Backfires, coughs, running rough

Tiny
75COOKIE
  • MEMBER
  • 2003 MITSUBISHI MAGNA
  • 3.5L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 240,000 MILES
My first problem was crack in radiator, installed new one myself. Running fine changed oil/filter 20-50w. Air filter. Problems; stalling at lights, backfiring. Called lube mobile. He said most likely sparks and leads (they were not proper mits leads. But while I am there should replace rocket cover and plug gaskets. I have done so. Now it is running worse than ever (no loss of oil though) inspected/cleaned up dizzy cap. Ran a scratch better for day. I am single mom at christmas time. Is there anything, something, I could have overlooked in reassembly or messed up that could cause this?
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Monday, December 12th, 2016 AT 4:30 PM

10 Replies

Tiny
75COOKIE
  • MEMBER
Lube mobile man plugged into computer said was no problems. But number six plug not firing.
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Monday, December 12th, 2016 AT 4:40 PM
Tiny
STEVE W.
  • EXPERT
Single cylinder misfire. If you still have the old wires, try swapping one with the number six. Not unheard of for a wire to be bad out of the box. If no joy, swap out the plug with a different one. Check the removed plug for damage/soot/oil that could point to something else.
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Tuesday, December 13th, 2016 AT 2:38 PM
Tiny
75COOKIE
  • MEMBER
Thanks for replying. Just got home from work. Am just starting to pull manifold off again! And I dont know why, but it takes me more than double the time people say it will, to do these things. Mech said leads were soaked in oil. Will a spray of engine cleaner on em b4 I try hurt much?
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Tuesday, December 13th, 2016 AT 10:35 PM
Tiny
STEVE W.
  • EXPERT
Wipe them down and it should be OK as a test. I'd like to get some of the engineers that come up with these engine designs in a room and seal it up.
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Wednesday, December 14th, 2016 AT 11:07 AM
Tiny
75COOKIE
  • MEMBER
Thank you. I had te cortina (78) and prem hq (72) popped bonnet was all there. Ready to be hit with hammer :)b4 magna. I cant see if car starts with different plug n lead till its all back together again yeah. Its just so time consuming. But id rather b sure (as I can b) that is all done properly. Thanks for your patience
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Wednesday, December 14th, 2016 AT 12:15 PM
Tiny
STEVE W.
  • EXPERT
On some of them it's actually easier to work from underneath. But you need to get it high enough to reach up into the abyss it lives in. I do that on a lot of vehicles that stick the manifold over the cylinder banks, usually cursing the designers and bean-counters who pushed it into production without any thought of maintenance.
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Wednesday, December 14th, 2016 AT 12:44 PM
Tiny
75COOKIE
  • MEMBER
Soz I took so long. Am just gettin mani on now # 6 plug was black as. Up the start of thread was gunky but it was in there tite (only 3wks old) have swaped lead. Cleaned up in side dizzy cap.( On upside I found steering fluid leak, is only in hose).
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Thursday, December 15th, 2016 AT 9:01 PM
Tiny
STEVE W.
  • EXPERT
Black plug isn't good, could be because it wasn't firing but could also be an oil issue. That would stop it from firing real quick.

Be careful with steering leaks. The high pressure side can cause injury if it's a pinhole leak.

Looked around and there is a group on these cars. Aussiemagna they might have some better info than I have for specific issues.
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Thursday, December 15th, 2016 AT 9:28 PM
Tiny
75COOKIE
  • MEMBER
Thanks for your all your time. & For taking me seriously, youve been ace, its all back together, no extra nuts or bolts(takes me awhile to get the guts to start it) was a ring clamp? Missing from 1 of the hose connections on steering side so I put another on, was black inside mani on that cylinder. I could see those valves (tappets?) Im not sure but the very end one looked to be on tiny slant compared to rest, mite just be angle I was looking too. An oil issue. I thought as long as its in there is all good.?
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Thursday, December 15th, 2016 AT 11:05 PM
Tiny
STEVE W.
  • EXPERT
Time isn't a problem. I'm semi-retired, and an insomniac. This site and a couple other things are diversions and I get to help other folks fix cars without getting covered in grease :-)

Oil issue - something like a stuck/broken oil control ring or intake valve stem seal letting excessive oil get into the cylinder. Oil creates black goo and carbon causing the plug to short out.
Black inside intake manifold could be something like a faulty PCV valve dumping oil vapor in. That could also cause the same problem with the plug. Oil doesn't burn very clean.
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+1
Thursday, December 15th, 2016 AT 11:28 PM

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