Adjusting the TBI on an 89 Pathfinder with a VG 30

[krmiller07]

Does anyone know the procedure for properly adjusting the TBI on a VG-30 V-6 ? I am trying to figure out why,when I set the idle speed to the factory setting and the turn on the fan or A/C the idle speed drops to about 4-500 rpm. I noticed 2 adjustable 'dash pots' on the front of the TBI as well. I have a 5 speed manual trans. The only way to keep the rpm's up to a decent level with the fan on, seems to be by turning the idle speed up while the A/C is running...to about 900 rpm's. But when I shut it off the engine idles at about 1100 rpm's in Neutral. I'd also like to know how you adjust the idle mixture setting as well.

 

Thanks for any input, I've called local dealers and nobody seems to remember how to work on the TBI engines.

 

krmiller07

Edited July 11, 2009 by krmiller07

[cstem]

Does anyone know the procedure for properly adjusting the TBI on a VG-30 V-6 ? I am trying to figure out why,when I set the idle speed to the factory setting and the turn on the fan or A/C the idle speed drops to about 4-500 rpm. I noticed 2 adjustable 'dash pots' on the front of the TBI as well. I have a 5 speed manual trans. The only way to keep the rpm's up to a decent level with the fan on, seems to be by turning the idle speed up while the A/C is running...to about 900 rpm's. But when I shut it off the engine idles at about 1100 rpm's in Neutral. I'd also like to know how you adjust the idle mixture setting as well.

 

Thanks for any input, I've called local dealers and nobody seems to remember how to work on the TBI engines.

 

krmiller07

 

 

Try calling the independent japansese specialists in your area. I find a lot of the old dogs from the dealers end up there to finish out.

 

Pass on what you find out.

[MY1PATH]

on the passenger side of the tbi just above the 2 coolant hoses are 2 Ilde up solenoids. one opens when the A/C compressor is running and the other opens when there is an increase in electrical load(blower, defogger etc) they have either failed, not conneted to the harness or the ajustment screw needs to be lootened to allow more air to bypass the butterfly when they open.

 

the ajustment screw is a large flathead between the 2 solenoids. it may be covered with sealant or rubber. when ajusted correctly the rpms should go UP 50-100 rpms when the solenoids open.

[krmiller07]

on the passenger side of the tbi just above the 2 coolant hoses are 2 Ilde up solenoids. one opens when the A/C compressor is running and the other opens when there is an increase in electrical load(blower, defogger etc) they have either failed, not conneted to the harness or the ajustment screw needs to be lootened to allow more air to bypass the butterfly when they open.

 

the ajustment screw is a large flathead between the 2 solenoids. it may be covered with sealant or rubber. when ajusted correctly the rpms should go UP 50-100 rpms when the solenoids open.

 

 

Hey thanks,

I tried adjusting the solenoid in the front of the TB ( loosening the lock nut and turning the screw inward) all that seemed to do is increase the idle speed when the fan swithch is off along with the A/C ? Do the 2 solenoids your talking about serve as some sort of 'fast idle' as well? Becauswe during the winter here in MN, I have to generally turn the fan on to get the engine to idle higher than when its warmed. I also remember having a brand new 87 Pathy and it always started up cold and idled at, at least 1500 rpm until it started to get some temp in it. Then it would gradually idle down to about 800 rpm when it was fully up to temp.

I'm going to look into those solenoids, but I haven't touched anything aside from adjusting the idle speed and the front solenoid.

It's really annoying to turn on the A/C and have the damn thing nearly die at stoplight etc. So I cranked up the idle to about 1100 rpm in neutral, 8-900 with the A/C on.

 

Any help would be greatly appreciated. BTW I have tried contacting some of the smaller non-dealer shops, including those who 'specialize in imports' and they all look at me with a 'deer in the head lights look' and a Talk to the dealer...answer !

 

krmiller07

[MY1PATH]

no the fast idle is controlled by a unit on the front of the TB w/ a coolant line goint to it. the speed it bums to is controlled by the Fast idle screw which points skyward.

the solenoids are on the side they look like 2 hexagon shaped plugs one is about 1" and the other 1.5". there is no lock nut, the screw is imbedded in the side of the TB bewteen these 2 hex cyl. if it has sealant, or dirt over it you will not see it because it sits flush insde its sleve.

 

I have a spare TB maybe I'll clean it up and post a parts/function beakdown w/ pictures for everyone who has the TBI because there is really allot of peices to the UNIT all so close together and some very similar to the adjacent ones.

[Madcat]

Would be it ok for you MY1PATH if I beat you to it? I have a tbi totally cleaned out and disassembled. I need a TBI gasket kit, but I can still take some photos. My buddy's camera is a few years old but takes some big pics.

Edited July 15, 2009 by Madcat

[krmiller07]

Would be it ok for you MY1PATH if I beat you to it? I have a tbi totally cleaned out and disassembled. I need a TBI gasket kit, but I can still take some photos. My buddy's camera is a few years old but takes some big pics.

That would be a great help. I've tried locating some service manuals on this and i can't find anything. I've also tried locating a factory service manual to no avail.

 

 

Thanks again,

 

krmiller07

[MY1PATH]

That would be a great help. I've tried locating some service manuals on this and i can't find anything. I've also tried locating a factory service manual to no avail.

 

 

Thanks again,

 

krmiller07

Ok I did a component listing, Theres allot of stuff listed w/ pictures and short descriptions. Hope it helps.

http://npora.ipbhost.com//index.php?showto...mp;#entry416255

[Madcat]

Im not sure if the service manual I have IS a factory service but it gets pretty verbose about the Pathy. Im having some problems with my pal's digi camera, so Ill try to find another way to take pictures. If I had a scanner I'd scan the manual too.

[MY1PATH]

if you want to post those on my TBI thread so that we have one great collection of information that may pove to be a benifical tool for many future members all in one thread.

http://www.nissanpathfinders.net/forum/index.php?showtopic=23251

[krmiller07]

if you want to post those on my TBI thread so that we have one great collection of information that may pove to be a benifical tool for many future members all in one thread.

http://www.nissanpathfinders.net/forum/index.php?showtopic=23251

[krmiller07]

Ok, I took out both solonoids on the drivers right side or (passenger side) and they both function properly and look to be in great shape. I tried turning the slotted or (flat head screw driver) adjusting screw both in and out, and didn't notice any changes in idle speed, with either with the A/C on, or off, or with the blower on. Are you sure this screw isn't some type of 'idle mixture adjuster' ? Also if you look real close, on the front of the TB there are 2 adjustable 'dash pots' both with small (maybe 4-6 mm) lock nuts on them. One is fairly obvious to see, the other is somewhat hidden close to the TB and down,close to the throttle shaft springs and intake manifold. What is the function of this ? 'Idle up' for the A/C or electrical load ?

 

Thanks,

 

krmiller07

Edited July 19, 2009 by krmiller07

[MY1PATH]

One is a dash pot and has not lines running in or out of it it just prevents idle from over dropping when you let off the gass the other is for your warm up fast idle and is controlled by coolant lines, both are metioned in my thread. and the screw directly contolls the air passage from those solenoids I have a dissasembled TB sitting rt in front of me and I can see thru the passages.