2000+ 3400 from the heads on up.

[fastback4]

My 1997 Monte 3100 had a rough December as most of us know. I flushed the motor in Nov. 2009 and forgot to reinstall antifreeze. The stock heads were warped .017 and .019 respectively, so i bought used 3400 2000+ motor (Bad crank) and installed the heads (machined flat) intakes, throttle body and the usual smaller items. Car starts well, idles smooth at all temp ranges but is only getting 21 mpg. The 3100 stock motor got 27.1 mpg at 250,000 miles.
Why the bad gas mileage? I'm running the EGR delete. I have not had this motor retuned yet cause i don't have 300.00 for a tuner. Any suggestions?.........Tom

[Guest]

Re-connect your EGR.

I don't understand why everyone wants to get rid of the EGR...

[fastback4]

Re-connect your EGR.

I don't understand why everyone wants to get rid of the EGR...

Reconnected the EGR valve, checked for codes, none detected, ran 1 tank of high test Marathon gas, mileage still at 21MPG. No changes in MPG since EGR is reconnected. Car still sluggish out of the hole but has lots of top end. So much for the 3100 top end swap 3400 heads, 3400 throttle body and 3400 larger port Intakes.

[SappySE107]

What injectors/fuel regulator are you using? EGR isn't gonna do anything for you but pollute your intake and intake valve.

[Guest]

What injectors/fuel regulator are you using? EGR isn't gonna do anything for you but pollute your intake and intake valve.

Yeah, that's why the OEM puts EGRs on thier cars.....

[SappySE107]

Its an inferior method of emissions control compared to cam timing. It most certainly hurts the efficiency of the engine when it isn't on, from covering the back of the intake valve with carbon. That carbon mixes with the oil vapors from the PCV and makes it worse. You think GM added the EGR for MPG? I hope not.

[Guest]

Actually it does help with that, among other things, like anti-detonation, at part throttle and low load.

It is not an inferior method of emsissions control, it does exactly what it's supposed to do.

I have seen intakes that have never had an EGR connected to them look just as "dirty".

EGR does NOT hurt performance or take anything away from the engine. Anyone who believes otherwise really needs to research what an EGR does and why recirculating exhaust gases back into the intake is a good thing for an engine.

I know your next rebuttle will be "Why don't we just connect the exhaust to the intake?" because you try to use extremes to support your claims. It doesn't work that way, we are talking small amounts of exhaust gases.

Do as you wish, I will continue to use my EGRs and even add them to engines that don't currently have them. (I haven't added one to the Datsun yet, I really need to get that done...)

[SappySE107]

Thats cool. Nothing you have said has made any difference in the real world. Pre detonation, non existant on my EGRless motors. No MPG loss from removing it either. No reason to run seafoam through any of my motors. All real world things that brought me to my conclusion. I promise you this much, its not going to help him get more than 21mpg, which is the actual topic. Trying to put me down with emoticons and all caps is not. Get a new hobby chris, arguing with me and assuming my replies got old 4 years ago.

[fastback4]

I'm running 2000+ 3400 injectors, rail, and fuel pressure regulator. I've read many times here that these 3400 injectors and regulators have very small differences compared to the 3100 injectors. Will a retune actually help me regain my 27 MPG ? My O2 sensors are new also. EGR currently re-connected for now....Tom

[Azrael]

94-99 3x00's: #19 injectors w/ 43.5psi FPR
00+ 3x00's: #22.5 injectors w/ 55psi FPR

The newer injectors flow close to the same but the added fuel pressure increases fuel flow. Try running your old regulator if it's still good as that will bring the injector flow rate close to 19 lbs/hr.

[95Grand-Am]

The fuel rail and injectors are your problem, the early 3100's that I have worked on have had 17lbs injectors on them. Find the part # on the injector and look them up on witchhunter.com. You should put you old fuel rail and injectors back on or retune it.

[SappySE107]

Oh no, the small port 3100 is 17# injectors. You have 21.3# now so yes, a retune could very easily fix your issues. I might be able to write a 97 PCM for the setup you need.

[fastback4]

Ben. If your able to write such a program, how would i install it to my PCM? I live in Kentucky 22 miles south of Cinn. Ohio. Anyone you know can tune my Monte and need some extra cash? So my fuel pressure regulator from the 2000+ 3400 is ok to use right?

[SappySE107]

It would be best to keep the 2000+ regulator and injectors but it needs to be tuned. I have a 97 PCM here that I can program for a 97 lumina and put your VIN on it and copy the code over for the newer motors. Id do that for 50 plus shipping and 50 core.