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Author Topic: Idle Control Air Valve;  (Read 1204 times)

KTM520EXC

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  • Posts: 12
    • 1991 Mercury Capri NA
Idle Control Air Valve;
« on: October 04, 2021, 05:51:04 PM »

I have a 91 NA Capri, it's got a Schizophrenic start up procedure where I have to feather the throttle constantly to keep it running for about the first 2 minutes, after that, it seems to idle fine on it's own. I could not see any previous posts to see if this was a common problem, or unique to my situation. Please note the BISS screw has had it's top removed, so someone has already been into the throttle body. I don't know if I should remove and clean the ICAV, or what to tackle next. Any advise appreciated !!!

Michael
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Rocketman

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    • 91 BPT AWD Capri & 1991 XR2
    • http://www.werbatfik.com
Re: Idle Control Air Valve;
« Reply #1 on: October 04, 2021, 11:10:34 PM »

Check the plastic bellows on the intake tube, they crack & cause a vacuum leak (car will run poorly or not at all if air is allowed in anywhere behind the VAF meter)
Very common issue on the N/A
Would also be wise to check for other vacuum leaks as well

Yes, probably wise to try to clean the IACV - watch the coolant lines they will be fragile
Could try adjusting the throttle screw, if it's already been tampered with, might be too far down

On a very cold day, it will idle kinda crazy at around 2k rpm until it starts to warm up, is this the case for yours?
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


KTM520EXC

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  • Posts: 12
    • 1991 Mercury Capri NA
Re: Idle Control Air Valve;
« Reply #2 on: October 05, 2021, 02:16:45 PM »

Thanks for responding Rocketman, much appreciated. So I took it upon myself to turn down the initial idle and the Schizophrenic start up seems to have mellowed out noticeably. Before it was 400 rpm, or die, then 2k, then 400, or die 2k ...etc. Now it is 500rpm, then 1.5k, no dying, back to 500, then 1.5k, etc..., so it appears I need to dial in the Base Idle Adjustment Screw, better known as the BISS screw, until I come to a happy medium. Once it warms up, not a problem.

Right now I am tackling severe vibration in the front end. Previous Owner, PO left it standing in 1 spot for 2 years w/o moving, so I don't know if I have flat wheel syndrome, or where I am. I plan on rebuilding the whole front end. I have already replaced the outer wheel bearings and seal, new rotors, rebuilt calipers, new pads and brake hoses. Before it would vibrate noticeably at 44 mph, I now have it at ~ 49mph before it vibrates and it vibrates pretty good unfortunately. Certainly not highway worthy at this point. I have new KYB front struts on order for 5 weeks (still have not received) :(, have lower ball joints, outer tie rods, ready to install and oh ya, forgot, I replaced the driver's side CV axle, thinking that was the problem, it wasn't.

Michael
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EShepherd

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  • Posts: 264
    • 1991 Capri XR2, 1991 Capri XR2 Rusted out Shell
Re: Idle Control Air Valve;
« Reply #3 on: October 05, 2021, 06:47:56 PM »

Thanks for responding Rocketman, much appreciated. So I took it upon myself to turn down the initial idle and the Schizophrenic start up seems to have mellowed out noticeably. Before it was 400 rpm, or die, then 2k, then 400, or die 2k ...etc. Now it is 500rpm, then 1.5k, no dying, back to 500, then 1.5k, etc..., so it appears I need to dial in the Base Idle Adjustment Screw, better known as the BISS screw, until I come to a happy medium. Once it warms up, not a problem.

Right now I am tackling severe vibration in the front end. Previous Owner, PO left it standing in 1 spot for 2 years w/o moving, so I don't know if I have flat wheel syndrome, or where I am. I plan on rebuilding the whole front end. I have already replaced the outer wheel bearings and seal, new rotors, rebuilt calipers, new pads and brake hoses. Before it would vibrate noticeably at 44 mph, I now have it at ~ 49mph before it vibrates and it vibrates pretty good unfortunately. Certainly not highway worthy at this point. I have new KYB front struts on order for 5 weeks (still have not received) :(, have lower ball joints, outer tie rods, ready to install and oh ya, forgot, I replaced the driver's side CV axle, thinking that was the problem, it wasn't.

Michael

If the vibration is at a very specific speed like that, it's most likely a wheel balance issue. It's entirely possible you've got flat spots in the tires, too. A good technician will be able to spot that when the wheel is spinning on the machine. I'd take it to a shop for a 4-tire rebalance, and let them know that it's been sitting so they know to look for the flatness.

Where'd you score the front struts? I could totally use a set as well.

Edit:
Just noticed this is only your third post here. Welcome to the club man! Hope you've been enjoying the new toy!
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KTM520EXC

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    • 1991 Mercury Capri NA
Re: Idle Control Air Valve;
« Reply #4 on: October 05, 2021, 07:40:27 PM »

That's good idea on the (4) wheel balance and bringing to Tech's attention of possible flat spot(s), I don't think it is that, but it could not hurt, perhaps I can get to 55mph with a rebalance. My butt dyno tells me to replace all the parts up front, the whole shabang. All the bushings are showing signs they have never been replaced. It is a California car, so our weather plays havoc on plastic and rubber. The brakes were scary when I got it, so tackled that first, whilst in there decided to change outside bearing and seal.

As far as the struts, I have been waiting (5) weeks, nada, zilch, nothing, >:( so no progress as of yet. Purchased on Amazon and Vendor did not state on website they were out of stock, until after I placed the order. Still looking for a matching set, I can get the KYB 234008 from Summit, but not the KYB 234009, kinda of looking for hens teeth on KYB 234009 unit.

So far, not really enjoying the car, still a ways to go. I am sure once I get everything replaced on front end and an alignment, perhaps new meats, I will indeed enjoy the Capri. I got this as a project, cause I like tinkering and to me it is wrench therapy, but the lack of parts availability is admittedly getting frustrating and taking some of fun out the project.

I appreciate the warm welcome !!!

Michael 

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Kiwimagic

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    • 1990 SA SOHC, 1991 SA Verde DOHC, 1994 XR2 Turbo
Re: Idle Control Air Valve;
« Reply #5 on: October 13, 2021, 02:43:26 AM »

Rockauto have the KYB234009 or 8. the only difference is the brake line bracket. You can make one out of a bit of 30 x 30 x 3 mm angle iron. Easy as. use the bolts that hold the strut to the hub to hold the new bracket. I got my struts in 10 days from Rockauto. Im in Australia so they are quicker than the post here between Melbourne and Sydney. Just ordered a new clutch kit and it will be here on the 20th.
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