StepMechanic

96 4.6 marquis idle bad in gear shakes... no codes
what has been done
New egr
pcv
iac
tps
o2 all 4
cats
wires
plugs
maf
coils
rebuilt injectors
tested injector pulse good
checked tps and iac voltages good
sprayed carb cleaner cant find vac leak
compression test all with in 5 of 165
the intake is new
could the intake leak in the valley and not be detectable bu spray? any help thanks in advance

Big Block Ford

Hi.

Are you sure the engine is misfiring.

Perhaps it is something out of balance.

Are the engine mounts and gearbox mounts good.

Does the engine run a mechanical or electric cooling fan and if mechanical is it possible that a blade is missing or the unit in need of repair.

I know these may sound strange but the engine may be uneven for another reason other than a misfire and it could be something out of balance somewhere. Just a thought.

If your certain the engine is misfiring then its time to think again although you have done quite alot already.

__________________
Lance
71 429SCJ Mustang

StepMechanic

definite miss its there out of gear but is much worse in gear. the maf when i unplug it doesnt change idle so tommorow i am checking voltage. i checked wires plugs tested with noid light and check tps and iac tonite all good I am thinking maybe no power to maf? thanks

professor

Are your injectors actualy working ?, pulse yes but mechanicly, is it delivering fuel, if they were new i'd say there right but i've seen serviced ones D.O.A. What do your spark plugs look like when you pull them out, this will tell you a lot about how your is running, I use a thin tube connected to an lpg supply and probe arround engine for vac leaks, revs rise when it sniffs gas, could be the ecu has a problem, i'd start with pulling the plugs and having a look at them.

StepMechanic

plugs all look good it has to be vac related or pcm everthing else checks out . my shop guy where i work did the injectors did them on a flow tester . plus i pull wires when running they all make a difference. I have a propane enrichment set up i will try that tommorow. it also hasnt been thru any drive cycles yet but i cant imagine that it would miss this bad thanks

galacticforce

Timing chain or belts or gears out of sink
recheck and fireup again
reckeck leads and plugs
if it is still misfiring.
recheck all gaskets and bolts
recheck injectors and wiring
and then read more books

StepMechanic

2 options left bad gas or the fact it hasnt completed a drive cycle