# rough idle with throttle hesitation until about 2k rpm



## mvh2011 (Feb 28, 2015)

My last post went pretty far off topic so I'm posting this as sort of an update.

the car is an 87 300zx turbo 5 speed, that's suffering the above problems. cold starts are imposible without the aid of starting fluid after its ran a bir The car starts nice and holds about 1000 rpms for just a few seconds then it dies down to about 3-400 rpms ( will stall eventually if I let it). 

SIDE NOTE, car will only start with timing advanced to about 30-35*before tdc. Barly gets any combustion with HSM recommended 15*

To me these symptoms scream fuel issues but the car holds steady 32 psi+/-2 psi between filter and rail at idle and will peak about 37ish when reved. With vaccume line disconected it will raise to about 42. Installed oe equivalent fuel pump, fuel filter and remanufactured injectors prior to this test. 

Engine codes: fuel temp sensor, cylinder head temp sensor, detonation sensor. These code have since vanished without me doing anything and a code 22 comes up now for fuel pump circut. I am confused as to why they seemingly came and went even tho I can see the fuel temp sensor is absent.

While driving it, it doesn't hesitate as much unless I sit at a nice long red light, but runs fantastic and will throw me back in my seat when I hammer down.

I found that unplugging the maf will instantly boost the horrible 400 rpm idle to 900-1100rpm, and it will stay there. 

I'm at wits end trying to figure this out, what tests can I do to help narrow this down.
(could this be caused by clogged cat or faulty o2 sensor?) The car had sat for about 13 years in the navada desert before I got it


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## ralph50 (Feb 24, 2015)

Have you checked the Idle up solenoid and/or Cold air intake valve (CAI)?

You could also check the ohms on the MAF.

Gut the cat. It will give you a few more horses.


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## BeyondBiscuits2 (Jan 18, 2006)

I'd take a look for vaccuum leaks. A can of brake parts cleaner (ether) or water will do the trick, just spray down your intake piping, intake manifold, hoses, etc. Most vaccuum leaks exhibit a rough idle, and sometimes even misfires, at idle, but these symptoms clear up over 2000 rpms. '80s and '90s Nissans are notorious for bad intake manifold gaskets, so I'd really check between the upper and lower intake, and between the intake and the cylinder heads.


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## mvh2011 (Feb 28, 2015)

BeyondBiscuits2 said:


> I'd take a look for vaccuum leaks. A can of brake parts cleaner (ether) or water will do the trick, just spray down your intake piping, intake manifold, hoses, etc. Most vaccuum leaks exhibit a rough idle, and sometimes even misfires, at idle, but these symptoms clear up over 2000 rpms. '80s and '90s Nissans are notorious for bad intake manifold gaskets, so I'd really check between the upper and lower intake, and between the intake and the cylinder heads.


I've checked for leaks time and time again and I can't for the life of me find any. It feals like it's a fuel/air ratio problem the hesitation doesn't happen constantly to it shows up and goes away. Could this be a maf problem?


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