chaseincats

Sorry to bump a 10 year thread up but I'm a bit confused. Should I adjust my TPS so that the idle pin disengages from the center pin with pedal movement or at 1400 rpm?

So I took it out, unfortunately there was traffic but after fiddling with it I definitely have control over the idle again. I really moved quite a few teeth on the black gear (maybe 13?) and got the car to cruise at 14.7 but it did really feel anemic so I dropped it down a few teeth. That said, there really was too much traffic to get reliable numbers so I think I'm going to put this on hold until the weekend when I can take it on the highway and get better numbers for you folks.

Well here's something interesting - I took the cap/diaphragm out last night to glue a tiny pinhole and now the bottom hose port not longer holds vacuum but the top now does. I think I'm going to plug the big hose directly into the canister and end this back and forth with the can.

Haha those numbers will be coming late afternoon. I'm going to run/tune it the evap disconnected later today - that way we take the potential vacuum leak out of the equation. Once it's set, I'll reconnect evap and see if the numbers change with it connected probably on Thursday. We're so close I can taste 14.7 lol Just to confirm, ideal would be this, correct?: Idle: 14.2 Cruise: 14.7 WOT: 12.3

I went to a local junkyard today that has some of these cars and grabbed a ring and diaphragm (you are absolutely right - there was a pinhole poked through where that dimple is). While I was there, I brought my vacuum hand pump and tested the cars on the lot. A bunch of them (mine now too) held vacuum on the larger lower hose but none held vacuum on the upper smaller one even though the diaphragms looked good...

So I went downstairs and popped the cap off the canister and took a couple of pictures of what I found. The diaphragm doesn't seem to be torn so I flipped the diaphragm over and put the cap back on (pictured is how it was originally) to see if that was the issue then tried my vacuum gauge but it sounds like vacuum is escaping around the cap. Any ideas? EDIT: the diaphragm was leaking around the sides and had some small tears. Since these are nla, can I just plug the big hose directly into the top of the canister? That would kill the on-demand part from the throttlebody but would that allow the canister to still function?

It seems neither inlet holds vacuum well. While the big hose's end won't hold vacuum at all, the smaller hose's valve can be pumped up with my hand-held vacuum gauge but the needle quickly falls after you stop pumping. I did try running the car last night with the large hose plugged into its intake manifold port (I didn't have the smaller one plugged in for whatever reason) and sprayed the canister's valve with starter fluid to see if the engine idle changed but oddly it didn't. How can it be leaking vacuum but not raise the engine idle when sprayed?

I wanted to avoid that stuff but if you think that's the only way then I'll go grab some. You need to wait 24h before starting the car, right? As a sidenote, could it be that since my gasket doesnt have the other side of the screw holes, the screws are bowing it out, creating the leak? EDIT: Do you think its possible to fix my carbon canister's leaky vacuum valve? Are these even serviceable?

@madkaw It's strange because I used some light sandpaper and sanded both the intake and and cold start valve side a well as the gasket and it still didn't work. @Captain Obvious The CSV definitely is used in the winter since I think it is triggered when the coolant is below just 50 degrees (even got a new one when mine died) lateron I wired it so that it triggers during each start regardless of outside temp because the car just starts so quick with it - very satisfying haha. I later figured out though that if you are starting it before the engine has time to cool it basically floods the mixture and you will be stranded until the engine cools down (ask me how I know) so I undid that. What do you mean by silicone sealer - do you mean RTV gasket marker? I was going to head to autozone to grab some gasket paper and cut a new one, but you think a new dry gasket won't do much?

I actually have the perfect solution for you guys. This is what I did and it is a very happy medium between a zippier car but without the issues of driving a super light flywheel: https://www.californiadatsun.com/flywheel/lightened-resurfaced-balanced-steel-non-turbo-225mm-flywheel.html The car definitely is quicker but not a pain to drive at all. I paired that with the 2+2's 240mm clutch kit for extra grip (the owner of that site can find you a 240mm flywheel if you call and ask). It was professionally lightened/balanced from a 23/24lb flywheel (the 2+2's is heavier of course) to around I think 17-18lb (I don't remember).

Looks like there's definitely egg on my face - I will be eating crow for dinner. @madkaw @Captain Obvious There was indeed a non-trivial vacuum leak coming from the cold start valve's gasket. Regarding the valve on the carbon canister, are those supposed to hold vacuum or are they a pass through because mine seems to bleed vacuum on this vacuum hand pump I got. After covering the cold start valve inlet hole, the gauge's idle went from 17 to 13 immediately - I think we're onto something. The cold start valve gasket had some bumps and unevenness to it which I sanded down and it still leaked after I screwed the bolts in with vigor, so it looks like I need a new one of those. I don't understand how it was leaking though as there are no rips...

Ok, so update for you guys: I went to autozone and grabbed a handheld vacuum pressure tester and discovered that my carbon canister valve didn't hold vacuum and was creating a vacuum leak when the pedal was pressed (this is supposed to hold vacuum, right?). So I disconnected the T-connector to the throttlebody and capped the hose port on the intake manifold and now I'm able to get to the 14s with a WAY leaner setting but the idle was still pretty lean up there. I tried what @Captain Obvious was saying and started it then watched the gauge as I unplugged the TPS connector at idle and it did lean out, so that should be working. I checked my altitude switch and that is set at off currently. I've smoke tested the engine a few times so it shouldn't have any leaks in the AFM boot etc though. The engine is warm now, so I'll wait until it cools off tomorrow to spray it with flammable chemicals lol. It did occur to me that maybe the idle speed screw seal is worn down or something inside, is that a thing? I have no idea how that looks internally. EDIT: my impatience got the best of me so I grabbed a fire extinguisher and got spraying. There MAY be a vacuum leak in the cold start injector inlet (I was messing with this recently). Going to grab a pack of cigarettes and a pump BBL.

I'd prefer not to mess with the distributor it is right bang on factory spec along with all the other sensors/contacts/valves etc (I went through the engine tuneup chapter of the FSM).

I'm pretty sure it's working - the vacuum bladder holds air and the plate is movable but I've never tested it with a vacuum pump. That shouldn't affect idle richness though I'd think.

WOT gets to low 13s Timing is at factory which if I remember is 10 degrees btdc Premium 93 octane Off cruise that lean felt pretty anemic There are absolutely no vacuum leaks in that engine at all - I've smoke tested it a few times and found a big one originally but it is perfect now The engine runs well enough at idle that you can put a glass of water on the valve cover and you won't get ripples so it isn't anything internal that's the issue

So I just spent a lot of time playing with the AFM to get it to cruise at 14.6 but I cannot get the idle to sit at less than 16.5 which is way too high with that setting on the black gear (brought the idle screw all the way in). Should I re-richen the black gear a bit and call it a day or leave it like that? I hear tiny little pops in the exhaust when holding it at 3k in my driveway (I did the testing under load though, that was just an observation as I didn't hear pops while driving). I have tested my coolant temp sensor and it is within spec of the FSM and set my TPS before installing the gauge by following the atlanticZ page so my system is setup correctly.

@jonbill Freeway speed sits between 12.3 and as low as 11.9 - I think it's safe to say I need to play with that gear a bit. Am I going to me really turning this wheel or will just a couple of teeth do it?

Stock L28 with original bosch injection. I was reading that with today's ethanol fuel levels, running that lean isn't good for our engines. Or is that a wives tale?

Good to know. I'll take it on the highway tonight and let you know what it says. I just changed the idle to 14.7 now, thx.

What rpm would you say is 'cruise' so I can have the pedal held when tuning it?

So you're thinking I should lean out the drive gear and re-richen the idle a bit? I thought the idle was supposed to be leaner than cruise, no? I did notice after leaning the idle out that the car off the line is a lot zippier. I almost smacked my garage door when turning away from my house the first time I drove it post-tune lol.

Ok gang, here come the numbers on my stock EFI system as-is: Idle: 13.4 2500 rpm shift points: ~13.2 WOT: 12.4 Highway cruise: TBD (will update tonight) NOTE: This is without the high altitude switch on (when enabled it seems to lean the mixture out 1 full point) Changes made: leaned idle to low 15s, will adjust big drive mix gear at a later time. @AK260 Is that chart (except for the ones labeled WOT) for idle, or highway cruise (4k-4500rpm)?

So I just finished wiring the gauge and will be taking it in tomorrow morning to have the o2 sensor bung welded in then I'll drive back and give you guys some numbers. Stock l28 with EFI. I pretty much followed this guys video (even got the same gauge): https://www.youtube.com/watch?v=XS_f2ciKVqo&t=9s

https://en.wikipedia.org/wiki/Air–fuel_ratio_meter#Wide-band_sensors

Again, this is not measured in the intake manifold, there is an o2 sensor welded into the exhaust headers.