1990 Nissan Pathfinder engine missfire

AASTE

MEMBER
1990 NISSAN PATHFINDER

Engine Performance problem
1990 Nissan Pathfinder 6 cyl Four Wheel Drive Automatic 250ooo miles

Hello,
My engine misfire when cold only. After warm up, works great. It started, I think, after I replaced spark plugs from NKG to CHAMPION. Then I got original NKG back and problem still persists. I suspect the spark plugs cables were compromised, or at the same time we uses gasohol creating problem with this engine. What else? No air leaks and clean air filer. (Also there seems to be small dirt deposit on spark plug base, perhaps preventing properly seatings, did not have any vacuum small enough to clean dow deep).

3 Replies

BMRFIXIT

MECHANIC
19,053 POSTS

Check for spark at coil wire and at each spark plug wire using a spark tester. DO NOT crank engine continuously for more than 2 seconds. Inspect secondary coil wire for arcing while testing spark at plugs, you can wet the wires and inspect for spark leak using a test light grounded at negative side of the battery, run test light close over the wet wire
Visually inspect all electrical wiring. Look for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and are not pinched or cut
Check engine mechanical condition with a compression gauge, vacuum gauge

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Saturday, October 16th, 2010 AT 6:35 AM

AASTE

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3 POSTS

Thank you for the professional answer. Unfortunately, I do not have the equipment to test the spark plug quality. Can you please give me a hint from your experience the order of a probable failure. I can only replace components one a the time. What should I replace first, second, etc.
You have not mentioned dirty fuel injectors, I assume this cannot be the cause.

The engine is working excellent after warm up, there are not loose wires or leaky vacuum pipes.

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Saturday, October 16th, 2010 AT 11:08 AM

BMRFIXIT