Having problems after 302-351 swap - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 01-01-2000, 09:53 PM Thread Starter
 
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Having problems after 302-351 swap

I have a 88 Bronco and yanked the 302 and had a 351 put in. It ran like crap so I found a processor from a 351 and put it in. Ran like a scalded dog except when i am at a red light the engine surges and then nearly dies. Don't know what the problem could be. Also the tranny acts funny. I found out that they did not make a 351efi with the AOD tranny. The processor I have in now is for a 351efi with c6 three speed tranny, which sends no message to the tranny...should run fine according to the Ford house. It has trouble down shifting when coming to a stop...ANY SUGGESTIONS

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post #2 of (permalink) Old 01-03-2000, 08:38 AM
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Re: Having problems after 302-351 swap

Just a thought... Assuming you have the AOD (all mechanical) trans. Have you adjusted the TV rod (may be a cable instead, on an '88, I don't know) from throttle linkage to trans? I know if the setting is wrong, shift points are off (also had a TV rod fall off once, after I pulled a carb off one too many times without replacing the plastic grommet. The shift points were messed up then. Had to do a parking-lot fix of wiring it back on!).
On the surging problem, are your Idle Air Control passages clean in the throttle body and in the IAC itself?
post #3 of (permalink) Old 01-03-2000, 10:18 AM
 
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Re: Having problems after 302-351 swap

I have an 88 with the 5.8 and the C6. The only control leading to the trans. from the engine is the Throttle Valve Cable. That is what controls downshifts. Without that cable, I would expect the transmission to shift normally, except without downshifts. I currently have a surging idle problem, too. I changed the EGR Valve and cleaned out the Throttle Body and Idle Speed Control Valve. This helped, but didn't eliminate my problem. Cleaning these parts is free, so give it a try. Good Luck.

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post #4 of (permalink) Old 01-03-2000, 05:11 PM
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Re: Having problems after 302-351 swap

Sounds like the guys at Ford are trying to make a dollar off you. The AOD and C-6 were not computer controlled in 1988. If your tranny is not shifting down when coming to a stop, then something is wrong with your tranny. I recently did a AOD to C-6 swap in an 87. It works better than the AOD ever did. It was a simple swap since there was no need to change the computer. I did, though, have to get the correct kick-down cable for the C-6. Want some more perforance out of your C-6, take your valve body to a tranny shop and put a kit in it. Also install the black-banded vacuum shift control module.
The surging might be from the throttle position sensor or possibly EGR valve.

post #5 of (permalink) Old 01-03-2000, 06:11 PM
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Re: Having problems after 302-351 swap

I think CJ meant he still has the AOD, that it was the trans with the 302 before he started. And the new EEC was to run the 351 that he swapped in.
On another item, I wonder how long the AOD will last with a 351 driving it. Full-size Ford and Merc Police cars had the 351 with the AOD through '91, and I think did OK with all the abuse there. Don't know how that will translate to Bronco-duty. Probably depends on the driver and what you do with it.
Oh yeah, get that TV setup right, before assuming too much about the trans. If the trans worked OK with the 302, it should work OK with the 351, assuming nothing broke in the engine swap.
UncleDon

post #6 of (permalink) Old 01-05-2000, 12:17 AM
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Re: Having problems after 302-351 swap

Last weekend I managed to get the same symptoms with my stock 86 302 AOD. After running a new power wire from the battery to an amp inside the car, I found the idle had gone bad, sometimes too high, then it would surge and try to die at stoplights. Also, the tranny shifted hard, especially on downshifts. Turned out I had knocked a vacuum hose loose. Just a thought..Are you sure all yours are hooked up?

NormSpeed
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