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Hey guys, I'm new here and recently purchased a 93 Bronco with a 351 that has a little over 200k miles on it. It initially failed Texas emissions testing horribly at both high and low speed with elevated hydrocarbons and CO. I have replaced the spark plugs & wires, distributor, ignition coil, new oil & filter, new air filter, fixed vacuum leak to MAP, and EGR reconnect (previous owner had apparently disconnected exhaust feed pipe from EGR valve) and timing was adjusted. It now passes easily at high speed, but still fails at low speed with slightly elevated hydrocarbons and high CO.

I assume there is a vacuum leak somewhere as a/c blows air from defroster when accelerating, but from dash vents when coasting/idle. Smoke test of vacuum system only had smoke coming from EGR valve and a little just below the throttle body, both of which mechanic said was ok.

AFTER these repairs, it was throwing codes:
P0303 generic cylinder 3 misfire
LOEO CM128 Monifold absolute pressure sensor failure / vacuum hose disconnected / damaged
KOEO CM 173 HEGO (HO2S) sensor fault/rich
KOEO CM 327 EGR valve position circuit below minimum voltage. EVP/EPT circuit below min. voltage
KOEO CM 332 Insufficient EGR flow detected
KOEO CM 334 EGR closed valve voltage high

I read on another forum that the codes 327, 332, 334 were contradictory. It was recommended to clear the codes and retest, which i did. So perhaps MAP sensor and EGR codes are all from before repairs being made (replaced vacuum hose to MAP and reconnecting EGR). Didn't run codes before above repairs were made. Now not giving off any codes, but maybe I haven't driven it around enough after clearing the codes.

Engine does seem under powered, idle is still a little rough/unsteady, but is sometimes fairly smooth. Also dash tachometer reads 400-800 rpms higher than the tachometer on the emissions testing dyno, but don't know if that means anything.

Any ideas would be much appreciated?
 
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