Bronco Forum - Full Size Ford Bronco Forum banner

21 - 26 of 26 Posts

·
The Tennessee Warden
96 XL, 5.8L, E4OD, BW1356, 4.56 gears
Joined
·
3,403 Posts
Discussion Starter #21
Thanks miesk5,

SO I take it this is NOT a vacuum line at all then, so it shouldn't be affecting engine performance then. Good to know.

I had a friend come look at it with me, and we went through and pulled plug wires as it ran, and it looks like there may be problems with the number 2 and/or 3 cylinders - there was no real effect on the idle when either wire was pulled. I will be doing a compression check next as well as pulling valve covers and inspecting rocker/valve movement. I don't see ANY white smoke, so I don't think I am getting any ring blow-by. Burnt valves maybe? Cam lobe problems? The vibration i mentioned above is apparent as you watch the engine and turn the throttle lever slightly.

I can hear some noise (buzzing) coming from the EGR, so that will be replaced as well.
 

·
The Tennessee Warden
96 XL, 5.8L, E4OD, BW1356, 4.56 gears
Joined
·
3,403 Posts
Discussion Starter #22
The more I think about it, and the more I read about this issue, the more I think I may have a burnt exhaust valve or two. This would cause lack of sufficient compression in the affected cylinder(s) and permit unburned fuel/air mix into the exhaust system, which may be the cause of the "spitting" little backfires I am hearing coming out of the tailpipe after the engine is warmed up.

Does this all sound feasible?

This would preclude the issue I mentioned about valves not opening, because the intake valve would have to open to permit fuel into the chamber, and if the exhaust valve weren't opening (and seating properly), then I would be seeing (and hearing) intake backflow/backfire issues, right?

Sorry to drone on and on about these issues, but the feedback I have been getting here has been invaluable!

Thanks everyone!
 

·
Registered
Joined
·
1,134 Posts
The more I think about it, and the more I read about this issue, the more I think I may have a burnt exhaust valve or two. This would cause lack of sufficient compression in the affected cylinder(s) and permit unburned fuel/air mix into the exhaust system, which may be the cause of the "spitting" little backfires I am hearing coming out of the tailpipe after the engine is warmed up.

Does this all sound feasible?

This would preclude the issue I mentioned about valves not opening, because the intake valve would have to open to permit fuel into the chamber, and if the exhaust valve weren't opening (and seating properly), then I would be seeing (and hearing) intake backflow/backfire issues, right?

Sorry to drone on and on about these issues, but the feedback I have been getting here has been invaluable!

Thanks everyone!
Your problem can certainly be with the valves. However, what these two cylinders have in common is the area between them being sealed by a head gasket. I've had this problem before on my 5.8 after my wife severely overheated the truck. Between overheating the engine, and me driving it around for about a month after that, there was a significantly sized hole in the head gasket between these two cylinders. A compression check will tell you a lot.
 

·
The Tennessee Warden
96 XL, 5.8L, E4OD, BW1356, 4.56 gears
Joined
·
3,403 Posts
Discussion Starter #24
Yes, flomaster -

That is true. The head gaskets certainly could be a problem here also. It looks like the heads are likely coming off anyway, at the least for an inspection of the valves, so new head gaskets will be part of this adventure! Thanks!

Looks like I may have some work cut out for me!
 

·
Registered
Joined
·
1 Posts
Motor Bogs Out In 2nd gear 4spd manual 3rd does the same going up hill 4.9L theres some whistling i hear an sometimes throttle gets caught on the rev an it cruise at 15mph with my foot off the gas, had no exhaust just a cat an 1st start after installing a muffler it wanted to bog out, revved it until it ran good, did so for about 3 days until i went to test on paved inclines. . I Changed the mapS. . previous owner claimed the injectors were bad an had the throttle body unbolted an started disassembling, ive put everything back, thru a new battery in an started it up changed the map an ran good until i put that muffler on, revved it out an ran good for 3 more days. . any ideas?
 

·
Super Moderator
Joined
·
24,974 Posts
Yo Navajo4x,
Welcome!
I assume you have an EFI Bronco, please post year, etc.8
162520


Will move your post soon for better visibility.
 

Attachments

21 - 26 of 26 Posts
Top