Should my IAC leak like this?

[RussAdams]

So my 1999 Ranger 4.0L OHV is still running awful.

I put a smoke machine on it this morning after replacing the IAC and the new one

leaks as badly as the old one I replaced. I replaced it because I couldn't believe it should leak like this.

Is this "normal"?

 

[RussAdams]

It's leaking all the way around this seam marked in purple.

 

[SenorNoob]

I can't see how it can work like that. Under vacuum the engine would be pulling unmetered air through that...

 

[Jazzer]

It looks like you have excessive crankcase pressure AND a bad IAC. How’s your PCV valve? Has it been replaced?

 

[RussAdams]

It looks like you have excessive crankcase pressure AND a bad IAC. How’s your PCV valve? Has it been replaced?

Hmmm. Excessive crankcase pressure? With a smoke machine? I connected the smoker to the throttle pipe and opened the throttle.

The PCV valve has been cleaned and it "rattles".

How would the pcv valve effect the iac?

Learning all the time!

Russ

 

[Jazzer]

My bad, missed the part of it being on a smoke machine and thought the engine was running. But If the pvc valve is stuck, crankcase pressure can build up instead of being relieved. It’s hard to get imagine a smoke machine building up that much pressure.

I just tried to blow through a spare IAC valve and couldn’t get it to leak where yours is leaking. Don’t know if what you’re experiencing is normal or not.

 

[RussAdams]

My bad, missed the part of it being on a smoke machine and thought the engine was running. But If the pvc valve is stuck, crankcase pressure can build up instead of being relieved. It’s hard to get imagine a smoke machine building up that much pressure.

I just tried to blow through a spare IAC valve and couldn’t get it to leak where yours is leaking. Don’t know if what you’re experiencing is normal or not.

No problem! Thanks Jazzer. I've ordered a true Motorcraft IAC from RockAuto. Will come back with a report when I get it and have it installed.

 

[RussAdams]

Returned the TRQ and installed a new Motorcraft IAC. Idle is under control, but the engine is still running very lean on bank 2. Also replaced the spark plug wires with Motorcraft. Again that seemed to help. But something is still really out of whack. I left the Ranger off with a local mechanic shop to do a diagnostic for me. Gave him a list of all the things I have done so far. Keeping my fingers crossed!!!

Here are the ForScan images of the issue:

 

[RussAdams]

Problem solved! The Ranger is back on the road and running great.

The primary problem was that I switched sparkplug wires 4 and 6 by mis-reading the wiring diagram. Counted from the wrong end!!!

EXPENSIVE mistake!

Secondary issue was the Throttle Position Sensor (TPS). I had replaced it with a Motorcraft one from eBay, but it ended up being bad.

The local mechanic wrote:

CHECK ENGINE LIGHTS ON
CUSTOMER SUPPLIED ALOT OF INFO SEE TICKET
CHECK ENGINE LIGHT IS ON WITH CODE P0174 FOR BANK 2
LEAN. TRUCK SEEMS TO HAVE A HARD MISFIRE AS WELL BUT
NO MISFIRE CODES STORED OR PENDING. START BY
CHECKING FOR VACUUM LEAKS FROM HOSES AND OR
INTAKE. MONITOR SHORT TERM FUEL TRIMS WHILE ADDING
FUEL. NO VACUUM LEAKS FOUND. AS REMOVING SPARK
PLUGS TO CHECK LEAK DOWN AND COMPRESSION FOUND
THAT THE #4 AND #6 SPARK PLUG WIRES ARE SWAPPED.
REMOVED PLUGS TO CHECK FOR FOULING AND REINSTALL
PLUG WIRES IN CORRECT POSITION. AFTER THIS CHECK
RUNNING CONDITION AND MISFIRE IS GONE. RUN KOEO TEST
AND KOER TEST BOTH TEST COME UP WITH P1124 FOR THE
THROTTLE POSISTION SENSOR FAULT. CHECK POWER TO
SENSOR IS GOOD. REMOVE AND REPLACE TPS AND RECHECK
TESTING BOTH PASSED. TEST DRIVE TRUCK MULTIPULE
TIMES FOR A TOTAL OF 30-35 MI LES. ALL MONITORS ARE SET
OTHER THEN EVAP SYSTEM AND NO CURRENT OR PENDING
CODES AT THIS TIME.

The above diagram is correct. It's an image for an SOHC and mine is an OHV, but the firing order and cylinders are identical.

I messed up and on Bank 2 (US Driver's side) I had cylinder 6 going to coil connection for cylinder 4 and cylinder 4 going to coil connection for cylinder 6.

Correct:
3 --- 6
2 --- 5
1 --- 4

My mistake:
3 --- 4
2 --- 5
1 --- 6

Cost me $400 to get it fixed. Something I checked several times, but just had it wrong in my head.

 

[RobbieD]

Problem solved! The Ranger is back on the road and running great.

That's great, and congratulations.

Thank you for posting the outcome.

I've been shadetreeing my own stuff for 50 years now, and I still don't trust myself with plug wires. I double-check and then triple check; they're so much easier to cross than most people think.

Another sad fact, is that "new" replacement parts these days are like a bad joke, quality-wise.

You're mechanic sounds like a good one.