No power/Hesitation at higher rpm or load

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macius8

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Hello all,

I've just recently purchased a 98 lsc but after a bit found it was hesitating at higher rpm, especially above 2.5k. Unfortunately I didn't have time to look at it myself and dropped it off at a local mechanic to take a look while I'm on vacation. He called me just before closing for the weekend saying its some electronic motor/controller (not sure) in the intake manifold. He did say its not produced anymore and only comes as part of the manifold, not sure if the upper or lower, and he will try to find it at bone yards. Anyone have an idea what it might be? Unfortunately I could not talk to him in detail, but would like to have more info before I talk to him Monday.
Thanks for the help.
 
It may be the irmc actuator. Looks like some people hAve had similar issues with it going bad. Can't find any for sale anywhere. Any ideas where to get one?
Thanks
 
Carlos would likely have one. Do you have Facebook? Look up the Mark VIII Enthusiast Community. It'll be easier to get you in contact with the right person to purchase a used one.
 
jbelcourt said:
Carlos would likely have one. Do you have Facebook? Look up the Mark VIII Enthusiast Community. It'll be easier to get you in contact with the right person to purchase a used one.
Click to expand...

I did request to be added to the community. Thank You!
Can I get a hold of him on the boards as well?
 
Do heated seats work or the AC? I think the IMRC controller is on the same fuse but I can not say for sure.
 
IMRC actuator was broken. The flaps were carboned up as well. All put back together but the car still hesitates.
Looks like when the I turn on the car the actuator fires and stays open. Was suggested by someone it might be the PCM. Any other suggestions on the issue are welcome.
 
IMRCS actuate when the car starts then change position around 3k rpm.

Have you pulled all your coils to check for oil soak? While not a COP system, my 96 drove fine until under load/higher RPM. It was a bad coil pack and at least two plugs were affected since they are pin pairs (wasted spark).
 
Just took a look at they coils. They are all oil soaked. What could cause oil to get in there? Bad valve cover gaskets?
 
So I'm trying to remove the drivers side valve cover. Trying to jack up the engine a bit to get some clearance. Removed the motor mount cross bolt but the engine is not budging. Lifting the entire car. Am I missing something?
 
This forum is quite dead. Anyway, any feedback is still appreciated. Replaced the valve cover seals, all plugs and all boots. Car still runs like poop. What else can it be?
 
does it have a misfire?
check engine light?
2nd gens have more monitoring abilities and usually catch IMRC and more severe misfire issues.
 
Yes it feel's like it's misfiring. Check engine light is on. Before I did the plugs, boots, and valve cover seals the code was irmc actuator stuck open. Which i's funny cause I replaced the actuator last week. Will check the codes again but more ideas and feedback appreciated
 
Code is imrc is stuck open. I figured out there's a air leak somewhere under the manifold. Guess it needs to be taken apart again. Hopefully that's causing the issues.
 
there is a plug on the bottom side of the throttle body.
unbolt the throttle body and have a look. it may have fallen out.
 
If the code is for an IMRC stuck open, that is what it is. They have a switch to verify position starting in 1996 with ODBII.
 
unity said:
If the code is for an IMRC stuck open, that is what it is. They have a switch to verify position starting in 1996 with ODBII.
Click to expand...

Well I have replaced it so I would imagine it wouldn't be the problem. It was a used one however, so maybe it was bad in the first place. I got a hold of a re-man one and will swap it out one more time.
The weird thing is it works. It opens when you start the car. It's not stuck open. It just doesn't work the way it's supposed to.
 
It? There are two. One on each side. One controller with two cables, but the controller just actuates them. If they are stuck then the controller throws a code. I would say the controller is faulty and throwing a bad code, but the odds of two are slim. The the intake comes off to replace the module, I think, were the IMRCs checked and controller actuation before assembly?
 
unity said:
It? There are two. One on each side. One controller with two cables, but the controller just actuates them. If they are stuck then the controller throws a code. I would say the controller is faulty and throwing a bad code, but the odds of two are slim. The the intake comes off to replace the module, I think, were the IMRCs checked and controller actuation before assembly?
Click to expand...

The flaps open up fine by hand, they are not stuck. I replaced the actuator twice. Still same thing. And second time I just took off the windshield wire assembly and took off the actuator that way. Real easy to reach in there with the wiper assembly off.

So here is the issue. I think the actuator fires when I turn the engine on, and flaps stay open. I am not sure if they close when I start driving. The car seems to run better with the actuator disconnected. With it plugged in it tends to struggle in the lower RPMs and completely dead in the higher RPM. I get no actuator codes with it unplugged. I would think it would throw codes immediately.

Another issue, a few weeks ago I gut a a lean code in both banks. Was thinking its a vacuum leak, a bad fuel filter or 02 Plugs. Boots and plugs were replaced a few months ago so chances both sides were bad were slim. I cleared to codes to see how quickly they come back and nothing for several weeks. Just today I get a lean code only in bank 2. Car shakes ever so slightly in idle. Coils are original.

In summary I dont think both issue are connected. But who knows. Please chime in. I have some time this Saturday to tinker around with the car. Hope to diagnose it then,

Thanks,
 
The actuators should move when turned on I think. For the vacuum operated 96 and earlier, they are that way. Then above 3k RPM (give or take 200rpm) then change position. So they are generally easy to check if they are working or not.
 
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