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Arricejr · 05-19-2017, 10:07 AM

So 1990 460 I think my number three and number four cylinders are not firing reason I say I think it's because when I pull the plugs off the distributor cap while running it doesn't appear to change but when I rev the gas it feels like it's all good also when I put it in drive I get a lil shaking a doot doot doot doot doot doot type idle I do have a exhaust leak in one of the under pipes where. Previous owner hit something so I'm sure that's wher the noise is ..did a compression test on both of those cylinders and getting close to 150 psi from both cylinders..?? So lost as this is carburetor

BFlinn181 · 05-19-2017, 11:19 AM

Pulling the plug wires and getting no change of RPMs is a sign of bad plugs or wires. Since you know compression in the 2 cylinders, the plugs should have shown signs of not firing or a bad gap. If you didn't do the compression test, I'd pull the plugs and inspect them, if they aren't firing there should be a difference in the deposits that gives further clues. You could also loosen the wire at the plug, then with engine running see the size and strength of the spark when the wire is held near a ground, if it's weak or not present, then it's the wire, the distributer cap, or rotor.

Arricejr · 05-19-2017, 12:21 PM

Quote:

Originally Posted by BFlinn181

Pulling the plug wires and getting no change of RPMs is a sign of bad plugs or wires. Since you know compression in the 2 cylinders, the plugs should have shown signs of not firing or a bad gap. If you didn't do the compression test, I'd pull the plugs and inspect them, if they aren't firing there should be a difference in the deposits that gives further clues. You could also loosen the wire at the plug, then with engine running see the size and strength of the spark when the wire is held near a ground, if it's weak or not present, then it's the wire, the distributer cap, or rotor.

New plugs and wires cap and rotor yesterday getting fire for sure ..was one of the reasons I tuned it up

Randalpho · 05-19-2017, 01:00 PM

Are you sure the plug wires are in the right order?

Could have been wrong before you replaced them, depending on which ones are crossed it can run pretty good considering.

Arricejr · 05-19-2017, 01:11 PM

Quote:

Originally Posted by Randalpho

Are you sure the plug wires are in the right order?

Could have been wrong before you replaced them, depending on which ones are crossed it can run pretty good considering.

You know I thought about that I switched them and looked up the routings everything seems fine and in order unless what I looked up was wrong

LETMGROW · 05-19-2017, 04:54 PM

Cylinders #3 & #4 being next to each other I would look closely for a vacuum leak in the intake manifold runner somewhere. Possibly a fitting with a hose with a crack in it or even disconnected.
At higher RPM the skip would be less noticeable. ( But really is still there )
Lynn

Arricejr · 05-20-2017, 12:57 PM

Quote:

Originally Posted by LETMGROW

Cylinders #3 & #4 being next to each other I would look closely for a vacuum leak in the intake manifold runner somewhere. Possibly a fitting with a hose with a crack in it or even disconnected.
At higher RPM the skip would be less noticeable. ( But really is still there )
Lynn

That's exactly how it seems on the highway she rolls like nothing wrong.. well I'll have to wait as I just blew a tire last night on my way to Orlando and now I'm stuck in Orlando can't get tire till Monday..so no trouble shooting till Tuesday maybe wensday when I get back

Arricejr · 05-20-2017, 12:59 PM

Quote:

Originally Posted by LETMGROW

Cylinders #3 & #4 being next to each other I would look closely for a vacuum leak in the intake manifold runner somewhere. Possibly a fitting with a hose with a crack in it or even disconnected.
At higher RPM the skip would be less noticeable. ( But really is still there )
Lynn

Also it was real bad at 1st I found a old dry rotten rubber plug that was on the carb and replaced it and what a difference but maybe as you said there's another I'm over looking

Arricejr · 05-23-2017, 06:41 AM

Ok so made it to jax from Orlando and I'm really leaning on the face of it's something to do with carburetor or vacuum because the coach runs 60-65 with no hiccups I know if I was running with 2 cylinders missing I would definitely know it at those speeds so back to the drawing boards

DryCreek · 05-23-2017, 11:14 AM

Here is a link to a chart that you can compare your information to:

LINK

I have to admit, being a Chevy/Chrysler guy really caused me some headaches with the first Ford I owned. Who would have thought that they needed to number their cylinders differently than the rest of the world?

Arricejr · 05-24-2017, 10:29 AM

Quote:

Originally Posted by DryCreek

Here is a link to a chart that you can compare your information to:

LINK

I have to admit, being a Chevy/Chrysler guy really caused me some headaches with the first Ford I owned. Who would have thought that they needed to number their cylinders differently than the rest of the world?

lol thanks a million friend

LETMGROW · 05-30-2017, 04:19 AM

Any updates?
Lynn

Arricejr · 05-30-2017, 11:43 AM

Quote:

Originally Posted by LETMGROW

Any updates?
Lynn

No Lynn haven't been able to get on the rig as of yet did make it back from Orlando Hoping between tomorrow and wensday

Arricejr · 11-21-2017, 04:48 AM

Well back on this chase I'm thinking it's fuel related because at times it runs smooth like during 1st crank up as it warms then it's running bad missing again when I drop it in drive it's really noticeable till I give it gas and get going have not as of yet found any intake leaks but I know for sure it's running rich as I can clearly smell it .. I guess I may have to get this thing smoked tested as I'm lost