258 dist. is changes timing with comp bypassed? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 12-28-2000, 08:55 PM
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258 dist. is changes timing with comp bypassed?

I recentl had enormous problems with my 88/4.2/carter.
it would run fine for 5 min then slowly die out.
EVERYTHING was covered in carbon, so I:
-rebuilt the Carter BBD
-replaced ALL vacuum lines
-replaced fuel filter
-tightened every bolt that had the possibility of vacuum leak
-Bypassed the computer and stepper motor(to eliminate it as a cause)
- New sparkplugs
After all of this I Made a fairly accurate placement of 8* Timing before I started it.
It ran just,but is was way smoother,at 300 RPM, I checked the timing with my light and it was at 7* so I moved it.
Then I tried to rev it, there was not very much throttle response, on the fourth or so rev attempt it jumped to 1500 RPM and stayed there. I checked the timing again and it was wayyy past 8*, it was on the other side of the pully I am guessing 30's of degrees btdc. I checked to make sure The distributor base did not move, it did not.
I moved the ditributer to 8* and lowered the idle 2 turns and it sputtered and stalled( the mix screws could be abit off).
I started it again and it would not go. So I advanced the distributor to where it was, it then started but again it was very low, I also tried to revit and it wouldn't rev. untill the fourth or so try and the RPM increaced again, along with the Timing.
How can the distributor just change the timing like that with no computer or vacuum hooked up?
Is the distributor scewed?
I Am going to do the "Ford Parts uprade" very soon, would that help?
I am really glad to see it run now but I know I will have to fix this.
Thnx in advance for anything(sorry about long post but I thought you would need a little detail )
KEEP ON JEEPIN!

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post #2 of (permalink) Old 12-28-2000, 09:20 PM
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Re: 258 dist. is changes timing with comp bypassed?

Set the timing to 9 BTDC with the engine at 1600rpms and the vacuum advance plugged.



post #3 of (permalink) Old 12-28-2000, 09:22 PM
 
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Re: 258 dist. is changes timing with comp bypassed?

When it idles is it smooth or does it very and surge? If so it may be a worn dist gear or bad timing chain/gear set.
Have you tried cleaning the inside of the dist? The centrifical advance may be gummed up. I like brake cleaner.
Hope this helps some.

Keith


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post #4 of (permalink) Old 12-28-2000, 09:32 PM
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Re: 258 dist. is changes timing with comp bypassed?

It will idle smooth but I really want to clear up what you mean by surging agrees with my thought.Wouldnt the skiped timing chin change the cam position overall and cause a rough run? I will try the distributor disection, is it easy?

post #5 of (permalink) Old 12-28-2000, 09:52 PM
 
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Re: 258 dist. is changes timing with comp bypassed?

The dist cleaning is fairly easy. just remove the cap and rotor. Then spray the shaft and weights, inside the dist, with brake cleaner. I like to hit the starter a little(half a turn or so) a couple times then spray again. I use brake cleaner because it doesn't leave a residue. Surging means the idle speed changes with no throddle, like a vacuum leak. The gear and chain can be worn without skiping time. That will allow the timing to change irradicly(sp). The dist gear can do the same if it's worn. Also a twisted dist shaft can give you headaces to. The easist way i know of to check for worn chain and gears is to set the dist on #1with the cap off. Then with a wrench crank shaft bolt, turn the crank clockwise till the dist starts to move and check the timing mark, or mark it on the pulley. Then turn it the other direction till the dist starts to move and check the difference. A few degrees difference is normal. But if it's say 15 drgrees or more you have a problem. Either a worn gear/chain or worn dist gear. But if it's running smooth at idle that's probably not your problem.

Keith


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post #6 of (permalink) Old 12-28-2000, 10:14 PM
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Re: 258 dist. is changes timing with comp bypassed?

In that case it is a constant RPM with the exception of a odd miss

post #7 of (permalink) Old 12-29-2000, 05:06 AM
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Re: 258 dist. is changes timing with comp bypassed?

Junkfood's telling you the correct process to check the timing belt. However, the spec for the 4.2 engine would be no more than 6 degrees of movement. Any more than than, and the belt or gears are toast.

The Distributor vacuum advance assembly can also be your source of problems. The advance plate will gum up and the springs holding the cent. weights can dish out (wear) the attaching posts. Look for those two items, they will cause the RPM to jump in an unpredictable manner. Also look for "fuzz" at the base of the distributor. Sometimes the distributor bearings wear and the vane that trips the Hall Effect switch at the base of the distributor will actuall hit the switch. This rubs a little bit of stuff off the switch housing and coats the vane. Then the vane will rotate and cause false firing or no firing depending upon how the "fuzz" has built up. You should be able to replace the whole distribuor from NAPA for about $70. That's about half again the cost for just the advance plate assembly or the hall effect swtich.

If you check the timing chain and gearing and it checks good... replace the distributor as an assembly. When I did this 3 years ago I was shocked to see what a difference it made. Prior to the replacement I was grabbing at straws trying to justify the replacement. It took actually repacing the distributor to understand what was going on... some times I'm just a little thick headed and too tight to let go of a dime... but that's another story.

Happy Holidays and Safe Jeepin'

Larry
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post #8 of (permalink) Old 12-29-2000, 12:23 PM
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Re: 258 dist. is changes timing with comp bypassed?

That could very well be, infact I remember when it was running good that it would intermittantly have the "perfect" idle at 700RPM but most often it would stay at 1100RPM, this could have been a first sign i suppose.Accept the cold inceaced it. Should I try to disect and lube it before I buy a new one?

post #9 of (permalink) Old 12-29-2000, 07:51 PM
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Re: 258 dist. is changes timing with comp bypassed?

My experiance was to tear apart the distributor and to attempt to repair it. I had over $30 into the hall effect switch alone before I deceded to buy a rebuid from NAPA. IMHO... it was the only way to go. It saved me a lot of downtime for little cost compaired to bying individual component.

Happy Holidays and Safe Jeepin'

Larry
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post #10 of (permalink) Old 12-29-2000, 10:03 PM
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Re: 258 dist. is changes timing with comp bypassed?

I took the distributor off an found lots of fraying and cracked HE or pickup coil wires,could this have caused the irratic timming change?

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