87_TA

Just picked up a 87 454 4dr dualie, upon purchase, truck idles about 2500 rpm and had horrible part throttle manners.
Found throttlebody gaskets to be bad - both of them real bad.

After fixing, idle came way down to normal ranges, but still dies when in gear and part throttle is still bad..
Removed IAC and cleaned and seems to work, and can hear on initial startup..

Is there an IAC learn routine to follow or something with these.

Also manifolds are real real hot, like 700 surface temp and smeels rich - checked after noticing extreme heat under hood. BLMs seem pretty good at idle 130 range.. O2 maybe? but dont know if that would cause the dieing problem.
And not sure 747 even use bl at idle? kinda new to 747s..

Have not scanned much, as truck is stock and have not tuned any yet- so figured I should get it right first..

Gonna get a G2 from craig and figured I could make it work, but better to fix it right than bandaid it with tuning.

7Point4

I would verify the base timing. Also, some of these trucks can be hard on caps and rotors. Fuel filter would be a good investment also.

It might be different, but my truck on the stock ecm, used an open loop idle.
Scanning it might help show why it dies in gear. might be as simple as the park neutral switch.

RBob

iTrader: (1)

No real IAC learn for the TBI setup. It will do a reset once the engine has been running and then shut off. Does the reset at key-off.

Check the EGR valve, can be an issue with it leaking.

As mentioned a lot of the BBC used open loop idle. Also no knock detect (ESC) system.

Check the injector spray at idle. Should be a nice even cone of fuel that strikes the TB bore right above the butterflys.

RBob.

87_TA

Thanks guys,
gonna check timing tomorrow - tried once but can't see line and was sick of it by then - as I just got done changing passenger manifold gasket (total pita)
and doughnut gaskets.

Injector spray looks great as you described - but looks like alot of fuel for idle.. As I figured as it smells real rich and probably causing the manifold heat.. or retarded timing..

Sorry did not complete sentence above, was a wierd post thing - it like auto posted then could not find it on page...

But was trying to say, sure I could buy the g2 and make it ok, but would rather find problem first..
Gear sensor I though of as well! does it have one? and where? and does it show on scan tool? did not remember seeing it nor timing either.
I'm sure its not on the trans as its a th400, or is it on the trans?

Thanks for help so far, will check the above tomorrow morning.

Oh also, changed cap and rotor,wires, runs alot better! but still same part throttle and idle.

7Point4

my 90 model bbc does have a esc system, but as always, they changed year to year, and model to model.

The park/drive switch does show up on a scan tool. again, does on my 90 model.

just a stab in the dark, but if someone or somehow the fuel pressure has been adjusted too high, that could cause some of what you are seeing.

87_TA

Well got the idle fixed this morning, it was the base timing was about 6* off far as I could tell, idles great now!! and even in gear.. But actually seemed to not have picked up any power at all.
This one has actually has esc but does not show on toll for what ever reason.
Took for a drive and was so excited it was idleing I forgot scan tool to check BLM while driving - If wife allows more car time today I will check or if she wants to go shopping in it! But 02 only 20 might as well change anyway.

I am actually thinking the cat is clogged, on my drive I could smell that rotten egg smell. That would surely cause alot of exhaust smell..
Thanks for help, still gonna change filter and check egr anyway - then hopefully have one good tow vehicle.

7Point4

Glad to be of some help.

87_TA

Just an update and also going to relocate the rest of this thread to TBI maybe..

Thought timing fixed idle, was not the case - but did find if I disconnect EST wire it idles great! in and out of gear.. but soon as you restart it starts missing and dies in gear..
Probably idles becasue its in limp home mode till restart.
Just pulled EGR and it moves freely, had pulled cat and thew on an old 3" flowmaster, truck has alot more power but still will not idle in gear and has very poor part throttle manners.. Hammer down and it runs great..

IAC seems to be operating just fine.... Replaced 02 also.

Maybe distributer? Dont know, getting frustrated with now.