Hey guys. First post here, I just recently got my first Bronco last month. It ran great for about 2 weeks and it's been nothing but problems since.
It's a 1992 5.0 302 bored out .030 over. The only things the previous owner new about it was that it had a RV camshaft in it and the motor had been replaced and had about 6000 miles on it. He said an engine shop did the rebuild.

So the problems started with it surging and jerking under load. It would run fine at idle and normal speeds, with a short hesistation here and there, but accelerating would cause it to buck and jerk.. sometimes.

The problem was on and off and I was currently busy replacing the power steering pump. It went away for a few days til I got the pump replaced. I went mudding with it for about 15 minutes and popped the power steering hose off and called it a day. Fixed that and drove it home fine. The next day it was back to bucking and jerking.

I replaced the fuel filter, plugs and wires. Same problem. I replaced the dizzy cap and rotor and put a new coil in it. Same problem. I tried to pull some codes on it with a worker at a parts store, and I got DTC 28, 37, 35 and 32. 35 is idle air control valve, so I replaced that. Same problem. In fact, it was getting a little worse where the idle wasn't smooth anymore and it would buck just driving down the road.

I took it to a mechanic and he ran a very expensive scanner on it and it threw 15 codes he said. He said there were things like lean mixture, vacuum leak and idle air control valve. I had him fix the vacuum leak and he cleared the codes and scanned again. He didn't explicitly tell me the results of the scan but said I needed to change the distributor because a sensor or something of the like in the distributor threw a code and you had to replace the whole thing, and the module (PCM). I left the shop and it was running the same, surging and bucking under load. I ordered a dizzy and PCM from the parts store. PCM was going to take two days to get there but I switched out the dizzy that day. Then the problems really began.

It was running just a poor, and even worse right after I changed the distributor. I took it home and the next morning it would barely drive. It sputtered, bucked, jerked, backfired and would barely move. I went through and checked the timing again and made some adjustments to smooth out the idle but it was still misfiring... but intermittently.

Another strange thing, when I put the timing light on it, with the SPOUT unplugged, the timing light wouldnt light up. With the SPOUT plugged in, it lit up....

I replaced the PCM today and it runs no different. It barely moves, bucking and misfiring, jerking around. It also sucks air like a Hoover. I mean, it really is sucking a lot of air through the filter, its really loud. I don't remember it pulling air like that before.

I'm at a loss as to what to check. I know I should probably do cylinder compression checks and fuel pump pressure tests but I wanted to see what you guys thought. I can't seem to find any threads that are having problems like this.. especially with the air pulling that hard.

 

Welcome to FTE and the Big Bronco Forum. Apologies for the delay in getting a response out there.

The answer lies in those 15 Codes your mechanic pulled. Did he by any chance write them down or tell you what they all were?

Everything can be troubleshot but you need the codes to know where to start, otherwise you are just going to throw time and money at this thing and you might catch a break... more likely, you won't. Scanners for EEC-IV aren't expensive at all. ($20-$40 average) and they are invaluable when it comes to dealing with the systems in any Ford vehicle that is equipped with the EEC-IV system. So, if HE said it was an expensive scanner, (or charged you an arm and a leg to use it on your truck) he's blowin' smoke.

All I am saying is that spending the money to replace a distributor and PCM that didn't actually fix anything could have been avoided. PCM failure has about a 1 in 10,000 probability of being the problem and if it IS the problem, there are very few instances where the PCM itself doesn't actually "tell" you that it has failed. Unlike personal computers, automotive computers actually WORK and their failure rate is relatively low by comparison.

Hope I haven't scared you with all of this. If you need assistance as to how to troubleshoot problems based upon fault Codes, post the code numbers here and we will certainly let you know the best direction to go next. Don't want to discourage you, just want to point you in a direction that will yield some positive results.

 

Hey man, thanks for the reply and the warm welcome. What youre saying makes sense. I guess the best thing to do would get a scanner of my own. Any idea where to pick up one for my bronco? The code reader I was using at the parts store either was junk or the guy wasnt doing it right... I could spare the change to get my own for under a hundred but I was thinking they were a lot more.

 

Here you go:


You really cant do anything with the truck until you find out what the codes are. I wouldn't drive the truck if its as bad as you make it sound. You don't want to make it worse. Just my .02

 

Code scanner should be here tomorrow. I'll update with the codes. Thanks for the help so far.

 

Just finished scanning her. I preformed KOEO and got a pass code 11. No continuous memory codes stored.

I preformed a KOER test and as soon as I hit Test/Hold the air flow decreased and the engine died off. The scanner then told me it was an 8 cyl vehicle (which should be the first thing it does, so it dies pretty quick).

Held the throttle open to keep it from dying and got codes 12 22 41 13 77 52. Nothing important really.. except MAP sensor and o2 sensor..

What are the chances I jumped a tooth on my timing chain? would that cause these issues?

 

was the distributor you got from the parts store by any chance a reman'd unit? Typically, the parts store brands (cardone) are reman'd units. I literally went through 5 distributors before i bought a NEW richporter distributor, which solved my problem. The issue is that the shaft of the distributor was magnetized, causing the PIP sensor in the center of the dizzy to get weird readings which would then cause the timing to go nuts and cause pinging and bucking. You can check your dizzy shaft with a nail and see if the nail sticks to the shaft by removing the cap and rotor and sticking it to it.

 

I also went through three re-manufactured ones. Finally bought a Motorcraft stator, found a friend with a press, marked EVERYTHING and it turned out great.