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My 2.8 developed a high idle. by CoolBlue87GT
Started on: 01-09-2019 11:30 AM
Replies: 15 (327 views)
Last post by: cvxjet on 01-24-2019 06:16 PM
CoolBlue87GT
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Report this Post01-09-2019 11:30 AM Click Here to See the Profile for CoolBlue87GTClick Here to Email CoolBlue87GTSend a Private Message to CoolBlue87GTEdit/Delete MessageReply w/QuoteDirect Link to This Post

My 2.8 Formula has developed a high idle, I've read the many - many posts dealing with this.

The high idle is like 3000 rpm, The tach shows near pegged at times. ( a separate problem, thinking of replacing the tach filter with a Rodney Dickman replacement.)

Here's the steps I've taken so far.

Replaced the TPS.

Replaced the IAC. Ran the codes after installing - before starting, this puts the IAC valve in the "home" position. I could hear the IAC clicking during this process.

Replaced the EGR tube, the egr side of the tube was cracked. Replace with a Rodney Dickman tube, replaced both gaskets. I did not replace the intake gaskets yet, the old ones looked okay, will replace at some point.- - the high idle didn't get any worse or better after replacing the egr tube.

Codes found, 15 & 22



I found when I plug the IAC port in the throttle body with my finger, the RPM's drop. I've searched for a vacuum line disconnected, I don't see one unhooked. Is this normal for the rpm's to drop when plugging the port ?

I even tried reinstalling the old IAC again, have the same result.

The idle screw adjustment is still covered, no one had fiddled with that.

I sprayed the brake clean around various area's while the car was running to see if the rpm's would increase, found none.

I guess my next step will be to replace the EGR valve.

If anyone has any ideas, please post them. I am trying step by step what I can find on the forum.

[This message has been edited by CoolBlue87GT (edited 01-15-2019).]

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Gall757
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Report this Post01-09-2019 12:08 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post

brake booster. 3000 rpm is a BIG vacuum leak. Pull the brake booster hose and cover the hole in the intake to test.

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CoolBlue87GT
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Report this Post01-09-2019 12:16 PM Click Here to See the Profile for CoolBlue87GTClick Here to Email CoolBlue87GTSend a Private Message to CoolBlue87GTEdit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by Gall757:

brake booster. 3000 rpm is a BIG vacuum leak. Pull the brake booster hose and cover the hole in the intake to test.


Thanks, I'll try that. Where is that hose on the intake?

[This message has been edited by CoolBlue87GT (edited 01-09-2019).]

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Gall757
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Report this Post01-09-2019 12:46 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by CoolBlue87GT:


Thanks, I'll try that. Where is that hose on the intake?



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CoolBlue87GT
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Report this Post01-09-2019 01:24 PM Click Here to See the Profile for CoolBlue87GTClick Here to Email CoolBlue87GTSend a Private Message to CoolBlue87GTEdit/Delete MessageReply w/QuoteDirect Link to This Post

Thanks, that hose was connected w/ clamp. I ordered replacement EGR valve & set of intake gaskets, and a tach filter, will pull the manifold off again and replace the gaskets. I'll recheck the hoses underneath the intake.

[This message has been edited by CoolBlue87GT (edited 01-09-2019).]

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Gall757
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Report this Post01-09-2019 01:57 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by CoolBlue87GT:

Thanks, that hose was connected w/ clamp.


Yes it is. What you are testing for is a leak in the brake booster. By detaching that hose and covering the hole in the manifold, you remove the booster from the vacuum system, and the idle should go down if there was a leak.

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CoolBlue87GT
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Report this Post01-10-2019 04:50 PM Click Here to See the Profile for CoolBlue87GTClick Here to Email CoolBlue87GTSend a Private Message to CoolBlue87GTEdit/Delete MessageReply w/QuoteDirect Link to This Post

I checked the hoses, the one located underneath the manifold may have been leaking, when I put the car back together, I'll double check that hose connection.

The brake booster hose was okay, I checked it before removing the manifold.




While I had the manifold off, I repainted it.

I have a few more parts on order, intake gaskets, tach filter and EGR valve. When I get these installed, I will update this post.

[This message has been edited by CoolBlue87GT (edited 01-10-2019).]

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Spoon
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Report this Post01-10-2019 08:32 PM Click Here to See the Profile for SpoonSend a Private Message to SpoonEdit/Delete MessageReply w/QuoteDirect Link to This Post

Don't forget the ATS (air temp sensor) in the air filter canistor. My 2.8 had a high idle once (3000 rpm) and a new ATS and a couple braided ground straps between engine & body and Engine to frame took care of everything. Never had a problem since plus it was a cheap repair..

Spoon

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CoolBlue87GT
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Report this Post01-10-2019 09:42 PM Click Here to See the Profile for CoolBlue87GTClick Here to Email CoolBlue87GTSend a Private Message to CoolBlue87GTEdit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by Spoon:

Don't forget the ATS (air temp sensor) in the air filter canistor. My 2.8 had a high idle once (3000 rpm) and a new ATS and a couple braided ground straps between engine & body and Engine to frame took care of everything. Never had a problem since plus it was a cheap repair..

Spoon




Okay, great idea. I placed an order for the ATS & and a new air filter. Thank you.

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CoolBlue87GT
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Report this Post01-15-2019 11:40 AM Click Here to See the Profile for CoolBlue87GTClick Here to Email CoolBlue87GTSend a Private Message to CoolBlue87GTEdit/Delete MessageReply w/QuoteDirect Link to This Post

Okay, got the engine back together, replaced EGR, egr pipe, TPS, IAC, air filter, manifold gaskets and tach filter.

Now I'm waiting on the ATS sensor and a replacement air cleaner shroud, as the ordinal one rusted out.



As it sits, I could probably start the engine now, but I'd rather have all the parts on to see if the problem is fixed.

The rest of the parts should be here in a day or two.

[This message has been edited by CoolBlue87GT (edited 01-15-2019).]

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CoolBlue87GT
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Report this Post01-21-2019 11:02 AM Click Here to See the Profile for CoolBlue87GTClick Here to Email CoolBlue87GTSend a Private Message to CoolBlue87GTEdit/Delete MessageReply w/QuoteDirect Link to This Post

Okay, installed all the parts. This is a cold start, about 39 degrees - (cold for SW Florida).

Idle is much better, still a little high when warmed up, but better than before.




Final code to sort out is a code 15, Explanation: Because the Coolant Sensor never has an infinitely high resistance, the measured voltage should always be lower than the reference voltage. If the measured voltage is the same as the reference voltage, a problem exists with the Coolant Sensor. The ECM will set this code when it detects a problem with the Coolant Sensor (or when the coolant temperature actually drops below -30°C/-22°F).

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Raydar
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Report this Post01-21-2019 11:37 AM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by CoolBlue87GT:

Okay, installed all the parts. This is a cold start, about 39 degrees - (cold for SW Florida).

Idle is much better, still a little high when warmed up, but better than before.



Since so much has been done, it's hard to tell where the idle speed will shake out.
It's supposed to readjust itself, when the car is driven over ~35 MPH.

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CoolBlue87GT
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Report this Post01-21-2019 09:03 PM Click Here to See the Profile for CoolBlue87GTClick Here to Email CoolBlue87GTSend a Private Message to CoolBlue87GTEdit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by Raydar:

Since so much has been done, it's hard to tell where the idle speed will shake out.
It's supposed to readjust itself, when the car is driven over ~35 MPH.


Ah, good to know. It's maiden voyage will be the 24th when I get the new sway bar links installed. I'll be interested to see how it does after the drive.

Thanks Raydar

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fierogt28
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Report this Post01-22-2019 09:35 PM Click Here to See the Profile for fierogt28Send a Private Message to fierogt28Edit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by Raydar:


Since so much has been done, it's hard to tell where the idle speed will shake out.
It's supposed to readjust itself, when the car is driven over ~35 MPH.


Raydar is right about the over 35MPH for idle re-adjust issue.

Not to many folks mention this; members info on PFF.

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fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.

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CoolBlue87GT
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Report this Post01-24-2019 11:19 AM Click Here to See the Profile for CoolBlue87GTClick Here to Email CoolBlue87GTSend a Private Message to CoolBlue87GTEdit/Delete MessageReply w/QuoteDirect Link to This Post

Took the car to the shop to have the tie rod struts & bushings replace.

The guys were impressed with the paint, it was raining this morning.





Driving home, I could feel the improvement, nice and sold feel. Did drive it at 50 for awhile, the idle seems to be okay.

Now, what else do I need to fix ? lol !!

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cvxjet
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Report this Post01-24-2019 06:16 PM Click Here to See the Profile for cvxjetClick Here to Email cvxjetSend a Private Message to cvxjetEdit/Delete MessageReply w/QuoteDirect Link to This Post

Always a good thing to tighten the loose nut behind the steering wheel....I have one of those on every car I own- even my boat....and it must be a funny size because no-one has a wrench that will fit it!

(Your engine idle sounds good!)

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