86 300 ZX Skips

[Wharf Rat]

Ok guys, I have changed plugs and cap and rotor. This engine runs fine at idle and when reving it up out of gear and when cold its ok but under a load when warmed up it stumbles and seems like it drops one or maybe two clyinders its not building coolent pressure or smoking and I have changed out plug wires one at a time with another thinking it had a bad one (I couldn't drop the sixty bucks for new) just used a long one I had from my truck! Coil maybe??? It's my Sweeties car (mine but hers) and I just got it out after sitting all winter, it ran fine for a few days and now this. Any Ideas? It's a non turbo auto trans.

 

She loves this car ! Please help:D

 

Peace WRAT

[Skib]

fuel issue maybe? I dont really know Z31's that well :mellow:

[72240z]

Did you add fuel stabilizer to the gas before you let it sit all winter? Have you checked the plugs? Fuel pressure?

 

Try running the codes?

[Wharf Rat]

I don't know, it's ok when cold, maybe when it goes lean after warm up, I will change fuel filter anyhow it's time.

 

Thanx Man:fu:

[Wharf Rat]

I changed plugs. No stabil in the gas but it ran fine then filled it again maybe I got a batch of crap, it started shortly after the fill up:(

[72240z]

Well not so much change but look, tell tail signs of lean or rich running and such. I had a 86 I bought to part and ended up getting it running well and sold it. Was sitting outside for almost 2 years before I got it. That's why I ask about the fuel, it was a definite issue. It too had a bog/miss under load but It turned out to be hair line cracks in the cap I couldn't see and eventually found when I got the shit shocked out of me timing it.

 

Try the fuel filter since you say its due anyway but I'd do a fuel system treatment and a full tank of super, just to rule all that out. I really don't think it would be the coil but you can buy one at advanced, try it then return it if it's not that.

 

Have you tried running the codes? It's really easy on that z. Maybe give you a heads up. There are other modes too and a maf burn off as well. People don't take advantage of the built in diagnostics nissan put into the 80's models.

[Wharf Rat]

Thanx, ya I will pull the codes, I thought it must be the cap too after I changed the plugs, oh well .... my gut is saying head gasket just starting, but no smoke or smell. Hope it's wrong and it's fuel or fire.

[datzenmike]

Remember that electricity always tries to find the easiest way to ground. It doesn't take much voltage to fire a plug at idle but more throttle means more air and fuel and it gets harder to fire. If the coil is bad or cracked the voltage might find it easier to jump onto the negative terminal. Easy and cheap to check. Once you are sure it isn't ignition then get into the EFI.

[yellowdatsun]

These engines are bullet proof, I highly doubt you have a head gasket blown.

 

I have been running one of these VG30's in my 510 for many years, and have had 2 300ZX's. The nice thing about these EFI systems, is that as far as electronically, they can normally function even when a few things are disconnected.

 

If it runs fine at idle, you can rule out the coil, plugs, wires, injectors, and most other EFI electronics.

 

If it stumbles under load your probably not getting enough fuel to the injectors. I'd first check the filter. Take it off and try to blow through it. If you can't, it's clogged. If that's fine I'd check the fuel pressure, the pump may be giving you enough fuel for idle and no load conditions, but not enough for loaded conditions. Fuel pumps on these are known to go bad on occasion. Mine did after sitting for a few months, just replaced it a couple weeks ago.

[Buzzbomb]

If you think that it could be a dirty injector or something fuel related along the same lines, fill the tank and put some Seafoam in it. The stuff really works and helps clean up dirty injectors and can help to neutralize the bad gas enough as to where it might run well enough to burn it off. It's good stuff, I've used it many times. It works GREAT as a fuel stabilizer, BTW.

[Wharf Rat]

Thanks guys I will let you know how I do today:)

 

Peace WRAT

[comply]

Is that a tiny dog in the back window?

[Wharf Rat]

Fuel filter, sea foam and a tank of high test then a air filter even though I knew it was not the trouble. I should have bought the plug wires too because that was it. Covered the engine over with a thick tarp and watched for sparks while a buddy put a load on it in gear sure enough down in the #5 hole. the wire I had used when I swaped them out most have been bad too. lots of close metal to ground out on in them V6 engines! I was looking at the coil first. Mike gets the booby prize:D I feel like a turkey! It's all tuned up now for my honey anyhow!

 

Thanx you birds:fu: and yes thats "Taffy too too" my toy rat terrier in the back window:)

[yellowdatsun]

I'm surprised, usually if it's a bad wire you'll have problems all the time, not just under load.

[Wharf Rat]

Me too this was messing with me and it would run fine until it got warm too.

[72240z]

Glad you got it sorted. I not surprised it was a power issue, just thought since checked with a dif wire it wouldn't be that. After my z31 bogging under load issue and yours and both being power related I'm going to make a mental note to check that 1st in the future lol.