Running bad

[jcougar88]

Have a 89 f150 300 6cyl. Changed tps, iac, tune up complete, fuel filter, replaced exhaust system and found out convertors have been reamed out(this could be good). Truck runs good sometimes, bad sometimes(surges, runs really rough), and spits black liquidy stuff out of tailpipe. Anyone got any suggestions on what could be going on? Thanks for any help.

[peppermrj]

Originally Posted by jcougar88

Have a 89 f150 300 6cyl. Changed tps, iac, tune up complete, fuel filter, replaced exhaust system and found out convertors have been reamed out(this could be good). Truck runs good sometimes, bad sometimes(surges, runs really rough), and spits black liquidy stuff out of tailpipe. Anyone got any suggestions on what could be going on? Thanks for any help.

How many miles and does it misbehave all the time, only cold, low speed high speed, etc.

Also a compression test would be informative.

[jcougar88]

Originally Posted by peppermrj

How many miles and does it misbehave all the time, only cold, low speed high speed, etc.

Also a compression test would be informative.

Has 64000 original miles. misbehaves at any time. When dribving, runs fine, real smooth like nothings wrong. At idle, sometimes it is fine, sometimes it's rough. Only at idle. Hot, cold, doesn't make a difference. Noticed when it does run bad, it turns over about 5 times before it will start hot or cold. When it runs good, turns over soon as you hit the key, hot or cold.

[peppermrj]

Did you check for vacuum leaks (hoses,brittle or gummy,base of throttle body, and around the intake manifold.
I would also check and clean the EGR valve if you have'nt already.

[jcougar88]

Originally Posted by peppermrj

Did you check for vacuum leaks (hoses,brittle or gummy,base of throttle body, and around the intake manifold.
I would also check and clean the EGR valve if you have'nt already.

have traced and checked every vacuum line on truck. Have not cleaned egr valve, but have cleaned throttle body with about a can of spray cleaner.

[peppermrj]

Clean the EGR first it is cheap just a gasket and some more carb cleaner. Make sure the pcv rattles and seals well ( I'm sure you did but what the hell). A bad MAP sensor can cause surging. Here is a generic link for testing a MAP sensor.
http://www1.autozone.com/servlet/UiB...3d8004f7cf.jsp
I doubt if it is fuel pressure, clogged or poor connections at the injectors being that it runs well at speed.
Is there anything resembling a choke thermostat?