OK, here goes. Engine has been swapped, all deletes undertaken including boost solenoids, egr, aiv, carbon canister. I have what appears to be a vacuum leak occurring causing a hunt that I just can't find. Nissan data scan shows no faults, everything runs except a/f jumps around from 101 to 108. Now here is the oddball, disconnected the Factory boost gauge and the engine stabilizes. Tried a boost leak test and managed to get 7 psi in but depletes within seconds. Any thoughts where to look?
This is your answer. Factory boost gauge sensor box or vacuum hose that goes to the sensor... Split boost hose at the boost sensor? Faulty sensor?
Sensor functional as it is following my aftermarket gauge. I should probably elaborate aswell, it stabilizes with the hose removed and left unblock, allowed to suck air into engine, almost like the engine is creating to much vacuum, it sits at around -6 mmhg. I'm thinking maybe a failed pcv, but I did do a blow/suck test and appeared functional.
yep sounds a bit like the idle control valve is playing up, also pay to check the cold start one as well..... another thing that can cause idle hunting is a bad alternator/battery, and we could never get that thing to keep a charge.
Cheers stu, new alternator went in with new motor, like I said datascan shows everything in the green and perfect, I'll adjust the base idle on weekend. Hoping to drop it down rondo the front bar today if I can get hold of rod
Seemed to clear it up a fair bit, can't set base idle without it hunting but I've flattened it out enough to drive, goes like a cut cat now, will push the are out in second at half throttle and makes for a grin on the face
Ok im ready to tear my hair out. Changed out iacv and air regulator, afm, cas, water temp sensor, all plugs checked/cleaned, all injector and coils firing, engine idle adjustment as close as possible to 850, tps is .42v and idle stop closed, timing both mechanical and ecu 15 deg. Car is factory manual. Engine and loom both swapped from an auto donor car as the loom in manual car was stuffed, was running faultless in donor car. Have done egr, aiv, boost solenoid, carbon canister deletes during plenum pull. Fresh cleaned injectors and rebuilt turbos, dual stage boost control. Now I have hunted and hunted for an air leak, was unsuccessful comducting a boost leak test as it would reach 7 psi, disconnect airline and it would bleed off within a matter if a couple seconds (suspect I was doing something wrong here?) Its weird, it will idle fine, then stumble, recover, and repeat every 20 to 40 seconds or there abouts. Touch throttle and it hesitates, took it for a drive on weekend and plenty of power, seemless driving except for trying to stall as coming to a stop. No ecu faults, aac at 12-15%, im frigging lost.
Whoops, did it wil the butterflies closed. It slowly build up to 7-8PS and then dropped off when the air source was removed so I honestly don't think that is going to be the issue. I've got the two Vac lines below throttle bodies blocked off but my other zed is the same with no issues. I'll swap out the tps tonight and reclean/adjust throttle bodies and see if that makes a difference. I'm guessing adjust throttle bodies so fully closed but bypass port still visible. I disconnected Oxy sensors one at a time last night also with the problem still existing. Anything else to start to look at.
Also I reused the manual alternator harness with the auto engine loom, as far as Im Aware the only time wiring needs touching is if the car was an existing auto being swapped to manual, have I possibly misses something here? I'll have to purchase the full version of nds 1 for my computer so I can do a bit more digging as the Android lite version has a little less functionality then I would like
I had a boost leak on mine I had a hall of a job finding, it ended up being the breather on the drivers side from the rocker cover to the intake, hard to see I could hear the hissing (it was bleeding pressure faster than I could search) but not find the pipe until I really started digging.
Yeah that's my next fun job, pull all the hoses back off, put aviation sealant on all surfaces and retention everything. Got a leak from one of the cam seals aswell I suspect to so I will have to fix that while half the motor is back apart. Should never had touched them, always the way, if it ain't broke don't f%#K with it, oh well.
I had similar symptoms after doing the aiv delete and replacing vacuum lines.. It took a while to work out but I ended up finding a vacuum line diagram in the tech section and found that it was caused by hooking a vacuum line to the wrong spot ?. I was tidying up the lines from memory (was many years ago) and ran them a neater way thinking that all vacuum points were the same (turns out they are not). With me it was only after doing the delete and changing line positions that I had the problem so it had to be what I had just done. Just had to persevere to find it. Good luck Dave
Car is factory manual with auto loom.. is the ECU auto or manual? When you hit the throttle, do the revs dip for a second, them come back up? Timing belt not out by a tooth? How are your spark plugs? Fuel pressure?
Manual ecu from a known good running car. I just changed timing belt before fitment, marks lined up and teeth count all good. Yeah it does dip then need to give it gas to recover. recovers, looks like most of the idle issue is settling down, just the hesitation issue mainly now. Plugs I fitted ngk copper plugs gapped to 0.813 and fresh, haven't tested fuel pressure yet so will look at that this weekend
OK I'm ready to pull my hair out now. Still hesitant if I touch throttle lightly, if I give not a hard rev no problem so I'm still leaning towards the tps as possible candidate. I managed to set up my boost leak tester, happily accepted 10psi and the only tiny leak is from the recirculating valve pin holes on diaphragm, not a biggy or enough to cause this issue I believe. It's absolutely minute and once pressure drops to 5 psi they stop and holds pressure so iys definitely not a vacuum issue. Fuel pressure is a solid 39psi at idle, and now it is running rough. I will swap the plugs out again for some new coppers tomorrow and swap the ecu for an auto one to see if that makes a difference, otherwise I'm freaking lost. Is there an earth over on the drivers side alternator harness I might have missed other than the one on the alternator itself? As far as I'm aware there is that one, the two bunches up on the rear of plenum, the fuel rail to lower plenum, the one near the a/c compressor. Also, when an electrical load is switches on such as the headlights, the aac value on data scan shows no movement/change, by rights that should be increasing shouldn't it to bring the idle up to compensate?
