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Discussion Starter · #1 ·
Hows it going guys. New member here whos working on a 1988 Ford Bronco 302 that has an odd vibration while idling and occasionally backfires if the engine speed is increased at a quick rate. It also hesitates when I open the throttle quickly and then shortly after the rpms increase. I did move the truck like hundred feet the other day and it stalled a couple of times while shifting from drive to reverse and vice versa.

A bit of history on the truck, truck had a blown head gasket and had sat for around 4 years. The engine was replaced with a long block from autozone. Many parts were replaced including the front end accesories, starter solenoid, all ignition parts etc. Other parts were serviced such as the trans and trans filter, fuel filter and fuel pump hangar and pump were replaced. All vacuum lines were replaced since the many of the old lines cracked while I was removing the engine. I did use one of the "how to's" on one of the other forums thats specifically for this vehicles platform.

Truck has no issue turning on and fires up instantly. I have checked the timing with a timing gun and it seems to read fine at around 12 degrees. Today I hooked up a smoke machine to one of the vacuum hoses and saw no smoke leaking from anywhere unusual. I'm starting to draw blanks on what it can be. I was thinking perhaps one of the fuel injectors is bad, but they're all brand new as well. Can it be that the tps is bad? Ill check the spark plugs tomorrow to see in what condition they are in.

Also, worst case scenario, what if the engine isnt the correct one. Meaning, what if its internal balance is incorrect? How obvious would one be able to see that the flexplate and harmonic balancer is the not the correct one for the engines internal balance? I dont see any odd vibrations on the harmonic balancer when the engine is running but Im still curious.

Thanks in advance..
 

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2014 Ford Explorer Sport
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What firing order are you using?
 

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2014 Ford Explorer Sport
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There is a chance the replacement engine uses the later model, 1994 and up, firing order. Did the engine come with any documentation stating what firing order to use?

1994 and up uses 1-3-7-2-6-5-4-8

1993 and earlier use 1-5-4-2-6-3-7-8

Also ensure the plug wires are properly routed away from each other to prevent cross-fire. Good reading here from Steve83: https://www.supermotors.net/registry/media/470416_1
 

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1986 Bronco Eddie Bauer 5.0 bone stock
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have you pulled your plugs to see what they look like? The vibration could be a misfire. A little mousey decided to snack on my number 7 injector wire and it had a shakey idle.

Bogging and hesitation could be related to firing order if it's off as mentioned above, but it could also be fuel related. Did you by chance change the canister filter on the inside of the frame rail? these are not easy to replace and are notorious for being neglegted then coming to pieces and gumming everything up...
 

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Discussion Starter · #6 ·
There is a chance the replacement engine uses the later model, 1994 and up, firing order. Did the engine come with any documentation stating what firing order to use?

1994 and up uses 1-3-7-2-6-5-4-8

1993 and earlier use 1-5-4-2-6-3-7-8

Also ensure the plug wires are properly routed away from each other to prevent cross-fire. Good reading here from Steve83: https://www.supermotors.net/registry/media/470416_1
I don’t recall if it had any documentation on the firing order since it has been a couple of months that I installed the engine but I will change the firing order later today and see if that will make a difference.

Also I did read about the cross-fire issue with the wires, I just didn’t think anything of it. I didn’t realize it was that big of an issue since I don’t have that issue with my 88 mustang, but I will also look into that. Thank you so much for your help so far
 

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Discussion Starter · #7 ·
have you pulled your plugs to see what they look like? The vibration could be a misfire. A little mousey decided to snack on my number 7 injector wire and it had a shakey idle.

Bogging and hesitation could be related to firing order if it's off as mentioned above, but it could also be fuel related. Did you by chance change the canister filter on the inside of the frame rail? these are not easy to replace and are notorious for being neglegted then coming to pieces and gumming everything up...
I will check spark plugs today and inspect the injector harness.
I did not replace that canister filter. Is that the one next to the fuel filter? I do recall seeing something next to the fuel filter but I’m not too familiar with Broncos so I didn’t know what it was and thought nothing of it. The fuel filter on the other hand was pretty nasty. When I emptied it onto a pan, there was this sand like material coming out of it
 

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1986 Bronco Eddie Bauer 5.0 bone stock
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You have two fuel pumps one in the tank and one on the frame rail behind the drivers front wheel and then behind that pump is a small black canister filter that may have a shield covering it up. If you only changed one pump you may need the other changed as well. You can check your fuel pressure and should have somewhere between 35-40psi if not that could be your problem.


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I will check spark plugs today and inspect the injector harness.
I did not replace that canister filter. Is that the one next to the fuel filter? I do recall seeing something next to the fuel filter but I’m not too familiar with Broncos so I didn’t know what it was and thought nothing of it. The fuel filter on the other hand was pretty nasty. When I emptied it onto a pan, there was this sand like material coming out of it
I believe he's talking about the fuel filter. Theyre rarely changed and can gum up the works. That other black plastic thing you're seeing is the fuel reservoir. 88-89 had them on the rail I believe. Probably worth changing it out as well, but I had a hard time finding the part.
 

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Discussion Starter · #10 ·
You have two fuel pumps one in the tank and one on the frame rail behind the drivers front wheel and then behind that pump is a small black canister filter that may have a shield covering it up. If you only changed one pump you may need the other changed as well. You can check your fuel pressure and should have somewhere between 35-40psi if not that could be your problem.


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You learn something new everyday. I was under the assumption that only the trucks with two tanks had two pumps. Didn’t realize that these had two pumps for one single tank. Another thing added to check on my list. Thank you so much
 

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Not all fuel reservoirs have filters in them:

A reservoir marked "DO NOT REMOVE CUP" does not contain a filter.

courtesy of Steve83
 
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Yo randomperson562,
Welcome!
Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19 @ Code Reader

PCM stores the Self-Test program in permanent memory. When activated, Self-Test checks the EEC system by testing memory integrity and processing capability, and verifies that various sensors and actuators are connected and operating properly.
The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test. Run it around to heat the engine up and shift thru all gears including Reverse. Make sure A/C is off and transmission is in Park (automatic); or in Neutral for a Manual & release clutch. Then turn off engine, all accessories/lights (close driver's door) , etc.

Do KOEO test First. Post Code(s) here according to KOEO & KOER.
A helper can assist you by counting the codes. Some use their smart phones to record them.

BEWARE OF FAN, BELTS, PULLEYS, HOT HOSES, IGNITION HIGH TENSION WIRES, AND ENGINE COMPONENTS

Or ask local mom and dad parts stores if they will test it for you.
Or purchase a coder reader such as Equus 3145 Innova OBD 1 Code Reader for Ford EEC IV Engines at Walmart & most parts stores.

Firing Order:
5.0; The firing order for 87-93 vehicles is 1-5-4-2-6-3-7-8. If #7 and #8, or #2 and #4 spark plug wires are routed next to each other at the separation bracket, an induction crossfire condition can occur. Distributor rotation: Counterclockwise --Xxx-------- The firing order for 1994 vehicles is 1-3-7-2-6-5-4-8. On these vehicles the #1 and #3, or #5 and #6 spark plug wires must be separated to eliminate the possibility of an induction crossfire. To eliminate the possibility of the coil wire becoming disconnected, route the coil wire under the spark plug wires at the distributor cap. Distributor rotation: Counterclockwise
See images.
Source: by Tank92 .

Or is site doesn't open,
TSB 94-4-14 for 5.0 in 87-90 Bronco, E 150, E 250, F 150, F 250; engine miss, spark knock
Font Rectangle Art Parallel Pattern

Source: by Ford via Chilton

●See my Vacuum leak test in post #11 includes jowens1126 HVAC Control Panel info @ Help with dtc codes and idle
Excerpts; " When vacuum leaks are indicated, search out and correct the condition. Excess air leaking into the system will upset the fuel mixture and cause conditions such as rough idle, missing on acceleration, or burned valves. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly. Or Air Conditioning when in MAX mode may switch to Defrost.

Here's the 1988 Ford Bronco & Truck Service Manuals by Larry J via member Kingfish999 in Google Drive @ 1988 Ford Truck Service Manuals (Thank you Larry Jorgensen) - Google Drive

1988 Bronco Dealer Brochure @ https://www.broncocorral.com/resources/1988_ford_bronco_brochure.pdf

Haynes Red Manual for 80-95 Bronco & F Series @ Hanes guide 80-96 bko f series.pdf by member BroncMom

For any Bronco questions or to chat about it's planned modifications or build, it's better to post each seperately in Noobie Bronco Tech Questions. Flame free zone. This will get more attention and you can build up your post count to get into other sections such as Bronco and Ford Parts/Accessories (50 posts required to participate due to scammers who preyed on our members).

See How to add your Signature @ Bronco Forum - Full Size Ford Bronco Forum by BigBlue 94

Forum FAQs includes for example, Hot to Use Search. How To Save (Bookmark) Threads Or Posts, How To Upload Images To Posts and more tips!

Baba Looey's Favorite FSB Links (lots and lots of tech links) including, "how do I get the tailgate glass to...", etc.

Find time to Participate and VOTE in our current Full-Size of the Month (soon to change to Quarter) Contest and later in the year, Full-Size of the Year Contest @ Voting You will get ideas by those competing. Prizes are awarded to the winner; a full spread in Bronco Driver Magazine with a year's subscription once the article is submitted; and a year's worth of premium FSB membership!
Al
 

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Discussion Starter · #14 ·
Yo randomperson562,
Welcome!
Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19 @ Code Reader

PCM stores the Self-Test program in permanent memory. When activated, Self-Test checks the EEC system by testing memory integrity and processing capability, and verifies that various sensors and actuators are connected and operating properly.
The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test. Run it around to heat the engine up and shift thru all gears including Reverse. Make sure A/C is off and transmission is in Park (automatic); or in Neutral for a Manual & release clutch. Then turn off engine, all accessories/lights (close driver's door) , etc.

Do KOEO test First. Post Code(s) here according to KOEO & KOER.
A helper can assist you by counting the codes. Some use their smart phones to record them.

BEWARE OF FAN, BELTS, PULLEYS, HOT HOSES, IGNITION HIGH TENSION WIRES, AND ENGINE COMPONENTS

Or ask local mom and dad parts stores if they will test it for you.
Or purchase a coder reader such as Equus 3145 Innova OBD 1 Code Reader for Ford EEC IV Engines at Walmart & most parts stores.

Firing Order:
5.0; The firing order for 87-93 vehicles is 1-5-4-2-6-3-7-8. If #7 and #8, or #2 and #4 spark plug wires are routed next to each other at the separation bracket, an induction crossfire condition can occur. Distributor rotation: Counterclockwise --Xxx-------- The firing order for 1994 vehicles is 1-3-7-2-6-5-4-8. On these vehicles the #1 and #3, or #5 and #6 spark plug wires must be separated to eliminate the possibility of an induction crossfire. To eliminate the possibility of the coil wire becoming disconnected, route the coil wire under the spark plug wires at the distributor cap. Distributor rotation: Counterclockwise
See images.
Source: by Tank92 .

Or is site doesn't open,
TSB 94-4-14 for 5.0 in 87-90 Bronco, E 150, E 250, F 150, F 250; engine miss, spark knock
View attachment 185194
Source: by Ford via Chilton

●See my Vacuum leak test in post #11 includes jowens1126 HVAC Control Panel info @ Help with dtc codes and idle
Excerpts; " When vacuum leaks are indicated, search out and correct the condition. Excess air leaking into the system will upset the fuel mixture and cause conditions such as rough idle, missing on acceleration, or burned valves. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly. Or Air Conditioning when in MAX mode may switch to Defrost.

Here's the 1988 Ford Bronco & Truck Service Manuals by Larry J via member Kingfish999 in Google Drive @ 1988 Ford Truck Service Manuals (Thank you Larry Jorgensen) - Google Drive

1988 Bronco Dealer Brochure @ https://www.broncocorral.com/resources/1988_ford_bronco_brochure.pdf

Haynes Red Manual for 80-95 Bronco & F Series @ Hanes guide 80-96 bko f series.pdf by member BroncMom

For any Bronco questions or to chat about it's planned modifications or build, it's better to post each seperately in Noobie Bronco Tech Questions. Flame free zone. This will get more attention and you can build up your post count to get into other sections such as Bronco and Ford Parts/Accessories (50 posts required to participate due to scammers who preyed on our members).

See How to add your Signature @ Bronco Forum - Full Size Ford Bronco Forum by BigBlue 94

Forum FAQs includes for example, Hot to Use Search. How To Save (Bookmark) Threads Or Posts, How To Upload Images To Posts and more tips!

Baba Looey's Favorite FSB Links (lots and lots of tech links) including, "how do I get the tailgate glass to...", etc.

Find time to Participate and VOTE in our current Full-Size of the Month (soon to change to Quarter) Contest and later in the year, Full-Size of the Year Contest @ Voting You will get ideas by those competing. Prizes are awarded to the winner; a full spread in Bronco Driver Magazine with a year's subscription once the article is submitted; and a year's worth of premium FSB membership!
Al
Given that I have not driven the truck, do you think the computer will store any codes from just idling? I’ve moved the truck around 100 feet but besides that, it has only seen idle time
 

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Given that I have not driven the truck, do you think the computer will store any codes from just idling? I’ve moved the truck around 100 feet but besides that, it has only seen idle time
Yo,
"...There are two types of EEC Self-Tests, Key On Engine Off (KOEO) & Key On Engine Running (KOER). While both of these will test for various "hard faults" that are present when the test is run, the processor continuously monitors various operating parameters whenever the engine is running. If the processor detects a problem, it will store a "Continuous Memory" code and light the MIL/CEL (Check Engine Light). These Continuous Memory codes are put out during KOEO Test after any codes associated with hard faults are output. Codes are displayed by flashing the MIL.
 

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Thank you, I will check to see which one I have.
If you have the reservoir with a filter, the correct filter (I used a Wix) number is Wix 33266. You'll need to use an oil filter wrench to remove the filter cup.

You'll probably need to unbolt the reservoir from the frame to be able to slip the filter wrench underneath it (two 10mm nuts). Be advised that the filter bowl will be full of fuel.
 

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Discussion Starter · #18 ·
Update. Checked the firing order. I had the 1-5-4-2-6-3-7-8. Changed it to the 1-3–7-2-6-5-4-8. Ran pretty bad. It ran but had an even worst vibration. So I went back to the other firing order. I did route the “problem wires” that can cause crossfiring. Truck does seem to idle smoother. Going to check secondary fuel pump to see if it has a serviceable filter and then check spark plugs to see what they’re reading. Thanks again guys!
 

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1990 Ford Bronco Custom, 5.0L EFI AOD Manual Hubs
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Hows it going guys. New member here whos working on a 1988 Ford Bronco 302 that has an odd vibration while idling and occasionally backfires if the engine speed is increased at a quick rate. It also hesitates when I open the throttle quickly and then shortly after the rpms increase. I did move the truck like hundred feet the other day and it stalled a couple of times while shifting from drive to reverse and vice versa.

A bit of history on the truck, truck had a blown head gasket and had sat for around 4 years. The engine was replaced with a long block from autozone. Many parts were replaced including the front end accesories, starter solenoid, all ignition parts etc. Other parts were serviced such as the trans and trans filter, fuel filter and fuel pump hangar and pump were replaced. All vacuum lines were replaced since the many of the old lines cracked while I was removing the engine. I did use one of the "how to's" on one of the other forums thats specifically for this vehicles platform.

Truck has no issue turning on and fires up instantly. I have checked the timing with a timing gun and it seems to read fine at around 12 degrees. Today I hooked up a smoke machine to one of the vacuum hoses and saw no smoke leaking from anywhere unusual. I'm starting to draw blanks on what it can be. I was thinking perhaps one of the fuel injectors is bad, but they're all brand new as well. Can it be that the tps is bad? Ill check the spark plugs tomorrow to see in what condition they are in.

Also, worst case scenario, what if the engine isnt the correct one. Meaning, what if its internal balance is incorrect? How obvious would one be able to see that the flexplate and harmonic balancer is the not the correct one for the engines internal balance? I dont see any odd vibrations on the harmonic balancer when the engine is running but Im still curious.

Thanks in advance..
Have you checked the MAP sensor?
 
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