SSJ

My 88 F150 has been idling poor or not idling at all, surging at stop
lights and poor acceleration like a plugged converter. I've changed the
exhaust system(converter also), IAC, EGR,plugs, wires,cap,rotor and fuel
filter.No change, but if I unplug the vacuum hose to the map sensor, it
idles good again cept for some black smoke from exhaust pipe.Dumb
question, but sound like I need a new MAP sensor?I'm tired of putting
money in where it doesn't belong.

Happy Traveler

'Some black smoke' indicates rich mixture - probably because with zero
vacuum, the MAP is doing its job and telling the computer that the engine is
at maximum load... If anything, seems that your experiment indicates that
the MAP is working.
This is a dumb question, but have you pulled the stored trouble codes? Ran
self-test diagnostics? Will be much cheaper than throwing money on parts. In
fact, you can do it yourself at a cost of a paper clip.

Shoe Salesman

"SSJ" <southsidej@rogers.com> wrote in message
news:b483fc8aa0e85d93c1850200bb2390bd@localhost.talkaboutautos.com...
> My 88 F150 has been idling poor or not idling at all, surging at stop
> lights and poor acceleration like a plugged converter. I've changed the
> exhaust system(converter also), IAC, EGR,plugs, wires,cap,rotor and fuel
> filter.No change, but if I unplug the vacuum hose to the map sensor, it
> idles good again cept for some black smoke from exhaust pipe.Dumb
> question, but sound like I need a new MAP sensor?I'm tired of putting
> money in where it doesn't belong.
To test the MAP, unplug the ELECTRICAL connector, not the vacuum and go for
a ride. If it is bad it will run better when unplugged. Plug and unplug with
the key off.

Backyard Mechanic

"SSJ" <southsidej@rogers.com> wrote in
news:b483fc8aa0e85d93c1850200bb2390bd@localhost.talkaboutautos.com:

> My 88 F150 has been idling poor or not idling at all, surging at stop
> lights and poor acceleration like a plugged converter. I've changed the
> exhaust system(converter also), IAC, EGR,plugs, wires,cap,rotor and fuel
> filter.No change, but if I unplug the vacuum hose to the map sensor, it
> idles good again cept for some black smoke from exhaust pipe.Dumb
> question, but sound like I need a new MAP sensor?I'm tired of putting
> money in where it doesn't belong.
>

Common problem also with bad Fuel Pressure Regulator, see if there is gas
in the vacuum port.

SSJ

Thank you. I'll try thr paper clip test. I haven't done it befor, but have
read many articles on how to do it. I'll follow the guidelines and see
what I come up with.

SSJ

Good plan and thank you. I'll try that and also going to try and read the
codes via paperclip test as the Happy Traveller suggeted.

SSJ

Thank you for the advice. I haven't considered the regulator. Also going to
try and read the codes via paperclip method as Happy Traveller suggests.

Rob

SSJ wrote:
> Thank you for the advice. I haven't considered the regulator. Also going to
> try and read the codes via paperclip method as Happy Traveller suggests.
>
how many miles on engine? is fuel filter replaced? air filter?
i know it sounds dumb but years ago i worked @ a lumber yard had a truck
that was so worn out (cat was also plugged) and vacuum was so low that
it had these symptoms.
1 check plugs and other tuneup items
2 check / replece o2 sensor
3 check fuel pressure
4 check cat convertor