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Burning #4 Spark Plug

irokgmc

irokgmc

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I have a 5.7 TBI motor out of a 94 in my 70 and started having some problems with it running rough. I could hear a miss at idle, and under acceleration it would hesitate and miss real bad. I replaced the cap & rotor, plug wires and plugs. When I pulled the plugs the #4 plug was burnt a bit and after about 10 miles on the new parts here is what the #4 plug looks like again and the same problems are back. Doesn't seem to be oil on the plug, what should be my next test to run?

TJ's 100.jpg

TJ's 099.jpg
 
I had a problem like that a long time ago and it ended up being a wiped lobe on my cam. Hope that ain't your problem.
Tarey
 
First off, is the engine still TBI or carbed? Secondly, this is my opinion but throw away any plug that isn't an NGK V-power plug. I've had the best luck with those plugs. That plug isn't burnt but just discolored on one side. What are you setting the gap at? Are those plugs for the 94 TBI engine or for the 70 engine? This is all info that is needed before anyone can help you. You could have too cold of a heat range plug or even too hot of a plug. As someone already suggested the very first thing to do is a compression check so that you know you're problem is tune up related.
 
Hello,
It is running the TBI unit, with the computer and harness from Affordable Fuel Injection. The plugs are ACDelco CR43TS and I ordered them for a 94 and set the gap at .035. I went to my local parts store this morning and picked up a KD Tools compression tester (all they had). The numbers it gave me are as follows.

1. 170 2. 165
3. 165 4. 165
5. 165 6. 165
7. 160 8. 170

When I pulled the plugs today the #6 plug was broken.

TJ's 101.jpg

TJ's 102.jpg
 
That plug doesn't look all that bad they are going to get brown and .035 seems a little small for a gap :rolleyes:
 
kgblazerfive said:
That plug doesn't look all that bad they are going to get brown and .035 seems a little small for a gap :rolleyes:
Click to expand...

The ideal color is very light tan.

White means lean, brown means rich.


.035" is on the small side for gaps; the spark plug gap is primarily based on the voltage provided by the coil. More voltage = larger gap which generally means a better burn.

.035" isn't necessarily too little gap by any means.
 
checked auto zone it does call for the cr43ts ac delco gapped @ .035.according to them all is good there.

I would like to see a better pic of #6! You did not drop any of the plugs when they were installed? The compression looks ok.

#6 bothers me,Any knocking from the engine? or anything got dropped into the engine?

Mike
 
I put one of the old plugs back in #6 today just to move the truck around. It does not sound like anything is in there. There is still a miss at idle. The first time I took it out it took about 20 miles of driving for it to start acting up, by the time I got to my street I couldn't even give it gas, just had to practically idle home. After changing the parts mentioned above I only went about 10 miles before it started happening. I would miss at idle and stumble at higher RPM's. I did do the paperclip deal to pull codes and I got code 42 the first time. I need to get an ALDL cable or scanner to see if there are any codes again.

TJ's 104.jpg
 
The old plug that I put in #6 to replace the new AC Delco that cracked is a Bosch Platinum +2, so no I did not re-gap it.
 
Chevy engines i've found don't like platinum plugs unless the manufacturer required them.
 
That's what I have been told by many people. They were in there when I bought the motor and that is why I stuck the ACDelco plugs in. So my next step should be to test the ESC? Could the fact that the AFI harness doesn't use the EGR be causing these problems?
 
I think it is either the distrbutor module or pick up coil.
Try replacing the module and see what happens.
Many auto parts stores like AZ will test the module. If you pull it and take it to them.
Pre ignition can crack plugs like the way yours are cracked. A bad module or pick up coil can mess up the timing bad enough to cause preignition.
 
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