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Discussion Starter #1
I'm new to the Bronco scene, I've been a Mustang guy for a long time. Please don't hold that against me, I only say that to baseline my knowledge of the 302 engine.

Weird problem, I can't get to work without fixing this.

The truck startes fine, has plenty of power... Until, the Temp get to normal.
Then the engine surges, like it's not getting any fuel.

Here's the weird part, I'm driving along after the surging starts, lose all power, then I turn off the key and start the truck back up and away I go.. For about a minute or so, then the surging comes back. I turn off the ignition, start it back up and I'm running fine again for about a minute.

I switched out the air cleaner, spark plugs, distributor cap and rotor, fuel filter, Nothing.
I then flushed the radiator, since it seemed like a over heating issue (even thought the Temp reads normal), it was Kinda dirty.

When the flush was in, and I was waiting for the engine to warm up, the surging continued. When I was clearing the flush from the system, with the engine already warm, I found out something interesting. If I left the valve open to drain the radiator, and left the hose running cold water into the top of the radiator (Run until clear water comes out of drain plug) The surging went away. The power was back like normal. Cold water kept the problem from coming back.

My conclusion, most likely wrong and going down the wrong path. A temp sensor is bad, telling the computer that it's too hot and to shut down. If I turn off the truck the computer clears the error for 1 minute and the truck runs until the computer gets the error code. where would I find a sensor like this and can I replace/remove/bypass it for now?

Thanks in advance.
 

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Airjeir said:
I then flushed the radiator, since it seemed like a over heating issue (even thought the Temp reads normal), it was Kinda dirty.

When the flush was in, and I was waiting for the engine to warm up, the surging continued. When I was clearing the flush from the system, with the engine already warm, I found out something interesting. If I left the valve open to drain the radiator, and left the hose running cold water into the top of the radiator (Run until clear water comes out of drain plug) The surging went away. The power was back like normal. Cold water kept the problem from coming back.

My conclusion, most likely wrong and going down the wrong path. A temp sensor is bad, telling the computer that it's too hot and to shut down. If I turn off the truck the computer clears the error for 1 minute and the truck runs until the computer gets the error code. where would I find a sensor like this and can I replace/remove/bypass it for now?

Thanks in advance.
the rad flush could be unrelated, but as you know an EFI 302 depends on enough temperature to keep the sensors hot enough to let the computer give best power and mileage.

I'd still be "powerful suspicious" of your ignition coil or the plug with the two wires that goes into it. Also whipped ignition wires are known to exhibit the same symptoms when they get warmed up.

Ford sells a new plug for the coil that has enormously larger wires going to their plug and you just crimp it on further back from the coil. The stealership is also currently offering a real deal on 9mm Ford Racing plug wires.

Heck it's Christmas time so why not spring for an MSD coil while you're in there. Coupled with the better wires and the cheapest Autolite plugs you can buy (they prefer them) gapped out to .055 you'll really wake up the power and mileage on your Bronco.

After a week like that, bump the timing to 13.5 from the stock 10 and watch it improve once more (do it to your stang too).

Don't say no one gave you nuthin' fer Xmas !

Sixlitre
 

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Discussion Starter #3
Coil & Wires not it...

I figured it was worth a shot, but it's not the fix. The coil was pretty old looking I replaced it with the MSD coil, just like the one on my mustang.

That got me thinking and I tried the code reader from my mustang and it plugged right in.

I got a 31, 63, and 67 with the key off

I got a 23, 44, 31, and 77 with the engine running.

I know the AC is bad, the clutch is screwed up, the 67 is expected.

23 is TP sensor & 63 is TP sensor

44 is theractor AC system, I guess that the Air Conditioner which is broken.

31 EGR, I don't know what or where that is.

77 seems like it could be real bad, but not my problem


So I've been down a week, tried a few more things and am stuck.

How do I test the TPS? I'm looking for a page to explain a test, So I figured I should post an update to my issue.

Any suggestions?
 

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Hey Sixlitre! If the plug gap on my 86 is .44 is there that much of a difference to go to .55 and change timing or do you need the MSD coil? Thanks!
 

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JKossarides said:
Hey Sixlitre! If the plug gap on my 86 is .44 is there that much of a difference to go to .55 and change timing or do you need the MSD coil? Thanks!
Although I noticed a great difference

and I still run an MSD coil, I will admit I've had it ruuning with a stock Ford coil with the plugs as wide as .060 and it ran alright.

For the full effect, in my experience it is uber-important to have VERY GOOD aftermarket plug wires, a better coil, the Autolite or Motorcrafts gapped out to .055 and the cap and rotor had best be "like new".

After you've benefitted from that for a week, bump the timing from 10 (doubt it's even there) to 13.5 or to the shy side of detonation and watch the mileage and throttle response improve even mo'.

Sixlitre
 

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OK I'm game, all my ignition stuff is fairly new so I'll give it a shot! Thanks!
Happy New Year everyone!
 

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If I was taking a stab at this I'd say a temp sensor. Those EFI's have two-a small one with one wire that pushes on (like oil pressure sender) which is for gauge. There is another larger sender with a plastic two wire plug-in style that is the sender for the comp. I'd would guess that your comp doesn't know that the engine is warm and which will act just like a carb with the choke stuck shut. By the way it will not give you a code generally, and is a relatively cheap place to start/ doesn't hurt anything to change it. It is 19years old. Also both sensors are usually located in the same general area of the intake manifold as the thermostat.
 
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