Running a advanced auto MAF only one screen. Took screen out and now it surges, gives me MAF high code and rich exhaust and starts like SH_T. 2000 rpm or higher sets code under it does not.
Any thoughts?

 

Put screen back in, or replace MAF if you trashed it.

Everyone thinks they're Smokey Yunick until something goes wrong...geez...

 

Over the years I have had zero luck with off brand or remanufactured MAFs. The only viable option in my opinion is a costly OEM Bosch unit from GM. They're around $300. The truth is that the MAF systems GM used on 3rd gen cars suck. Probably why they switched back to SD down the road. I guess they've finally got it figured out on the new LS series. Sad that Ford made it work back in '88.

 

Switched back?? What injection system was there before TPI (and don't say CFI it doesn't count).
First check for a vacuum leak after the MAF (also be sure you didn't break the heated wire) This could be the connection to the MAF and/or every vacuum line, including the ones going to the evap cannister. Then..
Try resetting minimum air and TPS, timing and then the computer, see if this clears it up.

 

SD = Speed Density
MAF = Mass AirFlow

GM's first EFI systems were SD, then they switched to MAF. They went back to SD in about 1990, and are currently back to MAF on everything.

GM Fuel Injection History started in the early 60s, when they offered Rochester mechanical fuel injection on Corvettes. The system was an engineering feat for the time, but no one was able to really work on it, including the GM techs! No one really understood how it worked.

The real secret to fuel injection was electronics. Cadillac experimented with an early EFI system before ICs (integrated circuits) were available, but the vacuum tube system took time to power up, and again, no one could really work on it.

The next major step by GM was the Crossfire EFI system first used on the '84 Vette. This system in and of itself was basically junk, but the principles pioneered on this system did filter down to TBI and TPI systems just a few years later. All TBIs are SD, but TPIs were made in both MAF and SD versions. The SD versions being more reliable

Currently GM runs SEFI on everything.

 

So before 1985 what EFI systems did GM make? The mechanical injection system was neither MAP or MAF..it was mechanical (yes, some of us are actually old enough to have seen it..new)

 

I think we're partially hung up on differences in terminology. There are three types of EFI.

1.) Sped Density, which uses manifold pressure referenced from a MAP (manifold absolute pressure) sensor to calculate the air mass entering the engine, and adjust fueling accordingly.

2.) Mass Airflow, which uses an MAF (mass airflow meter) to actually measure the airmass entering the engine and adjust fueling for a given airmass directly (faster than speed density, because the system doesn't have to interpolate the airmass, and then use a lockup table; it just uses a lookup table).

3.) Alpha-N, used only in racing. This system uses input on throttle position using a TPS (throttle position sensor) and a CTS (coolant temperature sensor). These systems are not suitable for street use, since all they can compute is fueling for wide open throttle, and don't take engine loading and other factors into account, which could cause dangerous lean conditions on the stret.

GM used the CFI (Crossfire Injection) on the '84 Vette. However, prior to this they experimented with a variety of other systems on Cadillac and other cars. None of these systems caught on, and most only lasted a year or two before beign radically changed, which is why no one supports them or uses them for performance today.

 

And their first truly successful FI was...MAF. I don't consider TBI (CFI included) to be a real fuel injection (I know I'll catch hell for this) they are merely a more efficent carb, a step in the logical progression to MPEFI.

 

I sort-of agree, in that TBI/CFI are literally injection systems but behaviorally more a bastardized carburetor design. Functionally similar, but instead of a venturi and accelerator pump, they have one or more injector(s).

 

Well, I'm not going to give you hell for it, but the fact is that TBI and TPI have way more in common that TPI does with GM' later sequential EFI systems.

Both TBI and TPI utilize bank/bank injector firing. The TBI only uses two injectors, which fire one at a time. The TPI uses eight, but fires them four at a time, or one cylinder bank at a time. Consequently, both systems only use two injector drivers in the ECM. The ECMs are actually quite similar, particularly the early '85 TPI system. Nearly all of the sensors are the same as well. There are only minor wiring differences.

In fact, Edelbrock currently has a system that essentially converts the TBI to a TPI. It's marketed for Chevy and GMC trucks with 350 and 454 engines and is called the Performer Multi-Point EFI conversion. It uses the factory harness, ECM, and sensors. A new manifold is provided with 8 injectors, fuel rails, and a short harness that is simply spliced in to the factory harness in the engine compartment. The stock throttle body is used, though the injectors are removed. A new fuel pump is provided to make sure the pressure is correct. A new PROM is provided to properly run the system. I am currently running a modified system based on this conversion in my Blazer.

TBI provides nearly the same fueling ability as TPI. There is some problem from the fact that the injectors are located before the throttle plates, so the distribution and atomization is somewhat worse than TPI, but TPI fires the injectors into cylinders that don't even need fuel, so it isn't really all that precise either. TBI offers a vehcile that is a significant improvement over a carbureted engine. Warm up and cold running functionality is vastly improved. Operation at severe angles is no longer a problem (the off-road guys love to point that out). Fuel economy is improved. Power is improved, particularly low speed and mid range torque. Emissions are reduced. Everything that TPI does, TBI does nearly as well. The only real benefit of TPI over TBI is slightly better fuel economy and slightly better power. The TPI isn't really any huge breakthrough in technology, and didn't start any real revolution in the auto industry.

The reason why is simple. Starting in 1985 Ford began producing a speed/density version of ECIV engine management. This system is SEFI, and the ECM has excellent logic and processing speed. The system is also easily upgradeable to the later model ('88-up) MAF system. Ford's MAF ECIV started a revolution in performance, and proved to the world that electronic engine control hadn't killed old fashioned hot rodding, in fact it had improved it dramatically. The GM systems of the day just can't hold a candle to the MAF ECIV systems. Even modern systems in a lot of ways aren't as good, because they aren't as modification firendly since OBDII has been added to the mix. As far as factory engineered performance EFI goes the Ford ECIV is about the zenith.

Also, neither system (TPI or TBI) can hold a candle to the new GM SEFI systems, which offer better power using less fuel, and much more sophisticated logic in the PCM (since now the computer also controls the transmission and other functions as well it has been dubbed the Powertrain Control Module).