TheSamba.com :: View topic - High Idle With New GW TB, But Good With Old.

Thu Jun 19, 2025 2:49 pm

Going through a new to me 1986 2.1.

New plugs
New ignition wires
New cap
New rotor
New injectors
New idle control valve
New Go Westy Throttle body
New throttle body seal

The vehicle idles fine with the old throttle body but screams with the GW TB. I can't get the idle to come down. No tach, but I would estimate the idle at 2500 t0 3000 rpms.

Is there a procedure that needs to be followed after installing the new GW TB? I assumed it would be a bolt on but seems this may not be the case.

Thu Jun 19, 2025 3:10 pm

I have the same problem, also can't figure it out. Watching this thread closely.

Thu Jun 19, 2025 4:35 pm

Adjusting that big fat idle screw did nothing?

Thu Jun 19, 2025 4:44 pm

Let's think cave man style about this, the old TB (throttle Body) was ok rev wise at idle, but the new TB revs too high at idle.....

I'm confidently guessing the new TB is letting though too much air at idle settings. I could be wrong, but I'm not. To save time, assume I'm correct.

Best way to tackle this is to make sure the single TB butterfly is fully home and closed. Next is screwing the by-pass screw all the way down.

Next is to assure the IAC (idle air control valve) valve isn't interfering, just clamp off the air flow via any tube/hoses.

BK

Ps we will figure this out.

Thu Jun 19, 2025 4:49 pm

Don't mean to hijack, In my case that large bypass screws is all the way down and idle still too high. When I clamp that hose, it does resolve the issue. Does that mean the IAC valve is still no good? I replaced mine with a new one from GW. It helped but now I am thinking these after market products may be the problem not being made as well?

Thu Jun 19, 2025 5:32 pm

Is this the "big fat screw" you are talking about? I did not adjust this at all. I will try screwing it all the way down/in. IACV is new, but that doesn't mean anything. I will clamp off the hose and report back my results.

Thu Jun 19, 2025 5:38 pm

Yes. That screw allows air around the throttle butterfly.
It sounds like from others experience that may not be enough though.

Thu Jun 19, 2025 6:01 pm

1988M5 wrote: Let's think cave man style about this, the old TB (throttle Body) was ok rev wise at idle, but the new TB revs too high at idle.....

I'm confidently guessing the new TB is letting though too much air at idle settings. I could be wrong, but I'm not. To save time, assume I'm correct.

Best way to tackle this is to make sure the single TB butterfly is fully home and closed. Next is screwing the by-pass screw all the way down.

Next is to assure the IAC (idle air control valve) valve isn't interfering, just clamp off the air flow via any tube/hoses.

BK

Ps we will figure this out.

To be even more caveman - are we sure the TB is perfectly mated to the intake without any air leaks?

And what about that adjustable bolt around the 12-o’clock position in the photo? I forget but does that set an idle limit of some sort? Maybe that got out of adjustment during shipping etc.

Thu Jun 19, 2025 6:17 pm

More info.

I installed a new rubber seal and was careful to tighten each side of the TB down equally. I am pretty confident there is a good seal there.

With the new GW TB installed I screwed the adjustment screw all the way in and then backed out 1/2 turn. Old IACV installed and it started right up, and it idled nicely from cold until up to operating temperature. Unplugging the IACV made the idle drop, but not by a lot.

GW TB with the new GW IACV installed, at operating temperature I started the engine, and it raced as before. Unplugging the IACV and the idle dropped. Could the new IACV be faulty? Any way of testing? Seems strange the old one lets the motor idle nicely whereas the new IACV the motor races, even with the TB adjusting screw turned all the way in.

Pulling off the IACV hose and the engine stalled.

Thu Jun 19, 2025 9:14 pm

What is the troubleshooting recommendation from Go Westy?

Thu Jun 19, 2025 9:17 pm

If the old one works, install it and send the over priced junk back to gowesty.

Thu Jun 19, 2025 11:29 pm

MSGGrunt wrote: Is there a procedure that needs to be followed after installing the new GW TB?

GW has this note on the product page: "Changing out any one part of your EFI system that is faulty with a new or rebuilt part may cause worse running because other settings may have changed over time to compensate for the faulty part you are replacing. Following the baseline settings procedure in the Bentley manual is required after installation."

zerotofifty wrote: If the old one works, install it and send the over priced junk back to gowesty.

:lol: :thumbsup:

If it ain't broke...

Fri Jun 20, 2025 3:52 am

Stock or aftermarket, the throttle switch adjustment is precise. You’ll need a feeler blade set and an ohm meter. As recommended, follow the factory manual procedure. Basically you back off the throttle plate stop till there is an air gap between the stop and the cable arm. This should ensure the throttle butterfly is closed. You then turn it in till it contacts the arm. Ohm meter connected, zero ohms. If that’s true, then you can set about the fine adjustment. I’d rather you check the manual, but memory is with a .004 to .006” blade between the stop and the cable arm you should have no continuity on the ohm meter or infinity.

This is how the ECU knows if you are idling or moving off from a stop. This is an oversimplified explanation. The manual is what should be followed. It’s a set it and forget situation. After that the large screw is your actual idle adjustment.

Fri Jun 20, 2025 4:00 am

Problem solved.

A bad GW IACV. Or at least with the ignition on, but the van not running, the original IACV vibrates as it should whereas the new GW one does not.

GW says no returns on electrical parts, but I hope this will be an exception. As long as the original one is working, I will stick with that one.

Fri Jun 20, 2025 4:03 am

Now to go about setting everything according to the FSM, which I thankfully have.

Fri Jun 20, 2025 6:04 am

there's lots of good reasons to keep the GW TB... no more worn bushings sucking air, hanging the throttle plate up as it becomes cockeyed in the bore, and proper switch operation.

some important questions:
- does your old TB work correctly with the new ICV? this verifies the new chinese ICV is responding with at least a ballpark air bypass.

- if you block the hose between the ICV and the rubber intake boot, can you get the idle lowered by screwing in the large idle screw on the TB? this is important because the ICV needs a LOW base idle to work with-- the ICV can only RAISE idle speed.

- if you can't get the base idle lowered with the idle screw with the ICV hose blocked, that demonstrates that the throttle plate adjustment is out of whack, despite that GW says it is adjusted by them and to not touch it. the Bentley and the Pro Training manual give a linear procedure to adjust the throttle plate position, verify switch operation, and set the ICV current by using the idle speed screw. you'll need a vacuum gauge and a meter that can read milliamps in addition to cutting one wire to the ICV to measure ICV current. it is easy and we can walk you thru this when you have questions.

TIP: once you cut one wire to the ICV to measure current, crimp mating quick disconnects onto the wire ends for ease in rechecking the ICV current at a future date.

Fri Jun 20, 2025 10:21 am

DanHoug wrote: and a meter that can read milliamps in addition to cutting one wire to the ICV to measure ICV current.

TIP: once you cut one wire to the ICV to measure current, crimp mating quick disconnects onto the wire ends for ease in rechecking the ICV current at a future date.

For anyone reading who doesn't want to cut the factory wiring, the special VAG 1315/A2 harness is available: https://techtonicstuning.com/product/test-harness-for-vanagon-digifant-injection-vw-1315-a2/

Fri Jun 20, 2025 6:20 pm

I will keep the GW throttle body, but going to return, if they let me, the IACV. Just placed an order for the test harness. Now to dive into the FSM and read up on the proper set up of everything.

Sun Jun 22, 2025 11:42 am

Used to be in the olden days when Peter owned Van Cafe he had a guy that rebuilt the TB to better than new. He didn't care if there was a groove worn in the body as he would bore it over and make a new plate. I've have one of his rebuilds in my truck and it's pushing 200K. The new guy that rebuilds them wants a perfect bore before he touches them.

I recently went through trying to get a smooth pedal and consistent idle on a customers van and a new GW TB bolted on and worked a dream. A buddy pointed out that the issue with the TB is that you can not adjust the switch while in place.

Are you sure all of your Vacuum hoses are properly in place?

Stacy

Mon Jun 23, 2025 5:23 pm

I did check all the vacuum lines and looked for any cracks in the TB to air cleaner boot and IACV rubber hose and they all looked fine. I have it idling fine now with the old IACV and when the test harness arrives, I will try to dial it in following the FSM. I am happy with the GW TB, just not the IACV. I did get an email from GW today saying they will accept it as a return.