stumped

[78blackpearlz]

ok guys gonna be a bit of a long post but here we go..

 

My Z has started to run extremely rough, whenever it gets up to running temp it will start to sputter and backfire from take off and will also seem to die out but suddenly come to life after the backfire and take off. The only thing I have been able to tell is that it only happens when the temperature outside is hot because in the mornings when I go to work the car will drive perfectly. I was talking to a friend about the issue and showed him what it was doing and he mentioned that a vehicle of his had done the same thing and he replaced the ignition control module and it solved the issue but I wanted to see if there where any other possibilities out there.

 

thanks.

[Patcon]

280's aren't my forte'. My first guess wouldn't be ignition, sensor or fuel pressure. Start in FSM and work methodically through it. Do you have a fuel pressure gauge and a multi meter?

[78blackpearlz]

I have run a fuel pressure test on it and everything was alright. It was a little while ago so I don't remember the exact results. I guess I should have mentioned that my car had begun to do this towards the end of last summer and as the temp outside lowered the problem went away and I got caught with other issues and this one slipped my mind.

[78blackpearlz]

This one has been the toughest issue so far for me of all cars I've diagnosed. I've even talked to two master mechanics and spent a lot of time researching with no results.

[Zed Head]

Your friend's suggestion was a good one.  But you kind of have a mix of symptoms with "come to life after the backfire and take off. The only thing I have been able to tell is that it only happens when the temperature outside is hot because in the mornings when I go to work the car will drive perfectly. "  Usually the modules stay screwed up until the engine is turned off for a short time.  I had one that worked fine until I revved the engine over about 3000 RPM.  Then it would run rough until I turned it off and restarted.

 

One clue about the module is the tachometer needle.  It won't read correctly, usually high, and the needle will jump around.

 

One test of the module that apparently works well is to spray it with a cooling spray.  You can buy them in various stores, I've heard.  When things are bad, spray the module and see if it goes away.  Here's an example, I don't really know where to get it.

 

http://www.amazon.com/Professional-Freeze-Electronic-Component-FR-777-777/dp/B000Z99ZCA

 

You can also wire in a GM HEI module, permanently or just for a test if you get frustrated.  They're about $20, and actually perfrom just as well as the expensive Nissan replacements.

[78blackpearlz]

Thank you for the help. My tachometer does actually jump or it will just stick in place and wont work right again till I shut it off and wont work right till it has slowly settled back to zero. I didn't realize that the ICM could effect that, but now that I think of it, it makes sense.

Edited July 19, 2015 by 78blackpearlz

[Kurbycar32]

The cooling spray is the same ingredient as canned air, it just blows the liquid instead of the gas.  The same effect can be achieved by spraying canned air upside down and its much easier to find.

[78blackpearlz]

Alright guys I pretty much just said screw it and went ahead and ordered a new ICM since it seems to fit the best. It should be here Friday hopefully, I'll post the results as soon as i can. Thanks again guys for the help.

[rcb280z]

You must be wanting to keep everything "stock"? ZedHead had a good solution to an expensive part in his post (number 5). Would have saved you a lot of money. Everyone that has done the switch is happy with the results. I'm just waiting for mine to go so I can try it.

 

Plus I'm just realizing you said a "new" ICM. Did you actually find a new one? I was under the impression new ones are long gone.

[Zed Head]

Sometimes the money-time-knowledge calculations just point to replace and hope.  I had meant to add a reply about the tachometers in these old cars commonly getting stuck high when they get hot.  It's usually a smooth problem though.  The jumpy needle from the module pumping out too many sparks is pretty dramatic though.  It's scary.

[78blackpearlz]

Yea I am trying my best to keep everything as stock as possible which is proving to be a bit of a challenge. But I did find a new one its not an OEM part because they don't manufacture them anymore. I got lucky and found one on rockauto for $120 when everywhere else wants $200+ for them. I read a lot about the HEI "conversion" with it and just decided for some reason to go with the ICM. And I'm hoping this isn't to much of a "plug and play" since my z is a daily driver and it gets a little hairy at times with this one.

[Fred Sigarto]

Googled Blow Off Freeze Spray, a lot of different sized cans, Walmart carries it.