Need help getting the Bronco running better

[Mike74Bronco]

I just got the Bronco back from the shop and it passed safety and emissions! Now that I've got it back on the road for the first time in 11 years I need help getting everything running right. Here are my concerns so far:

1) What should the alternator gauge read under normal operating conditions. Mine reads just barely above 0. Is this normal? Is there something I can do to test the gauge before suspecting alternator problems?

2) When I am driving the bronco (it is moving) my oil pressure gauge reads around 40, but whenever I stop at a light the guage slowly drifts down to very close to 0 and then it drifts back up to 40 once I get moving again.

3) The engine idles rougher than I would like it to. When I stop at a light it sounds like it wants to die, but it never does. I've played with the idle screws a little bit and the drivers side is about 2 turns out to get the smoothest idle. The passengers side screw I can't get to make much difference, but it is about 2 turns out as well.

Here's some numbers on the engine if you see anything to be concerned about let me know. I have a 302 with a rebuilt 2150 carb.

Idle Speed: 650 RPM
Timing: 6 BTDC
Manifold vacuum at idle: 12 - 13 inHg
Compression Test (1 - 8): 130, 122, 120, 110, 130, 110, 112, 110

Emission Results:
15 MPH (1294 RPM) CO2-11.7 O2-0.8 HC-299 CO-4.23 NO-492
25 MPH (1304 RPM) CO2-11.5 O2-0.9 HC-309 CO-4.57 NO-384

Thanks to everyone for their help. I wouldn't have gotten the Bronco this far without ya!

 

[Colo77Bronco]

alternator guage is not a volt meter so it reads differently. I would ignore it and put in a volt meter.

Advance the timing now that you passed emissions and it should smooth things out a little.

New jets may help also. To pass emissions they set up the carbs pretty lean.

 

[johnmlebel]

the gauge read draw/output so at idle it should be close to zero alternator is spinning slowly but while going down the road it spins fast putting out more power. mine hovers around zero at idle/stopped and jumps to about 30 will driving

 

[jedblake]

Carb: I had a similar stuttering problem at red lights. I ended up turning my idle screw (edelbrock 600cfm) up up a bit more. Idles at around 750 in Park but when in Gear steady at 550-650.
On Alt: Some vendors now have a replacement face plate for the gauge to change from Alt to Volts. or simply add a new gauge cluster. My original gauges were so inconsistent I was forced to go w/ the latter.

 

[blubuckaroo]

1) Once the battery is fully charged, the ammeter should read zero.
2) Oil pressure will change with engine speed. Yours is pretty low. I'd check with a tempory pressure guage. What weight oil are you using? These things are dinosaurs you know. I wouldn't run anything thinner than 10W-40 in mine.
3) Check for vacuum leaks and bad plug wires. I struggled with idle problems for years before I found that my vacuum brake booster had a leak. Does it have an EGR valve? You might need a new one if it leaks.

 

[Mike74Bronco]

So perhaps the alternator gauge is working correctly if it is supposed to read 0 when the battery is charged. One reason I am concerned with the alternator is that when the lights are on, they dim in sync with the rough engine idle. Is this normal?

I am using 10W-40 engine oil. I didn't notice the low pressure until I started driving it around. When I had it idling in the garage it always read 40. I'll check it again with an external pressure gauge.

I have tried looking for vacuum leaks but have not been successful. I did unplug everything from the manifold vacuum tee and the rough idle still existed. So if I do have a leak it must be in the intake manifold. Any pointers on checking for an intake manifold leak?

I'm wondering if the rough idle is related to the fact that the idle mixture screw on the passengers side doesn't have any effect on the idle. If I have a clogged idle jet what is the best way to clean it out? I tried to spray it with carb cleaner when I had the carb out last weak, but it made no difference.

 

[blubuckaroo]

You could have a clogged air bleed on that side of the carb. The mixture adjustments actually meter air. This air acts as an eductor and pulls fuel in for idle. The more air the richer the idle mixture. Try pulling out the idle mixture screws and spray Berryman's Chem-Tool carb cleaner into the adjustment holes using a long nozzle on the spray can. This will clean the air passage that starts in the carburator air horn. Do this with the engine off. Cover your eyes because this stuff really is strong! Reinstall the idle screws all the way then back them out a couple of turns as a starting point then make your mixture adjustments.

 

[bronko69er]

One reason I am concerned with the alternator is that when the lights are on, they dim in sync with the rough engine idle. Is this normal?

Yes, it is normal for the voltage to be low at idle and pick up at about rpm or so. If your lights are flickering above 1000rpm you can swap your stock regulator with a solid state version (Napa PN VR440SB) to fix this.

 

[Kenny]

Is your idle speed of 650 rpm while your tranny is in park or drive? If that's the park number, then you probably want to bump it up a bit.

Experiment with your timing. 6 BTDC is the factory setting, maybe for emission reasons? I think most like advancing it to around 8-12 BTDC. That should also bump up your idle a little as well as your vacuum. You'll need to mess with your idle mixture screws after finding the timing you like.

I usually find vacuum leaks by spraying starting fluid next to the base of the carb and manifold. If your idle increases, you've found the leak. Be careful, because it's pretty flammable.

One more thing. Could try a 20w-50 oil for a little more oil pressure.

BTW - How many miles on your motor? Your compression numbers of 110 to 130 deviate more than 10%. Low vacuum and low oil pressure are also signs of an older motor. I'm not saying that it needs replacing, but could be contributor to rough running. Maybe some of the more knowledgeable motor guys will know?

 

[bamabronc74]

I hyad similiar problem with oil pressure and found it to be a destroyed timing gear. The stock gear was plastic and had come apart and totally clogged the pick up in the pan

 

[bronko69er]

My oil pressure has always behaved that same way with 3 different engine conigurations (old 302, old 289, rebuilt 302) 2 different oil pumps (original and high volume) and 2 different gauges (stock and aftermarket mechanical) running 20W-50.

 

[Mike74Bronco]

I took the carb out today and cleaned it really good and put it back in. At first I was excited because the engine was idling much better. Then as things warmed up the idle got rougher and rougher. Also when the engine was cold I had a solid 40 PSI of oil pressure. It didn't drop down to 0 until it got warmed up. I hooked up an external guage to measure the oil pressure and it is definitely below 10. My guage goes up to 400 psi so it isn't real accurate in the lower numbers. Do you think the rough idle could be due to low oil pressure? How much pressure is ideal (and what is the minimum required at idle)? Maybe I need to jump up to 20W-50 instead of 10w-40.

 

[blubuckaroo]

Sounds like time for a rebuild. Sounds like the oil pump is working but the bearings are loose. If you need the car and it is OK to drive, you could use it while comming up with a replacement motor. I ran a car for over a year cleaning oil fouled plugs once a week. You gotta do what you gotta do!

 

[johnmlebel]

i run kendall 10w30 and always have 45-55 lbs oil pressure

 

[Mike74Bronco]

hooked up an external guage to measure the oil pressure and it is definitely below 10.QUOTE]

I checked again and I read the gauge wrong. The first tick mark I have is 20psi and it is somewhere below that. I'm still trying to determine if the low engine idle is caused by the rough idle or the rough idle is caused by the low oil pressure. Perhaps it is time to replace the oil pump and see what happens.

When I put it in park the idle goes from 650RPM to a little above 1000 and the oil pressure goes up to about 20psi. In park the idle is pretty smooth.

 

[Kenny]

hooked up an external guage to measure the oil pressure and it is definitely below 10.QUOTE]

I checked again and I read the gauge wrong. The first tick mark I have is 20psi and it is somewhere below that. I'm still trying to determine if the low engine idle is caused by the rough idle or the rough idle is caused by the low oil pressure. Perhaps it is time to replace the oil pump and see what happens.

When I put it in park the idle goes from 650RPM to a little above 1000 and the oil pressure goes up to about 20psi. In park the idle is pretty smooth.

Assuming your motor was warm, 20 psi at 1000 rpm is good. I'd do some more checking and tweeking before jumping into a new oil pump....they're cheap, but kind of messy job, and I get the feeling it's not your problem. Did you try advancing your timing? A lot have success between 8 - 12 BTDC. I run mine at 12 BDTC and it makes a difference in power and smoothness. Did you try the starter fluid method for vacuum leaks? Also, you mentioned that it was smooth until warm......maybe choke related?

 

[Mike74Bronco]

Assuming your motor was warm, 20 psi at 1000 rpm is good. I'd do some more checking and tweeking before jumping into a new oil pump....they're cheap, but kind of messy job, and I get the feeling it's not your problem. Did you try advancing your timing? A lot have success between 8 - 12 BTDC. I run mine at 12 BDTC and it makes a difference in power and smoothness. Did you try the starter fluid method for vacuum leaks? Also, you mentioned that it was smooth until warm......maybe choke related?

I tried advancing the timing a little bit and it didn't make any difference. The only timing mark I can see is the 6 degree mark because someone painted it white. I'll have to clean things up a bit so I can see the marks better and then I will try again.

I tried spraying around the manifold with carb cleaner and didn't notice any leaks. Does starter fluid work better for this?

I don't think the problem is choke related because I thought the choke was fully open before it started getting bad. I'll check again to make sure.

I'm pretty clueless when it comes to diagnosing engine problems...I'm just learning as I go.

 

[Kenny]

I tried spraying around the manifold with carb cleaner and didn't notice any leaks. Does starter fluid work better for this?

I'm pretty clueless when it comes to diagnosing engine problems...I'm just learning as I go.

I think carb cleaner is fine.....I just have starter fluid lying around so that's what I use.

Are your plug wires in good shape? PCV system hooked up? Any pix?

Diagnosing problems is often a learning process. I've been in your situation before, and it has basically been a process of elimination for me. All of my suggestions have been based on personal experience over the years. Keep at it, and/or hopefully someone else can chime in. Also, if you have a second set of eyes to check things out, it couldn't hurt, because you might have missed the obvious......doesn't have to be someone who is experienced with EB's.....just basic knowledge in old V8's.

 

[Mike74Bronco]

I tried advancing the timing to 8, and then 12, and the idle was the same. I picked up a better oil pressure gauge and found that I have less than 5psi at idle. I only have 10 psi at 2000 RPM once everything is nice and hot.

Here is a video of my engine idling. Maybe it will help explain what it is doing.

http://youtube.com/watch?v=4496mACECIU

 

[Kenny]

Here is a video of my engine idling. Maybe it will help explain what it is doing.

http://youtube.com/watch?v=4496mACECIU

After seeing the video, it definitely reminds me of a vacuum leak.

I noticed a breather on your driver's side valve cover without a hose. This is part of your PCV system. One side (passenger's valve cover on mine) should have a PCV valve with a hose leading to a vacuum port on the intake manifold. The others side (driver's on mine) should have a hose leading to your air filter.

Also noticed that you have vacuum assist brakes. Blubuckaroo mentioned having a bad vacuum assist that gave him problems. Maybe unplug the hose from the vacuum assist and plug with your thumb or check to make sure the hose isn't bad?