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2.9L loses power on long day trips


Perkinator104

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I am humbly requesting advice from Bronco II owners with a 2.9L Cologne.
On long trips on hot days, the Bronc starts losing power and getting slower and slower. When I let it cool with the hood up, it gets better, but eventually will fail again.
The coolant temp guage is showin it is perfectly cool, but it's hot under the hood.
I've heard of a "TFI unit" causing problems. Any other things I can look at to fix this? It really puts a damper on road trips. I'll post the fix when I find it, so it may help the next guy.
 


Uncle Gump

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As you probably know... these 2.9L don't like being overheated. They're prone to cracking cylinder heads if they do. So good for you on taking precautions.

The TFI modules typically just quit when overheated. Then when cooled down they work again... until they don't. Could it cause your symptoms... sure. But it isn't the normal failure mode for a TFI module. The easiest thing to do would be to replace the TFI module and see if the problem still persists. Word of warning... there are a bunch of cheap parts these days. I wouldn't buy a big box parts store house brand or the cheap units from ebay or Amazon. I would buy a Motorcraft TFI... I've also heard folks have had good luck with the Accel units. In the end if it doesn't fix it... it's never a bad idea to have a good working spare TFI module in the glove box... because they usually fail at the absolute worst time.

On long trips... everything gets warm simply be the duration of time. I would put together a tool kit to do a bit of testing when it happens again. Have your fuel pressure gauge to check fuel pressure... spark tester to test quality of spark from coil... DMM to check battery voltage to ensure alternator is putting out properly. Check the clutch fan to ensure it locks up to provide proper cooling. ETC...
 

Perkinator104

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As you probably know... these 2.9L don't like being overheated. They're prone to cracking cylinder heads if they do. So good for you on taking precautions.

The TFI modules typically just quit when overheated. Then when cooled down they work again... until they don't. Could it cause your symptoms... sure. But it isn't the normal failure mode for a TFI module. The easiest thing to do would be to replace the TFI module and see if the problem still persists. Word of warning... there are a bunch of cheap parts these days. I wouldn't buy a big box parts store house brand or the cheap units from ebay or Amazon. I would buy a Motorcraft TFI... I've also heard folks have had good luck with the Accel units. In the end if it doesn't fix it... it's never a bad idea to have a good working spare TFI module in the glove box... because they usually fail at the absolute worst time.

On long trips... everything gets warm simply be the duration of time. I would put together a tool kit to do a bit of testing when it happens again. Have your fuel pressure gauge to check fuel pressure... spark tester to test quality of spark from coil... DMM to check battery voltage to ensure alternator is putting out properly. Check the clutch fan to ensure it locks up to provide proper cooling. ETC...
Thanks for these great pointers. I'll try to drive ready to test these things.
 

89Bronco2Micheal

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Your catalytic converter could be clogged up causing heat to rise back into engine compartment. Would also cause loss of power during acceleration engine needs to breath in and out easily, also check fuel filters, air filter. Other things to do, pressure wash your radiator get those bugs out, check your coolant level. Your TFI module should be fine but if its old you better buy a new one keep it in glove box with tools, it will die while you are driving due to heat and the old heat sink paste drying up. Don't let the guy at the auto store tell you to use dielectric grease that stuff will last you about 5 miles then your TFI will overheat and die, you need that white paste that comes with a new TFI. I hope this helps.
 

Uncle Gump

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Catalytic converter could be acting up. I've typically seen that once they plug up... they're always plugged. Not really an intermittent type failure... at least from my experience.

However it's simple enough to test. All you need is a vacuum gauge. If exhaust is plugged... engine wont make good vacuum. Add one to your tool kit and see what happens when your condition exists.
 

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