offbase. To weed out a head gasket breach they should perform a compression test, cooling system pressure test, and hydrocarbon test; all very simple to do.

A proper, by the book tune-up also means a valve lash adjustment and inspection of the PCV valve. It’s possible that a 5 dollar, intermittently sticking PCV could be behind the problem and it only takes a few minutes to replace.

Even in a worst case scenario involving the head gasket this is not that big a deal on these models. I used to see quite a few of them while working for Nissan and they’re great cars. Don’t get disgruntled and throw in the towel on a wonderful car just yet. The car just needs to be properly diagnosed rather than throw parts at it.

One oddity of several that could cause this may be a turbocharger trying to seize up IF your car is the turbo model. The majority were not turbocharged so I’ve assumed yours is naturally aspirated.


#4

The car has over 248,000 miles. The smoke just has an exhaust smell. I don’t know what either should smell like. The spark plugs were checked and 2-3 changed out. The compression was recently checked and was low on only one cylinder. I don’t know if a leak-down test but I will ask to have that done.
Thank you for your rapid response.
Marilyn Misenhimer


#5

A compression test was done but I don’t know about the other tests. I will ask the shop to do those tests.
I do have another question for you. The hinge on the driver’s seat is broken and the back cannot be adjusted. Is there any way to fix this without buying a new seat?
Thank you for your quick and thorough response. It gives me hope.
Marilyn Misenhimer


#6

I would not worry about a leakdown, cooling system, or hydrocarbon test at this point. The compression test showing low compression on one cylinder is enough for concern.

Now it’s possible that this low compression on one cylinder could be due to either a head gasket fault or tight valve lash. (Valve lash means the adjustment specification between the rocker arm and valve stem. Too tight will lower compression and burn a valve. This means a valve job and a head gasket anyway.)

When low compression is shown during a test what should be done is to follow it up with what is called a wet test. This means squirting a small amount of oil into the low cylinder and rechecking it. If the compression goes up a bit there is a piston ring problem. If it stays about the same it’s a head gasket or valve problem.
The former would mean a complete engine overhaul or replacement; the latter just a repair of the cylinder head.

Without seeing the seat I have no idea how difficult a fix on this seat would be. I’ve repaired seats before so it can be done. The big issue is whether it’s cost effective or not. On something like this you might consider talking this over with an auto upholstery shop as they would likely be more familiar with a repair like this as compared to a general garage; and likely cheaper too.
The other option would be to find a complete used seat assembly and swap it out but it might take a little footwork on eBay, Craigslist, or a 280 forum to locate one without being robbed blind on the cost.

If the car were mine I’d run a wet test on that low cylinder (should have been done originally) and determine if the problem is the top end (valves, head gasket) or the lower end (rings) of the engine and then decide what steps to take. Hope some of that helps.


#7

I can take your information to the shop and know I’m asking for the right test instead of just asking them to figure it out. I will have the wet test done. Thank you so much for your response.
Regards,
Marilyn Misenhimer


#8

Blue smoke = Oil, Black smoke = fuel, White smoke = coolant.
More than likely you will need to replace the head gasket. This is the only thing I can think of that would explain the not happening till it’s warm (7 stops), the hard starting, low compression on only one or two cylinders, and the white smoke. Be sure to take a real good look at the bottom surface of the head while you have it off, a small hairline crack could do the same thing.