Low vacuum, timing OK

[Dan R]

Rough running, misfiring and rough idle is driving me crazy! It seems to be getting worse. Not sure how long the truck will idle for in the future.
Vacuum reading is 14 inches but timing is OK. About 9 degrees and wavers slightly when I open the throttle.
I have checked the all the vacuum lines I know. Perhaps the camshaft sensor in the distributor? Vacuum leak in the heater flaps? They are sometimes slow to close and bleed hot air when I want cold. No hissing though around the dash.

Thanks

Dan

1993 Ranger 3.0 V6

 

[Rhett]

Are the plugs all torqued down? I've seen them come loose and the engine lost vac and idled terribly.

Regarding the camshaft sensor / synchronizer, mine never went "bad", but it got noisy. When it was noisy it wasn't affecting idle, but if it were malfunctioning I could see it happening. Hopefully yours isn't as much of a pain to change as mine is on the 4.0.

I'm assuming you already ruled out coil pack / wires and plugs.

How is your intake tube? Any cracks or holes in it? How about the throttle body-to-upper intake mani gasket area? I'm assuming you also went over your upper intake mani for cracks? Did you re-torque it? How about the vac line under the throttle body?

I'm not super familiar with the Ranger 3.0, but those are some things I'd look at on mine.

 

[Dan R]

Thanks, Rhett.
I have changed the plugs, wires, coil, MAF.
I changed the upper intake gasket.
I will take a fresh look at the vacuum lines.
Dan

 

[Turdle]

I saw your other thread about an oily evap box, this and the low vacuum would make me want to check the engine compression.
Check all cylinders , write down the PSI value and report back please.

 

[FR-425]

I saw your other thread about an oily evap box, this and the low vacuum would make me want to check the engine compression.
Check all cylinders , write down the PSI value and report back please.

Now there's a thought. Maybe the purge valve is stuck open and it is constantly sucking gas fumes up from the tank and into the throttle body.

 

[Dan R]

Interesting.
The oil seems to be coming from the canister rather than as a bystander effect. Very little smell of gas though.
The canister and purge valve will be replaced. And compression will be tested.
Vacuum reads 12 in Hg at idle. Timing is 9 degrees. Maybe it is still some tricky vacuum leak?
The vacuum hoses are in amazing good shape for a 23 year old vehicle. Little cracking and still flexible.

To be continued.........

thanks for the suggestions!

 

[OneofMany]

You could do a bit of a process of elimination... disconnect and plug vacuum sources and retest. Also check your pcv valve. And your Egr if you have one.

 

[Dan R]

I saw your other thread about an oily evap box, this and the low vacuum would make me want to check the engine compression.
Check all cylinders , write down the PSI value and report back please.

Well I eventually got round to checking the compression. Cylinders are all around 130.
The oil around the evap canister is probably from auto oil cooler lines or from the steering pump.
Good compression seems to eliminate jumped timing chain as cause of rough running.
I will prepare to change the lower intake gasket.
There is a moderate trickle of coolant at the front of the engine. Would indicate gasket too?

 

[natenkiki2004]

I don't know that 130 is good, seems a bit low to me. But if all the cylinders are even, that's more important. You just won't get as much power as a new engine (obviously). Could be that your engine is getting a bit tired. Though, you're talking the 3.0L? If so, 130 could be normal.

As said by FR-425 and OneofMany, plug up the vacuum lines or pinch them off with clamps and see what that does.

 

[Centaurious]

Did you run the compression test with a fully charged battery, all the plugs out and the throttle held open? If not it will affect the readings

Not to imply anything about your skills but are you SURE that the plugs are fully seated and that the plug wires are in the proper order and fully seated in the coil pack and on the plugs? The passenger bank is front to rear and the wires are also front to rear on the coil pack. The drivers bank is Not, I just can't remember the pattern.

 

[malohnes]

Did you run the compression test with a fully charged battery, all the plugs out and the throttle held open? If not it will affect the readings

Not to imply anything about your skills but are you SURE that the plugs are fully seated and that the plug wires are in the proper order and fully seated in the coil pack and on the plugs? The passenger bank is front to rear and the wires are also front to rear on the coil pack. The drivers bank is Not, I just can't remember the pattern.

I have to agree with Centaurious. Since you replaced plugs and wires, super rough running could very easily be wrong plug wiring...this is a common error. Cylinder 1-3 go in exactly the same coil plug numbering. Cylinders 4-6 are different, the go to coil plug 5, 6, 4 respectively.

Visually, should look like this on the coil pack.

3,4
2,6
1,5
front

 

[Dan R]

Thanks for the tips guys.
I have checked the ignition leads of this 1993 distributor engine.
I have labelled the wires at the distributor cap and at the spark plug boot.
I am now half way through replacing the lower intake manifold gasket.
Bolts are loosened and I will pry off the manifold and clean it today.
The engine is also getting a new distributor and cam timing sensor.

 

[malohnes]

Oh, I just reread you original post. I somehow missed that you are working on a 3.0L not a 4.0L engine. I have no experience with that engine...sorry for the confusion.

I hope all goes well

 

[Centaurious]

We both missed the year, last 3.0 I worked on was distributor-less. Yours is a clockwise rotation so don't get it wrong.

I worked on a friends mazda truck decades ago and after spending two days fighting to get it running right he tells me he changed the plug wires. Yep, he got the rotation wrong and two of the four cylinders were wrong. I almost hit him for that one.

Good Luck and keep us informed.