backfire now
Thread Starter
|
Senior User
Joined: Feb 2010
Posts: 395
Likes: 0
backfire now
okay, my 94 bronco 302 auto, is now sounding like a backfire. just did a tune up, plugs wires cap rotor. i've been narrowing down a lack of power problem. so i have just changed the tps sensor. truck runs tons better but now i have a backfire, or so it sounds. did they relocate the Ignition control mod to under the cap now? im use to seeing them bolted to the side of distributor.
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
Ford moved the ICM in late 91 from the distributor to the driver's inner fender to help alleviate heat-related failures.
As for the backfire issue, double check firing order. Make sure the #7 & #8 wires are not crossed. 302 (5.0L) up to 1994 firing order is 1-5-4-2-6-3-7-8 and the distributor rotates counterclockwise.
I know this is typically common knowledge but it never hurts to reiterate it. If the firing order is not the culprit, check that no two plug wires cross each other more than once between the cap and the plugs.
As for the backfire issue, double check firing order. Make sure the #7 & #8 wires are not crossed. 302 (5.0L) up to 1994 firing order is 1-5-4-2-6-3-7-8 and the distributor rotates counterclockwise.
I know this is typically common knowledge but it never hurts to reiterate it. If the firing order is not the culprit, check that no two plug wires cross each other more than once between the cap and the plugs.
Thread Starter
|
Senior User
Joined: Feb 2010
Posts: 395
Likes: 0
nope they are not crossed. its only an occasional backfire, but it does it multiple times then stops. while its doing that the truck hardly wants to move at all. then it comes right out of it and she'll take off with tons of power. how the hell does a efi motor even backfire any more????
Hotshot
Joined: Jul 2002
Posts: 14,285
Likes: 12
From: Bend,OR
Perhaps your coil is bad or failing??
what did you gap the plugs to and what plugs are you running. Greystreak mentioned the wires being crossed, if they are also touching in some cases could cause crossfire
what did you gap the plugs to and what plugs are you running. Greystreak mentioned the wires being crossed, if they are also touching in some cases could cause crossfire
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
Did you reset base timing after the tune-up? If the base timing is far enough off, the computer may be trying to compensate beyond the physical limitations of the system.
And as suggested, make sure no two plug wires cross more than once especially the same two. High humidity doesn't help in this case either. If you installed new plug wires, then just make sure they run as direct a route as possible to their respective plugs and that you try to keep about an 1/8-1/4" gap between them. Modern ignitions are such high output that even the best plug wires can experience cross firing if they all run over and through each other.
If you suspect issues, you can do what I like to call the "nocturnal emissions" test. Find a nice dark location (or turn the lights off in the garage) at night and have a look under the hood with the engine running. Cross firing or spark "leaks" will be evident by the presence of tiny blue sparks (arcing) along the length of the plug wires or at points where the wires touch each other or other metal components.
And as suggested, make sure no two plug wires cross more than once especially the same two. High humidity doesn't help in this case either. If you installed new plug wires, then just make sure they run as direct a route as possible to their respective plugs and that you try to keep about an 1/8-1/4" gap between them. Modern ignitions are such high output that even the best plug wires can experience cross firing if they all run over and through each other.
If you suspect issues, you can do what I like to call the "nocturnal emissions" test. Find a nice dark location (or turn the lights off in the garage) at night and have a look under the hood with the engine running. Cross firing or spark "leaks" will be evident by the presence of tiny blue sparks (arcing) along the length of the plug wires or at points where the wires touch each other or other metal components.
Thread Starter
|
Senior User
Joined: Feb 2010
Posts: 395
Likes: 0
i ran the plugs exactly as the factory had it. no i did not adjust base timing i will have to hit it with a light to check it. i did not check voltage but it did have a dead spot when i ohmed the sesor.
Trending Topics
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
Be sure the engine is at full operating temp and you remove the SPOUT connector before checking the timing.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Thread Starter
|
Senior User
Joined: Feb 2010
Posts: 395
Likes: 0
so i changed the Ignition control mod. it was the original 1994 unit, so i figued what the hell. so now no check engine light but still have the dead spot in acceleration. i dont freakin get it. i've wrenched on a lot of motors and i've been ase certified for about 10yrs. and i am stumped. i do still need to check base timing i ran out of day light for today. i wasnt able to pull any codes with the code reader other than some real odd ball ones. one was my tps was not reading full sweep during test. the others were 172 and 668....not sure what the hell 668 is. now my code reader wont connect to my ecm. and this is why my 408 for my mustang will have a big ol' holley carb sitting on top...lol
Hotshot
Joined: Jul 2002
Posts: 14,285
Likes: 12
From: Bend,OR
well it could be bad as well. you also cant just take the old one off and install the new one. if you notice there is some adjustment to that tps. go to ww.fordfuelinjection.com and look up the info on setting the tps properly. also while you have the Throttle body off the intake be sure you clean it good with a Throttlebody cleaner. Do not use Carb cleaner or you will have other issues
Thread Starter
|
Senior User
Joined: Feb 2010
Posts: 395
Likes: 0
i cleaned the TB months ago when i cleaned out the iac. the oddest damn thing happened tonight when i started the truck. my cel started to flash codes at me as i was waiting for it to warm up a bit. popped off a bunch of codes then the motor just stopped as if i had shut the key off. off all the damn times to not have a pen and papper. i've never seen that happen before....it is true the new one could be faulty.
Thread
Thread Starter
Forum
Replies
Last Post
reflections
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
1
Sep 15, 2009 07:42 AM
benoit81F100
Ford Inline Six, 200, 250, 4.9L / 300
6
Aug 22, 2002 08:17 AM
Jesse Wardlow
1973 - 1979 F-100 & Larger F-Series Trucks
5
Jun 28, 1999 11:53 AM
