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420A Help with damaged spark plug

Cypherfox

Probationary Member
8
3
Jul 18, 2021
Houston, Texas
I would like advice or direction to get my car fixed properly.
These are parts that I replaced and not updated on my profile -spark plugs (ngk IX Iridium 6418) and Duralast gold wire set. The care ran with no noticeable changes. Two days later I was driving on the highway (idling at 55mph) when the car just shut off. I did not hear any noises nor was there any smoke coming from the engine. I pulled over and tried cranking the engine and it would not start. I had it towed home and started looking for the problem. The car cranks flowly but will not start. I pulled the sparked plugs and saw that cylinder four had major damage to the electrode. What should I do to diagnose this problem? I'm thinking I should pull the valve cover and engine head assembly, check timing belt and components, have a machine shop check the head for damage, reassemble if everything is okay.

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JeffGS-T97

Supporting Member
691
422
Mar 22, 2019
Muncie, Indiana
Pull the timing cover see if the crank position sensor is still in one piece. If the crank has play the trigger plate will destroy that sensor and the car will immediately shut off. If it did break hopefully if thats what happened the timing belt didn't jump time. If you have a code device the sensor should show up on there if you were trying to start it after blowing the Crank sensor.

Oh im sorry i answered too quickly i just realized your engine is the 420a and this issue may not be common for your engine.
 

JeffGS-T97

Supporting Member
691
422
Mar 22, 2019
Muncie, Indiana
I’m going to remove the valve cover and timing cover. I’ll post a update. I feel like there is serious mechanic damage inside the cylinder since the spark plug electrode is pushed so far in. I know I torqued it correctly.
I agree unfortunately, i hope its not too bad. The damage to that plug is nasty i have literally never seen that before. Sounds like you got a good game plan set, good luck on your repairs.
 

dustyboner

DSM Wiseman
1,678
824
Mar 13, 2016
abq, New_Mexico
you should plan on pulling the head. if its an issue with the timing belt your gonna have bent valves. Even if its not, there has to be a chunk of something bouncing around in the cylinder to damage the plug like that.
 

Cypherfox

Probationary Member
8
3
Jul 18, 2021
Houston, Texas
I’m planning on pulling the head off and getting it checked by a machine shop. It’s my first time doing this so I’m doing it carefully. I’m not sure about a few things though. Is it necessary to get the timing on TDC if I’m going to remove the engine head? Is it okay if I have the engine sitting without any oil? I’ll take some pictures of what I have done so far and post later today.
 

Dericsh

Supporting Member
768
162
Nov 25, 2002
Pearl River, Louisiana
You’re gonna need it on TDC to reinstall the belt, so you might as well put it there before you remove it. If you can, that is, it’s not broken?
It’s fine to leave it sitting without oil while you’re repairing it. When it’s not running, the oil is just sitting in the pan anyway.
 

JeffGS-T97

Supporting Member
691
422
Mar 22, 2019
Muncie, Indiana
I’m planning on pulling the head off and getting it checked by a machine shop. It’s my first time doing this so I’m doing it carefully. I’m not sure about a few things though. Is it necessary to get the timing on TDC if I’m going to remove the engine head? Is it okay if I have the engine sitting without any oil? I’ll take some pictures of what I have done so far and post later today.
Lots of pictures and organizing bolts and parts during your disassembly is highly recommended. It already sounds like you got the right idea so far but it would be wise to reference the manual to make sure you follow the correct order of operation to prevent damaging anything or doing unessassary work.
 

1990TSIAWDTALON

Moderator
8,323
4,201
Nov 14, 2013
Independence, Kansas
I’m going to remove the valve cover and timing cover. I’ll post a update. I feel like there is serious mechanic damage inside the cylinder since the spark plug electrode is pushed so far in. I know I torqued it correctly.
Use a borescope in the sparkplug hole and see what it shows.
 

Cypherfox

Probationary Member
8
3
Jul 18, 2021
Houston, Texas
Lots of pictures and organizing bolts and parts during your disassembly is highly recommended. It already sounds like you got the right idea so far but it would be wise to reference the manual to make sure you follow the correct order of operation to prevent damaging anything or doing unessassary work
I understand and agree that labeling and referencing bolts, fasteners, electrical conections, etc. is important. I'm using both "Haynes" manual and "AllData" as reference guides. Although I still get stuck or I'm unsure about some things. Exp. right now I'm having trouble removing the motor mount bracket that is near the timing cover. I cant get the two bolts far enough out so that i can remove them. I could raise or lower the engine so that i cant have more room to remove them. i could loosen parts adjacent to the mount; timing cover, power steering lines, egr lines, and maybe that will give me more wiggle room. Maybe im doing the whole thing wrong LOL. I"ll attach pictures of what I see.
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JeffGS-T97

Supporting Member
691
422
Mar 22, 2019
Muncie, Indiana
The numbers on the page are they the order of operation im guessing?
I never dug that far into my 420a back in the day, black98dsm is a very knowledgeable guy on the 420a he probably knows a trick or two on that little issue. In the meantime ill dig a bit and see if i can find something.
 

BLACK'98DSM

Proven Member
2,979
990
Feb 9, 2019
Alabama
That bracket is a pain to remove with the engine in the car. But it's possible. Done it twice. What I did is put a jack and block of wood on the oil pan and jack the engine up high enough to slide those bolts out. Then it's a matter of wiggling that bracket out. It fits tightly in there.
 
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