I have recently purchased a 93 Bronco. It is in good shape for its age minor rust and if I could only get it to run right it would be a great vehicle. It has a 351 in it and as of right now when it starts cold it starts right up just idles a little rough. The warmer it gets the idle is sometimes worse and sometimes good. While driving out on the highway it does fine unless I need to grab a passing gear. Like wise while taking off from a light it does the same as long as I don\\\\'t need to get going in a hurry it seems to do fine some times others it seems to dog out and fall over itself. Also when coming to a stop light have to shift to neutral and keep throttling it so it doesn\\\\'t die, if it does die its a pain to get started again, I have to keep pressing the throttle til if finally starts. When at idle if I give it full throttle it throws out a large amount of black smoke, also while driving it there is a bad fuel smell and same with the black smoke. Before spending large amounts of money just throwing things at the problem, I was hoping to hear some insight from a few of you hoping someone might have had the same problem. I know the black smoke is too much fuel but not sure the reason why, the truck has 175000 on it and everything works good other than the way it runs, tranny shifts good. I have done both koeo and koer tests and it says system pass and an o2sensor but not which one. Then the when read again I get #8 misfire but plugs and wires are all new and good. Then if ran again I will only get system pass. My CEL is intermittent after running for a while and driving, but like I said comes and goes and no warnings or signs to predict when. I was thinking maybe the MAF or possibly the TPS and some o2 sensors but I am not sure and help or thoughts would be appreciated. Thanks Guys

 

First, welcome to FTE. Everyone here is great at trying to help. Here is my non professional effort.

First, codes. So you got 111 on KOEO and 111 on KOER. Was the engine warmed up? The Continuous Memory (CM) is displayed right after the KOEO test. I have found error codes there and it remembers the CEL alerts. Since you mentioned O2 sensor that would be my guess and it needs be be replaced about every 40K anyway. Mine was only throwing a code in CM when running 70 MPH and lifting my foot off the throttle. Your '93 should be like my '94 with only one O2 sensor. It is easy to replace if you remove it with the exhaust hot. It is the most important sensor of all. Separate the 5 and 6 plug wires to keep them from cross firing. Check the IAC. The #8 plug could have been dropped or maybe it is carbon tracking. I have always used Motorcraft copper but went with NGK V-groove the last time and I like them better. Pull the spout and check the timing on a warm engine. If you make any changes to sensors or timing remove the battery cable about 20-30 minutes to reset the codes then drive about 20 minutes at varying speeds for the computer (PCM) to relearn the parameters.

Again, Welcome!

 

make sure #8 plug wire isnt touching or crossing over #7 plug wire, they are notorious for causing the cross firing issue. like mentioned you only have 1 o2 sensor, changing this is an option. i would also check your fuel pressure at the rail with a proper gauge, its possible you are getting to much fuel thus the black smoke. I always run motorcraft copper plugs and see no reason to run anything else. the cost just doesnt provide the improvement you may get from those expensive plugs.

double check your timing as well. check your oil for the presence of gas this will also indicate over fueling, or pull the vacum line (engine off) running to the fuel pressure regulator, if gas drips out the FPR is bad.