Alright folks, I'm back.

Three weeks after the engine transplant, the car is in decent driving condition and I'm safely thinking its pretty reliable again. However [ut oh, i know!], when sitting at idle or in neutral while moving, the damn thing still has a speratic idle, then tries to sputter and die! It's kind of like a surge. YEA YEA YEA< i know, check my IACV right? -- I did. I bought one on ebay (probably used) and probably not working properly. It's much cleaner than my old one and this one still has the little screen inside, but I fear it may be faulty.

I have an exhaust leak where the exhaust manifold hits the down pipe and i'm waiting on a new exhst. header and downpipe (do in 2 days! yaya~)! --- The damn bolts stripped out during removal of the old ones cause they were nasty rusted and just wouldnt go back in. Some guy quoted me 80 bucks to re-tap and gasket, so I bought a header and downpipe online with all the hardware for 52 bucks, hah.

I also have a new 02 sensor coming.

Notes:

Speratic idle is GONE during warmup and engine is cold.
Speratic idle is GONE if I keep foot on brake and slightly release clutch, but will settle down and sputter after about 10/20 seconds of this.
Sometimes idle will slow down to normal, then it'll slow down way below normal and start to put and puff black smoke( a simple tap to the gas brings back the speratic idle and black smoke goes away.

I'm going to wait on the exhaust header and downpipe before I install the new o2 sensor (pain in the *** removing a rusty old 02 sensor).

Also:

Took car for emissions test; Ran training mode; Car's speratic idle sits between 625/775 rpms. Was getting a RPM Violation and the states computer will not let the test continue if it cannot get a correct RPM reading. The car was around 1400 RPM in third gear at 25 mph, and then it threw the RPM violation. Can anyone confirm what the RPM should be at 25mph in 2nd gear and 3rd gear?

Any tips appreciated guys, i guess if all else fails, i'll go get a brand new IACV (124.99, UGH) and try that out.

 

5 speed or 4 speed trany??

 

In addition to a faulty EACV, a vacuum leak or air bubbles in the coolant system (mentioned in other threads by mxs) might also produce your idle problems. So you also might want to check hoses and connections for vacuum leaks and to bleed the coolant system.

Finally, isn't it also feasible that your idle problem stems completely from the exhaust leak? Maybe you should fix the exhaust leak before replacing the EACV.

 

My 02 Sentra Se-R has a similar issue, When the heat or a/c are on the rpm's will dive every now and then.

 

If the Sentra is similar to the Civic, then the ECU senses and compensates for increased electrical/engine load by increasing the idle rpms. Your Sentra may have a problem in sensing or responding to increased load.

 

I just replaced the alternator as well, The problem was before and after the replacement.

 

Obtain a service manual for your Sentra and determine how it controls idle speed under conditions of increased electrical/engine load. This is where you would begin troubleshooting your problem.

 

I actually have one, thank you for the tip

 

Dude, this is a HONDA FORUM, **** NISSAN!!!!!!!!!!!!!!!!!!!!! RAWR :: BANG BANG :: --- heheehe.

The idle problem was there since the old motor. There was no exhaust leak before and it's idling just the same.

I never thought about it, but I haven't bled the coolant system since the first head gasket I've done on this car!!

Current surguries to date;

Head gasket (twice)
water pump
timing belt

and finally an engine transplant after excessive fluid loss of the main arteries (me being stupid there, sounding like a doctor).

Never bled the coolant system once. Only drained it and filled it as the repairs were complete. --- Can anyone tell me how to bleed the coolant system? I noticed a bleed screw on the upper radiator hose on the cylinder head side, but I sure don't know how to use it!

 

Okay, sorry guys, used the handy dandy search feature and found out how to do it. --- Back in a flash with an update!