86 Z31 won't idle

[macevanscb]

I got this non-turbo '86 300ZX back in 2003, replaced some engine and steering parts, and had a great running little pocket rocket. I've driven it around for for several years with no problem.

But this summer, it started stalling and was hard to start. But after getting it to start, it ran perfectly. Finally, I couldn't get it to start. At the time, I thought it was a tuneup problem as I hadn't touched anything for a long while. So ... new plugs, wires, cap, rotor ... still no start. Replaced all the vacuum and pcv hoses ... still no start. Tried a different used ECU ... no change.

But, with the help of a friend, I did figure out that it would start and run. Had to floor the gas pedal to get it to start and then had to keep the engine above 2000rpm to keep it running ... let the rpms get too low and it would just stall.

Since I had no idea when the timing belt was last changed [and it looked worn out], I changed it out ... that was fun, but it is timed correctly ... and still no change. Finally, I just replaced the MAF sensor ... still no help.

I know there's no major engine mechanical problems. The car is drivable if I keep the engine reved up ... and it has full power and acceleration between 2000 and 4500rpm ... runs GREAT as long as I never have to slow down or stop!! I'm at my wits end here .... does anyone have any ideas??????

[evildky]

sounds like the IACV, as if the car can't get the air to run unless he holds the throttle open, you might not be getting any idle air through, this explains your situation pretty well

[macevanscb]

You know ... somethings are really obvious ... after some one shows them to you.I've had the IACV off and on several times, but never thought to check it for blockage.---sigh---

[jtiet87]

we're you able to fix your idle problem?

[macevanscb]

Just replaced the MAF this afternoon ... didn't appear to fix the hard start problem, but the weather is terrible right now ... very cold and snowy here. Took the car out this evening for a drive. Was very hard starting but got it going and drove around town. Took forever to warm up. With the new MAF, the engine feel was very different: still stalls at idle, but was more stable at lower rpms. Drove most of the time in 2nd gear to keep the rpms up. This drive, I was able to pay attention to the gauges. The digital tach/boost shows very low manifold vacuum. Everyone's been telling me there's a big vacuum leak .... this confirms it. I've replaced every vacuum hose on the engine and there's no whistles or odd sound. Now all I have to do is figure out where the damn leak is.

[evildky]

if it's a vac leak, a mechanic's stethescope can help, you can spray carb cleaner around all the hoses and fittings but be careful as if can catch fire if it hits the hot exhaust