Swapped to 3.1 but with problems

[ignoreance]

I have done some searching and can't find an answer. I have called different companys and gotten different answers. This is to those that have done a 2.8 To 3.1/3.4 swap in TBI Trucks.


So its been done for awile and ran into problems with getting the fuel under control. Thought this would be a bolt up and it has been a long time running. The build as it stands.

3.1L Engine with Semi stock exhaust. from the y 2 1/4 into the cat and all the way back... that handles the exhaust side and I had it at a shop to have them button it all up.

The swap was a crate 3.1 front wheel. that I drilled to RWD. put a cam in it.

.422 intake .444 exhaust duration at .050 204 intake 214 exh.

1.5 true roller rockers

Intake manifold was port matched. and put a Holley 2.8L big bore TBI on it.
added a FPR to tune Injectors. as well as tried tuning vai allen key on TBI.

The call was placed to holley and they are stating that the cam has changed the MAP pressure and the ECU is dumping to much fuel. I had this problem From day one of start up even i can't lean it out and run 9psi fuel. cam isn't a hog or at least i don't think it is it runs un goddly rich. The O2 is new. I have called and they state I need to have it taken in and have a dyno tuned chip made. Blah don't have the money for that.

The option i think is good is smaller injectors.

Holley list these at 116.25 per injector but they insist i have the right injectors.
Issues I have is it is so rich it blows back and the spark ignition catchs fire.
Timing is set to about 12-18 and i know should be around 10 but at ten doesn't run because to rich.

The engine reprogram i could understand if it was a huge cam. but if i had doen that I would have popped the heads and ported those too.


Help Please.

By the way if your local city is hounding you about to many old cars in your drive way then they are assholes like mine and I only have two.

[geoffinbc]

Ditch the holley TBI and bolt on a 4.3L throttle body (same size as your Holley) and run stock 2.8L injectors. Then go to a junk yard and find a Lumina APV Van with a 3.1L with iron heads and TBI and steal the ECM. You can also get one from an Isuzu Rodeo, Pontiac or Transport Van. Plug it in and it will run like new. I am using this combo on my Trooper with a 3.2L and a COMP 252 cam.

A 2.8L ECM will run the 3.1L with few problems and maybe a slight bump in fuel pressure considering it runs my 3.4L just fine.

The Holley is a nice unit but they always run rich. Plus replacement parts are expensive and hard to get. The GM stuff came on millions of cars an trucks.

Read This too > http://members.shaw.ca/betterthanyou...3tb/28to43.htm

[ignoreance]

So it is a fuel issue. I Know I could have used that option but I guess the figure that the holley was adjustable at the time got to me. I have bashed my brain over on this. Why in the hell are they putting 65LB injectors on it. Because that is what these are for. I guess I will swap to the smaller injector. I will also try the junk yard and see if i can still find my old TBI for the old stuff. I already know I have to by new clips.

Thank you. I figured I was on the right track

So If I keep the holley move to the 45lb injector and then. Source the chip for the 3.1 Rodeo/Pontiac/Chevy 3.1 van.

I think i will try and get a TBI for the 4.3 cuss I'm taking a trip to the junk yard to look for an ECM to bring it close to where it should be.

[geoffinbc]

WTF they use 65LB injectors that massive over fueling. Do you have the Holley 502-3 or another unit? Thats the size of 350 V8 injectors.

The 2.8L and 3.1L used 33lb/hr injectors. 4.3L engines use 45lb/hr injectors but they are a little big for a 3.1L

[ignoreance]

Holley list there injectors on the tard scale now as I guess there Pro Jection systems..

They rate the injector at a 21psi run so when you run it at that its a 65lb injector but then converted rate is a 45lb @ 12psi it is all jacked up.

If you went to any retail like jegs, summit or other online vendor they list the injector at holleys spec max PPH.

All holley lists are from max pressure you have to either call a tech or do a lot of digging to find this out.

32 PPH @ 12 PSI; 45 PPH @ 21 PSI . . . . . . . . . . . . . . . . . . . . Part # 522-81
45 PPH @ 12 PSI; 65 PPH @ 21 PSI . . . . . . . . . . . . . . . . . . . . Part # 522-54
50 PPH @ 12 PSI; 72 PPH @ 21 PSI . . . . . . . . . . . . . . . . . . . . Part # 522-80
60 PPH @ 12 PSI; 85 PPH @ 21 PSI . . . . . . . . . . . . . . . . . . . . Part # 522-43

I like how they bounce the numbers around. Like um why didn't you put that in order that would be #'ical order why is 43 the biggest and 81 the smallest but 80 and 54 is between........

The 502-3 is stock with the 522-54 injectors

That chart is the reason they run rich. On almost all there systems they could run a step smaller injector(My Thoughts).

My guess is two reasons.
One they sell more BULL.
Two they figure people buying holley must have heavy modifications.

[geoffinbc]

Ok thats a 21PSI. It is stupid they rate them that way since no TBI pump will be able to support pressure that high. But the 522-81 injectors supply 32lbs/hr at 12 PSI which sounds perfect.

[Ray Hamilton]

Which one of these ECM's will work in my iron head 3.1 S10 Blazer?

http://shop.ebay.com/?_from=R40&_trksid=m38&_nkw=lumina+ECM&_sacat=See-All-Categories

http://cgi.ebay.com/ebaymotors/89-97-ISUZU-RODEO-COMPUTER-BRAIN-BOX-ECU-ECM-3-2-V6_W0QQitemZ370137001124QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item370137001124&_trksid=p4506.m20.l1116

[geoffinbc]

According to the discription this one

http://cgi.ebay.com/ebaymotors/91-93-LUMINA-APV-TRANS-SPORT-3-1-TBI-ECM-16149405-AZAU_W0QQcmdZViewItemQQ_trkparmsZ72Q3a1205Q7c66Q3a2Q7c65Q3a12Q7c39Q3a1Q7c240Q3a1318Q7c301Q3a0Q7c293Q3a1Q7c294Q3a50QQ_trksidZp3286Q2ec0Q2em14QQhashZitem220373804747QQitemZ220373804747QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

The second Isuzu one is wrong that one is for a 3.2L SOHC or DOHC motor

[Ray Hamilton]

Will that ECM fit in my Blazer with no size mounting or wiring issues? This one is for an auto trans.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=170321134981&ssPageName=ADME:X:AAQ:MOTORS:1123

Thanks.

[geoffinbc]

No thats not the right one. That is an Isuzu specific ECM used on their 3.2L motor. It is not a GM computer.

[Ray Hamilton]

I bought the the first one, Lumina. It also was for an auto trans.

Thanks again.

[95Grand-Am]

When you set the timing, on some of the older GM products there is a wire that you have to disconect. This elimates the advance so that you can set the inital timing. If it is popping through the intake that is usally cause by a lean condition or late timing.

[Ray Hamilton]

Yes, I'm familiar with that.

[ignoreance]

I got new injectors from holley and they did seem to tone it down quite a bit. It doesn't smell hog rich. But it still has to give me grief on the timing it still pops under load.

Ok question if you have a cross flow manifold ie. I have opened up the Manifold Divider in the middle of the two on these throttle bodies would that throw the pressure off drastically to make the MAP sensor real picky??

I have yet to get the 3.1 computer but I would think that this thing should run better than it does. I didn't think the computer looked at that many items. What about checking and adjusting the voltage coming from the map sensor.

Last can any body tell me what the pressure should be on there map port from the Manifold?

I really doubt that i over tighting the rockers but do you think i Should pressure check the heads?

[geoffinbc]

You should have 18" of vacuum at idle or close to it. If you have the correct flowing injectors the next thing to do is set the fuel pressure. On that holley you should run around 10 or 11 psi