924Board.org

[bureau13]

Interesting. I have the smoke tester hooked up to my compressor (set pretty low). I've never tried to plug the exhaust before but I could give it a shot. I usually don't even bother plugging the intake at the AFM because it was leaking through the torn boot before it started coming out the air cleaner, but I have a way to plug that. Makes sense to create some more pressure.

For whatever reason I've never tried the carb cleaner trick. Maybe time to give that a try. I just thought if there was a leak the smoke tester would find it, but that's not always true if it only happens when there's a vacuum, as you say. One other thing I forgot to mention, even though idle seems good, it is showing only about 11 on the vacuum gauge, whereas I think it's supposed to be closer to 17 or 18. I'll try this stuff tomorrow after work.

[bureau13]

OK, an update. I sprayed some carb cleaner into various places that seemed like they may be prone to vacuum leaks while the engine was running, didn't notice anything. I will have to do this again though because...

I decided to seal off the air cleaner properly this time and smoke the car for a while, and sure enough, I found two leaks. Neither were as obvious as the one from my torn compressor intake boot, but still. One appears to be the top of he throttle body, right under the little cam thing. The other was from my #2 injector. So I need to redo the carb cleaner test and specifically target those areas. I'm not too sure if it will show up that way though, because my idle is fine. I don't have a problem until I give the car gas...even reving it in neutral it's not obvious (although you can detect it if you're paying attention).

I'm not really convinced either of these is the issue, but they both clearly should be addressed. Is there some reason these would have a greater impact than a larger leak in that intake boot?

I see some injector o-rings at FCP Euro that I will order. I'm not really sure what is available for the throttle body, however. It looks like the Ideola site used to have a kit made specifically to address this, but sadly it's no longer open. I will reach out to see if Dan has any extra kits lying about but I'm not hopeful. Anyone know where I might find this stuff? Or should I just take it apart, fish out the o-rings (or what's left of them) and go find a match?
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[bureau13]

Dan got back to me and pointed out that Arnnworx sells the throttle body rebuild kit, so I've ordered one of those as well.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[bureau13]

I just rebuilt the TB using the Arnnworx kit. Either I got another part mixed up when I took my old TB apart, or I've failed to put back a small, thin washer. I only see one referenced in the instructions, the one that goes under the circlip on the TPS side. I definitely put that one back. However I have another one, which I don't see referenced and I don't recall taking off. Very annoying, I'm terrible at documenting as I go.

The other thing I've noticed: When I rotate the shaft to open the butterfly, I can detect the click in the TPS for the idle switch, but there is quite a bit of travel before I hear the click. For an idle switch, I would expect it to be very close to the closed throttle end, but it's not, really. It seems closer to the middle of travel, to be honest. Unfortunately I didn't think to listen for that before I took it apart, but this is one area I did document with pictures, and I have it on just like I took it off. Maybe it's normal and I'm just being paranoid...
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[bureau13]

Working on that injector vacuum leak now, FCP Euro shows o-rings. Which, having never pulled the injectors out of this car, that made sense. They're fairly thick, green o-rings. Well, there are no o-rings to replace, unless they've disintegrated completely. The injectors threads into a threaded sleeve, which in turn threads into the head. There is just a thin copper crush washer between the injector and the sleeve.

Another interesting thing...I had done some research (clearly not enough) and I thought that sleeve was supposed to be something fragile, some sort of ceramic. Mine are metal. I've seen metal aftermarket ones, maybe someone has been in here and replaced them? Or maybe the later cars got metal ones?

Anyway, looking at PET it doesn't show an o-ring...what I thought was an o-ring is apparently just that crush washer. Anyone ever use PTFE thread sealant on this stuff to prevent leaks? Or do I just replace that crush washer and call it a day?
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[Fifty50Plus]

I believe the NAs have the green O ring and the turbos have the screw in type.
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1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car

[bureau13]

Yeah, that would make sense. FCP Euro specifically lists the turbo in their fitment guide, but it must be a mistake.

[bureau13]

Update: Rebuilt TB and put a new crush washer, along with some PTFE thread sealant on the threads of both injector and bung. No fuel leaks and no more vacuum leaks...I smoke tested it (with the intake blocked off, no short cuts) for a while, no hint of smoke.

Started it up, the vacuum is now about 18 inHg, about where it should be. Makes sense. Idle is high...1500 or so, even with the idle screw all the way closed. Not sure I like that. Mixture was about where it was before, mid-13s, so I could lean that out a bit and see what that would do but I haven't bothered yet, because as I understand it, that is just idle, which is not my problem.

Went for a test drive: SAME *&^%$ING PROBLEM! WTF. I would guess that I've been chasing vacuum leaks, and vacuum leaks are not causing the issue, despite the fact that the symptoms were consistent. At least I wasn't fixing things that didn't need fixing. Vacuum leaks are bad, I had them and I fixed them. So, good for me I guess.

I'm still intrigued by the idle switch click. It's happening nowhere near the first part of travel. Say the car never trips that switch. What would it do? I'm not sure how the idle switch works on this car, there are no fuel maps, etc. I'm pretty sure in my light throttle test drive I'm not tripping that switch. I had assumed if it were a problem, it's one I just caused in the rebuild, however, and obviously this problem predates that.

Frustrating!
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[bureau13]

Re: TPS/idle switch.

I see some inconsistent info floating around. I found an old post where someone says the TPS just sends a WOT signal. If that is all it does, then that click is a WOT click and that makes MUCH more sense.

On the other hand, I see threads where people are trying to test their idle switch, so I'm confused. Maybe that's not a part of the TPS?
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[bureau13]

Update. Note: Some of you may have seen this on Facebook, so sorry if its a repeat. I just am stuck, so trying to get any expert eyes on it that I can.

So, to recap:

Car starts and idles fine (a bit high actually) AFR is fine.

I found and fixed vacuum leaks in the low intake bellows, pop-off valve seals, injector #2 seal and the butterfly shaft seals on the throttle body.

Verified that TPS switches are acting as they should, per the wiring diagram.

Verified that the frequency valve is active when the fuel pump relay is jumpered (I have no way to measure exactly what it's doing, but it's doing something, so I have no good reason to suspect it).

The symptoms are as soon as you give it throttle to drive down the road (very light throttle and <3K RPMs, no boost) it spikes lean and bucks and jerks. You can limp it down the road but it's basically undriveable. It does this cold or completely warmed up.

I have a new fuel filter to put on, because why not, but I doubt that's it. From what I can tell, the WUR isn't doing anything drastically different in this scenario from what it does at idle, so I don't think that's the issue. Doesn't seem like a fuel distributor type of issue either. Please correct me if I'm wrong.

Fuel pump? Again, when jumpered it runs fine. Runs fine at idle. I have not tried the drive test with it jumpered, not sure it makes sense for a relay to cause something like this, but I will try it.*

I'm really at a loss. It seemed so much like a vacuum leak problem. Then I had myself convinced it was the frequency valve or controller. But those all seem fine.

*Now I have to wait for a new throttle body-to-upper charge tube o-ring, because I pinched it in half again. This because I was having to remove it and put it back multiple times, trying to get the upper and lower charge tubes to mate up after putting in that *&^%ing bracket. That will teach me...I've had the car four years without it, no issues. I am not loving this car at the moment!
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[Fasteddie313]

Still sounds like a vac leak..
High idle must be getting air on the vac side of the tb somewhere..

Maybe try plugging the brake booster line and such.. Maybe you have a blown diaphragm in one of the vacuum things or something..

Unless you adjusted your tb butterfly stop wrong?
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80 Turbo - Slightly Modified

[bureau13]

I marked the throttle plate and everything, but that thought did occur to me. How "air tight" should it be, when closed? Because there are definitely small gaps.

That being said, my vacuum, which used to be about 12 in Hg, is now about 18, which seems like what it should be. I'm not seeing any smoke from the smoke test, but even all those leaks that I fixed...none of them put out as much smoke as would blow through that idle mixture adjustment screw on the fuel distributor before I put a cap on it, and I ran like that without any of these problems before. I feel like the high idle is something other than the bad problem. I still don't know what's going on with the light throttle lean spikes, etc. Driving me nuts...

[Fasteddie313]

Butterfly stop should be just barely to where the butterfly isn’t hitting in the bore.. Just a touch to keep it from wearing the bore basically..

Only vac leaks on the vacuum side of/after the tb would cause a high idle like that.. Before the tb wouldn’t do that..
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80 Turbo - Slightly Modified

[bureau13]

They would still show up with a smoke test, wouldn't they? Also, wouldn't they tend to lower the idle vacuum?

In any case...I didn't have a particularly high idle before I "fixed" stuff, so the two problems do not seem to be the same root cause.

[kondzi]

Didn't have time to read the whole thread... So sorry if I misinterpret something

1. Fixing one thing in these classic old cars usually means there will be something else to fix soon. You might have done good job with TB rebuild, but something else, not considered before is messing this up.
2. Vacuum leak is usually observed with idle and low RPM range. When you open TB, the percentage of air via vacuum leak is minority and doesn't change much.
3. Can you record these leans spikes on the gauge by your phone or sth and share it? I've seen faulty WB controllers behaving strangely. Do you feel these spikes on the way how the car rides, or it's just the reading?
4. You can try to blow compressed air into intake (via sealed and opened TB) and listen with your ear where it's coming out of the pipes. Just an idea, but helped me once.
5. Lean AFR spike can be caused by misfire. Oxygen is not burn resulting in lean reading at the WB controller. Maybe that’s the reason?
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Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)