Vacuum Leak - Spark Plug tube seals?

[banjo1981]

So I’ve been trying to diagnose a rough running cruiser (1993 FZJ80 with 277k miles).

So far I’ve checked, cleaned and replaced the following:

Removed and cleaned the EGR valve and EGR vacuum solenoid. Both are in working order and flowing freely now.

Replaced the PCV valve and grommet.
Replaced the PCV hose and valve cover breather hose.
Unhooked the brake booster hose at the top of the intake and blew smoke into the intake. Only saw smoke coming out of the air filter box after a few minutes.
I unhooked the valve cover breather hose and blew smoke into the valve cover and heard air escaping somewhere. I took off the cover for the first three spark plugs and I could hear the air leaking up from around the plug tube seals.

My question now is: could the spark plug tube seals, if all combined, amount to a big enough vacuum leak to cause the engine to run but run poorly??? It idles poorly and has a lack of power under acceleration.

Thanks in advance to whoever may have some insight.

 

[CharlieS]

Absolutely.

 

[ITRJ]

No. It uses PCV so there’s no vacuum in the crankcase (or shouldn’t be). If you’ve ruled out vacuum leaks, the other common culprits would be O2 sensors or coolant temp sensor for the EFI. That being said, I have the same issue with mine and have replace both those things with no luck so keep me posted if you find anything.

 

[CharlieS]

I could be wrong, but here is my logic: there are two hoses that go from the top of the valve cover to the intake manifold allowing air movement between the two. Yes, one has a PCV valve on it, which I understand to be a one way valve allowing gasses to flow to the intake manifold to be burned up, but not allowing air from the intake to the valve cover (do I have this backwards?). The other is just an open hose - but I don't know if there is anything restricting air flow - nothing I can see... So if air can flow from the valve cover to the intake, a vacuum leak at the spark plug seal or valve cover gasket sucks in air, which then can flow to the intake. This is unmetered air. If any unmetered air is introduced into the intake (after the intake air measurement), it could lead to altered idle and poor running.

I could very well be wrong. I'm genuinely interested in having someone explain where I am getting it wrong. I could learn something in the process.

 

[banjo1981]

So I pulled all six plugs, checked the gap, re-gapped to 0.031” and reinstalled them. Plug #6 looks like this:

Checked the distributor cap and rotor, both looked fine.

Borrowed a vacuum gauge and checked vacuum for my elevation. It’s reading normal at idle and when opening the throttle.

I’ve ordered a valve cover gasket and spark plug tube seal kit, plugs, wires, distributor, rotor, and a timing light. Right now I’m leaning towards spark. If that doesn’t fix it, I’ll go down the fuel side of things.

 

[ITRJ]

that plugs looks wet. Could be a leaking injector or head gasket.

 

[banjo1981]

that plugs looks wet. Could be a leaking injector or head gasket.

coolant level is steady and oil looks normal. The exhaust even smells normal. So I’m leaning towards spark then probably gonna pull the injectors if the new parts don’t resolve the issue. Again, it’s not throwing any codes which isn’t super helpful

 

[mudgudgeon]

I agree any vaccum leak into the engine/crankcase is unmetered air finding its way into combustion chambers.

Also agree the plug looks wet.

 

[banjo1981]

“Certain things have come to light, and you know, has it ever occurred to you, that instead of uh, you know, running around, uh, uh, blaming me, you know, given the nature of all this new sh1t, you know it, it, it, this could be a,a,a,a lot more uh,uh, uh, uh, uh, uh complex. I mean it's not just, it might not be just such a simple, uh, you know?”
-The Dude

So I replaced the distributor cap and rotor. Found wet oil on the boot of #6 plug where it goes into the distributor cap. So I ordered a new o-ring.

Currently replacing the valve cover and plug tube seals and have access to replace these vacuum hoses.

 

[ZackR]

“Certain things have come to light, and you know, has it ever occurred to you, that instead of uh, you know, running around, uh, uh, blaming me, you know, given the nature of all this new sh1t, you know it, it, it, this could be a,a,a,a lot more uh,uh, uh, uh, uh, uh complex. I mean it's not just, it might not be just such a simple, uh, you know?”
-The Dude

So I replaced the distributor cap and rotor. Found wet oil on the boot of #6 plug where it goes into the distributor cap. So I ordered a new o-ring.

Currently replacing the valve cover and plug tube seals and have access to replace these vacuum hoses.

View attachment 3597228View attachment 3597229

It's extra work but if you pull the top half of the intake manifold off accessing and replacing all of the vacuum hoses is much easier. You'll also be able to take care of the PHH, throttle body coolant hoses, fuel filter, wiring harness inspection and repair (if needed), etc..

At this point who knows which vacuum hoses are leaking and which ones are ok. Mine looked the same as yours before I replaced them all.

 

[CharlieS]

It's extra work but if you pull the top half of the intake manifold off accessing and replacing all of the vacuum hoses is much easier. You'll also be able to take care of the PHH, throttle body coolant hoses, fuel filter, wiring harness inspection and repair (if needed), etc..

At this point who knows which vacuum hoses are leaking and which ones are ok. Mine looked the same as yours before I replaced them all.

I agree 100%. Replace all of the rubber bits and eliminate them from the equation. Agree that it is a lot easier to get to everything with the upper plenum removed (don't forget new plenum and throttle gaskets for reassembly).

 

[banjo1981]

Buttoned everything back up after replacing the valve cover gasket and tube seals. Replaced distributor cap, rotor, plugs, plug wires, still not running right. Pulled the dipstick tube and replaced the o-ring and grommet.

Started futzing with the timing but didn’t know about the jumper wire on the port. Got the timing way out of whack. Had to pull the valve cover, turn the crank to top dead center, checked the cam timing marks, re-stabbed the distributor at the correct timing. All of the internal parts I can see with the valve cover off look to be in perfect alignment.

Going to put it all back together and see what’s up. Questions:

1. At what point do I replace the actual distributor (not the cap and rotor)?
2. What should I check next? Vacuum at idle with the engine warm is 15. I’m at 7000’ elevation above sea level.

Thanks in advance.

 

[CharlieS]

Did you jump terminals TE1 and E1 in the DLC? It may be good to review the FSM procedure if you aren't familiar with it. I mark my timing marks with a white paint pen to aid visibly

I don't see any point in replacing the distributor itself unless it is broken.

Is the accelerator cable set up appropriately, not pulling on the throttle cam while at rest?

I'd start by searching for gross air leaks (smoke test at intake tube) and inspect for an internally worn throttle cable not allowing the throttle to close fully.

 

[ITRJ]

I would replace the coolant temp sensor for efi as it’s fairly cheap and you have to remove it if you want to test it so might as well. It’s the 2 wire sensor in the head close to the front. Next step check your O2 sensors. You mentioned that you smoke tested the intake system for leaks earlier but might be worth double checking that as well.

 

[CharlieS]

I would replace the coolant temp sensor for efi as it’s fairly cheap and you have to remove it if you want to test it so might as well. It’s the 2 wire sensor in the head close to the front. Next step check your O2 sensors. You mentioned that you smoke tested the intake system for leaks earlier but might be worth double checking that as well.

I mighty misunderstood the OP. When they said "blew smoke into the"... It didn't sound like a proper smoke test with a slightly pressurized source of constant smoke (smoke testing machine). Lots of leaks aren't that obvious and require the pressure, smoke, and a bright light to properly observe. Removing the intake hose from the AFM and inserting a snug fitting cone or balloon is a better procedure. ...in my opinion.

 

[banjo1981]

I mighty misunderstood the OP. When they said "blew smoke into the"... It didn't sound like a proper smoke test with a slightly pressurized source of constant smoke (smoke testing machine). Lots of leaks aren't that obvious and require the pressure, smoke, and a bright light to properly observe. Removing the intake hose from the AFM and inserting a snug fitting cone or balloon is a better procedure. ...in my opinion.

I will redo the smoke test with the intake hose removed and something covering the intake. Good suggestions. If that doesn’t yield any results, I’ll try the coolant temp sensor as @ITRJ suggested. Thanks for the replies.

Just put it all back together and jumpered TE1 & E1 and set the timing to 3°. Still running rough. Smoke test time.

 

[banjo1981]

@CharlieS yes the throttle cable seems to be adjusted properly. Idles where it should, just rough and no power when accelerating.

 

[banjo1981]

@ITRJ I’m going to do the temp sensor, since I’m throwing parts at this beast. Will this work? It says it fits and is 2 wire plug.

 

[ITRJ]

Looks right.

 

[banjo1981]

Replaced the sensor. No change. Going to change the oil and do a smoke test inside the garage. Will see what happens