Ignition Coil spark plug & secondary cleaning

[Sho"ney"]

I put about 1300 miles on my 98 SHO since purchasing her a few months ago. Recently she began developing a little trouble maintaining steady idle. randomly small 50-75 Rpm fluctuation and have now become more noticeable at startup or normal idling (live in so cal = traffic)

After looking in previous forums + v8 sho suggesting to replace the coil on plugs (cop system). I found a nice denso combo on Rock Auto and decided to take on the added challenge of removing the intake manifold to clean secondary butterflies ensuring they continue to roar nice and loud (love the sound - unlike anything I ever heard)

Having some mechanical background + experience of maintaining shoehorned motors in smaller 90 civics in my 20’s, I feel up to the challenge. I read a few “How To’s” but personally feel best being a visual/ hands on learner.

If you have lasted this long, any words of wisdom would be appreciated. Possible photo/ videos online diagrams of old work even better.

Different diagnoses? Feeling humble to learn some knowledge.

https://photos.app.goo.gl/c8Mcb2BmJnoYwMiKA

 

[Sho"ney"]

Parts should arrive Wednesday 6-10 and plan to change following Saturday. Hope to succeed and share some pics

 

[stephen newberg]

Be sure to clean the IAC sensor as well.

smn

 

[luigisho]

Budget some extra time for the learing curve 1st time through. Take your time and get comfortable removing the rear intake with surge tank. Most of the access to the engine and other parts crammed by the firewall often needs this out of the way. You should be fine. bag and tag stuff if needed to remember where they came from.

 

[98SF19]

You don't mention explicitly if you believed these rpm fluctuations were "misses", or whether the changes in rpms were UP or DOWN? If they were DOWN sporadically, then I think you may be on the right track. If UP, then investigating IAC like Stephen said might be a good start.

As for the secondary opening sound . . . those are distant memories for me and many. It's impressive that there are still Gen3's with working IMRC. I often wonder if some early owners rebuilt them with a metal gear instead of the plastic ones that, along with snapping cables, were one of the causes of failures of the unit. Root cause of both were high strain on parts resulting from gummed up lower intake. So regular cleanings of secondaries, and maybe running a con can, are likely to explain your IMRC's longevity.

 

[Sho"ney"]

You don't mention explicitly if you believed these rpm fluctuations were "misses", or whether the changes in rpms were UP or DOWN? If they were DOWN sporadically, then I think you may be on the right track. If UP, then investigating IAC like Stephen said might be a good start.

As for the secondary opening sound . . . those are distant memories for me and many. It's impressive that there are still Gen3's with working IMRC. I often wonder if some early owners rebuilt them with a metal gear instead of the plastic ones that, along with snapping cables, were one of the causes of failures of the unit. Root cause of both were high strain on parts resulting from gummed up lower intake. So regular cleanings of secondaries, and maybe running a con can, are likely to explain your IMRC's longevity.

RPM’s have only gone done not up, previous owner told me he replaced all valve/ coil when cams were welded at 60-70k. Looking at how easy it is to the clean the IAC should have been my first stop.

I stopped driving it more than 2 miles and keep pedal light. The thank you all for the kind words of advice.

the butterflies are unlike a sound I ever heard and love when they crank open. Bring a huge smile Every time.

 

[SHOZ123]

With the engine warm and idling disconnect the IAC connector. It should stall or go to a really low rpm. If not it's dirty and stuck.

 

[98SF19]

Paul, as it might benefit OP, do you know offhand what voltage I should measure coming to IAC from KOEO, cranking, and while running? Also, what range of resistance between 2 contacts on IAC? If you haven't seen my monstrosity thread, I'm having issues which on their face, seem to point to IAC. A new one didn't help (BWD) but I have a Delphi on the way.

 

[SHOZ123]

Not off hand. To give the IAC more head room (assuming it is working)

On a warm engine let idle, disconnect IAC.

Back the throttle stop screw out until around 400-450 rpm. Turn off engine disconnect battery and reconnect IAC. When stating back up let idle until it settles down, then turn on the AC and let idle till it settles down again. Shift into gear too and repeat the idle learn.

 

[Sho"ney"]

Package arrived early and was able to replace front four coil/ plugs before my enthusiasm wore off.


Car seemed to idle incredibly Strong/ well during first start. I plan on taking her out for a drive to work tomorrow (56 mile round trip).

downside, denso coil clips did not sit perfectly against harness. I put small pieces Of electrical tape outside coil sensor to create a small bond.

really appreciate all the great side information reads.

 

[Sho"ney"]

Not off hand. To give the IAC more head room (assuming it is working)

On a warm engine let idle, disconnect IAC.

Back the throttle stop screw out until around 400-450 rpm. Turn off engine disconnect battery and reconnect IAC. When stating back up let idle until it settles down, then turn on the AC and let idle till it settles down again. Shift into gear too and repeat the idle learn.

Idle issue seems to return when hot and randomly. I disconnected IAC and stalled. When I restarted car, idled perfectly again.

A good cleaning is in order tonight.

then idle relearn curve.

 

[xenialouna]

Be sure to clean the IAC sensor as well.

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