280 running rough

[=Resurected280=]

I second what daddz said. I had the same problem with my 280Z and after going through almost every item in trouble shooting section of the EFI section of the FSM one of my fathers friends said I should check the gas tank because of how clean EFI systems need to be to run correctly, and sure enough there was rust in the tank, I HATE RUST!!!! . But anyways I had my tank steam cleaned and re-lined and my car ran like new.

Just as a side note the rust in my tank was caused by a looonnnnngggg period of sitting (17 years) and there was quite a bit of rust in it.

[Brawley]

When I bought my 77 280Z it would barly run at all. The previous owner tried nearly everything except the gas tank. It was full of rust and starving for fuel bad at any load but idle. I redone the tank and used a liquid plastic liner and have been driving it everyday for nearly a year with no problems.

[Master_Shake029]

I know this probably wont be of much use, but you said you just had the enjine rebuilt, maybe by some ill saken chance the piston rings became bad and it aint getting good compression, that would explain why you need to pump some gas. Its happen to me.

[daddz]

daddz, do you really own all of those cars on the bottom of your post:surprised and good luck with your 77

To answer your question: yes, unfortunately! The '77 280Z that I am speaking about used to be mine (HLS30-375108 02/77) but I gave it to my father about four years ago and he drove it for about a year and then a leaky injector kept the car in the garage. Finally after having swapped a used injector another one began leaking and at that point I convinced my father to tow the car southward so that my ex-Nissan mechanic could attend to the injector problem. Only thing he is sloooooow and it has taken the better part of two years to bring it to this point. At least he caught the beginnings of another problem while replacing the heater valve under the dash and installed a new heater core while we were at it.

In any event I replaced the valve cover breather hoses as well as the auxilliary air regulator hoses with new Nissan pieces and while I was at it a new Nissan fuel filter. I drove the car about 65 miles roundtrip last evening and that seemed to do the trick. The fuel pressure regulator that the Nissan dealer sold me was the wrong one (it is for a '78) so that one will go into the inventory.

So for now there will hopefully be no need to drop the gas tank.

BTW, if anybody's interested my avatar car ('78 280Z HLS30437667 11/77) is going to be for sale this month.

[jinsei888]

First of all, how are you getting 35 PSI? "I am having a problem starting it. I have to pump the pedal to get it running and it will not idle now. I have to keep reving it to get it going."

You said you had about 30 @ idle before in your second response which is low. If your Z is Stock, it should be maintaining 36.3 @ idle. Do you smell gas at all? Sounds like you got a Fuel Leak somewhere. Check all your rubber fuel lines for any cracks or tired out fuel hose clamps that could be leaking under the hood and under the car where the fuel pump is. Another possible cause could be a vacuum leak somewhere in the system. The Fuel Injected Z's will not tollerate any vac. leaks. Something as simple as a loose oil cap will cause running problems so check for any possible vac. leaks as well. Check your A.F.M. Rubber boots for cracks when looking for vac. leaks. If the A.F.M. boots are cracked, Unmetered air enters which fouls air/fuel mixture because the E.C.U. is operating off of what it's receiving from the A.F.M. (How far the air is moving the flap) and the E.C.U. is unable to compute the extra unmetered air which is what fouls everything up. Hope I made sence. It's tough to explain

Best of luck and don't give up. Patience is the Key

DatsunZsRule, I am reading less than 30psi from my after-fuel-filter fuel gauge; I'm getting around 28-29psi at idle...and I DO smell fuel as I drive and when I'm at a stop light...I should check my fuel lines I suppose...yikes

[RogerZ]

If the distributor is hard over against the stops it is possible the gear driving it is off by one tooth. the shaft which drives the oil pump is also the distributor shaft. You can change this by dropping the oil pump and moving the gear one tooth in the direction which would give you more play in the slots. Easy if you have someone to hold the shaft when you drop the pump otherwise a little trickier. I use a 5" m8 bolt with the head cut off as a guide pin otherwise everything falls out in your hand and you don't know where the thing was to begin with. You may have more than one problem i.e. distributor off and fuel supply problems. Keep at it. You need to check your fuel pressure under load. Just watching the pressure in the garage while you rev the engine doesn't tell you that you have sufficient fuel supply. Check all the connectors for corrosion. I've heard of many problems such as you describe be caused by afm connector corroded.

[Obie87]

I'm having a similar issue in my 76 280z.

When the car is started cold, it runs great- smooth idle, no hesitation, and great power.

After a few minutes, it warms up and the performance starts to degrade. Hesitation, rough idle, little bit of popping coming from the intake (i think) and loss of power, most noticeably under load especially at lower RPMs.

Here's what I have done so far-

Checked all electrical connections, replaced a few.

New Fuel Filter

Cold Air induction

Replaced AFM to Throttle body boot

Checked for Vacuum leaks

Checked timing

New Alternator

New ignition switch

New exhaust - Monza, sounds awesome

Ran Bosch L-jetronic diagnostics- everything working like it should

Found- cracked diaphragm in the vapor cannister's vacuum advance control valve

Anyone know where to find this diaphragm? Nissan dealer, motorsport auto, and other parts guys don't know where to find one. Will it matter if I leave it alone? How important is this little piece of rubber? What should I use to try to patch it?

I'm going to check the distributer vacuum advance soon, recheck timing, and test fuel pressure. Hopefully this will find the problem so I can fix everything.

Am I missing anything else important?

Thanks,

Rob

[sblake01]

Water temperature sensor. I didn't notice it on your list but I assume that you checked the connection there. If the sensor is bad it will run okay cold but as the engine warms up, the sensor is supposed to decrease in resistance as the water temp rises. If it doesn't the fuel enrichment and pulse stays the same as if the engine was cold.

[Sailor Bob]

I'm no mechanic, but I have to say that I had a recent problem with running rich and based on advise from the forum I checked the water temp sensor connection and found that it required cleaning - cleaned the injector connections as well. Working fine again. Simply used electrical contact cleaner and a air hose.

[TomoHawk]

On the 280Z with EFI, there's no need to pump the gas when starting. Pumping will do nothing unless you have carbs with accelerator pumps.

I know that disconnecting an injector will make the engine run rough, so have you checked or cleaned up the connections to the injectors?

[dimitri_zee]

Just a thought, do the 280Z's with EFI have a cold start injector like the 280ZX's? I'm thinking if that is stuck open/leaking, that will give an overly rich mixture/black smoke and poor running.

[sblake01]

I'm no mechanic, but I have to say that I had a recent problem with running rich and based on advise from the forum I checked the water temp sensor connection and found that it required cleaning - cleaned the injector connections as well. Working fine again. Simply used electrical contact cleaner and a air hose.

So your periodic rough idle and shut down problem is solved?