280zx engine runs lumpy/misfire?

Ped

Ped

Club Member
My 280zx (standard set up) is running poorly, here are the symptoms:

  • Engine starts straight way, no problem
  • Engine ticks over OK
  • Give it a bit of throttle and it misfires, like its running on 5 cylinders
  • When driving the lumpy running is intermittent, usually under load
  • Once the car is fully warmed up it runs sweet, only very occasionally has momentary power dips (once in ten minutes for half a second)
Things already checked:

  • It has had a new fuel pump (the old one was squealing like a piggy, then died)
  • All leads are newish Taylor ones from Mr.F, and seated properly
  • All plugs have been checked and set
  • Dizzy cap and rotor arm are good
  • Cant see any problems with vacuum hoses/dip stick/oil cap
  • 97 Ron petrol is fresh
  • Battery is new and charging as it should
  • Exhaust is new and sealed
I am planning on adding an inline fuel pressure gauge to see if there is a problem there.


Anyone had similar symptoms? Don't really want to splash out on a Fuel Pressure Regulator until I have made a few other checks first. :confused:
 
niroshann

niroshann

Club Member
I can't say I've had the same issue but I would check if fuel filter is getting clogged although this is highly unlikely. The other one to check is the EGR valve if your car has one. It's on the firewall end if the manifold. It might need a clean. You can reach under it with your fingers and open or close the valve. Or you could just take the vacuum supply off it and disable its actuation. Obviously then seal off any open vacuum ends.

Anoter thought...I've also had split manifold vacuum lines in the past. Check for hissing etc.
 
niroshann

niroshann

Club Member
Just had a look at your gallery and if this is the car you are having trouble with then ignore my comments about EGR valve. I've had a few 280zxs with these valves hence my theory.

Would look into fuel pressure as you say. You could also test the valve on the fuel rail. I can't remember exactly what it does but might relieve fuel pressure when no vacuum (might be stuck open)
 
AndyMinto

AndyMinto

Inactive
Possibly a fault with the air flow meter or the advance retard on the dizzy. Mine had similar syptoms a few years ago.
 
Ped

Ped

Club Member
I finally got round to putting the car into a fuel injection specialists to have a look at, and its now a lot better. There was a bad connector plug on the temperature sender, hence poor running when cold. The guy also said it was running too rich so tweaked that. He showed me the misfire on the screen but it really only occurs under load. He said to give it a good run before trying anything else. I took a run over to the Kop Hill Climb on Sunday (60 mile round trip), and the misfire is now loads better, but still there a tiny bit, but not at a constant speed. I will probably change the plugs next, and see how it goes...
 
Ped

Ped

Club Member
Finally got round to changing plugs, rotor arm and dizzy cap... and it's fixed it, in fact it was running really nice. It's the first time I have been able to gauge the new exhaust without the misfire, and it's sounds good. suppose I could have checked to see which items were at fault, but just glad it's sorted! Smells like it's running a little bit rich but will need to take it on a good long run to be sure.
 
D

DatsunMan

Active Forum User
Glad you're all sorted now, but as I've just joined & just bought a 280ZX, & can't find how to start a new post! All I can do is to add my request for advice here I guess...
My car is also suffering from a misfire, for want of a better description.
It's also an injection engine, & I'm suspecting a fuel problem, but might be wrong of course.
Runs smoothly, then drops to running badly...can remove plug lead on either 1, 2, or 3 to no effect...
but on removing either 4, 5, or 6 the effect is to stop the engine...
hence it appears that I'm loosing half the engine, then it returns, then goes again, etc. etc.
Any ideas please?
Many Thanks!
Geoff, in the Isle of Man!!
 
candy red

candy red

Club Member
Hi Datsunman to start a new thread you need to click on Forum at top left on home page then pic what category you want the thread to go in click on that and you will see Thread at top left of page click on that and start you own thread .

Derrick
 
D

DatsunMan

Active Forum User
Thanks candy red, it's not very user-friendly then is it!
But I'll have a go now, following your instructions.
Thanks again
 
D

DatsunMan

Active Forum User
Nope, still can't master the new post idea, give us another clue please!
Anyway, I'll post here in the meantime!!

My car is also suffering from a misfire, for want of a better description.
It's also an injection engine, & I'm suspecting a fuel problem, but might be wrong of course.
Runs smoothly, then drops to running badly...can remove plug lead on either 1, 2, or 3 to no effect...
but on removing either 4, 5, or 6 the effect is to stop the engine...
hence it appears that I'm loosing half the engine, then it returns, then goes again, etc. etc.
Any ideas please?
Many Thanks!
Geoff, in the Isle of Man!!
 
D

DatsunMan

Active Forum User
UPDATE on misfire (also posted here, while I couldn't find out how to post!)
I think Monza might just be on to something, with the ecu firing in banks of 3 (1-3 & 4-6)
That's exactly how the engine misfire seems to present itself, with half the engine having no effect at times...
Also, the noisy injectors do all seem to be clicking, although to be fair, even tho removing the leads from 1, 2, or 3, has little or no effect on the engine running (when lumpy) there does appear to be a spark there still (as I do get a kick from it, & here the spark jumping the gap etc.)!
One final clue - the car has done less than 1000 miles in the past 4 years, so not really been used...
In fact, it's only got approaching 38,000 on it now, & that is genuine!
Compression test produces circa 190 on every pot.
Just wish it would stay running smooth tho, it's sounds & looks fantastic when it does!
I keep you all posted! Of developments!!

Meanwhile, it need new disc pads, front & back, a new exhaust system, & new wheels & tyres...
Yes, they're the metric wheels with Dunlop Dunovo run-flat tyres on still...20 years old?!
 
You must log in or register to reply here.
Top