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RE: TBI Min idle speed spec
Is there a question in this post or is it just information?
Just info. I've seen and been asked of it often enough that I figured it would be good to post it up.
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udidwht
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04/18/23 04:52pm |
Class A Motorhomes
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TBI Min idle speed spec
Looking at the 1994 service manual for 454 TBI under fuel systems (Section 4-4A) the 'Min idle speed' setting is... (Factory set screw)
For the 7,4L auto trans in Drive is 625 (+-25rpm) Closed loop
Controlled Idle Speed is as follows:
454 7.4L in Drive 675 (+- 25rpm) IAC count 5-30 (Closed loop) at operating temp 196-222F (add 2 counts for every 1000ft above sea level
The 'controlled idle speed' is obtained by the control module positioning the IAC valve. A high/low coolant temp or AC clutch engagement may signal the control module to change the IAC counts.
IAC counts will be above 60 if idle is too low and zero counts if idle is too high. Things to check if so...
1. Vacuum leak/s
2. System too rich
3. TB obstruction
4. PCV issue
5. AC issue
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udidwht
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04/17/23 10:50pm |
Class A Motorhomes
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RE: Difficulty timing a 1995 Chevy 454ci
So at the beginning of the thread you said you got nothing.. nothing as far as the motor goes or nothing on your timing light.. then further down the thread you said it kicks but won't run.. that sounds like a bad distributor module.. could be lots of other things but that's cheap and easy to change
I know this thread is a bit of a saga at this point :). Over the course of this process I have replaced the entire ignition system with brand new ACDelco parts. It will now start at the bump of a key. However I need to do further testing with the engine warmed up, which currently I can't do because the water pump bearings are completely toast. That's why I'm pulling the pump. Since the pump is out of the way it isn't that much more effort to pull the timing cover and check for a jumped chain or a sloppy one, which could very well be why the engine is still not running right.
To be clear, all the work I've done is making it run better, but it's not right.
If you do the water pump don't forget to replace the clutch fan as well. With north of 200K on the engine the timing chain very well may be the issue with the miss in the ignition system.
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udidwht
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04/16/23 05:11pm |
Class A Motorhomes
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RE: Difficulty timing a 1995 Chevy 454ci
Updates
After much sweating and swearing the water pump is off. Next step will be to pull the timing cover and check for a jumped tooth and/or sloppy chain.
There is a cross member underneath that can be removed for easier access to front of engine. This is the cross member to remove...
https://www.irv2.com/forums/f65/what-did-you-do-to-your-old-rv-today-133779-444.html#post5713099
Once out it gives this access...
https://www.irv2.com/forums/f65/what-did-you-do-to-your-old-rv-today-133779-443.html#post5712066
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udidwht
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04/16/23 08:50am |
Class A Motorhomes
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Micro 4k throttle stop screw
The 4K has what is called an 'Throttle stop screw' to adjust it the generator has to be running with no load.
Adjustment is as follows:
The following is from Micro 4K spec B manual (pg 8-13) same for other 4K models.
A throttle stop screw is provided for adjusting the
“closed” position of the throttle plate to obtain proper governor response when loads are being disconnected. (See Governor Adjustments on Page 8-9)
To adjust the throttle stop screw:
1. Connect a frequency meter (Kill O Watt) and start and run
the genset until it has warmed up to normal operating temperature.
2. Disconnect all loads. Pull the governor linkage
toward the front of the genset so that the tang
on the throttle lever bears against the throttle
stop screw. Adjust the stop screw to obtain a
frequency of 54 to 56 Hz on 60 Hz gensets (44
to 46 Hz on 50 Hz gensets).
For manuals:
https://www.smokstak.com/forum/forums/onan-generators.1/
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udidwht
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04/15/23 09:27pm |
Class A Motorhomes
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Micro 4K choke adjust
The following is for the Micro 4k...
The correct method for choke adjustment is as follows:
1. Allow the gen set to cool down. In side the housing needs to be the same as ambient temp.
2. Loosen the adjustment screw holding the adjustment plate.
3. Slowly rotate the adjustment plate until the bi-metal choke shaft connection is visible in the sight window. This is the correct setting for ambient temperature of 70 F (21 C) If the ambient temperature is higher or lower than 70 F (21 C), make a mark on the choke coil housing opposite the center mark on the adjustment plate. Each mark on the adjustment plate is equal to 10 F (12.2 C) of difference from 70 F (21 C). If it is warmer than 70 F (21C), rotate the plate clockwise. If the temperature is less than 70 F (21 C), rotate the plate counterclockwise. Tighten the adjustment screw.
Example: If the ambient temperature is 90 F(32 C), rotate the adjustment plate two marks clockwise from the 70 F (21 C) position marked on the housing.
4.Move the choke lever back and forth to check for free movement. Verify that the choke does not bind or stick.
5. Done.
One can use either the video camera on their phone or a snake camera that connects to your phone to view into the sight window on the generator choke housing.
Such as the following: https://www.amazon.com/s?k=snake+cam...f=nb_sb_noss_1
For manuals:
https://www.smokstak.com/forum/forums/onan-generators.1/
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udidwht
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04/15/23 09:09pm |
Class A Motorhomes
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RE: Idle speed control acutator info
As for the part number on this item...
GM 17084953?
And the item in question is #16 in the following diagram...
https://lt-truck-gmc.7zap.com/en/g15+g1500/49295-1994/0-0-1904162379/0-1623891437-0-0/
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udidwht
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04/15/23 09:05pm |
Class A Motorhomes
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RE: Where are my spark plugs? Found them....
Gas or Diesel?
If diesel it will have glow plug/s not spark plugs.
What chassis?
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udidwht
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04/15/23 08:18pm |
Class A Motorhomes
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RE: Difficulty timing a 1995 Chevy 454ci
There is a plethora of TBI info on the following site: http://www.gearhead-efi.com/Fuel-Injection/forumdisplay.php?10-GM-EFI-Systems
Found the following regarding fuel regulator spring identification...
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?3145-TBI-Fuel-Pumps-Specifications-and-Regulator-Springs!
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udidwht
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04/15/23 12:45am |
Class A Motorhomes
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RE: Difficulty timing a 1995 Chevy 454ci
Updates
Got the new injectors in and it is running better. Spray pattern looks better too.
Finally got down to checking the time under computer advance after setting it to 4 BTDC and I found today its advancing 20 degrees. I think that is why it's popping when under computer advance. Is 20 degrees normal at idle? A possible X factor would be that there really isn't much water in the cooling system at the moment so the ECT probably isn't reading as closely as it should.
After rebuilding the distributor on my 1994 P-30 chassis 454 TBI at idle with the wire connected it will idle at 16. Idle RPM 800.
I use a bluetooth ALDL phone app and the following...
http://www.1320electronics.com/12pin_ALDL_BT_MK2.html
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udidwht
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04/12/23 10:39pm |
Class A Motorhomes
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RE: Difficulty timing a 1995 Chevy 454ci
What was the fuel pressure at?
94-95 years was 26-32psi (preferably higher than 26psi)
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udidwht
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04/07/23 02:02pm |
Class A Motorhomes
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RE: Difficulty timing a 1995 Chevy 454ci
Be sure that once you confirmed the dizzy was out of position that you correct reoriented the wires in their correct positions.
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udidwht
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04/03/23 10:03pm |
Class A Motorhomes
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RE: Difficulty timing a 1995 Chevy 454ci
How is this coming along?
Haven't had time to work on it, other more pressing projects had to get done. I hope to put a little time into it this weekend. I've got a brand new Delphi dizzy that is supposed to be the OEM one that's come in. I'm hoping with that, plus fixing my timing light that I'll be able to get this thing timed and running.
I'm also intending to inspect the vacuum passages the MAP is hooked into and clean those, along with making sure there are no blockages in the MAP tubing itself.
Lastly, my FPR spring arrived and I need to install that. Fingers crossed good things will happen this weekend.
Thanks for the feedback. Keep us updated on the outcome as this will definitely help one down the road.
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udidwht
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04/01/23 12:28pm |
Class A Motorhomes
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RE: Difficulty timing a 1995 Chevy 454ci
How is this coming along?
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udidwht
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03/31/23 11:26pm |
Class A Motorhomes
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RE: Difficulty timing a 1995 Chevy 454ci
Manuals for some year TBI models can be had here:
https://www.gmt400.com/threads/88-98-service-manuals.43575/
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udidwht
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03/25/23 05:28pm |
Class A Motorhomes
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RE: Idle speed control acutator info
Manuals for some year TBI models can be had here:
https://www.gmt400.com/threads/88-98-service-manuals.43575/
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udidwht
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03/25/23 05:26pm |
Class A Motorhomes
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RE: Idle speed control acutator info
As for the adjustment of the 'Idle speed control actuator' (Vacuum can) aka throttle kicker...
Idle Speed Control Actuator Adjustment
Procedure: (from manual)
Before adjusting ISC actuator you must first check the minimum idle speed to be within specifications. Refer to SPECIFICATIONS/IDLE SPEED. (ISC actuator must have vacuum applied so that it is not contacting the throttle lever.) See image VIEW A.
Remove vacuum hose on ISC actuator on warm engine.
Adjust ISC actuated idle speed to 1300 +/- 50 rpm. See image VIEW B.
Install vacuum hose.
In the even the vacuum can is leaking and not holding vacuum and you're unable to source another. You'll need to get at the 'Idle adjustment screw' that is covered by GM on the front side of the TBI. Turn it open roughly 1 turn. This will open the throttle blade slightly. The IAC will/should make up the difference.
As for the adjustment of the 'Idle speed control actuator' (Vacuum can) aka throttle kicker...
Idle Speed Control Actuator Adjustment
Procedure: (from manual)
Before adjusting ISC actuator you must first check the minimum idle speed to be within specifications. Refer to SPECIFICATIONS/IDLE SPEED. (ISC actuator must have vacuum applied so that it is not contacting the throttle lever.) See image VIEW A.
Remove vacuum hose on ISC actuator on warm engine.
Adjust ISC actuated idle speed to 1300 +/- 50 rpm. See image VIEW B.
Install vacuum hose.
In the event the vacuum can is leaking and not holding vacuum and you're unable to source another. You'll need to get at the 'Idle adjustment screw' that is covered by GM on the front side of the TBI. Turn it open roughly 1 turn. This will open the throttle blade slightly. The IAC will/should make up the difference.
Prior to doing this you must make certain that the min idle speed is set first.
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udidwht
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03/25/23 05:20pm |
Class A Motorhomes
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Idle speed control acutator info
This is in reference to the earlier older topic here:
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/26389052.cfm
As for the 'Idle speed control actuator' it was not installed in all models of GM. I believe only in the truck models such as the P-30 chassis. It is the vacuum can on drivers side of TBI attached to throttle cable. It has a vacuum line running to the 'EGR valve control solenoid' which is on the passenger side of the TBI just forward of it attached to a bracket.
See pic of mine for aforementioned items: https://www.dropbox.com/s/ow3nt7k4hf4gimd/20180512_232309%5B1%5D.jpg?dl=0
Idle Speed/Throttle Actuator - Mechanical: Description and Operation
Purpose: The idle speed control actuator system assists the idle air control system in controlling the idle speed, primarily at cold temperatures.
Operation: The idle speed control actuator is a vacuum operated device which opens the throttle slightly (2 to 3 degrees of angle) to increase the cold engine idle speed, to improve the mixing of the air and fuel, and to allow lower warmed up engine idle speeds. The idle speed control actuator is controlled by the EGR valve control solenoid, which is controlled by the power control module. To increase the idle speed, the EGR valve solenoid is turned "OFF," and no vacuum is routed to the idle speed control actuator, allowing it to open the throttle slightly. To decrease the idle speed, the solenoid is turned "ON" and vacuum is routed through the solenoid to the idle speed control actuator, allowing the throttle to fully close.
In conjunction with the idle speed control actuator system, the idle air control continuously monitors and controls the engine idle speed to the desired idle speed. A Tech 1 scan tool will read the control module commands to the idle speed control actuator system.
The throttle actuator provides another function. The larger the TB, the more the bores expand as the engine gets hot. The 92+ 454 equipped truck ran much hotter than the older square body version. And GM had switched to a heated intake instead of the small heater plate, which was much more effective at heating the TB and keeping it warm after the engine was shut off. Well, a larger bore means the throttle plate must be closed more to keep idle speed low. No problem, right? Just reduce minimum air by turning the throttle stop and you're done. But if you do that when the engine's hot, the next day when you go to press on the accelerator while the engine's cold, the throttle plate is stuck. Not so good. The throttle actuator allowed a way to reduce idle speed when hot yet keep the throttle far enough open when the engine was off so a cooling TB wouldn't seize the plate.
The following is the correct OBD-1 code chart for the early 90-95 years: https://www.troublecodes.net/gm/#codesobd1
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udidwht
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03/23/23 11:04pm |
Class A Motorhomes
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RE: Difficulty timing a 1995 Chevy 454ci
This can come in handy for troubleshooting the TBI...
https://harristuning.com/Tbi/troubleshooting/
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udidwht
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03/23/23 04:10pm |
Class A Motorhomes
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RE: Difficulty timing a 1995 Chevy 454ci
Figured out the yellow wire. It's a tach wire, which this RV doesn't have.
The yellow wire...is it part of the chassis wiring harness itself? The engine gets RPM info from the ICM. As for the distributor being the issue, seen this many times folks will get another aftermarket distributor and end up pulling their hair out with an issue that ended up being the new distributor. When it comes to parts and these TBI engines GM and/or Delphi or nothing.
You upload a pic to Dropbox and I can take a look at the wiring you have.
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udidwht
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03/21/23 08:49pm |
Class A Motorhomes
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