Vacuum Line Issue: Upgrading Throttle Body from SOHC to DOHC

[dbest671]

Really? They have the same holes on the inner part of the TB?

[stealthee]

They both had the same vacuum ports on top.

As Rich said though, vacuum is vacuum. All that matters is he is getting vacuum to the proper components. If he tees the single one he will be fine.

[dbest671]

This is what I am talking about... it has to do with the ports on top, which are also routed to small holes inside the TB. It will cause idle issues if they are not the same type set-up.

[stealthee]

I have a NA DOHC Fed Spec TB and it only has one hole and there are no idle issues. Vacuum is vacuum.

[Dbeltran24]

I found a diagram of the 99 vr4 vacuum lines, and if its anything like my 99 sohc then the two vacuums I have are for the egr solenoid and egr valve. The missing vacuum is on the plenum and is for the purge canister. I would delete the egr but I don't know how to prevent a CEL.

[dbest671]

If you want the N/A throttle body I have pictured above, you can have it for the cost of shipping. It's a 1st Gen Cali-Spec. But all you get is the part that is pictured, I have already disassembled it for parts LOL. So you would to use your shaft/plate/springs/fiav.

The 99 VR4 TB I have only has two vacuum lines also, and one big hole on the inner part.

[Dbeltran24]

The insides of both did look significantly different. But I don't remember what the inside vacuum hole looked like. I'll compare tomorrow. I think I remember reading a thread about having to adjust the idle when swapping TBs

Would hate to get rid of this one since it's been polished.

I'll snap pics of both.

[dbest671]

You may be able to "T" off the the one vacuum port... I don't know how finicky the 98/99 egr/map sensors are. The 95 TB look identical to the 96/97 except for the holes on the inner part (which has to do with the idle) after reading the manual. I've learned a lot of TBs in the last couple of years, but never really dealt with the SOHC TB... the only reason I had one was because the seller thought it was a DOHC. The only reason I have the cali-spec NA was because somebody used it on a TT and didn't realize it had non-reinforced shaft seals.