1992 Geo Prizm it seems to be misfiring

Tiny
AVABELLA6308
  • MEMBER
  • 1992 GEO PRIZM
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 19,800 MILES
Now that ive changed the plugs and wires and made sure I had a good connection to them, it still sounds bad, dies when left to idle or when stopping, and just doesnt want to move even when flooring it. What comes next in my process of elimination?And how?
Sunday, December 13th, 2009 AT 10:16 AM

5 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check for an excessive exhaust backpresssure due to a clogged-up catalytic converter.

Engine misfiring can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.
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Sunday, December 13th, 2009 AT 11:54 AM
Tiny
BIGJIM79
  • MEMBER
  • 239 POSTS
Was there a rotten egg smell?
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-1
Monday, December 14th, 2009 AT 2:47 AM
Tiny
AVABELLA6308
  • MEMBER
  • 2 POSTS
No rotten egg smell. Fuel filter and plugs replaced and still the rough idle, stalling easily if im not giving it some gas, and a lot of power lost. I could put the pedal to the floor and was not getting anywhere most of the time. Car will gain speed but very slow and it sounds bad.
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Monday, December 14th, 2009 AT 3:01 AM
Tiny
BIGJIM79
  • MEMBER
  • 239 POSTS
Sounds like it may have jumped time! Did it backfire or anything before rough idle?
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Monday, December 14th, 2009 AT 3:09 AM
Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
Check base timing by shorting Te1 and E1 on diagnostic link. Set mechanical timing to 10 degrees BTDC.

Remove valve cover and inspect timing belt for missing teeth.

Other possibilities are fuel pressure, fuel pressure testing on this car requires a special tool set. Could also be a bad ignitor.

And as Raz mentioned, the convertor could be clogged. The CAT is bolted on, so remove bolts and inspect interior. If you see any melted material, chunks, then CAT is bad.
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Monday, December 14th, 2009 AT 7:54 AM

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