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Discussion Starter #1
I described this thing in another thread,but it was in the wrong place.(thanks for the assist,redwagon)

My '87 was running perfect until about a week ago.It was holding a smooth and steady idle at about 650rpm,when it suddenly just started missing,surging up to about 1500rpm,back down and then stalling.When that happens,it fires right back up,but runs the same.It does seem to get a little worse the longer it runs at operating temp.

Because the distributor is fairly new(4 months),I thought maybe it worked itself loose,but it didn't.
I threw a set of plugs,cap and rotor on it since I had them in the garage but that caused no change at all.
After checking whatever vacuum lines I could find,I sprayed the intake manifold and carb base with starting fluid but couldn't find anything wrong there either.
The check engine light came on after that,but then it went out.:banghead

What can I do to diagnose and fix this mess?
Any help at all would be greatly appreciated.


I forgot to mention,the carb is a rebuilt replacement(4180?) and the wires were changed at the same time.That was in July.
 

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Does it have power? If it will rev up but has no power and smokes black, it would seem that your coil is going bad. I would check it and go from there. Usually "all of the sudden" power losses can be caused by this. Do you have a clear fuel filter on your supply line? If so, is it full of fuel? It should be. Check those things and go from there.

Chris
 

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Discussion Starter #3
It doesn't really lose power and the exhaust is definitely not black.I changed the fuel filter and sprayed the carb with cleaner but no change.I figured maybe the choke was sticking so I pinned it open,but it still fluctuates between about 600 and 1600 rpm's.At 600 it barely runs and I have to stay on the pedal.Sometimes at that point,it will flatten out and run perfect only to start missing again.

I really don't know what else I should look at or how I should test anything.
 

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1) does it have 2 fuel filters there should be one in the carb wear the fuel comes in and another on the frame rail
2) if I do recall my 85 had some what the same problem and I had to ajust the flost in the carb and it became a real headach I would rebuild or replace the carb or better yet do fi convertion on it( it my be that the float is takeing fuel in to it or the float spring is going band )
3) check your fuel pump put a pressure gage inbetween the pump and the carb and watch the fuel pressure.
hope this helps
 

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Discussion Starter #5
When I did the carb in July,I added an inline fuel filter a few inches back from the carb inlet.I figured it couldn't hurt,and it didn't.
I changed that one yesterday(stayed almost full when running) and looked at the one in the carb,but it at least looked OK.
Float adjustment did nothing either.

You're thinking the pump might be bad?
 

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My 83 with the 2150 had a leak in the power circuit that is controlled by vacuum. The diaphragm had a leak allowing gas extra gas into the engine. I don't know if the 4180 has the same setup but I had similar issues. As others stated ignition issues too. I used to carry a spare ign module but that was always a no start when it failed.
regards
rikard
 

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Discussion Starter #8
Chris,I had a rebuilt long block installed 3 years ago,the chain hasn't been changed since then.It doesn't only smooth out at higher rpm.Sometimes it runs perfect at idle,and then it starts crapping out.Weather doesn't matter at all either.

And rikard,I'm real familiar with swapping out that POS ignition module.I always keep a spare with me.;)
 

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Is your exhaust plugged up? What do the cap and rotor look like. The more I read, the more I think you have water in the dist. I would still not rule out the fuel though. As far as the CE light, that will not tell you much as the carbed versions only did emissions and timing. Also, take a ground clamp/strap and clamp it to your intake or head bolt. Clamp the other to the - terminal on the batt and see if that changes things.

Chris
 

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Discussion Starter #11
I changed the cap and rotor 2 days ago along with the plugs even though they all looked OK.
The exhaust is all about a year old from the manifolds back with no cat,single.That seems to fine too.

It's starting to pour outside so I'll try the ground tomorrow.
For now I'll just go back to the "search" function.Been doing ALOT of that lately.
 

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Discussion Starter #13
Well,it has to be an ignition problem because now I'm not getting ANY spark out of the coil.
I have a spare module and coil that I tried in my buddy's truck and they both worked fine when we did a quick swap in his truck.
Put the coil in mine and still no spark.Plugged in the ignition module,and still nothing.
I'm in the middle of doing a continuity test on the wires from the module to the coil to see if there's a break somewhere,but figured I'd post to see if there's anything else I can try.
Could it be the little resistor/condenser(I don't know what the hell it is) that's mounted on the bracket that holds the coil?
 

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Well,it has to be an ignition problem because now I'm not getting ANY spark out of the coil.
I have a spare module and coil that I tried in my buddy's truck and they both worked fine when we did a quick swap in his truck.
Put the coil in mine and still no spark.Plugged in the ignition module,and still nothing.
I'm in the middle of doing a continuity test on the wires from the module to the coil to see if there's a break somewhere,but figured I'd post to see if there's anything else I can try.
Could it be the little resistor/condenser(I don't know what the hell it is) that's mounted on the bracket that holds the coil?
i dont think so...thats just for radio noise.
 

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Discussion Starter #15
Can anybody help clear up steps 50-57 on section 5-5 of the Haynes manual for me?
I'm starting from scratch again,and I think I'm doing something wrong here.
I'm not sure what #'s are the combined stator/harness.
 

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Discussion Starter #16
Well,nevermind about the screwy numbers I was getting on the ohm meter.
I went back to visual inspection on all the wires from the module,distributor and coil and I found the problem.

The green wire that goes from the mod to the tach side of the coil was just touching the valve cover,and it wore the slightest bit of insulation off.
I cut it off 3" from both ends,crimped on a new wire and now it's running like it's brand freakin new.
I guess it must have been some kind of "partial ground" when it wasn't running right,and then it finally shorted out when I had no spark.

Anyway,thanks for listening to me whine and for the help.
 

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Discussion Starter #19
fartman,you have no idea just how many unresolved threads I went through during my search this week.

I hate that.
 
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