I put a new ign. coil on #3 cyl. of my 5.7 Hemi when I first started it in the yard it ran great /I went for a test drive and in about 1 city block my 4wd light and my svc light as well as my electric throttle light came on ,I have no brake boost and it runs suoer rough .Any ideas?
How old is your battery?
Are the connections clean and tight?
What’s the charging voltage at idle?
A dislodged or split vacuum line could cause symptoms like this.
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Your #3 cyl issue might be masquerading as a dead cyl issue. Do you have cyl deactivation? Hemi motors of a certain vintage have issues.
It sounds like a valve problem of some sort. Suggest a compression test. Some mopar engines by the post we get here can have problematic valve springs. You might try the forum search feature to see what others have said, upper right link, this page. I don’t seem to recall this being an issue on RAM 1500’s though.
How about a broken vacuum line to the brake booster? Is the line even connected? This could be a huge vacuum leak causing both issues. The good news is that this would be a cheap and easy fix.
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