280z problem - smoke + no power

[tech9]

Hey, i'm a little new to z's, but i bought a 1977 280z and were trying to get it running. At first it wouldn't start at all, and a little replacing of fuel line, cleaning out the tank, fuel filters, etc. we got it running and idling perfect. Very little smoke

 

The problem is when you actually give it gas, sometimes at cold start it will rev up almost perfect and its actually drivable for about 2 minutes, then it just loses power. There is smoke coming out the exhaust, and we made sure its not water, but we haven't ruled out fuel or oil. We tested all the electronics and they seem good.

 

It will produce a smokescreen at high rpms (if you can get it there - 1500+) but will have little smoke at idle. The smoke smells a little like gas, but a lot like fuel.

 

The plugs have oil on them, and were still trying to determine where its coming from, it has good compression, so i'm thinking the head. But is this why there is such a performance decrease?

 

I'm going to try and find a junkyard head and try that one out, could there be an electronic problem?

 

Thanks for the help.

[Pilgrim]

Sounds to me like the FI is running extremely rich. I don't know the computer system in this car or how much of a system there is...but it sounds like something is confusing the system. That could easily point to a bad sensor.

 

#1 thing I would do is find a factory service manual and start looking for tests I could run based on its directions.

 

I'd run a wet/dry compression test on it (easy to do) just to set a baseline for the compression.

 

I don't have an explanation for having oil on all the plugs - but I'm not convinced it's oil. I'm wondering if they're actually wet with fuel. Oil makes no sense to me with the minimal information you have at this point, but a compression test would tell you whether there is a head leakage issue, or perhaps very bad rings.

 

I'm wondering if the smoke you see is blue or black. Black is fuel, not oil. Blue is oil.

 

 

My advice: DO NOT start changing parts!!!!!!!!!!!!! Don't worry about the head or changing it until you have a factory shop manual and have done a LOT more testing. the most challenging part of working on a car isn't changing parts, it's making a good diagnosis. Get a diagnosis FIRST!!!!!!!!!

 

One thought: I once owned a '66 GTO which still had good compression but it had been gotten so hot that the oil rings on the pistons lost their temper and stopped working. A compression test wouldn't show that failure, but oil consumption would. That GTO burned a quart in 50 miles. This is extremely unlikely to have happened to the Z.

[tech9]

Compression test - dry = 120 on all cyls, none were off much much. So i'm going with good rings.

 

The smoke seems white, or a little grey (i will post a video soon)

I tested all the sensors using the factory manual and they all tested "good" but I'm not sure what is happening.

 

I will post picture / video soon.

[tech9]

Click here to watch 280z-exhaust-idle

 

Click here to watch 280z-rev-up

 

You can't hear it well, but you can tell its leaning / riching the engine so it ends up losing rpms.

 

[Pilgrim]

Hard to tell, but I'm far from convinced it's an oil problem. I would not be hunting a head at this point, I'd be looking at the fuel system and its regulation.

[Daeron]

First off, go get some NGK plugs.

 

Seriously, before anything else. New NGK plugs (replacing not INCREDIBLY old NGK plugs) have repaired a not entirely dissimilar problem for me on my 87 subaru. yah, apples to kumquats, BUT autolite == crap.

 

Secondly, go back and check your TPS a second time. If it check out, then try to find the associated pins on the ECU plug and test the TPS operation at the ECU plug; this will ensure that the wiring to the TPS isnt janky in any way. (this sounds like a TPS problem to me, but thats just a SWAG)

 

Thirdly, gasoline and carbon build up can look ALOT like oil on the plugs.

 

What do you mean by "The smoke smells a little like gas, but a lot like fuel."??

 

And finally, when you say the engine wont "turn over" do you mean that when you crank it it doesn't even TRY to start? Most people consider "turning over" to be the rotation of the engine caused by the starter; if. by "turn over" you mean "try to fire" then some clarification is needed... if you mean, literally, that the engine wont turn over (IE immobilized, starter motor does nothing) then I am going to start asking questions about battery connections and grounds, etc.

 

hope this helps

[spacecase70]

the smoke i saw looks just the way mine looks! I rebuilt my head and the same problem still ensued, so i think Daeron though of the oil control rings losing their tension is a strong probability. mine has great compression too but it still burns oil. when i pulled the head off i found oil on top of the valves both intake(not much) and exhaust( a lot more wet) I hope i have been helpful and I know Daeron has givin me some insight on this problen too. thanks D!

 

P.S. oil smoke has a light blue tint, water looks more white, and gas or fuel rich is black,and lean is a grey color

[spacecase70]

also check your FPR(fuel pressure regulator) and make sure your not losing fuel pressure you may also have a bad fuel damper, it is located right next to the fuel pump in front of the gas tank

[sweetleaf]

Test your Fuel pressure, It sounds like it's running rich. If you FP checks out, I would check the tension and traces in the AFM. Also make sure that the contacts in your tps are at the correct points.

[datsun40146]

Check your thermotime and water temp sensor, they are found near and below the thermostat facing the radiator. Please check for the following in order of likely-hood.

1. Make sure that both sensor's contact points are clean and dry

2.Make sure that they are not swapped with one another (often and easily done as they are the same plug)

3. Check downstream of the sensors for two bullet connectors. These are about a foot downsteam, clean them.

4. Check for wires that are pulled out of the sensors but that are still in the plug. This doesn't happen often but it does happen.

5. Near the two sensors I mentioned is a third sensor but I forget its name. anyway its a female bullet connector, dissconnect it and clean it.

 

One of those should be your running rich issue if its computer/sensor realted. I hope that helps.

[tech9]

Well now I've tried almost everything.

 

I'm thinking maybe still a head gasket cause the coolant is a little foamy now. Oil still looks clear but who knows. I tested all the fuel injectors, found 2 and 3 were crossed, injectors work, in my opinion they aren't spraying good, but they are spraying fuel. Checked all vac lines, cleaned all electrical connections, including the coil and all the wires around it.

 

I did find that my thermo time switch is bad, tested and theres full resistance.

I'm going to junk yard again tomorrow, they have a 77 280z there, missing the computer and some of the engine parts, but most are there, so at least I have some spare parts. I did want to swap a known working computer in there, but after testing it seems to be working fine.

 

I hope its just the headgasket causing all the problems.

[datsun40146]

There's your problem if the thermotime is bad it will cause this kinda of problem. Fix it and all your problems should be solved. The reason is that since this is bad is the ECU thinks you car is cold all the time and is dumping fuel into the motor, which is why it runs so much better on frist cold start up....... I think

[ZDrifter]

Dont say all his problems will be solved quite yet.... If your problems still continues after you replace that, do a leak down test. This will tell you if you have bad rings, valve seats, or a head gasket..

[Pilgrim]

Given the 120 PSI compression test (low but probably adequate) there is no reason to think you have a head gasket problem.

 

I'm with the others in thinking it's a sensor that's giving the computer bad info, and as a result it's running incredibly rich.

[tech9]

Given the 120 PSI compression test (low but probably adequate) there is no reason to think you have a head gasket problem.

 

I'm with the others in thinking it's a sensor that's giving the computer bad info, and as a result it's running incredibly rich.

 

I replaced all the sensors, wires, plugs, put a new airflow meter on, tested all the wires and sensors. It's like trying to fix the problem in the dark, I can only think engine problem. There was so much white smoke that it has to be burning coolant. The head needs valve seals anyways, so I might as well pull it. Who knows what goodies are in a 14 year old engine.

[datsun40146]

You shouldn't shotgunning parts at a motor, this in most cases is very expensive, time consuming, and doesn't fix the problem right away. Yeah you'll get the problem something but it might be 800 USD and alot of new parts down the road. Before you went and replaced all those sensors did you even bother to check thier resistance with a meter agaist specs in the FSM? I still belive FIRMLY that this is a fuel injection issue. If your valve seals were the problem I belive you would be buring oil NOT coolant as you so belive you are doing. Also most of the time when those seals begin to fall they will only puff smoke at WOT and burn a bit of oil. This shouldn't cause the white could you are seeing. BTW could you give me a list of all the parts you have replaced with KNOWN TO BE GOOD parts so we can narrow it down. Then at least i'll know its not the senors hell it could be a worn wire on that sensore somwhere downstream thats grounding out. Thats why you need to check the resistance. Check it and we can almost pin point the problem.

[tech9]

I checked the resistance twice now actually, a kid down the road said he had the same problem and it was his ECU, so hes going to let me borrow his. I got the head so clean it up a bit, and there is a ton of carbon buildup in the CC. I'm also going to fix the valve seals while i'm at it.

 

I got all the spare sensors at the junk yard, so its worth while.

[Pilgrim]

Sounds like you're on the right track - I support the idea of doing all that's possible to diagnose a problem via sensors, etc. before tackling a major mechanical task. It just makes sense to eliminate other possibilities before taking on a 10+ hour job. It may indeed be coolant that's causing white smoke but without a demonstrated head gasket leak, I'd put it at less than a 50% probability. Not impossible, just less probable. If the coolant level is dropping or there's other evidence of a leak, probability increases.

[WingZr0]

Hello All Out There

 

I also have a '77 280Z 4 speed with N42 Block and N47 head that has

the exact same symptoms.

The previouse owner had the engine rebuilt but who ever reassembled it put on (or) ordered the wrong gasket kit.

The intake / exhaust gasket was the Carborated 240Z/260Z kind with no

holes for the fuel injectors to squirt through.

I have since replaced that with the correct N47 kind.

Before I did that she was over heating to the redline temp.

 

I suspect this was the case the P.O. was having as well since there

were spare parts in the hatch like he was trying to fix the

problem too not knowing the Int/Ex gasket was wrong.

 

Well my Question is are the head gaskets for the

240Z / 260Z different from the 280Z ?

Assuming they ordered a complet but wrong engine gasket kit.

 

My compression is 150 across the board and with a teaspoon of oil it is

170-175.

 

My NGK plugs have oil on them and there also appears to be oil in

the radiator which looks like Brown Chocolate Swirls,

white smoke blows also and she hesitates as if the fuel is being

blocked by back preasure in the lines.

Number 4 Fuel Injector not working aswell, changed Injector and

spark plugs and now #4 pings like it's misfiring making the engine

"tilt" to one side when it pings.

I think it may have a stuck valve from needing a

valve adjustment though BTW.

Not 100% sure if it's #4 pinging as I shut her off before pulling

the injector conector or plug wire to see if engine idle changed,

figured best to turn off before blowing something.

 

Any help would be apriciated on the head gasket though

please cause I think it might be blown,

among other "dominoed" problems from the overheating .

 

Thyanx ~Z~

[jasper]

Coolant temp switch is an area of concern. On older cars, the rubber boots over the connectors dry rot, moisture gets in and corrodes the terminals. This causes high resistance and lies to the computer about the real engine temp. ALL CONNECTORS ARE SUSEPTABLE TO THIS PROBLEM.

Leaky/sticky injectors are another concern.