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Discussion Starter #1
Hey guys, it's been a while. The 5.8 in my bronco started running bad last year and I parked it thinking maybe just bad gas, since it sits a lot. It is very sluggish and has no power (seems to be after it warms to a normal temp). It will bog down and seems to backfire to the intake. If I can get it to a higher RPM (2000) it seems to go better, but that's no good in the rocks. It's due for Smog in a couple months, so it needs to be running good for that and hopefully a trip or two soon.
Wondering if anyone in the wide world of Broncos has had this issue and what was the fix. I'm sure I can track it down, but any Ideas would be great. It has no Cats so a clogged converter is ruled out. I'm hoping that it's just in need of a tune up, but my gut is sayin timing set. What do you think? Ordering tune up parts and maybe a timing set too.
What I've done so far:
Swapped the computer (didn't think that would be it but I had it anyway)
Changed the fuel filter ( had it sitting on the shelf anyway)
drained completely and added fresh fuel

Next on the list:
full tune up plugs, wires, cap and rotor. (I always do these before a smog anyway)
Timing set, water pump, (while I'm there) and gaskets.
 

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If it is not a Bronco, it's just not worth driving.....
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My dollar is on a vacuum line either has a hole or is completely broken. It is very common to have your symptoms with a vacuum leak. It is also very common for these old trucks to have vacuum leaks.

I would start there before diving in to the timing gears....
 

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Discussion Starter #3
My dollar is on a vacuum line either has a hole or is completely broken. It is very common to have your symptoms with a vacuum leak. It is also very common for these old trucks to have vacuum leaks.

I would start there before diving in to the timing gears....
that's a great suggestion. I did look but that was when it was on the trail and hot. I'm going to look again, and maybe block off a few nonessential lines. I'n not putting my money on it though, it still idles good and is pretty good until it gets to operating temps.
 

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Yo,
Lack of POWER:
Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19

Some no code usual suspects by Ford;
As advised, Vacuum leak, see my leak diagnosis link in post #11


Air filter, is it relatively clean?
Air inlet atop radiator support to filter box and to throttle body; look for obstruction; damaged tubing, openings in tubing, loose fit at throttle body or if equipped, at MAF sensor.
Fuel quality; Oxidized fuel often turns darker over time and may even smell sour. You can check stored gasoline by pouring some into a clear glass container and comparing it side-by-side with known fresh gasoline. If your old sample looks noticeably darker than the fresh gas, you have strong evidence the gas has gone bad.
Electrical connectors; inspect for corrosion, etc at coil, firewall, ICM, distributor, PCM, etc. especially those with broken locking tabs.

E4OD:
Pull the transmission dipstick out when the engine is running at normal operating temp. The level should read FULL.
Look for leaks around pan from (front) Pump seal. Observe color and odor of the fluid. It should be red, not brown or black. Dark brown or black fluid that has distinct burnt odor, indicates a transmission in need of repair or overhaul.
Odor may indicate overheating condition, clutch disc or band failure. Use an absorbent white facial tissue and wipe the fluid level indicator. Examine the stain for evidence of solid particles and for engine coolant signs (gum or varnish on fluid level indicator).
If particles are present in the fluid or there is evidence of engine coolant or water, the transmission pan must be removed for further inspection.

E4OD Transmission Control Indicator Light (TCIL), it is a LED and overdrive on/off switch at end of the Transmission shifter stalk; flashing OD light is an indication of a transmission related trouble code in the Powertrain Control Module (PCM).
➡Is it flashing while driving?
 

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Discussion Starter #6
Went hunting for Vacuum leaks and found a couple maybes but nothing big. I did go ahead and do the cap, wires, and plugs. I always do plugs and cap/rotor before I take it for smog anyway. It is a SD system so no MAF sensor to check. Still no power, seems to bog down, and occasionally back fires in to the intake. Kinda reminds me of when the accelerator pump is bad on a carb.
 

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what kind of fuel pressure are you getting? at idea you should be around 32 psi with vacuum and it should bump to about 40 with the vacuum disonnected. Pretty sure that's correct.
 

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1984, 300 L6, smogless, manual 3speed with overdrive.
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I have typically found backfiring into the intake is usually a timing issue.
 

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Discussion Starter #10
what kind of fuel pressure are you getting? at idea you should be around 32 psi with vacuum and it should bump to about 40 with the vacuum disonnected. Pretty sure that's correct.
I'm going to have to check on this.

I have typically found backfiring into the intake is usually a timing issue.
me too, thats why I'm thinking timing set. nothing has been changed on the motor side of this rig in 8 years, other than spark plugs and oil/filter.
Have you checked it for exhaust flow? A clogged CAT can play hell with your power.
nope cant be that, 1 is gone and 1 gutted, I have a good Y-pipe with cast I put on for smog.
 

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YoT,
Have you tested for Codes yet?

some Ford No Code Lack/Loss of Power in Acceleration or Cruise Suspects;
Although you did replace vacuum lines, see my leak diagnosis link in post #11 it includes HVAC System.
One way to do a quick check is to grab a vacuum gauge. Some parts stores will loan you a gauge with refundable deposit.
The vacuum gauge should read between 15 and 22 in-Hg depending upon the engine condition and the altitude at which the test is performed. SUBTRACT ONE INCH FROM THE SPECIFIED READING FOR EVERY 1,000 FEET OF ELEVATION ABOVE SEA LEVEL.
The reading should be quite steady. .
When engine is rapidly accelerated (dotted needle), needle will drop to a low (not to zero) reading. When throttle is suddenly released, the needle will snap back up to a higher than normal figure.

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 and air conditiner air Flow will switch to defroster outlets.

Air filter, is it relatively clean?
Air inlet atop radiator support to filter box and to throttle body; look for obstruction; damaged tubing
Fuel quality; Oxidized fuel often turns darker over time and may even smell sour. You can check stored gasoline by pouring some into a clear glass container and comparing it side-by-side with known fresh gasoline. If your old sample looks noticeably darker than the fresh gas, you have strong evidence the gas has gone bad.

Electrical connectors; inspect for corrosion, etc at coil, firewall, ICM, distributor, PCM, etc. especially those with broken locking tabs.
 

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Discussion Starter #13
So an update.
checked vacuum and idles at 15 (I'm at just above 2000 Ft above sea level)
I have Hydro boost brakes and the cruse control is blocked off too, so that didn't leave much left to check.

Went ahead and changed the timing set and water pump, Hadn't done it since I've owned it so it was time to look any way. Timing is still at 11* where it has been for years.

I had a code 67 and read that it was one of 2 things, the AC compressor or the trans selector switch. I had the compressor disconnected so reconnected it and found the code remained. After re-seating the the connector I came up with a code 11 which is no code found. test drive said that's not it, but now it won't crank on occasion so I'll have to look in to the switch and it's connection some more.

Checked fuel pressure and it was 30-35. Since it did have bad gas before I started all this, I drained the tank and had refilled with 5 Gal fresh gas and replaced the filter (was my first guess). Since gas prices are down low I went and put 25 Gal in it last night.

Today I'll be looking into the trans switch some more and. since I have a couple BAP sensors around I might toss one in just to eliminate it.
Thinking about TFI module too, since it seems good until it reaches operating temps. Unfortunately I don't think I have one laying around, or the socket to remove it.

Keep the suggestions coming, surely there's something I've overlooked.
 

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1984, 300 L6, smogless, manual 3speed with overdrive.
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Discussion Starter #15
Just took a short test drive with the BAP sensor I pulled from another truck and the results were good. Thinking it's stuck. no code came up for it.
I'll take a longer drive later but this seems to have it working good. Now it'll be more reliable this summer with a new timing set and water pump. Plus the plugs, rotor, cap, and wired are ready for the next smog in Aug. Now if the lock downs will end and trails open up, we'll be good.
 
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