87 taurus rough idle,poor acceleration,backfire

[rudyh]

This vehicle has 230k miles. When starting it will die immediately- maybe several times. It then idles very roughly. Upon accelerating it has a very severe hesitation and if too much throttle is applied it backfires in the exhaust. During the hesitation if you back off of the throttle the vehicle seems to want to speed up slightly.
New plugs,wires,good compression,cleaned throttle bore and idle air bypass valve.

Any ideas would be appreciated.
Thanks

[red53]

Originally Posted by rudyh

This vehicle has 230k miles. When starting it will die immediately- maybe several times. It then idles very roughly. Upon accelerating it has a very severe hesitation and if too much throttle is applied it backfires in the exhaust. During the hesitation if you back off of the throttle the vehicle seems to want to speed up slightly.
New plugs,wires,good compression,cleaned throttle bore and idle air bypass valve.

Any ideas would be appreciated.
Thanks

My '87 had a very similiar problem. Turned out to be two injectors were bad. Try idling with one plug wire at a time removed to see if each cylinder is carrying it's share of the load. If you have spark at each wire, yet one or more disabled cylinders don't seem to affect the idle, then the injector or wire to it is at fault (probably).

[~manuel~]

Originally Posted by rudyh

This vehicle has 230k miles. When starting it will die immediately- maybe several times. It then idles very roughly. Upon accelerating it has a very severe hesitation and if too much throttle is applied it backfires in the exhaust. During the hesitation if you back off of the throttle the vehicle seems to want to speed up slightly.
New plugs,wires,good compression,cleaned throttle bore and idle air bypass valve.

Any ideas would be appreciated.
Thanks

check fuel pressure. check it with key on engine off, it should hold steady at around 35 psi.if it drops suddenly then you hav a bad pump or regulator.also check it at idle to see if you have a weak pump.