I picked up a poor mans BB(Junkyard TBI454) and put it into my blazer. Bone stock tbi setup with the 7747 ecm, ecept dual 2 1/2s, open element, and coil. I think the motor i picked up may have a cam. It lopes a little at idle and light throttle. Either that or something is wrong.

My questions are
1. is it normal to idle in open loop and only enter closed loop when pressing on the gas?

2. Is it normal to idle mostly on the rich side?

2. The code scanner said my base idle was 0. But it idles about 750 when warm. Do i need to set base idle via the IAC adjustment article in the tech section?

3. At vary light throttle the engine surges and O2 volts jump from 0.0 to about 8.3 in closed loop. What could cause this besides a cam?

Thanks for any responses



Charlo

 

Put your stock TBI unit on and see if you have the same results. When you go with a larger TBI you really need to change your chip. Also did you bore your intake manifold to accept the 2" bores of the 454 unit? You may have a rough idle because of the size differences and causing turbulence in the incomming air. What size injectors did you use? Did you put the stock injector pod on? If you didn't than those injecotrs are way to big for your application and so is that TBI.

 

No, its an actual BB. Not just the trhottlebody. It has 454 cubic inches of displacement. I took the harness and ecm from the donor vehicle. It should be a factory setup from an 89'r 3500. Thanks for the response though. I am going to see the referee tomarow morning and want her running as good as I can get. Thanks

Charlo

 

Oh oh oh. I thought you picked up just the 454 unit not the whole motor. My bad on that. My geuss is that it is out of tune due to a bad sensor or some other mundane detail. I would do some data logging and see what exactly is going on. Have you done just a basic tune up? That may help with stuff right off the bat. it could be as simple as a bad plug or wire. Check all the basics before tearing it all down.

 

If that Blazer came stock with a small block I don't know how you expect to pass California emissions. They will do a visual inspection and see its a BBC.

 

Thats why I am meeting with the referee. If I match the setup of a 90 1500ss pickup with a 454 I am legal once I pass inspection and sniffer. Hence the TBI big block. A carb like the blazer came with would be much easier to setup. I have already matched the setup and passed the visual last time I saw the ref but I was missing the ESC module, preheater hose, and hose from valve cleaner to air cleaner housing.

Stuff ihave replaced on the motor so far,
plugs, wires, coil, cap
knock sensor
O2 sensor
thermostat
VSS

Things I have checked
coolant sensor is working properly(acording to guage)
TPS has been adjusted and working properly
Map sensor appears to be working properly(readings make sense comparative to throttle posititon)
Thats all I can think of, but it doesnt leave too much.
Oh and new oil,filter,airfilter. I even gave her synthetic.
Thanks for all the responses soo far.


Charlo