3400 Swap

[Buttjupp]

Hmm . . well I thought that beretta with the same setup as my car and multec2's ran like a 14.9?

He also had slicks and ffp underdrive pulley when he got that time iirc.

I believe that was Nate from Colorado's 92 GT with a 2002 3400.

So what should I be doing here swapping to 3100 injectors or do you think its possible to get the 3400 multec2's going strong?

[Cliff8928]

Hmm, you must be the one michael was working with then. The stock 3400 injectors shouldn't run worth a crap with the stock chip.

That HAS to be specific to the Multec2 Injectors... I should go visit you sometime Ben, it's not THAT far for me...

Cliff Scott
89 BerettaGT <-regular Multec injectors
89 Volvo740 <-also has Multec =)

[SappySE107]

Nope, its not and it would be well worth it. Use the 3400 injectors, i dont care which kind (i think the newer ones are prone to clogging...but I may be wrong).

[Cliff8928]

I've heard the same thing about the newer injectors aswell...

it looks one of the problems with them is that the connectors that can oxidize easily and cause a misfire..

http://service.gm.com/gmtechlink/images/issues/jun03/TLJun03e.html

other than that it looks like GM doesn't reccomend cleaning of any of the Multec or Multec 2 injectors....

Cliff Scott
89 BerettaGT
89 Volvo740

[BowtieKid79]

The multec 2s are the spawn of satan! I had a hell of a time tuning Nate's car with them. I also had a hard time with John's car.

For some reason they seem to vary from car to car. the code that worked in nate's car seemed to suck in john's car. The 99 3400 does not have the multec 2s, so it probably wont be as bad.

Gor... see if you can get a set of 3400 injectors from a 99 or earlier car. They seem to work better.

Tuning a chip is definitely worth the trouble and money. It made a very noticable difference in Nate's car... both in power and driveability.

[Mechanic]

One problem you guys might be running into with the Multec II's, is that they were designed to run at a different fuel pressure than the Multec I. If you use them, I suggest that you swap the entire fuel rail (e.g. the fuel pressure regulator being the important part here), and you should see much better results.
Here is some spec info on the Multec II, its a pdf file so you need the adobe reader:

Multec? 2 Injectors

[SappySE107]

Hmm, I had heard that the 3400s got a higher fuel pressure, but I heard that after 2000 which I believe is multec 2 era. Its good to 72 PSI! Wow, what the heck are the Multec 1s good to?

[Cliff8928]

One problem you guys might be running into with the Multec II's, is that they were designed to run at a different fuel pressure than the Multec I. If you use them, I suggest that you swap the entire fuel rail (e.g. the fuel pressure regulator being the important part here), and you should see much better results.
Here is some spec info on the Multec II, its a pdf file so you need the adobe reader:

Multec? 2 Injectors

The fuel rail, lines, etc... off the engine in Gor's car were never removed from the 3400... it was installed as-is right out of the car it came out of..

Cliff Scott
89 BerettaGT
89 Volvo740

[JohnyG]

One problem you guys might be running into with the Multec II's, is that they were designed to run at a different fuel pressure than the Multec I. If you use them, I suggest that you swap the entire fuel rail (e.g. the fuel pressure regulator being the important part here), and you should see much better results.
Here is some spec info on the Multec II, its a pdf file so you need the adobe reader:

Multec? 2 Injectors

I realize that, that is why I have two FPR's, one at 55psi (multec2's) and the other off a 94' 3100sfi motor (45psi) for the old 3.1L injectors

Oh, and I do recommend a FFP chip, they did an awesome job

-John

[korbendallas68]

Ok, here is my setup for my 3400: I have the Injectors from the 3.1, 3400 fuel rail, 3400 fuel pressure regulator. Would that effect the car in any way?

[JohnyG]

Ok, here is my setup for my 3400: I have the Injectors from the 3.1, 3400 fuel rail, 3400 fuel pressure regulator. Would that effect the car in any way?

If the 3400 is a 2000 or newer, I would recommend getting a pre2000 fuel pressure regulator (45PSI)
(junkyard, $5, of for free if you hide it in your pocket )

I found that it ran a bit better, plus fuel mielage went up.

-John

[korbendallas68]

Oh, Ok thanks! What is the Pressure on the 2000+ Regulators? I want to add this info to my guide.

[JohnyG]

55psi IIRC

-John

[korbendallas68]

Would you be able to fill me in on why a higher PSI would casue the car not to run better? And thanks.

[Cliff8928]

basically if you use the new injectoers (designed for Higher PSI) you have to use the new regulator... If you use the old injectors with the new style regulator or vice versa you will have too much or too little fuel..

Cliff Scott
89 BerettaGT
89 Volvo740