Engine dies on idle

[1972VWbus]

How are all the vacuum lines? Check them carefully your MAP one looks iffy.

[D Gardiner]

TBIs are very simple early OBD engines. As such all of the normal checks you would do on a vintage carbureted vehicle is paramount on a TBI injection engine. That would include simple things like checking for vacuum leaks, distributor timing, and the alike.
You or your mechanic should also read the trouble shooting page (link below) and even print it out.
https://harristuning.com/Tbi/troubleshooting/

Originally Posted by ACNB

Hello!
Really need some help.. my rv engine really struggles with idle and if I lift off the gas and apply the brakes and can stall completely- I’ve fitted new leads plugs rotor arm and distributor cap as a precaution, new Idle air control valve, in-line fuel filter and still it’s the same - has anyone got any other ideas?
Being in the uk doesn’t help as it’s not a common vehicle - most people are guessing!
Alan

[1972VWbus]

There is also signs of critters (mice) living on the manifold.

[ACNB]

Great thanks, VIN is 1GBKP37N1V3306299

Originally Posted by 1972VWbus

Post up the VIN number.


97 should have Vortec. Unless someone (PO) swapped in a TBI motor.


Fuel pressure for the 94-95 TBI years was 26-32psi. Previous TBI years were 9-13psi. Attached a pic of mine (1994).

[1972VWbus]

Pull code/s from OBD connector...

https://www.youtube.com/watch?v=i_Y7TiVqsBA

[nikkievix]

did you check to see if the spray is equal on those showerhead injectors? mine was doing something similar, turned out the electrica connector for the left injector was not locking dpwn, so i replaced both connectors. if yours are uneven or not spraying right, could also be fouled nozzles.

[153stars]

If engine runs great beside idle I would still be after that idle control solenoid/servo ,maybe wiring and clean it's port into manifold 100% ...you said you replaced ,it looks old to me.

[ACNB]

100% is new IAC valve, those someone had snapped off bolt at some point, but can see the vallve move in and out when air cleaner is off Have checked vacuum lines, have checked and clean EGR valve.

The throttle kicker is a strange one as the vacuum is suck that it pulls i right back 10mm away fro the throttle linkage, is this normal? I assumed it would be close and if engine started to stall it would pop out to nudge the throttle but doesn't seem to. Next plan was to replace the MAP sensor, think the temp sensor is ok as the idle is high on cold start up then settles down once engine warms up.
Cant attach video but here it is on YouTube https://youtu.be/rPhWmJV2ONc

Ive looked the injection nozzles they both seem to spray consistently, maybe its normally but seems strange butterflies are completely closed on tick over?

[1972VWbus]

Originally Posted by ACNB

100% is new IAC valve, those someone had snapped off bolt at some point, but can see the vallve move in and out when air cleaner is off Have checked vacuum lines, have checked and clean EGR valve.

The throttle kicker is a strange one as the vacuum is suck that it pulls i right back 10mm away fro the throttle linkage, is this normal? I assumed it would be close and if engine started to stall it would pop out to nudge the throttle but doesn't seem to. Next plan was to replace the MAP sensor, think the temp sensor is ok as the idle is high on cold start up then settles down once engine warms up.
Cant attach video but here it is on YouTube https://youtu.be/rPhWmJV2ONc

Ive looked the injection nozzles they both seem to spray consistently, maybe its normally but seems strange butterflies are completely closed on tick over?

1. Did you verify that the new one has the correctly sized pintle? There are (2) sold with different pintle sizes.


2. How are the vacuum lines?


3. Check the TBI base gasket using small shot/s of carb spray around the base of TBI while engine is idling.


4. Did you verify fuel pressure (critical with TBI). 26-32psi


5. When is the last time you changed fuel filter (chassis frame rail)?

[donr103]

You may be on to something.. when you mentioned throttle kicker.. it just looks sick.. follow the vacuum line to the solenoid that controls the vacuum source and check that vacuum connection and electrical connection on the solenoid that control throttle kicker.. one quick test.. just unplug it and see what she does.. easy and free.. you may set a code.. but if you disconnect the battery for few minutes it will normally clear it.. oh.. something else.. do you have battery disconnect switches by the door? Only reason I ask.. sometimes po will change the wiring around.. and they remove power to ecm.. and it loses memory every time you hit battery disconnect.. then computer must go thru entire re leaning process.. so make sure.. if you do have battery disconnect switches... that ecm .. always has power..
Good luck and keep us posted

[ACNB]

So I think I have made progress, the throttle kicker has some sort of vacuum control valve? When I remove pipe form carb and block off carb end it runs better - so am trying to identify what its called and find new one. Weirdly it has a pipe missing on the mack and no sign of what should be connected

[donr103]

So I think that is part on decel valve.. so 1st check and see by sucking thru vacuum hose and see if diaphragm in throttle kicker is bad.. it looks like it.. do that 1st.. see if diaphragm holds vacuum and not leaking.. next.. use your cellphone with flash on and record over top of radiator support.. and see if vacuum diagrams are there.. when it was new.. gm put vacuum diagrams on it some where.. you just have to find it.. could be on air cleaner.. so look around.. looks like hack job by many po.. so you are going to need repair book.. if no one chimes in.. I will pull out my old books..
Good luck and keep us posted

[1972VWbus]

This is what you need...(EGR valve control solenoid/Motor)



https://www.rockauto.com/en/moreinfo...pt=4380&jsn=16

[77Travco]

Install a new EGR.