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2.8 issues


Jay_4_hut

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Hello,
Have some issues with vacuum on my engine. It is pulling so hard regardless with the pvc valve closed off and will not idle for nothing. I have my high speed setting is about 2k rpms just to keep it to run. Let me know your thought
 


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Hi, and welcome to the forum. I moved one of your threads and closed two other duplicates, you will receive more help and more relevant responses if we keep everything in one spot.

What troubleshooting steps have you taken so far? Carb cleaned/rebuilt? Wiring to the various engine sensors intact? Adequate fuel? I am not real familiar with the feedback carbs like you most likely have, I'm assuming that's the case since your in CA and have to pass smog so your truck has not been Duraspark swapped?
 

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Hi, and welcome to the forum. I moved one of your threads and closed two other duplicates, you will receive more help and more relevant responses if we keep everything in one spot.

What troubleshooting steps have you taken so far? Carb cleaned/rebuilt? Wiring to the various engine sensors intact? Adequate fuel? I am not real familiar with the feedback carbs like you most likely have, I'm assuming that's the case since your in CA and have to pass smog so your truck has not been Duraspark swapped?
Yes I have rebuilt the carb. I have have been eliminating a lot of the smog garbage on this motor. I have cleaned the gas tank. The vacuum is so strong coming from the oil cap even if I plug off the pvc valve. I haven’t diraspark this engine
 

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Unfortunately on the 2.8L with computer controlled carb (CCC) system a lot of the "smog garbage" is related to how well the engine runs and idles. A couple of more questions to help us:

Did the truck run OK to a point, and if so was something changed at the point your current problems showed up? (example: was it when the carb was rebuilt?)

What all have you removed or disconnected? Especially, since the carb's been rebuilt, is the solenoid on the rear of carb still in place and connected?

It's been over 10 years since I Durasparked mine, so it's been that long since I've dealt with the CCC system. I think if it were me, I'd start by temporarily disconnecting all of the vac lines at the manifold, plug the manifold vac ports and see if I could get the engine to idle. Then go from there.

Do you have a vacuum gauge, as a diagnostic tool? Very useful, and well worth getting one.
 

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Unfortunately on the 2.8L with computer controlled carb (CCC) system a lot of the "smog garbage" is related to how well the engine runs and idles. A couple of more questions to help us:

Did the truck run OK to a point, and if so was something changed at the point your current problems showed up? (example: was it when the carb was rebuilt?)

What all have you removed or disconnected? Especially, since the carb's been rebuilt, is the solenoid on the rear of carb still in place and connected?

It's been over 10 years since I Durasparked mine, so it's been that long since I've dealt with the CCC system. I think if it were me, I'd start by temporarily disconnecting all of the vac lines at the manifold, plug the manifold vac ports and see if I could get the engine to idle. Then go from there.

Do you have a vacuum gauge, as a diagnostic tool? Very useful, and well worth getting one.
The Branco had some overheating issues that cause the head gasket to giveaway so I have to reduce them. But I was thinking of taking all the vac hoses off and cutting it down that way, but I wanted to hear from another person as well. And I’ll connect it to my vaccine gage before I start disconnecting hoses. I’ll keep you updated to see if I run across anymore
 

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RonD

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Yes, if you have a vacuum gauge what are some numbers?

18-21" at sea level to 2,000ft elevation is normal but as high as 24" is not unusual, if you live below sea level(low dessert) then vacuum gets pretty high
PCV Valve should be mostly closed at idle, it opens when Vacuum is LOW

Spark timing needs to be set with vacuum advance unhooked and hose plugged, or SPOUT wire unplugged
10-12deg Before TDC is spec

Any history on this engine?
2.8l uses a timing gear, no chain, so can't really "skip time", as far as valves are concerned, but it could be rebuilt with incorrect valve timing
But this generally lowers compression which lowers vacuum
 

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Yes, if you have a vacuum gauge what are some numbers?

18-21" at sea level to 2,000ft elevation is normal but as high as 24" is not unusual, if you live below sea level(low dessert) then vacuum gets pretty high
PCV Valve should be mostly closed at idle, it opens when Vacuum is LOW

Spark timing needs to be set with vacuum advance unhooked and hose plugged, or SPOUT wire unplugged
10-12deg Before TDC is spec

Any history on this engine?
2.8l uses a timing gear, no chain, so can't really "skip time", as far as valves are concerned, but it could be rebuilt with incorrect valve timing
I’ll double check all this and keep everyone updated
 

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If you can test compression on some cylinder that might help you
 

Jay_4_hut

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If you can test compression on some cylinder that might help you
I have preformed a comp test on the engine. But I’ll do another one with the other efforts mention above. I’ll keep everyone updated if it fixes things or if it gets worst
 

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Need the Numbers
What were they?
 

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The Branco had some overheating issues that cause the head gasket to giveaway so I have to reduce them. But I was thinking of taking all the vac hoses off and cutting it down that way, but I wanted to hear from another person as well. And I’ll connect it to my vaccine gage before I start disconnecting hoses. I’ll keep you updated to see if I run across anymore
Can you pass smog after you take everything off? If you can, you should swap it over to a duraspark II distributor and ignition system. Your engine is computer controlled, think of it like a early fuel injected system. You would not go out to one of your more modern fuel injected cars and start taking stuff off of it would you? I know you wouldn't, you know it would mess it up and it would not run correctly. Your old Bronco is the same way unless you convert it over to a older style distributor. I did mine for the same reasons, and now it runs great.
 

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Yes I have rebuilt the carb. I have have been eliminating a lot of the smog garbage on this motor. I have cleaned the gas tank. The vacuum is so strong coming from the oil cap even if I plug off the pvc valve. I haven’t diraspark this engine
So are you seeing air sucked INTO the oil cap breather hose or are you seeing air blowing OUT of it? You should not have a vacuum in that location, the oil cap breather hose is positive pressure. I am confused about this, it was common on old, worn engines with blow-by issues to see blue oil smoke puffing out of that breather hose while it's running. Is that what you're seeing?

I'd be totally shocked if you can legally remove any of the smog equipment and still pass. The other issue with doing that is if you remove any of it, you should be removing ALL of it, and doing a Duraspark swap... it's like removing sensors and stuff from a fuel injected engine... it is all necessary for it to run correctly.
 

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He will have a slight vacuum on the oil cap if the engine is in really really good shape and the rings are sealing good. The PCV valve sucks air and junk out of the engine, air enters the engine through the other valve cover via the hose to the aircleaner housing.

As the engine gets older and older, and the rings seal less and less, the pressure in the engine increases over time, till it gets so bad that the PCV valve is overwhelmed, and the pressure starts going out of the breather cap and starts going up inside the aircleaner housing.
 

Jay_4_hut

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He will have a slight vacuum on the oil cap if the engine is in really really good shape and the rings are sealing good. The PCV valve sucks air and junk out of the engine, air enters the engine through the other valve cover via the hose to the aircleaner housing.

As the engine gets older and older, and the rings seal less and less, the pressure in the engine increases over time, till it gets so bad that the PCV valve is overwhelmed, and the pressure starts going out of the breather cap and starts going up inside the aircleaner housing.
Oil side is pulling so hard it’s really difficult to pull off the oil cap. Last night I went out to mess with it a little bit and pcv is sounding like a paint can rattling around.
 

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