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Spark Plugs Kill Engine?

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Mar 11, 2019, 5:33 AM

Post #1 of 3 (533 views)
Spark Plugs Kill Engine? Sign In

I admit I'm not super savvy when it comes to vehicle repair so I'm at a loss when it comes to my truck dying on me. I have a 1995 Toyota T100 and recently experienced a rough idle with jumpy RPM and horrendous gas mileage. I read online it could be the spark plugs and since that's an easy fix I swapped out all the plugs and when I tried to restart the engine it would turn over but not start. I pulled one of the plugs out to see if I was even getting a spark and when I turned the key the engine fired right up no problem. I quickly turned the engine off and reinstalled the plug I removed and tried again....but oddly enough the engine would turn over and not start again. So I got out and disconnected the coil but left the plug screwed in....I then turned the key and the engine started right up. I reconnected the coil and went on a test drive and it was fine (although the rough idle remains so apparently I didn't fix it).

This morning when I left for work I popped the hood, disconnected the coil, started the engine, then reconnected the coil and drove off (ghetto fix I know). I got about half a mile down the road and the engine started jumping and died. I got out, disconnected the plug again, restarted the car, and decided to just drive on the 5 cylinders. I got another 4-5 miles down the road just fine but then suddenly the truck died again without warning. I coasted into a parking lot and attempted to start it back up with no luck. I was able to get it started with the coil disconnected but the engine was running extremely rough, so I reconnected the coil and suddenly the truck was running fine again. I was able to finish the last 3-4 miles of my commute without issue.

Has anyone heard of something like this happening??? The gaps on the plugs are fine and I didn't have this issue until I put the new plugs in. Could it be the plug wires? Could there be a short somewhere? I'm at a total loss for where to go from here.

EDIT: I could also be using the wrong word when I say coil here. What I mean is the piece that snaps on to the top of the spark plug.

(This post was edited by BlackFlag on Mar 11, 2019, 6:12 AM)

Tom Greenleaf
Ultimate Carjunky / Moderator
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Mar 11, 2019, 7:20 AM

Post #2 of 3 (507 views)
Re: Spark Plugs Kill Engine? Sign In

OK - "You read on line it could be the spark plugs" }}

Those and dozens of other reasons so incomplete. `95 Toyota with a V6 would run like total crap with one cylinder not working, why yet to be found.

What did that plug look like compared to the others - the old ones?

You also said "if will not turn over" have to ask if you mean doesn't crank or cranks but doesn't start or run? If engine didn't turn with starter motor that one cylinder might have been full of coolant or oil or the whole problem.

What do you want to do now and no offense AT ALL but if not sure what is a spark plug wire and what is a coil you could use some help to even diagnose this HANDS ON.

Does this engine use a belt to run water pump as some cars with V6 did? The coolant would be low and it might not run if that failed if so.

1st things first fluid checks, oil level too up to compression test.

It's seriously close to 25 years old all fine you do need to know what things have been done along the way or on time both miles and # of months.

Sorry it's not much of any help to you there's too many things it could be so I suggest some experienced hands on help just to diagnose it and the tools to do so,


Hammer Time
Ultimate Carjunky / Moderator
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Mar 11, 2019, 10:51 AM

Post #3 of 3 (499 views)
Re: Spark Plugs Kill Engine? Sign In

Are you sure you have the firing order correct? see the diagram

This is a waste spark system. Each coil fires 2 plugs so you may be losing 2 cylinders when plugged in and only one when disconnected but I warn you, disconnecting one of the plug wires can damage the coil if it's not grounded.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

(This post was edited by Hammer Time on Mar 11, 2019, 10:53 AM)

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