Misfire and hesitation at low throttle

Same thing happened when I tried to r&r my tb.. well almost.
The head of the bolt started to strip. So I just put it all back and it's been fine since then (8 months ago)

I think he has the driver's side PCV vent tube plugged at the plastic lnlet pipe? Should be fine in regards to the breathers.

Also, IIRC, there is a small vacuum fitting under there by the throttle. Perhaps, it's snapped off? I even think that one is blocked by the throttle plate when it's closed. So if this is open, it would explain why you have a massive vac leak and stumble at the off-idle transistion. When you pressurize it, maybe move the throttle and see if air blasts out.

With regards to the PCV line the driver's side is now hooked up normally to the intake pipe. I'm about to install a new PCV on the passenger side and hook up the OEM hose to the manifold to make sure that the breather isn't the problem.

I noticed the vacuum fitting under the throttle, and it has new silicone hose on it. But that appears to be where the air is leaking, even with the throttle closed. If not, there is air coming out somewhere along the bottom of the throttle body, even after I removed it and installed the proper gasket.

The air actually seems to come out of the bottom of the throttle body less if I open the throttle. Perhaps I'll try another throttle body after I replace the PCV valve, since I do have one around somewhere.

I'm hoping it is either the PCV or the throttle body for some weird reason, because I'm not sure what else it might be. Also, pressurized with the throttle open did not reveal any noticeable leaks down the line, at least not that I could hear, though obviously the air must be escaping somewhere.

EDIT: Turns out I don't have the extra throttle body I thought I did. Any ideas on how to know if the TB is the problem? Shouldn't be the vacuum lines to and from the TB as they are new.

"With regards to the PCV line the driver's side is now hooked up normally to the intake pipe. I'm about to install a new PCV on the passenger side and hook up the OEM hose to the manifold to make sure that the breather isn't the problem."

Just take that line off and plug the port on the intake pipe. Leave the line open for now. When you open the throttle, you are probably losing all your test air out the tailpipe. Shove a rag or something in the exhaust, and listen again when you crack the throttle to test the plenum area.

You can use rtv as a tb gasket, it may seal better than the oem gasket.
As for the small vacuum nipple that's on the under side of the TB, you can simply just put a vacuum cap on it. That is used for the egr solenoid, which you Have deleted.
Also are you using all oem na intake piping?
The pipe that comes after the maf has a nipple on it too

les, you are right about the TB vacuum lines, I traced it and I have it capped off anyways because it went to the EGR, so I'll just cap it off wherever that line originates. You are also right about the intake piping, I thought I grabbed the 86 intake piping to reinstall but it was actually from an 88 NA, the 86 piping does have the nipple for the carbon cannister, so I'll hook that up. I guess I could take off the TB again since I'm doing other stuff anyways, and I have rtv around.

Thanks for all the advice so far everyone.

Here's what's I've noticed now. The bottom of the throttle body still appears to leak for some reason (maybe need to use the rtv to seal), but with the throttle open and the rags in the exhaust, I found what seems to be an exhaust manifold leak on the passenger's side towards the front of the car. I can't tell if the manifold is cracked or the seal is just bad, but I have new gaskets and a new manifold if necessary. Could that be part of the problem?

Also, I noticed something about the leak on top of the plenium that I've mentioned a number of times before that apparantly goes to the vacuum cannister and to to the cruise control. When it is blocked off, the car won't idle. When it is left open, which I did accidentally, the car struggles, but will eventually settle into an ok idle, with some movement. This tells me that I need to adjust the idle with the throttle body screw, because otherwise with the idle stuff deleted there's really not much air going in at idle. The other thing is, with no cruise control I'm not really sure where to route that line, because as I said the inlet and outlet on the vacuum cannister near the passenger's side headlight are very small.

Basically, I'm hoping that by adjusting the throttle screw, attaching the vacuum lines to the proper place instead of capping them, and fixing the exhaust leak will clear this up at least somewhat.

This means that I've got a few things on the list for tomorrow:

1. Fix the fuel line that got pinched and cut somehow. (Unrelated)
2. Manually adjust the idle using the screw to prop open the throttle, readjust the TPS as necessary.
3. Remove passenger's side exhaust manifold, install new gasket and/or manifold if necessary.
4. Install 86 pipe and the line from the charcoal canister to the intake pipe so that the air is metered.
5. Seal the upper intake pipe and leave the driver's PCV line open to air?
6. Check and tighten all electrical connectors and grounds.
7. Install the line coming from the top rear of the upper intake manifold somewhere?

I also have videos with the manifold line both blocked and open, which I can upload if they will be of any help.

I suggest keeping the pcv tubes hooked up to the stock locations. And yes you'll have to adjust your throttle plate since you've blocked the iac.
Also make sure you have no open vacuum nipples.
As for the one that should run to the cruise control, reduce it to a 3mm hose and attach it to the small vacuum tank that's.above the carbon canister

Sounds good for the one that goes to the cruise control, right now it is blocked off.

Anyways, progress:

I replaced the fuel line and adjusted the throttle to idle between 800 and 900, as well as the TPS accordingly. Blocked off the throttle body vacuum nipples and the line at the top of the manifold. Basically, cylinder 5 may have been misfiring this whole time. Now that it can finally idle without completely random misfires, I noticed that it was rhythmic. Unplugging spark plugs showed that the misfire went away when cylinder 5 was unhooked. I'm going to check the spark plug connections, but I think it is more likely to be the injector connection. Either way, I think that if I can get cylinder 5 to fire properly, that will be a major part of the solution.

More observations about the misfire:

I am fairly certain that it is cylinder 5 because it the idle is rough periodically. When I unplug the cylinder 5 wire, it settles down to a smaller periodic pop that is less noticeable. The others don't do this. Basically it idles rough and then actually gets a little bit better when I unplug cylinder 5.

This tells me, then, that I have spark to the cylinder because removing spark changes something. With new plugs, wires, and distributor stuff I would hope so. That leaves fuel and compression. However, I think that I am also getting fuel, because sometimes it will just stop missing for a minute or so. Basically, this makes me think that something in the injector wiring for cylinder 5 is messed up, so I'm going to go searching. I hope the cylinder itself isn't dead because I was hoping to drive this car places over the weekend, but ultimately it wouldn't be a big deal because I have an engine to swap anyways.

I can take a video of the behavior with 5 plugged and unplugged, but I am fairly certain that is where the misfire is originating from. If I unplug the other cylinders, I can hear their misfire as well as the rougher misfire from 5, if that makes sense. Unplugging 5 seems to change the misfire from a rough "bad combustion" sort of thing to the simple pop since nothing is happening.

It's common for those injector connections to corrode and turn green.

I'm currently rewiring to pre campgain, but that doesn't appear to work. I may just refresh and solder the batch fire connections.

Edit: pre campgain just made it worse, but even refreshing (cutting off the ends that were being used and re stripping) the factory wiring and soldering it back left the same misfire. Could it be a clogged injector? If so can I throw the 88na injectors I have into the car?

Videos in case it helps: https://www.dropbox.com/s/27nx4he1j2…2020.49.56.mp4

https://www.dropbox.com/s/m9t6hy0fg1…2020.51.05.mp4

I'm thinking that I might install the 88NA injectors just to see, I know I need the 88NA ecu which I have, though it is for an auto. Other thing is, the oxygen sensor doesn't match, so how much of a problem will that be? Either way, I can check out the original injectors when I get them out.

If your o2 doesn't match it won't run right, I was using an na o2 sensor on my na2t and it ran way too rich all the time… put the turbo o2 (different part numbers) and it feels way better and no backfires at all
Just fyi
One other thing you can do is while the engine is running take a long flat head screw driver and hold it against the fuel injector connector and see if you can feel it ticking. They should all tick the same, also you should ohm check each injector itself, every injector should be within .2 of the others.

Based on http://redz31.net/pages/fuel.html, it turns out I can run the 88 injectors with the 86 ECU, so the O2 sensor won't be a problem.

However, I installed the newish injectors, and there was no change. If anything, it wants to die a bit more at idle, though that may just be because it was cold. Anyways, I suppose fuel deliver isn't the problem, and spark delivery isn't the problem, so it must be vacuum somewhere I'm missing. But I still don't totally understand why that would cause a rhythmic misfire, as if one cylinder was causing the problem every time.

Anyways, I'm out of ideas and for now pretty much out of time, but if you have any suggestions I'd be glad to hear them.

Make sure head temp sensor and it's short harness are in good shape. Sometimes people rig it with a resistor as a "repair".