gx2

hi all,im new here,im in ireland,i have a 91 swb z32,its twin turbo manual,i love this car but it has me tortured with problems,latest is its been lying up this past 6 months at a mechanic's,he put a timming belt on it and he disconnected two pipes behind the front bumper and blocked 1 end of them to give the wooosshing noise (he insisted there was no need for dump valves as my engine is completly standard),anyway got it back today,didnt run right at all,hunting at idle (very rough),hesitation,while driving once you stop accelerating rev's drop way back to 1000 rpm then back up again,i put the pipes back on and it did help idle but didnt cure it,drives better but not as it should,about 2 years ago the car lay up for some time and if i remember correctly i had similar a similar problem then..any advice would be great,thanks in advance...

ZLover4Life

LMAO.

First off, you cannot disconnect recirculation valves and have them operate as blow off valves. A blow off valve is closed at idle to seal the intake system, the OEM recirculation valve is open at idle... when your genius mechanic disconnected them, he created a HUGE vacuum leak. Leave the recirculation valves properly connected. (I'm still laughing at your "mechanic" about this. He did *not* know something that the rest of the Z32 community didn't. Those who want the sound know that they must purchase a proper blow off valve or modify the insides of the recirculation valve to be closed at idle - usually involving stiffer springs.)

I would guess you have other vacuum leaks. Search TwinTurbo.NET for "boost leak tester"... it's basically a plug that fits into the intake T (where the filter is) and connects to an air compressor so you can pressurize the intake system (don't go more than 5psi). You'll be able to hear air escaping from any leaks.

Beyond that, test your injectors. 91 model year means I wouldn't be surprised if you had bad injectors. Remove the connectors, use a multimeter to read resistance across the injector leads. Should be 10-14 ohms. I'd bet at least one of your is much higher.

Goofyz

What RPM is your idle appear to be on the tach?
Have you checked the timing?
Have you checked to see if you have a dead cylinder?

Idle shouldn't be 1000 unless you are running the A/C, even then I think around 900 is factory.

It should idle at 650-750rpm.

I am not sure what you mean by, "while driving...rev's drop all the way down to 1000rpm then back up again", can you elaborate?

I think your mechanic tried to adjust the Idle valve to compensate for his self inflicted vacuum leak. That or timing (twisted the CAS), or maybe a cylinder due to bad injector or coil or plug.

gx2

Thanks guys 4 your help,I actually have a boost tester so hopefully tomorrow I can get working on the car,what I ment about rev's dropping while driving is when you accelerate to say 60 mph and u ease off the throttle to hold at that steady speed the rev's will drop way back 2 idle then back up,it's as if u can't hold a steady rev..also while accelerating there is alot of hesitation and spluttering.now that I have them pipes back on it does idle between 750-800 rpm but still feels rough..

ZLover4Life

Test injectors, post results, and we'll go from there.

gx2

She's alive again :-),done a boost test,it was leakin around the oil filler cap,thank you so much guys 4 all your help!merry Xmas to you all!