Poor Idle - 1998 Mark VIII

G

gravelguy

Registered
Here's what I started with: 60K miles, perfect idle, 99% unmolested stock car.

Added: Focus SVT fuel pump, 3200 stall converter, deep trans pan, new trans filter, oil, Speedcal, and 4.30 gears.

What happened: Sometimes idle speed was perfect, other times it "pulsed" between 500 and 1000 RPMs. Occasionally died at long stoplights. Idle could be "smoothed out" by oh so slightly pushing down the throttle pedal.

Repair attempt & upgrades: new plugs, new COP boots, new fuel filter, new IAC valve, new SCT Xcal2 with BOC tune, new K&N panel filter, cleaned MAF.

Idle problem still present. There's only been 700 miles between the start & finish of this story. What's next - EGR valve or Seafoam?
 
Poor Idle

Poor Idle

I'm going to get to work tommorrow. Seafoam & check codes. Lonnie was told about the Focus pump, but I'll check to see if it is in the tune. The car was perfect until the SVT fuel pump went in & transmission taken out. I have to think there is a relationship. I need to get this idle problem fixed so my wife will ride with me...
-Ron
 
Code Pulled - D1519 IMRC Stuck Closed - B2

Code Pulled - D1519 IMRC Stuck Closed - B2

I doubt if this is still a problem since the car runs 14.4's easily. I'll try the Seafoam though. The first owner never took the car over 2K rpms would be my guess why they might stick.
 
You should really change the plugs after using Seafoam as they can be fouled from it. Let the engine warm up a good amount and suck the seafoam through the PCV valve. Make sure to rev above 3200rpm so you know it cleans out the IMRC's and hopefully makes them unstick. Then go WOT around the block. With the mods you have you can easily run 14.4 with the IMRC's closed since your 60 foot time was 2.0. Look at your 1/8th mile MPH and tell me what it was.
 
Poor Idle

Poor Idle

I did the Seafoam by holding the throttle at 3500rpm & sucking up half a can through the brake booster hose. I got the smoke show. I shut it off for 10 minutes, cleared the DTC code, then drove around for an hour or so. It seemed to run OK. Parked at home. A few hours later, I went to put it in the garage, and the idle was all over the place. No codes found. I think datalogging might help find the problem. I'm going to leave the plugs alone; they have a whole 75 miles on them now.
 
Here is what you need. You take a get a small piece of tubing and put it down into the can and let the engine vacum suck it into the manifold. It has detergents in it to help desilve the carbon deposits that buid up around the various intake components. I would suggest that maybe you have a bad IAC. Napa has one that is an OEM replacement. Some of the others just don't hold up, and fail prematurely.
 

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Alkymark8 said:
Which one should I get? and you raise the rpm and pour it in a vacuum line?
Click to expand...

Only keep the rpms up enough so the engine doesn't die...you may even be able to let it idle if the fluid goes in slowly enough.

Roadboss gives the proper procedure. You'll be running high rpms after you let the fluid sit with the engine off for about five minutes.
 
Roadboss said:
Here is what you need. You take a get a small piece of tubing and put it down into the can and let the engine vacum suck it into the manifold. It has detergents in it to help desilve the carbon deposits that buid up around the various intake components. I would suggest that maybe you have a bad IAC. Napa has one that is an OEM replacement. Some of the others just don't hold up, and fail prematurely.
Click to expand...

What is an IAC????
 
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