I'm thoroughly stumped.

My '83zx (n/a) has this twice a year thing where it doesn't want to idle. It also bogs down when accelerating, belches a bit of grayish smoke, black watery stuff comes out the tailpipe... It's a mess. It usually works itself out, but this time I have a little money and decided to fix it. Here's what I've done thus far:

New NGK plugs
New fuel filter
New air filter
MSD Blaster 2 coil (8 ohm resistor in place, running 7mm wires, 8mm coming soon) I replaced the coil because the old one was 27 years young and decided to upgrade.

Now, after the coil went in, it ran excellent for about a day. Today, things got strange. While going to work (Highway speeds not faster than 75mph), I let off the gas to slow down a bit and when I needed to speed up again, it sputtered a little and poofed some gray smoke... felt like it caught and started running fine again.

I fired it up to go home, and it idled for a few minutes just fine. Right before I took off, the idle dropped to only one line on the tach (disco dash) and it ran rough as hell. Had to keep my foot on the gas to change gears or it was going to stall. For the first 5 minutes on the highway, I couldn't go faster than 65. The engine would bog like hell when giving it just a little more gas. Then the engine blurped and it ran fine.

Here's the kicker. I have this little "hesitation" around 3,200 RPM. It's been there for the 13 years I've had the car. Usually lets me know I'm hitting 77mph (in 5th gear... or any gear if I hit that rpm range) and I need to back off. It's become kind of like a friend. If I stay on the gas after 83mph, it's not there. With these new issues, that "hesitation" goes away. Makes me believe something is really wrong.

Kicker #2. This is my daily driver. Right now, I only get one day off a week to work on it... and yesterday was my day off.

So... I need some Master Guru help. My next thought... Fuel pump may be going out. Am I on the right track? What else do I need to check?

I really need help on this one!!!!!!!!

 

Sounds like its dumping fuel into the system almost when it does that. Have you checked your CHT and AFM yet? I'm betting it something in the AFM myself

 

being you did the normal tune up type stuff, try checking fuel pressure, it should be about 36 psi at idle. you can usually borrow the guages or just get one and install it perment in line like i did. it also could be the regulator. pull the rubber line off while its running and check no fuel is comming out the regulator. this means the diaphram has a hole. if its not any of those. you could adjust the afm, but test and check the tps. use an ohm meter and your manual for pin # and measurements

 

BK-- CHT? The AFM is fine. I may need to tweak it a bit for the new coil, but other than that, it's is good working order.

Shady-- I'll check that out today.

 

Cylinder Head Temp sensor on the side of the head with the spark plugs. almost sound like its trying to ground/short out or something.

 

Ah... gotcha. Yeah, I taught a friend's daughter how to do an oil change a few weeks ago. I'll check to see if she spilled oil on it or if it got bumped.

 

Ok... CHT looked fine, cleaned the contacts just for fun. I don't have a fuel pressure gauge, but the regulator is not leaking.

When I fired it up, it ran just fine. Didn't take it for a drive, gotta get ready for work. I'll let you know what's up after work (After 1am west coast time).

 

It could look fine but doesn't me it cant go bad lol Well good luck

 

Have you checked the trace on the AFM circuit board? This really sounds like a worn AFM trace.

 

Well... I'm going to have to guess that cleaning the contacts on the CHT did the trick. It ran great all the way to work and all the way home (70 miles round trip). I didn't get on it, per se, but it did feel good and strong like it used to.

The plastic is broken where the retaining clip goes (on the CHT), so it just kind of sits there. Maybe it worked itself loose... Who knows. But it needed the tune up anyway.

Once again, this forum has saved my a$$. I know I don't post all that much, but you guys came through for me anyway. Thanks!

 

^ Glad you got it going again. To save you some headache down the road. I would replace that connector at the CHTS. Get a quick release one from MSA. It is well worth it. Then you can snap it into place. And you should be good to go. Also would be a good idea. To replace your fuel injector connectors. With the quick release ones also. Good luck, and keep that Z moving along.

 

I've had the same kind of nightmare. Like you were going through. And all it was, was a loose CHTS. That small problem, made me have to call a tow truck. When all I had to do, was plug the sender back in. lol I learned my lesson from that mishap. These Z's, don't like running very well. When that sender is not quite making contact. Or any sensor for that matter.

 

Cap and rotor toasty ?