I converted my '85 SE V6 to a 3.4, using the 2.8 induction/control system; At first it wouldn't hardly run, and I found out that a number of the 3.4 injectors were not working, so I reinstalled the original injectors and it ran decently. However, it is not completely happy.... It passes smog, gets good MPG, and has good power. Here are the sympoms; 1) It idles high when cold, and once it's warmed up, it tends to surge a little; 2) It dies easily, especially when cold, like if you aren't perfect with the clutch feathering; 3) Hair trigger throttle; 4) Surges when driving in 2-3 when in town below 35 mph; It's not a lot of fun to drive because of the throttle response...I've tried adjustments and some replacements, but nothing seems to have much effect.

Does it whistle?

The high idle could be a vacuum leak.

No...I had that problem long ago when I removed the top of the intake manifold and thought the EGR tube was flexible....oops! It idles high (2000) when cold, then after it's warmed up, it idles at 1000 but then starts surging sometimes.

Did you ground out the conecter when timing?

I'm confused are you using the fifteen lb injectors or the 17 lbs? What about the cold start injector?

And u are usuing stock ecu

I think you may have a small vacuum leak. 1000 rpm is not bad depending on the IAC counts. 25-30 counts are normal. If the IAC counts get down to 0 and the rpm is still 1000 then you should get a SES light and a code in the ECM. Are there any stored codes?

The surging can have a few sources. One is a bad ground. The ECM has, as part of it's code, an adjustment to the time the injectors are open due to voltage to the fuel pump. This is because the FP will put out a lower pressure with less voltage and higher pressure from more voltage. Lower pressure from lower voltage due to a bad ground means less fuel through the injector. The ECM will try to compensate by adding fuel and opening the IAC. This brings up the rpm which ups the voltage which ups the fuel but now it's too much and round and round we go.

Do things settle down when the car is warm and in closed loop?

[This message has been edited by Hudini (edited 10-04-2010).]

2.8 inj (15) are too lean, need 17 lb

How does the ECM know what voltage is sent to the fuel pump since there is no connection from the fuel pump power supply wires to the ECM?

So doesn't the fuel pressure regulator control fuel pressure not the fuep pump?

Don't know where it gets the information. I suspect it's the difference between two different 12 volt reference signals.

When I had my oil cooler fan powered from the ignition controlled side of the fuse panel TunerPro RT showed fuel pump voltage in the low 13 to high 12 volt area. Once I moved the power source directly to the battery it smoothed out at 13.2 volts. The idle is smoother and the INT and BLM are more steady too. Much easier to tune when it's not jumping all over the place. Still trying to get the cold start idle to be OEM smooth but it's trial and error. I'm using 30 lbs/hr injectors so much fun to be had.

EDIT: Missed your second question. I misstated what happens to the fuel pump. The flow increases when voltage increases. Pressure is regulated by the FPR as you noted. See http://www.kennebell.net/ac...apump/boostapump.htm

[This message has been edited by Hudini (edited 10-05-2010).]

There is no way for the ECM to read fuel pump voltage. All the ECM knows is it's supply voltage. What TunerPro reports as fuel pump voltage is actually just the supply voltage to the ECM.

Fuel pressure is regulated by the fuel pressure regulator, unless the fuel pump can't generate the fuel pressure of the regulator. Once the pump can generate the pressure of the regulator excess pressure is just bled back. Excess fuel flow is just returned to the tank and does nothing execpt keep the gas in the lines cooler, and heat up the tank a small amount.

And the reason for "FUEL INJ OFFSET VS. FUEL PUMP VOLTAGE" is what?

It doesn't read fuel pump voltage - it reads supply voltage and assumes it is fuel pump voltage.

The original 15 lbs injectors- the 17s the guy sent me were bad...I could hardly get it to run with them. I have two grounds on the engine and have checked them; The biggest problem by far is the hair trigger throttle...it's really hard to drive it slow, like around town, smoothly.... but is much easier when I go for broke, especially on a curvy road.

Hair trigger throttle? As in it sticks closed? And then more pressure and it 'pops' too far open?

Oh, believe me, I went around in circles with the engine mounts; Bought Gm "super soft" mounts and sheered them in two days, then bought WCF poly mounts and couldn't make them fit, then found some after-market ones that had nice hard rubber, modified and installed the WCF front T-mount with rubber bushings and the dogbone has one side replaced with poly. I check them regularly. I have checked the IAC valve and the TPS. I've also done some work with the ignition, including replacing the coil when it died a year ago. The throttle cable works very smoothly; When I try to give it a little gas @ 25 mph it will suddenly jerk forward. Then sometimes when I try to get off the gas (a little), it suddemly jerks back. Like I said, It's very hard to drive smoothly at low speeds...The other day I met a very nice young lady at the Pet Food store, walk out, slide in the car and back out...then start to go and kill it, kill it a second time....By now I figure I'm looking really cool, and started in with the french translation routine....

How is the vacuum line to the MAP? Free flowing when disconnected? Do you have a spare MAP to try? Try plugging the other end of the manifold T (temperary disconnecting the fuel regulator) so it just runs to the MAP and see if that improves drivability. Stock ECM?

Well get the proper injectors for the car, as has been stated above.

Lean running all over the board will cause popping/poor throttle response, general crappy driveability.

install proper injectors ,if investment portfolio low on sheckles ,buy used from injector cleaner company.

YOU KNOW you need the injectors,even if this is not the problem..

When injectors are not used they have tendancy to clogg up & malfunction.

RC engineering is my fave injector cleaner in California,,have injectors cleaned & they will replace BAD ones..injectors are very long lived.
..the stock GM injectors are rated "worst" newer styles much superior.
..never soak injectors to clean
..Go to injector company sites like FIC(Ga),Fuel injector connection,, or Linder tech(ind) ,,or Cruizin performance (mich)

[This message has been edited by uhlanstan (edited 10-06-2010).]

OK- Fine! I'll go install bigger injectors...What are the recommended manufacturers? Bosch, Accel, etc...and yes, I expect that some are manufactured by one Co and labeled by another...I didn't fall of the turnip truck yesterday....it was actually day-before-yesterday....

quote Originally posted by cvxjet: OK- Fine! I'll go install bigger injectors...What are the recommended manufacturers? Bosch, Accel, etc...and yes, I expect that some are manufactured by one Co and labeled by another...I didn't fall of the turnip truck yesterday....it was actually day-before-yesterday....

I don't know that there is a specific list of who the "recommended manufacturers" are, but I can tell you that:

1. The recommended size is 17 pounds for a typical pushrod 3.4L engine swap.
   
   
2. Accel (available from Summit Racing, and others) is the brand I used successfully with my own 3.4L engine swap, which was completed in December, 2006.

The Accel part number for one set of 6 injectors is "150617" --- the "150" being their designation for injectors, the "6" being the number of injectors you'd obviously want for a V6 Fiero, and the "17" indicating the poundage of each.

I hope that clarifies things for you, cvxjet, so that you now know you're ordering the correct injectors for your application.

Good luck to you with your 3.4L engine swap project, and please keep us posted on how it turns out.

That's the ones I was looking at! Thanks for confirming they're good ones; Too often, in buying parts for old cars, you get stuff that doesn't work properly. I had a '73 mach 1 that I installed a 5.0 and AOD into, and redid the brakes and suspension. It handled really good, but the biggest problem was almost every part I replaced had to be replaced at least twice....I started to doubt my abilities, so I wrote down all the problems and their cause, and finally proved to myself that the problems lay with defective parts, not a defective me! Although, I've never proven that I'm defect free....

Any chance your set up to run winALDL?

Not at the moment; I have a Macbook Pro...can it be set up to run that?

doubt it.

Hey there.

I have a 3.4 in my Fiero.

The injector change might help. I went the adj. pressure reg route and found that I could get the bottom end right, but was lean at the top, or get the top right and was rich at the bottom. I have since changed to a '7730 and tuned it myself.

You may not get it really right without a new tune.

The voltage vs fuel correction factor is for the injectors, not the fuel pump, and does exist. The more voltage, the faster and longer the injectors stay open (Increased current flow, longer dropout). Check all the regular sensor stuff as suggested.

Are you running DIS? Stock ECM? Just curious. Mine in on distributor and does just fine.

Off idle, the important sensors are throttle position and the map. They control the fuel enrichment. I found that when my fuel pressure was low (IE: Small injectors) that I had lag off idle, like a carb but worse. It was a stumble, then it would rev ok. My experience has been that the 3.4 likes a bunch of fuel to get going.

If you just want to drive it n/a I'd try an adj fuel pres reg, it may be cheaper than 6 injectors; then get a tune. Mine would be no good for you because I made a twin intake manifold for mine, and used $59 code in the 7730 ecm getting ready to add a turbo. Well, I'm adding it now actually.

Chay

So what do you think about a 7730?

The OP is running the stock 2.8 ECM. I haven't heard anyone who's figued out DIS on a stock ECM.

So Chay - or anyone else - so since the final answer seems to be 7730, why mess with bigger injectors or fuel pressure? Unless you're maxing out the injectors, it just seems like it's a misstep.

quote Originally posted by phonedawgz: So Chay - or anyone else - so since the final answer seems to be 7730, why mess with bigger injectors or fuel pressure? Unless you're maxing out the injectors, it just seems like it's a misstep.

The stock 2.8 computer with factory programming will run the 3.4 acceptably well by scaling up the fuel flow rate accordingly. 17 lb/hr injectors are the easiest way to do this.

And even if you're not "maxing out" the injectors, it's still preferable to maintain the factory "headroom".

Why mess with an ECM swap (wiring, chip burning...), or an adjustable fuel pressure regulator, which is another complication, as opposed to the factory fixed regulator, which is a bolt-on and forget it thing.

[This message has been edited by pmbrunelle (edited 10-07-2010).]

I hear ya. I think personally I'd like the 7730 just to play with but if accecptable driveability can be obtained with just the injector swap, yeah.

hmm

I'm in California; Does the 7730 swap have an affect on smog testing? I was considering doing the computer change, but wanted to see what the prevailing thoughts were on here...

Does anyone know if it would pass smog in California if I installed a 7730?

Exactly WHERE in the camaro/firebird "donar car" is the Computer located ??? going to the boneyard, will try to "snag one". Thanks

Most computers in the muscle cars (gm) are found in the footwell in the passenger side or under the passenger sides flare fender. It should be the same.

You can't run DIS on the original ECM. I was wondering if was switched out or not.

Anyway, the old ECM should run the car, just not optimally. Bigger injectors or adj. fuel pres reg should do the trick for the most part. Mine still wanted more air up top.

The '7730 by itself won't help. You have to reprogram the '7730 to work with whatever injectors you have anyway.

I think the original injectors (15#) will do fine with a reprogram of the original ECM, of a cusatom '7730.


Chay

quote Originally posted by Lou6t4gto: Exactly WHERE in the camaro/firebird "donar car" is the Computer located ??? going to the boneyard, will try to "snag one". Thanks

I'll sell you the one off my '95 3.4L. Remember those were the OBD 1.5 ones with the flash memory, not eproms. Not very tuner friendly. The plus side is you can run the 4L60-E trans with it! Too bad it's for a rear wheel drive car..