89 454 TBI problems

[Scrubby]

My dad and I just bought what we thought was going to be the ultimate tow rig: 1989 crew cab dually 4x4 454 TBI. It runs ok, but we have been really disappointed with the performance. We pulled a 72 suburban back to Boise from Denver and gowing up hills we would slow down to almost 40 mph. Not even big hills it would do this. Now, my friend said he hauls with his stock 83 454 dually all the time and never slows down on hills, so I am thinking something is wrong.

Another problem we are seeing is that sometimes after shutting it off for about 30 minutes (like stopping to eat), it wants to stall when you start it again. It takes about 5 minutes of feathering the throttle to get it to run ok again, then you can take off.

The previous owner put in a MSD ignition box and it looks like a MSD distributor, not sure if that is affecting things or not, but doesn't the ECM need to adjust the timing, and I am not sure it can do that with a MSD distributor.

I am new to TBI and computer controlled trucks, so I don't know where to start. The SES light is not on, so will a scanner do me any good? Any insight from you TBI guys?

Thanks

 

[Scrubby]

I forgot to mention. 4:10 gears with stock size tires, so I don't think it is a gearing issue.

Also, runs the same on either tank, so I am guessing the fuel pumps are ok.

 

[Thunder]

Is the MSD system right for your truck? You should have the MSD late moder Dist with no coil in the cap and a remote coil. It is also best to have the MSD to GM wireing harness. so everything is hooked up right. If things are hooked up right the MSD box should work fine with TBI.

If you have the right Dist.
The hard starting problem may be the distributor module going bad. If its a MSD module that is prolly the problem they are not as good as GM modules.
Lack of power can also be from a clogged fuel filter. They should be replaced yearly.

 

[dyeager535]

Check the coolant temp input at the ECM with a scanner when the engine is cold and after running it for awhile.

Improper coolant temp input will allow the engine to run, but can cuase quirky starting problems. Easy enough to do if you have an actual scanner anyways, as opposed to just a code reader.

 

[James670X]

Like the others on here have already said check your ignition first, if this doesn't solve your problems I would run a scan tool on it, than if your still chasing it I would have the fuel pressure measured (my regulator needed to be replaced on my 88 BB, signs of this are stalling while cornering, hesitation/stalling when shifting gears, etc, etc...), if all of the above suggestions fail to yield any results go thru the thing and tune the snot out of it (ie. change plugs, plug wires, cap, rotor, pcv, crankcase filter, air filter, O2 sensor, fuel filter, check timing should be 4 deg. I think, take TBI apart and clean the injectors, etc..., etc...).