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13 Posts
Discussion Starter #1
Greetings Ford Guru’s,

Not sure how much info you need, but the more the merrier right? Anyways, my apologies for this long winded post.

To avoid starting several different posts, I’ll condense them all here as there’s only a “few” issues I need help with. I have Googled & used the search function here on the forums & have had other questions answered as I lurked (Thanks!!) and on the others, mixed results.

Now down to the nitty-gritty:

About a year ago I bought an ‘89 Bronco XLT with the 351w. It’s an automatic with the C6 in it and it’s currently rolling on 31’s. I bought it dirt cheap from an elderly fella that I have since come to find out, most likely never opened the hood if judging from the condition of the components under it. Of course during the test drive it drove great, if not exactly fast. Still the price was right @ $1k even.

Severe Lack of Power

On the flats, it drives OK. It’s not fast, (I read somewhere that Broncos were really heavy?) but it scoots along more or less fine and I’m not a speed demon so I’m not worried about spinning the tires.

However, as soon as I face one of the 3 medium grade hills in the city I live in, the Bronco starts to whimper & whine. I’ll hit the hill doing 45 mph & then my speed will begin to quickly bleed off until I’m doing around 25 mph about a minute later. My RPM’s will stay the same @ 2k. As soon as I make it to the top, I’ll pick up speed again like nothing happened. I initially took it into the shop for this reason and they told me that because the previous owner had installed an aftermarket set of gauges in the cab, (Oil Press & Coolant gauges in cluster are dead) they bypassed the Coolant Temp Sensor & oil press sensor with an aftermarket unit and was told that if I Installed the correct coolant temp sensor and reconnect the harness it’d fix my performance issues. So I had the repairs done & ZERO difference.

4 different local repair shops later, not to mention 3 Craigslist "specials" and I gave up on getting a straight answer out of anyone and so I just started started throwing parts at it so that I KNEW the parts were new.

Within the past year, I have done the following repairs: (About 4k miles total on new parts)

1) Replaced Coolant Temp Sensor
2) Replaced the spark plugs.
3) Replaced the Cap & rotor.
4) Replaced the spark plug wires.
5) Replaced the MAP sensor.
6) Replaced the ICM.
7) Replaced the EGR. (Not the EVP though)
8) Replaced the Fuel Filter.
9) Replaced the IAC.
10) Replaced the TPS.
11) Replaced the front brakes.
12) Replaced the accelerator cable
13) Replaced the PCV
14) Replaced the o2 sensor Pre-CAT.
15) Had the C6 checked at a local transmission shop & it got a clean bill of health. (I'm on the fence with this)
16) Had the Fuel pressure checked multiple times. 35 & 45 psi.
17) Had the fuel regulator checked. OK. Also held vacuum and no fuel leaks.
18) Had the timing re-done yesterday and set to 8 BTDC. It was at 5 when I bought it and after both reading & being told I should have it set to 12, I did 6 months month ago. Ran even worse and then died and so it sat parked for 3 months. I recently got it back up & running.

Cylinder Compression Test (Done 1/6/17)

1: 97 PSI
2: 105 PSI
3: 100 PSI
4: 105 PSI
5: 105 PSI
6: 110 PSI
7: 105 PSI
8: 105 PSI

Vacuum Lines
I had the canister & vacuum lines tested. All held vacuum. (Have not tested the Intake itself for leaks, though a tech gave it the once over and said nothing was visually amiss.) I recently discovered that the previous owner had hollowed out both the CATS and so the tan brown vacuum line to the TAB was broken off. However, I again read and was told that the TAB & TAD weren't needed and could be capped off. Is this true?

Slow Rolling Idle
At low rolling RPM’s, such as when I pull into my apartment’s parking lot, my idle always surges & stumbles and it goes away if I give it gas but will come back the moment I take my foot off the gas. It mostly only happens after I have driven the truck for a short time. Such as after driving it the 7 miles home from work. I noticed that the Idle screw has at some point been messed with by someone (one side of it is chewed up & stripped) Once warmed up & in gear, my idle is at approx. 750 RPM. Is this the normal range?

I have done the KOER & KOEO tests and the codes that came up I repaired/replaced. No Check engine light is currently on, but it will "sometimes" come on after the truck gets good & warm, but not always. However, I still have 0 power and it recently DID die at a stoplight and was very hard to get back up and running.

Any suggestions?

Thanks very much in advance!

Super Moderator
869 Posts
Are you sure you have a c6 instead of an aod or e4od? It sounds to me like, other than what was stated above, your base idle needs to be reset and the transmission is on its way out. Does it have overdrive?

13 Posts
Discussion Starter #5
Compression readings are low , signifying general engine wear . You tried a wet compression test ? This explains ,

Part 2 -How to Test Engine Compression (4.9L, 5.0L, 5.8L)
Good morning,

No, the tech only did the dry test. The link you provided is actually the link I used when I printed out the entire procedure for the tech should he have needed it. He said he didn't. However, after he did the test & left, I was reading through it and noticed that the tech had not:

1) Pulled all of the plugs before starting.
2) Disabled the Fuel Pump (Bypassed directly to the starter with a hand held push button power switch)
3) Have the throttle wide open during the test.
4) Allowed the motor to warm up 1st. It had been sitting for a week. The outside temps were sub-freezing.

Does any of this matter?

Are you sure you have a c6 instead of an aod or e4od? It sounds to me like, other than what was stated above, your base idle needs to be reset and the transmission is on its way out. Does it have overdrive?
I checked the bolt pattern when I first bought the Bronco and then when I took it into the tranny shop, they verified it was the C6. 3 on the column & no "OD." I was told by the shop that it was OK.

What are the vacuum readings at idle and then holding at 2000RPM.
These readings I do not have, as the tech did the test with the engine cold & off.

Thanks everyone for the replies!

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