very high idle after changing the plugs

2003 DODGE RAM

177,000 MILES • 4.7L • V8 • 4WD • AUTOMATIC

JIMHAAS3

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I have a very high (1,100+ rpm) idle that began the moment that I changed all the spark plugs and turned on the ignition to check my work. Checked all hoses, they seem okay. Even changed the IAC valve; no change. A friend of mine has suggested that maybe a plug was simply poorly installed. Could this be a factor? (I've noticed that as the engine temp rises when running for a while, the idle goes past 1500 rpm - makes it VERY difficult to control the car and I am concerned about damaging the tranny)

Feb 21, 2015 at 8:17 AM

HMAC300

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48,601 POSTS

Hello,

This can happen if you have the wrong spark plugs installed here are the correct plugs and gap.

Spark Plug Type .................... RC12MCC4 (Champion)

1.01 mm (0.040 in)

Here is a video to show you how to set the gap

https://youtu.be/c9_NVXiwvYg

Please let us know what happens.

Feb 21, 2015 at 10:13 AM

BOOPERIII

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1 POST

Thanks for this post I had the same problem had to get the correct plugs all fixed! I love this site.

Jul 17, 2019 at 1:31 PM

COWGIRLEMT07

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2 POSTS

I replaced the coil packs and now having trouble with the truck not going above 3000 rpms it acts like a restricter is in place and it isnt gaining any power I went through the spark plugs are at proper gap checked all the wires and all are connected good a check engine light code of coil h primary and secondery circuit malfunction is appearing it does have a custom exhaust due to an accident 4 years ago.