webslinger67

Ok, so my 90 GT (30 over with just a cold air intake and aftermarket coil) has been sitting for a while, as i do the body work on it, i would start it ever month and it would run fine....,,,

now, i have it on the road, its hard starting, and , between 2500 and 4000 rpm it stumbles, cuts out, and sometimes taking off from a dead start it backfires...

i have replaced the plugs with autolite platinums, i didnt replace the cap and rotor, they are worn , but i cleaned them up just for the road test, i cleaned the MAS with electronic cleaner and made sure the idle control valve was not stuck.......


i took it back out for another run.... still stumbles, feels hesitant and will not even hit 5000 rpm, let alone redline....

so, to see if it was lean or fat running... i took the K&N filter off for a test run, and it got even worse.... so that tells me its starved of fuel, maybe through the secondary circuit?

or, could this be the cap and rotor and i must replace that?

could it be the fuel filter?

has anyone run into this problem before?

could it be the setting of the throttle position sensor?

or even timing?


this has never happend, my 5.0 has always been a perfect running beast and now it barely pulls its own weight.......

hellllllllp!!!!

347gt90

Check your coil. I had an Accel coil that did the same thing.

webslinger67

Mine is an MSD , has anyone had any problems with these?

other than the coil , anyone had similar results with something else being wrong?

webslinger67

nope, its not the coil...... anyone else.....

i changed out the coil to another msd i had, and the stock one..... both it would barely start


could dirty injectors be causing this.... but why the back fire every now and then?

anyone anyone?

webslinger67

anyone got anything else i may check?

Pure5.0

There are 3 main components to power: Fuel, Ignition, and Air.

It looks like you have taken care of two: Ignition and Air

But you still haven't dug into Fuel. Check your fuel filter and fuel pump. Also make sure your pressure is running out ok.

AlabamaCobra

seafoam will cure anything

webslinger67

ok

1) Seafoam does not cure everthing.... I have ran that for this problem.... no dice...

2) I changed out the Fuel filter and cap and rotor, so now a full tuneup has been done.....

as for Fuel delivery and maybe the secondary circuit not opening.... i dont think we have to worry about that.... i filled up a few days ago , and now looked at my gas mileage compared to the amount of gas i used.... for 106 miles i have used 3/4 of a tank.... yes that is 75% of the tank of gas....for 106 miles...

so, I am really down to the cats again beginning to go bad and restrict flow, hence needing to push down on the pedal more, using more gas, with the flow not so good and possibly some back flow every now and then would cause backfiring through the intake......

sound about right?

webslinger67

ok found out my timing somehow got moved from 14 deg btdc to 6 deg btdc......

i have one of those dial timing lights..... i hate them, i dont think the actual 0 marked on the dial is correct...

so i bumped it back up to what i think 14 deg btdc is... and it pulled all the way to 5000 rpm pretty good..

its still hard starting , so going to buy a standard timing light tomorrow and check it again, and also change the oil , even though not many miles i think its still old from sitting...

going to check the TPS also..

What else could cause hard starting? could the EGR cause that?

I am also springing for a Pypes X-pipe with cats to open it up

thunderjet429

bad gas??????