JohnWongFat

Ok, so not sure if anyone is following this, but I solved part of my problem. The engine running horribly was, in fact, that TPS. My problem was my own doing. There is a lever on the TPS that I had on the wrong side of the lever that is supposed to move it. This probably means my original is still good, but oh well, I have a backup now. So, if anyone ever has this problem, make sure you have the damned thing put in there so that the lever is actually moved when the throttle is moved.

Now, back to my original problem, I STILL have a vacuum leak somewhere!! At least I think that's what it is. When it's warmed up, the idle is faster than normal, about 1100 RPM. I also noticed that when it's cold, I hear a bit of a hiss when I apply the brakes, particularly when I apply them hard. Also, when it's warm and I have it idling, if I apply the brakes and release them, the RPMs jump up to about 1400-1500 for a second or two before dropping back to the 1100. Does this give anyone a clue as to where my leak might be? I've sprayed throttle body cleaner everywhere I can think and can't find any more leaks. The one in the throttle body seems to be fixed (or at least patched) with the RTV. Any input would be greatly appreciated!

cruiser54

Squeeze the hose to the brake booster closed with a pair pliers and see what happens to your idle.

rrich

A very easy test to find a vacuum leak is:
Engine off.
Connect a long vacuum hose to an intake manifold vacuum port.
Put a piece of tape across the throttle body top to seal it.
Blow smoke through the hose.
Any leaks, even under the dash, will become obvious.
Even manifold to head leaks.
Smoke should not be able to get out.

Sometimes if it's not easy to see where the smoke is coming out - use a strong pencil beam flashlight while the garage is darkened.

freegdr

sounds like brake boosters leaking disconect and plug the vacuum hose to it see what happens....sounds like a good time for booster upgrade

JohnWongFat

This is getting aggravating! It does sound like the brake booster, but when I pulled the tube from the brake booster and plugged it, it still idled a little over 1k. I will pull it from the intake side tonight and plug that port to make sure it's not the tube or fitting that's leaking. It seems like it definitely has something to do with the brake system though. I noticed today on the way to work that when I'm braking, I will get a bit of an RPM spike right about when I hit the 1k mark. It will very briefly jump up a couple 100 RPMs and then drop back down. There's also the fact that it does that when I'm in park and apply the brakes while idling. Are there any other vacuum components that would be affected by applying the brakes? Thank you guys so much for all the help! In regards to upgrading the brake booster, is there one that you would recommend? Is that one of those things I can liberate from a junk yard, or should I go with a new one?

jeepodus

i got one of those too, maybe lol. does it run into the tranny? i fugured it was just an easy way to put fluid in there. dont quote me on that though im not a pro

JohnWongFat

Jeepodus: I was told earlier in the thread that it's a breather tube for the diff and to not mess with it. Being that everything I've messed with so far has caused me more problems that I've fixed, I'm taking that as sound advice!

JohnWongFat

Victory! I finally found the damn thing! Of course, like all my other problems, it seems to have lead to another problem. To start, I found that it was leaking from the intake manifold. I had tried spraying it (and every other thing I could think of) with throttle body cleaner to test for leaks, and someone suggested I use starter fluid instead. I did that and found the leak at the front of the manifold. The odd thing is that I got the opposite reaction I expected when I hit it with the starter fluid. When I sprayed it, the engine bogged down instead of revved up. I'm not really sure why. Regardless, after I found that, I quickly found that the bolt at the top of the exhaust manifold was extremely loose. I didn't even need a wrench to pull it out. So when it heated up, it would expand enough to leak.

Now on to my problem, I'm pretty sure that I'm missing a bolt on the underside of the exhaust manifold:

https://i.imgur.com/Y0tJi.jpg

There's a hole there that looks like it should have a bolt in it, but when I poke into it, it stops at the head. If there's supposed to be a bolt there, it's broken off in the head. Is it possible to use an extractor to get it out of there, or will I have to take it in to the shop?

rrich

Tighten that loose bolt -= then do the smoke test. It may not be leaking underneath. Simple, fast, easy, costs nothing!

89Laredo

there should be one there... I just tightened it up on my renix...

JohnWongFat

LOL! Sorry, I guess I should have mentioned that I tightened down the bolt and it fixed the problem. Back to idling at 750 RPM at normal operating temperature. I also solved the brake mystery as well. I disconnected the brake booster from the intake manifold, plugged the intake manifold, and plugged the brake booster, and when I apply and release brakes, no RPM rev. I'm still somewhat concerned that I may have a sheared off bolt in my head, but at least it's better now. I also tightened up all the top bolts, but none of them were loose like the end one was.