MAC TB/Plenum install and problems

thomas91169 · Oct 14, 2005

recently installed a MAC 75mm TB and Plenum. car ran fine with no idle or throttle issues before this mod.

first issue - gas pedal is very stiff. its only stiff for the first mm or so of movement, the rest of its play is just like normal. its just that first touch of the pedal that is stiffer than the rest. its not really a issue, im getting used to it, just annoying sometimes in traffic to have to do the rev before taking off.

second issue - rpm's hang after revving/driving. i can turn the car on, idles at 800ish. give it a nice rev and itll come back down and hang up at 1200 for a few seconds, then plop down to 800. or if im driving and come to a stop itll do the same. also in 2nd gear i can almost let the car drive itself at those rpm's with no throttle applied. this is severly annoying.

any suggestions? or just POS MAC products?

BLUE03GT · Oct 14, 2005

ive never heard of a TB/Plenum setup not having problems with the idle... it happened on 3 of my friends cobras/GT's and all u need to do is tune it...

TweekedGT · Oct 14, 2005

Mine has a crazy idle too. I have a Granatelli Plenum and Accufab 75mm T body. The car basically takes off on it's own at idle now. It sometimes sits as high as 2000 rpms for about 10 seconds at start up. Sounds like your having typical plenum/T-body issues.

twogts4us · Oct 14, 2005

The idle will get better within a week...

thomas91169 · Oct 14, 2005

BLUE03GT said:
ive never heard of a TB/Plenum setup not having problems with the idle... it happened on 3 of my friends cobras/GT's and all u need to do is tune it...

what do you mean by "tune it"?

if i set the idle with the predator itll still hang before coming down to the set idle i give it.

if i cant figure this out, im just gonna stick the stock tb back on. the gains(if any) from the 75mm tb arent worth the annoyances it gives.

btw theres also a screw i found on the TB that looks like it intersects with the TPS sensor, would this change anything by adjusting it?

stng · Oct 14, 2005

I have heard that it is very common with the MAC TB to stick a bit with the first mm or so of movement... Never heard if it resolves after driving it for awhile or not (Maybe it will wear in and fix itself)

As far as the issue of the idle jumping up or staying up after a rev my car does that exact same thing sometimes and to the best of my knowledge it is the stock TB unless the previous owner put on an aftermarket one before I got it. I was wondering if I had a bad IAC and that was what was causing it?

WillDuhhBeast · Oct 14, 2005

This thread makes TB's and plenums seem like more trouble than they are worth.

03ghoststang · Oct 14, 2005

it could aldo be the tps sensor not seated correctly or need to be adjusted a little

twogts4us · Oct 15, 2005

WillDuhhBeast said:
This thread makes TB's and plenums seem like more trouble than they are worth.

But they really aren't bro. Sure, I had the same problem with the hanging idle, but after resetting the computer, within a week it was 90% better. It was never really THAT bad, a bit annoying, but not a huge thing...and I'm pretty picky. The benefit to me was well worth it - at 3K plus, it just pulls like never before - a noticable difference...very noticable.
I'd avoid MAC, as I've heard to many bad stories with their TBs.

twogts4us · Oct 15, 2005

thomas91169 said:
what do you mean by "tune it"?

GOOD question - what the heck is that supposed to mean, Blue03GT???

thomas91169 said:
if i set the idle with the predator itll still hang before coming down to the set idle i give it. if i cant figure this out, im just gonna stick the stock tb back on. the gains(if any) from the 75mm tb arent worth the annoyances it gives.

Reset the computer if you haven't done so yet, and trust me, almost everyone goes thru this...it'll get better in a few days.

thomas91169 said:
btw theres also a screw i found on the TB that looks like it intersects with the TPS sensor, would this change anything by adjusting it?

Don't mess with any screws on the TB...the only adjustment you could make is to the TPS...by loosing those attaching screws and rotating the TPS left or right to raise or lower the idle. But the hanging is a result of the additional air it's able to drink...it's just gonna take a little driving to adapt.

thomas91169 · Oct 15, 2005

twogts4us said:
Don't mess with any screws on the TB...the only adjustment you could make is to the TPS...by loosing those attaching screws and rotating the TPS left or right to raise or lower the idle. But the hanging is a result of the additional air it's able to drink...it's just gonna take a little driving to adapt.

well i tried adjusting whatever it is, but it did nothing. so i just put it back to where it was.

the TPS is in there as far as it will go, so i know thats all good.

and i fixed the sticky pedal. up on the top left of the TB(if youre looking straight into it from the pass fender) theres the throttle blade control stop nut(or whatever its called). i loosened it, and moved it out a thread, so the throttle stops a thread earlier, and stops before it gets to the "sticky" feeling part. nifty.

ill reset the battery again. maybe spray out the maf and ISC again(was having idle problems with ac on when i first got the car, that fixed it) with my electrical terminal cleaner, and see what happens.

StangPro · Oct 15, 2005

WillDuhhBeast said:
This thread makes TB's and plenums seem like more trouble than they are worth.

The problem is, that people buy junk parts like MAC and then give the mods bad names.

I've both done personally, and sold over 100 Dragon and/or Accufab combos. NOT ONE has ever had an idle problem. We only install and recommend those parts specifically for that reason.
The Dragon TB/combo is flawless so is the Accufab set-up.
NO tuning ever required, no ide adjstment required.

When you buy garbage, you get garbage results.

thomas91169 · Oct 16, 2005

ive come to that same conclusion.

i think ill just slap on a accufab 75mm tb and sell the mac to another poor soul.

thomas91169 · Oct 16, 2005

ive come to that same conclusion

i think i might buy a accufab 75mm and sell the mac tb to some other poor soul who wouldnt mind a annoying throttle hang and sticky pedal.

Fubar02GT · Oct 16, 2005

funny...am i the only person that hasn't had a problem with thier MAC 75mm TB? it went on with a cheapo GMS intake plenum too...not one single hitch at all. the idle sits right about 750 where it always has. pedal feels the exact same as stock, and turning down the idle set screw did make a slight difference for me...basically i closed it off totally and let the ECM manage it per the install guide suggestion...i have had zero issues and i definitely felt the difference making it the best 249 bucks i spent on the car so far...that was for the plenum and tb together...

jivepepper · Oct 16, 2005

No problems here. $217.00 shipped for both.

GDawg · Oct 16, 2005

I bought a MAC throttle body and it was so crappy. It stuck bad and it never idled correctly. I got rid of it and bought an Accufab. The Accufab was like butter. It was perfect from the get go.

redfiregt559 · Oct 16, 2005

why dont you make sure there is no kninks in the cable and every thing is good then lube it to get rid of the stick until it works itself in?

Dark Knight GT · Oct 16, 2005

StangPro said:
The problem is, that people buy junk parts like MAC and then give the mods bad names.

I've both done personally, and sold over 100 Dragon and/or Accufab combos. NOT ONE has ever had an idle problem. We only install and recommend those parts specifically for that reason.
The Dragon TB/combo is flawless so is the Accufab set-up.
NO tuning ever required, no ide adjstment required.

When you buy garbage, you get garbage results.

I can vouch and say that the Mac throttle bodies are garbage. I had one. It never idled right, and the throttle blade wouldn't close all the way. Worse part was Mac's customer service. They didn't want to do anything about it, and tried to make me out to be an idiot.

Little off topic, but do you have any updates as to whether Dragon is making a lower intake to match their upper intake ?

StangPro · Oct 16, 2005

Dragon has throttle bodies and uppers.

Problem with making a lower is that the expense is significant, and there isn't much power there.

The lowers that are out there are picking up less than 20hp, and just a plenum gets you more than half of that with 10% of the cost.

MAC TB/Plenum install and problems

thomas91169

I'd donkey punch my sister.

BLUE03GT

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TweekedGT

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twogts4us

thomas91169

I'd donkey punch my sister.

stng

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03ghoststang

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twogts4us

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thomas91169

I'd donkey punch my sister.

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thomas91169

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Dark Knight GT

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