Gain extra benefits by becoming a Supporting Member Click here find out how!

Classic Performance Products Classic Parts
American Auto Wire Classic Industries
Danchuk Catalog
Hellwig Products IncPerformance Rod & CustomNu-Relics Power Windows



Username Post: 1994 454 high idle code 36        (Topic#359389)
owl 
Newbie
Posts: 4

Reg: 01-06-20
01-06-20 12:43 PM - Post#2783825    

My 94 454 idles high and shows dtc 36 (idle speed control actuator). The actuator works. When the engine temp reaches a certain degree the solenoid opens and vacuum is applied to the actuator and the plunger retracts away from the throttle arm. The truck does not have a cat in the exhaust. All other sensors appear to be functioning.



 
someotherguy 
Senior Moderator
Posts: 29054
someotherguy
Age: 49
Loc: Texas
Reg: 08-01-03
01-06-20 03:25 PM - Post#2783838    
    In response to owl

Welcome to Chevytalk,

I haven't had to troubleshoot an idle actuator problem (fortunately) and it's not a common issue that gets brought up around here much, if at all! Hopefully someone else can chime in that has experience with the system.

I've got the 1994 factory service manuals and can try to take a peek at them tomorrow to see if anything sounds helpful.

At first thought though it sounds like the code may be setting because the PCM commanded the actuator to retract, and although it did so correctly, the idle speed is still higher than expected - this seems to point to an external cause of the high idle condition. Have you checked your CTS to be sure it isn't reading false cold, checked for any vacuum leaks around the TBI (particularly the throttle shaft if it's a high mileage unit), temporarily disconnect throttle and cruise cables from the TBI to be sure they aren't pulling on it, and check the TBI base gasket in case it's swollen and interfering with the throttle blades?

Richard

06 Silverado ISS / 06 Silverado SS / 06 300C SRT8


 
owl 
Newbie
Posts: 4

Reg: 01-06-20
01-06-20 04:10 PM - Post#2783842    
    In response to someotherguy

Thanks for the reply. I'm a newbie. One of the " best mechanics around" thought it was a vacuum leak and replaced the tbi gasket and when that didn't solve the problem he ripped the intake off and replaced that gasket also. 500 dollars later still got code 36.Back in 2009 there was a post with someone who had the same problem, but i don't know if he ever resolved the problem. I only know enough about wrenching to be dangerous, but c'mon this is obd 1 and there are only a handful of sensors. I will say that when i first start plowing snow, while the engine is warming up and there is a load on the engine the engine runs correct for a couple of seconds before idleing up too high. It does this a couple times when plowing and it makes me mad because the engine temporarily runs wright It's like it tries to "find itself" but then senses a condition to raise the revs. After it is warmed up it rev's too high always.I bought a ecm but really don't want to go there yet, but that's what i'm leaning toward. By the way, 1994/1995 were the only years that they used a idle speed control actuator on 454's. Chiltons say's nothing about them in their book.



 
65_Impala 
Very Senior Member
Posts: 4370

Reg: 12-29-02
01-06-20 06:18 PM - Post#2783858    
    In response to owl

I'd suspect the IAC. It won't idle at the right rpm if the IAC doesn't work and generally speaking the ODB1 stuff didn't throw a code for a bad IAC.



 
someotherguy 
Senior Moderator
Posts: 29054
someotherguy
Age: 49
Loc: Texas
Reg: 08-01-03
01-07-20 02:33 PM - Post#2783940    
    In response to 65_Impala

FSM says (and it certainly isn't the end-all of the discussion) code 36 can be set when temp is above 132F, VSS present, above 10mph, and TP angle is above 10%. From OP's description that it retracts the plunger once the engine reaches temp, I suspect the actuator and its circuit are operating properly. The weird thing is I would almost expect a code 35 (IAC error) along with it, and FSM suggests it does often accompany code 36.

Since code 36 is based partially on TP angle, do you think a flaky TPS could be a suspect? If the IAC was the cause, the TP angle wouldn't be a factor here IMO. But again I have never had to troubleshoot this code.

Richard

06 Silverado ISS / 06 Silverado SS / 06 300C SRT8


 
65_Impala 
Very Senior Member
Posts: 4370

Reg: 12-29-02
01-07-20 04:16 PM - Post#2783943    
    In response to someotherguy

It could be the TPS. I would also check the throttle body for shaft bore wear in case that is why it's hanging up.



 
owl 
Newbie
Posts: 4

Reg: 01-06-20
01-07-20 04:20 PM - Post#2783944    
    In response to someotherguy

Thanks for the input. I bought this truck new in 1994 and it only has 130k on it. It has had this code 36 "high idle" for probably 12 years or more. When i brought it to a chevy dealer a few years back, they said it needed an idle speed control actuator, and that part was unobtainable. No kidding. I can't even find a picture of one, but i do have a gm part number for it. But, the actuator does work. What's funny is that the actuator only has a vacuum hose going to it, no wires at all. So how can a mechanical only component trigger a code. The solenoid that controls the actuator has been replaced. That also wasn't the problem. I did bench test the iac last year. The ohms were in range.
I don't use the truck much except for truck stuff. A 454 isn't very economical. This year i was able to register it as antique auto. Except for the check engine high idle issue, the truck actually is a pleasure to drive. It goes good, and that's why now after a dozen years or more, ITS PERSONAL !!



 
stumppuller 
"9th Year" Gold Supporting Member
Posts: 877
stumppuller
Loc: Canada
Reg: 11-01-04
01-09-20 10:44 PM - Post#2784104    
    In response to owl

  • owl Said:

So how can a mechanical only component trigger a code.




Because the PCM controls the vacuum to it with an electrical solenoid. When the solenoid is commanded on/off, and the PCM does not see the engine rpm change as it should, it will set a code.

Since you know the actuator is retracting, you need to verify that the throttle is actually moving closed as well and not hung up (I think someotherguy gave a few pointers on what to look for).

I found a good description of the system...

Attachment: CCF01092025.jpg (888.05 KB) 3 View(s)




-91 Sierra C2500, now K2500
-81 Chev K20


 
owl 
Newbie
Posts: 4

Reg: 01-06-20
01-10-20 01:00 PM - Post#2784139    
    In response to stumppuller

Thanks, i have never seen that description before. There isn't a lot info about this idle speed control actuator out there. Try to find a picture of one. There is a good distance between the actuator plunger and the throttle arm when the actuator is retracted, so maybe the throttle is hanging up. However, i have had three different mechanics over the years try to figure this out and no one could. I would hope that would have checked for it hanging up. As i said in an earlier post, during the warm up of the truck there is a couple of times for a few seconds at a time when there is a load on the engine, like pushing snow without your foot on the gas ( because it's still idleing 1200 or so) the truck rpm's drop down to where they are right. But it goes back up after 2 or 3 seconds. Something is telling the ecm to command the tbi for more fuel. It even smells rich. Maybe this spring when i'm done plowing and the boat is in the water, i will try me 69 dollar rebuilt ecm from flash master. Back in 2009 someone from this forum also posted a couple pages out of a service manual that has a great description and trouble shoot procedure pertaining to this 1994 454 code 36.



 
Icon Legend Permissions Topic Options
Report Post

Quote Post

Quick Reply

Print Topic

Email Topic

179 Views
FusionBB
FusionBB™ Version 2.1
©2003-2006 InteractivePHP, Inc.
Execution time: 0.203 seconds.   Total Queries: 14   Zlib Compression is on.
All times are (GMT -0800) Pacific. Current time is 06:59 PM
Top