My 2.8 developed a high idle. (Page 1/2)
CoolBlue87GT JAN 09, 11:30 AM
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).]

Gall757 JAN 09, 12:08 PM
brake booster. 3000 rpm is a BIG vacuum leak. Pull the brake booster hose and cover the hole in the intake to test.
CoolBlue87GT JAN 09, 12:16 PM

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).]

Gall757 JAN 09, 12:46 PM

quote
Originally posted by CoolBlue87GT:


Thanks, I'll try that. Where is that hose on the intake?
CoolBlue87GT JAN 09, 01:24 PM
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).]

Gall757 JAN 09, 01:57 PM

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.
CoolBlue87GT JAN 10, 04:50 PM
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).]

Spoon JAN 10, 08:32 PM
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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"Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut

CoolBlue87GT JAN 10, 09:42 PM

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.
CoolBlue87GT JAN 15, 11:40 AM
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).]