Waiting on another TB to try, I came across a thread on Rennlist where a bad FPR caused a similar situation, because the diaphragm was leaking air and allowing fuel to enter the manifold... Life has me too busy to go check, but I ordered a new FPR incase I find that it might be the problem.
Re: Where to look next? Feedback/advice?
Posted: Mon Nov 17, 2025 3:23 pm
by Efren
I was going to say search Rennlist since I have seen several or many post describing what you’re going through.
For me seems each item I touch shows signs of wear and ordering them as I move on to the next one. Long process of waiting for parts.
On my issue think I have a fuel delivery issue as one mentioned a few days ago. I’m thinking this because of how it started. I was cruising on a highway and all of a sudden I lost power as the engine is barely running. Shut it off and try to restart. It restarts but immediately starts to almost die out.
Re: Where to look next? Feedback/advice?
Posted: Mon Nov 17, 2025 6:37 pm
by Tom
Just to close the loop on one issue, I put the cluster in this afternoon and did a little testing, and can confirm that the ISV is able to maintain the commanded idle RPM even when the car is running rich. Not surprised by this, but thought it might help. Fingers crossed the new TB does the trick...
Re: Where to look next? Feedback/advice?
Posted: Mon Nov 17, 2025 7:00 pm
by spacecad3t
Thanks Tom! Them some nice gauge clusters!
Re: Where to look next? Feedback/advice?
Posted: Mon Nov 24, 2025 2:32 pm
by spacecad3t
Update.
The throttle body I got off eBay arrived. It's used, but a nice time capsule example... very clean and dry, functions well, included a TPS, which tested well. It also included a return spring that was significantly shorter than mine was, found that interesting.
For reference, I checked what the idle bypass was set to, 3 turns out from seated... At this point, I just cleaned it up and grabbed a new o-ring.
Installed the tb in the car, hooked up the timing gun, and started the car. 1050rpm. Great! Im 3 turns out... Adjusted it down to ~900rpm and then let it warm up. Followed the idle adjustment procedure, reached 840rpm, 1/2 turn from seated. During all of this, the ICV maintained steady idle through full warm up.
So, it looks like my throttle body, which appeared factory installed, may have been rebuilt at some point and incorrectly... With the car now running better, I'll look closer and post some photos.
Appreciate the help everyone.
Re: Where to look next? Feedback/advice?
Posted: Mon Nov 24, 2025 2:57 pm
by Tom
spacecad3t wrote: Mon Nov 24, 2025 2:32 pm
Update.
The throttle body I got off eBay arrived. It's used, but a nice time capsule example... very clean and dry, functions well, included a TPS, which tested well. It also included a return spring that was significantly shorter than mine was, found that interesting.
For reference, I checked what the idle bypass was set to, 3 turns out from seated... At this point, I just cleaned it up and grabbed a new o-ring.
Installed the tb in the car, hooked up the timing gun, and started the car. 1050rpm. Great! Im 3 turns out... Adjusted it down to ~900rpm and then let it warm up. Followed the idle adjustment procedure, reached 840rpm, 1/2 turn from seated. During all of this, the ICV maintained steady idle through full warm up.
So, it looks like my throttle body, which appeared factory installed, may have been rebuilt at some point and incorrectly... With the car now running better, I'll look closer and post some photos.
Appreciate the help everyone.
Yippee! What a journey! All your testing pretty much narrowed it down to the TB -- very glad you got to the bottom of it!
Re: Where to look next? Feedback/advice?
Posted: Mon Nov 24, 2025 3:39 pm
by Efren
spacecad3t wrote: Mon Nov 24, 2025 2:32 pm
Update.
The throttle body I got off eBay arrived. It's used, but a nice time capsule example... very clean and dry, functions well, included a TPS, which tested well. It also included a return spring that was significantly shorter than mine was, found that interesting.
For reference, I checked what the idle bypass was set to, 3 turns out from seated... At this point, I just cleaned it up and grabbed a new o-ring.
Installed the tb in the car, hooked up the timing gun, and started the car. 1050rpm. Great! Im 3 turns out... Adjusted it down to ~900rpm and then let it warm up. Followed the idle adjustment procedure, reached 840rpm, 1/2 turn from seated. During all of this, the ICV maintained steady idle through full warm up.
So, it looks like my throttle body, which appeared factory installed, may have been rebuilt at some point and incorrectly... With the car now running better, I'll look closer and post some photos.
Appreciate the help everyone.
Wow congratulations. I’m it sure how much you paid but if the TPS came with it it’s well worth the money..
I haven’t had a chance to work on my issue yet. Too many things happening and Thanksgiving around the corner. It will be mid next week by the time I get to look again
Congratulations again.
Re: Where to look next? Feedback/advice?
Posted: Wed Nov 26, 2025 8:59 am
by spacecad3t
Took a look at my original throttle body. Aside from the plate, the only other interesting damage is inside the throttle bypass bore, which looks like metal fatigue, wonder if this engine ate those bits at some point...
I was able to unscrew the plate screws without any effort, they were not peened...
The plate is aluminum. I flipped the orientation so that the 4 is facing outward and reinstalled the screws. It operates fine. Very little gap. However, my replacement is overall nicer.
Re: Where to look next? Feedback/advice?
Posted: Thu Nov 27, 2025 7:20 pm
by rheidtman
Regarding TB plate material, I've come across primarily brass (with the #4 front facing), but also have a few turbo TBs that have flat aluminum, as well as dimpled aluminum plates - interesting.
Also, I have two NOS NA throttle bodies still in the box... I will get them from storage, but I've not seen internal damage as you listed in the previous posts.
Re: Where to look next? Feedback/advice?
Posted: Fri Nov 28, 2025 3:29 am
by spacecad3t
rheidtman wrote: Thu Nov 27, 2025 7:20 pm
Regarding TB plate material, I've come across primarily brass (with the #4 front facing), but also have a few turbo TBs that have flat aluminum, as well as dimpled aluminum plates - interesting.
Also, I have two NOS NA throttle bodies still in the box... I will get them from storage, but I've not seen internal damage as you listed in the previous posts.
Interesting. I wonder why some have dimpled aluminum plates. Do the ones you have with alu show the "4" facing in(manifold) or out?
