I replaced my NA TB with a 74 when I put the DCAI's on. one small issue I have after the change was when the car is cold, as in colder weather on a fresh start, it starts and runs just fine. But if I don't let it warm up and as I pull away, I have to start off with a light throttle because if I accelerate too much it suddenly dropps off power between 1st and second. It stumbles, loses power and then I back off the throttle and returns as normal. Once the car is on the road and warms up it's fine and doesn't do it again. Cold starts in the summer rarely, if ever do this. It began right after I put the larger TB and larger duals in.

So it seems to me to feel like a MAF issue, that the cold air rushing in overwhelms the gas input resulting in the stumble, but when the bay is sufficiently heated then the sensor doesn't notice more air intake for the fuel provided. Does this make sense? Anybody else have this issue? It doesn't bother me that much, all in all, but if there's a fix for it then i'd like to do that.

 

its been couple months...has the issued continued?? im getting ready to do the same swap...

 

Well, maybe good news. A couple of weeks ago I tossed in maybe a 1/2 bottle of chevron fuel cleaner and after 1 tank the issue seemed to lessen alot. Still don't quite trust completely yet. But I think there may have been varnish or gumming on the plate. I was gonna toss the rest of the bottle in the next tank. It is winter here in MN so not driven as much, but it seems to have. cleaned up the issue a lot. The pull on the low end with the 74 is noticeable.

 

Did you use the sensor that came with the 74mm MAF or reuse the old one?
I used the old MAF sensor and had no trouble at all. That was what I was told to do.

 

Not sure if I understand this right, but what you said leads me to believe that you think that the fuel injector cleaner will clean up the throttle plate. If so, then I can tell you it will not, all that goes by the throttle plate is filtered air and blow-by from the valve cover vents ( if you don't have a catch-can ).
You have to remove the TB and clean the plate up yourself .....

 

Used the MAF that came with the kit, so have no idea how many miles were on the TB or the MAF. And no I wasn't saying the plate itself was cleaned by the FI cleaner stuff, as that's the air control, I was just commenting mainly on the the intake after I put the new tb on, and then it started acting up in the cold and started thinking it as a system. So started with the tpo area and down. My next go was to replace it with the maf I had and still have. Just trying to figure out where the hiccup was in the most logical and inexpensive process is all. The question was raised if it was fixed, and as of now it seems to be. There was just this hiccup that perhaps was in the feedback system for some reason. But it had to do with the replacement, the engine was going I think really rich at those times

 

I had the same problem with the 74mmMAF when I first installed. I took the 68mmMAF sensor and replaced the 74mmMAF sensor. Problem went away. I do think I had an air leak on the MAF gasket ( the gasket probably was wrinkled. I put a film of lube on it to help it slide on easier. My 06 LTD Roadster is at 211.4 RWHP on the last dyno at Eurocharged Performance.

 

Hmmm. Thatks tinker, perhaps that might be the issue. It was really quite cold the day it was installed, and maybe the gasket wasn't quite seated. I'll look at that when it warms up. I know that my mpg's really decreased this year, more than normal, but I was attributing that to the run rich and lagging issue. The mpg's seem to have gone up a bit, not as much as they are in the summer, but I've found that to be the case with the cold temps and slippery roadways anyway. But given the lack of snowfall then the MPG should have been closer to the normals that I get in the summer. So maybe we do have a gasket issue.

 

I also had a problem with the "O" ring on the TB at first. You can also have alignment issues due to slp in the mounting screw holes. Reach in the throat of the TB and feel the bore lip to make sure it is smoothe all the way around where the TB and manifold meet. Don't over tighten either. Hope this helps. Drives you crazy when you know it should run better and it doesn't.

 

As I said earlier change the MAF sensor, it is calibrated for an engine that uses practically twice the air that the 3.2 uses.

 

OK, that's what I thought.
I should get my $50 74MM TB today, I will retain the 68mm MAF and see how it goes .......

 

This is an issue that has been solved.

Use the 74mm throttle body with the 74mm MAF housing in which the old 68mm MAF sensor has been fitted to replace the 74mm MAF sensor which came with the 74mm MAF assembly.

The 74mm MAF housing comes with a 74 mm MAF sensor, throw the 74mm sensor away and use the 68mm sensor instead. Single or double intakes, the engine can only use so much air no matter what is available. The 74mm MAF sensor is not smart, it just gives signals based on air passing it, those readings will be as if it was in a V8. The 68mm MAF sensor signals will be closer to the requirement as it was calibrated for use with this engine.

 

180 - if that was in response to my post, please understand that I am in complete agreement with you.
Heck, I don't even HAVE a 74mm MAF sensor .......

 

I found this thread completely confusing, so I just stated facts.
It appears to go in circles. LOL

 

yes, I think that's the ticket. new 74 TB, old 68 maf sensor

 

Not to burst anyone's bubble, but I went through the same problems with my first 3" MAF. I actually scoured through the M/B forums and found out that the generic MAFs are the problem. I bought one of the cheapos on ebay; What a mistake. Luckily, I found a used SL Bosch OEM one at a salvage yard down the road and managed to talk them into swapping it for the new one I had. Solved all my problems.

I 'm thinking that the generics don't use the same Bosch sensors that the SL ones use.

Just to remind everyone...only use the Bosch OEM 3" MAF. And if you want a new one, make sure to buy it from a reputable parts dealer and that it has the Bosch OEM p/n 0280217810. Ebay will list some of them as being Boschs, but alot of them are foreign knock-offs with the name "Bosch" stamped on them. A quick look around the net showed that AutohausAZ had the best price for the OEM Boschs. Around $150.

And no, I didn't have to change out the sensor. It was just plug and zoom. It re calibrated just fine. Been running it for a year now without a single hiccup....smooth as butter!

Then again, if money is tight, buying a generic one that is much, much cheaper in price and changing out the sensor is still a very viable option.

 

slight hesitation on initial acceleration (after cold start) - 07-23-2007 , 12:43 PM

the above is a small thread I found after I got the idea that it may be the TPS that's doing this. It appears that this is a "normal" issue, for some cars, as what happens to mine is exactly as described above. Exactly. Now why that is on only some is a question, but at least I know mine's not really the only one. Why it started only after the 74 and DCAI upgrade is beyond me, but I'll swap out the old maf and sensor and see what happens.

The old maf of course has the baffle grid in the throat and I seem to recall that folks have taken that out, maybe Mike in Orange mentioned that. Anyway, if so, what has been the benefit or the deleterious affect of that, obviously before I do that. the baffles I'd guess are there to break up and smooth the airflow.

On a side note, I put the rain gutter trim on. 7/16" wide, and mentioned before that the secondary benefit was that it broke up the wind getting sucked into the car at speed, so now I can keep the windows open without the inside booming.

So my motorcycle screen has always bugged me because the air hits me right over the top of the screen in my forehead creating buffeting and windnoise in my helmet. So I got the bright idea while looking at the car and put some of that trip along the top of the screen first, first one way then the next upside down. Found that in one position it didn't do anything, but in the other it raised the wind flow between 2 and 3 inches. Unbelievable that somehing that small would do that to that degree and substantially quieted the ride. I then played with trim on the sides of the screen but that increased the turbulence across the area of my body right behind the screen, so off that came. Fun times playing with that stuff.