problems after 3400 top swap

[fat rabbit]

I'll take the blame in cracking the upper intake, when I first installed the large port intake I torqued down each bolt 1 at a time to spec resulting in cracks around the tabs instead of gradually torquing each bolt in steps. I have noticed it does seem easier to crack a large port upper intake do to the having less bolts to spread the clamping force as compared to the small port upper intake with 2 bolts per runner.

I still have my old set of heads and upper/lower intakes but those are are planed to be bolted onto my buddies 88 Buick Regal that he turbo charged.

How did your post 2000 EGR not work right?

Otherwise another update: Last week I let my girlfriend barrow my car to take out to Chicago, getting it back I got a "service engine soon" light. After a couple days I had time to check what the codes were and I got PO102, PO122, PO300, and PO442(I get on/off since the top swap). What really confused me was 3 days ago all the codes went away.

I tested the wire harness and found no problems, grounds are good, I'm getting 5v ref. to the TPS/MAF and the MAF is getting 12v to for the heating element. So I got this great idea to unplug the MAF sensor and WOW!!!!!!! I'm in love all over again with my car, I got all my low end power back, idles more smoothly, lost no high end power, the car feels amazing Some times with the MAF unplugged the engine searches for idle (200 rpm bounce) but other its a night and day difference.

Does this mean my MAF sensor is bad?

[Purple pit]

It could be bad. Did you try to clean it? I'd do that first.

[fat rabbit]

Around 2 months ago it was taken apart and cleaned, I felt a little bit of a difference but not much. I know the engine is defiantly running lean with the MAF sensor plugged in, why its running lean I have no clue.

I remember the shop guy saying that I was leaking badly from the throttle body shaft seals when he smoked my engine for leaks, so I went down to the junkyard and picked another 56mm throttle body and throttle linkage cables from a 99-05 impala. I'm thinking I damaged the throttle body seals when I adapted my linkage to the housing causing it to leak, that would allow un-metered air to enter causing a lean but I'm still not sure if that's the root problem.

Does unplugging the MAF sensor cause the engine to go to a speed density setup or how exactly does the ECM compute the air/fuel ratio?

[3400-95-Modified]

Yes no maf results in speed density... It computes the a/f ratio by the MAP sensor reading and the air temp sensor... As well as other inputs like TP coolant temp and such.

[Purple pit]

Never seen a shaft seal. The only seal that I know of is the O-ring seal on the TPS. The TB has bearings for the shaft. If you have seen a skateboards wheel bearings then you know what they look like(and I would say they are the same size too). If there is a seal then it would have to be between the body and the bearing. I didn't see anything like a seal when I took the 3100 shaft out and put it into a 3400 TB(also a TCE).
I don't like that crap, there is always a dealer or a shop trying to sell a 700 buck TB when it's not needed.

[fat rabbit]

I'm sorry, when I say seals I'm referring too the bearings that seal the shaft to the throttle body housing.

I never saw any O-ring seals ether when I switched my linkage from the the 52mm to the 56mm housing, all I saw was those bearings on each end. I know when I popped the linkage out of the 52mm throttle the shaft was a snug fit with the bearing, a little hard to slide out but when it came to the 56mm it just felt like it slid in too easily. That's were I'm thinking my possible air leak is coming from if I take what the mechanic said as truth, I try to take what they all say with a grain of salt.

Would unplugging the MAF sensor put the ECM in an open loop speed density mode or a closed loop speed density mode?

[Purple pit]

Ok I see what you are saying. Guess I've been lucky. If you ever need another 3100 shaft I have a few.

You turn it into a speed density system. So you will have both.

[fat rabbit]

If I could leave the MAF sensor unplugged all the time I would, the car is a blast to drive around now. I have noticed though that when I first start up the car and drive it around the RPMs like to bounce(to the point of stalling out) when I'm at a complete stop, it'll fix its self after a few mins of driving though. Is that just because the computer was originally tuned to run on both MAF and speed density together(and now I'm running without a MAF sensor) or is there something else wrong with my engine?

The car doesn't like WOT from a dead stop ether when its in speed density, this just brings up more questions then answers. I wish I knew more what the computer is doing so I can problem solve whats wrong with it, today was even the first day I learned what Alpha N mode is.

[3400-95-Modified]

MAF equipped cars have speed density tables to fall back on when a sensor is failed aka Limp mode... they were not tuned and setup to run the car 100% perfect on them... SO unless you have the ability to tweak the tables to make it run more like a factory speed density car then I would suggest trying to find the vac leak that is causing this issue with your MAF so you can plug it back in and run it as its designed.

[fat rabbit]

Oh be leave me when I say don't want to drive it around with the MAF sensor unplugged, I'd like to drive it the way it was designed to run.

I picked up a can of carb spray to go along with the throttle body, hopefully that'll fix or at least lead me in the right direction. I scanned the codes again with the MAF sensor unplugged and I get all 4 codes back PO102, PO122, PO300, and PO442 just like when I got the car back from my girlfriend, when I plug the sensor back in all the codes go away within a trip or 2.

Why does the TPS low voltage code follow along with MAF low voltage code?

[fat rabbit]

Last weekend I went and installed a non modified 56mm throttle body along with the cables to go with it. My old OEM throttle body cable was badly stretched, the gas pedal is more responsive now with the newer throttle body cable. I've found that if I unplug the MAF sensor the engine doesn't search for idle like it did before nor does it stumble now when I take off from a stop, I don't know though if that's now from the non modified throttle body/different TPS/non stretched cables.

The throttle body shaft was so loose I could wiggle it around in the housing, I didn't tighten down the bolts to the coin vary well... I sprayed down my engine a few times during a cold morning with carb spray and the only leak I could find was from the bearing to the throttle body shaft, so I'm back to squire one again.

Does anyone have a non leaking 56mm throttle body I could buy off them? I'll be posting later in the buy/sell/trade section, I just never remember the engine being this picky with air leaks before. when I had my old setup I had a big crack in the PCV return hose for the longest time and I never had a lean hesitation nor any codes for it, maybe I'll need to get re-tuned or the MAF is really on its way out.

[fat rabbit]

I don't mean to bring back from the dead an old post but I thought I'd share the solution to the problem that I had encase anyone were to ever run into something like this.

The solution ended up being me replacing ECM, when ever I would unplug the MAF sensor the car would obviously throw a code for the MAF sensor being unplugged but it would also throw a code for the TPS. I finally ran into a throttle body that didn't leak at the shaft bearings and bolt it in along with a new delphi TPS and I was still at squire one. With all the vacuum leaks gone and a new sensor I was still getting a hesitation and a code for a bad TPS when I would unplug the MAF, exhausting almost every option I plugged back in the stock ECM and 44psi fuel pressure regulator and the problem was solved. The hesitation cleared up in less then a day and the low end was back, then if I unplugged the MAF sensor the only code that would show up would be the MAF sensor being unplugged.

I wanted to thank Purple Pit, 3400-95-Modified, 19Cutlass94, TGP37, caffeine, talon2swords and Ben for helping me out. One of my friends had been bothering me to sell my car to him so he could give it to his niece to be her first car, after a few months of owning the impala and the Lumina sitting in the drive way I gave in and sold it to him.

[carbon]

Thanks for posting the update!