Yeah, this intermittent miss that I keep 'solving' keeps coming back.. now it's at the point where it's just all the time, when my converter locks up it's really obvious.
So.. this intermittent miss all starts after I start throwing 11s for CM, KOEO and KOER.. well, yesterday I drove all night hoping to clean something up (fouled plug or something, you know) and after a long cruise it wanted to die on me when I came to a stop. Finally, around a turn, it died. I thought I was set, I'd have some codes to be able to fix it.

11 KOEO, 11 CM and... KOER will not finish for some reason. At the point where you hit the throttle after the single flash, it just stops. The engine returns to a good idle and the test stops running.

I'm also noticing my O2 sensor's head turns black after a couple hundred miles, that's not normal is it? On a cold start, sometimes, it stumbles then 'catches' itself, shoots to 1500RPMs then returns to a normal idle.

So anyways, I'm starting to think computer. Do you guys agree? I dunno where else to look. It's running sooo good in every other area except for this stupid 'steady' miss or just rough running. I also thought it was related to a terrible bucking I was getting, but I found out that was just a busted crappy Duralast VSS, mixed with some other issues caused by a busted crappy Duralast MLPS.. so I've sorta been chasing unrelated problems with similer symptoms. That low-speed bucking is completely solved but I've done everything to solve this miss.

I think I fix it by replacing a part, then two days later it starts up again. Replace another part I think is causing it, then two days later it starts up again. "it's the heat", "it's when cold", "its my transmission", "its my ignition", "it's my fuel" .. the only thing that I've ever known to be so random were solid state electronics. I did OHM tests and range tests on every sensor I know of. Did a balance test pulling injector wires, I can't get to 3 or 4 but every other one was fine and my plugs have been replaced once. (before replacing, it was intermittent).

I'm at such a loss.. it's not fair, just as the Bronco is running amazing, almost like new?

 

a code 11 is system pass. the o2 sensor tip being black is normal.

what is your timing set at, have your checked for vacum leaks? what size tires are you running?

 

O2 sensor tip should not be black immediately. Have you checked fuel pressure through all of this? Almost sounds like a rich condition. PCM can only regulate fuel pressure as a reactionary move based on conditions that are monitored by sensors. If this ability is hampered in some way, the computer does not necessarily know it. If the condition is not enough of an issue to push any particular sensor "out of range" then you won't see any Codes triggered. (Example: an 800 ohm resistor in place of your ECT sensor will make the truck run like a monster but destroy your mileage (AND PLUGS) if you leave it that way for an extended period of time. This will not trigger any Codes because the resistor leaves the readings that the PCM expects to get from the ECT "within established parameters" however, it forces the engine to run very rich no matter what the temperature is at. This is a street racer's trick to get more out of the engine for short drag runs. Thats just one example and one that you can actually control. However, this type of condition can exist due to stuck temperature sensors as well.)

Injector leak down could be a possible cause as well. Does the truck start quickly and rev high from dead cold?

 

My 87 does the same thing, bucks , cuts out dies when you come to a stop sometimes. Ive done a major tuneup, plugs wires cap and rotor twice, got a bad one the first time and it took me forever to find that problem. New IAC,o2 sensor,map sensor, egr was completly clogged so I put a new one on, fixed vacuum lines..It will run fine for alittle while sometimes a few days. Then I thought I had it with one of the vac lines, the idle smoothed right out. I drove it about 4 miles then wham its back again. Do you think I got another cap and rotor problem?? Surely not. but its allready happened once.

Im starting to think its more vacuum problems, you know these fords love thme blasted vac lines, geez there all over the place.. Its driving me insane..When it runs good, man she idles so smooth and purrs like a kitten but its been a stubborn ole girl lately..Any help fella's would be greatly appreciated!!!

 

I believe I got mine figured out. Ive started it twice since I changed the cap and rotor and no miss. I let it cool down the second time. Ive ran it at operating temp and cold. The weird thing is its the 3rd cap and rotor!! The first one I bought was just bad, then an accel cap and rotor. Now a cheap o from autozone..We will see what happens next.

 

Been a rough week..

I changed the fuel filter, what came out of it was black and it was definitely clogging (kept having to rotate it to empty all of the fuel).. that definitely didn't help the problem, but I didn't notice the immediate difference I was expecting from it.

I will do resistance tests on my ACT and ECT, they're both AZ parts which I absolutely do not trust.. but I've not really taken it on much of a test drive since the fuel filter, so I'l just see after that. I did a full range test on my autozone TPS and it matched all throughout the range, so I'm definitely not blaming that anymore.

I changed the screens and cleaned my injectors (myself) maybe 2000 miles ago? I doubt I have any vacuum leaks, however, I think I need to take a look at my intake gasket. I think this all started when I changed my valve covers, but I did so much to it that I'm just not sure.

If my injectors were leaking I wouldn't be able to hold fuel pressure, right? When I pushed my fuel valve to do the filter, I couldn't believe how much pressure I had built it.. it put all doubt out of my mind that I wasn't able to hold fuel pressure. I do get an immediate rev (1500RPMs?) for a second when If first start it, it drops to 900RPMs, I tap the throttle and it drops to about 800RPMs.

Funny thing happened, I found what could have caused the problem TWICE and neither seemed to be the issue.

1. I pulled a spark to look at it and the insulator fell apart in my socket.
2. My dirty fuel filter

im confused.. I'm gonna take it on a drive tonight though.

 

Oh, and I might want to change the cap and rotor. I started all of this by swapping those..

first, my new Summit Rotor went bad.. then everything seemed fine, but my dizzy went and I went ahead and kept the cap and rotor that came with the new distributor. Maybe I should put my Summit cap back on? I liked the cap at first but it doesn't hold as well on the distributor as my old Summit one did.

Immediately after putting my new distributor in, the truck ran the best it ever has.. then a few days later, I started getting bucking.. thought it was ignition/fuel, so I 'fixed' some stuff.. then changed the VSS which really fixed that, but then I had a miss. I knwo it's simple "just undo what you did to fix it", but I did? Plug wire routing and stuff.

Basically, I had two problems I was trying to fix, both unrelated but with similar symptoms.

 

Did a 120 mile drive tonight. it happens under load.. when going up a hill or when the TQ is locked up on the highway I can feel it the best. My cruise control isn't working right but that might be a symptom of it not having enough power.

I did throw a Code 34 intermittent, the EGR sensor one.. the EGR sensor is new though.

You know the solenoid it hooks up to through the vacuum line? Should it buzz at me for a couple of seconds when I shut the truck off? Also, when I apply vacuum to the solenoid it buzzes. I solved 34 for a while when I changed the sensor, I hate that it's back.

 

im gonna just try pulling that vacuum line.. if it is something dumb like leaving EGR open all the time, or opening up too much, then I'll know right off the bat. EVP out of range could mean that EGR is getting too much vacuum at all time, which would definitely cause drivability issues.

I'm hoping, if you guys want you could wish me luck? Or even offer some more advice.. i dnuno where to even find the solenoid if it is broken.

 

that sensor shouldnt make any noise. it may need replaced and will cause a code 34.

Check your fuel pressure with a gauge both key on and again with engine running. Its also time for a compression test.

 

Tried unplugging the solenoid and noticed no difference, though it didn't bog down on me from a fresh start like it has been doing for two days. But, I just changed my cap back to the Summit cap, messed with my PCV valve and now it's back to being intermittent. I can feel the Bronco wanting to run alright, then it gets bogged down. It's not wanting to die on me or anything (unless its after a looong highway cruise), just sorta smooth to non-smooth.
Makes staying at speed a pain because I get bursts of torque with my foot steady on the pedal.

I'm starting to wonder if maybe my plug wires are no good.. for me to make ANY change in how it was running, especially after a 140mile trip with a 100% consistant miss, with just messing with those items, logically one of the items I messed with has to be the cause?

Oh, I got KOER finished as well. Code 44, which makes absolutely no sense since I've fixed this thing a dozen times. I'm wondering if they're all just going out.. is there a common ground or relay or something at TAB, TAD and EVR solenoids that I should maybe look at?

Stupid gremlins, that's all it is.

and the fact that it's back to being intermittent (yay, intermittent is better than consistent!) has me almost sure it is not physical damage. I'd expect a knock or something if it were anyways, but I still had a nagging feeling that it was something internal, now I'm not so sure.

 

how many miles on the motor? you may have a timing chain that is stretched, low compression wont make any noise that you would notice.

get some ford 9mm wires, make sure you route them properly and they are seperated properly. # 7 & 8 can not touch.

the evr is more prone to failure then the tab/tad sensors unless there is a vacum leak on one of the lines going from those solenoids. what degree tstat do you have in your motor?

 

Oh, I dunno, 220,000 or so? Forget it, the timing chain is coming off.. I maybe have 20 degrees movement at the crank before I see my rotor turn.

So.. Now I'm getting into an area I've never dealt with before. With the timing chain, do I buy a roller timing chain even though I don't have a roller block? Since I have the chain off, should I go ahead and replace my cam and pushrods? I can't afford cam + timing set + rockers right now and dunno if I want to, eventually I might just refurbish the heads. How far should I go with this and what do I buy? The cam should be an easy change if I need one, I have to pull my upper intake anyways to change the gasket.

I'm looking at $100 without the cam.. but if I can and should change the cam, I definitely would like to.

My water pump was being really nice, bolts came off easy until the last two which had to break off on me. I also found out my thermostat was giving full flow at cold, so it being stuck open definitely wasn't helping (surprised it didn't throw codes for ECT?). My water pump was also packed full of mud.. not rust, not rusty water, but some piece of it let mud in and it was just sitting there. I was getting occasional leaks (just wetting around the pump, nothing serious) anyways so, ya know. Plus with a small leak at the seal, I might as well.

It hit me.. I have had low vacuum since I bought the truck. It ran decent enough so I didn't care.. but the 14hg might have been enough for the truck to run decently, if things wore enough to drop to 13 or 12hg, then I might see some problems.

 

yea truck should have 19hg of vacum.

comp cam 35-255-5 or the Crane cam that conanski uses which i forget the numbers. it should be a direct swap and shouldnt require any additional changes.

I would get a roller timing chain, water pump, 195* tstat. I would also recommend taking your radiator to a shop and have it gone thru because that crap is probably in there also.

make sure that you number the pushrods, they must go back in the exact same place. I always use a deal of cardboard and push the pushrod thru and number. Lifters would be smart to replace being a new cam also. lifters wont need replaced.

get a haynes manual to help with install of timing chain, cam etc.. good book to have.

 

I might just do the timing chain for now.. The Bronco eats up waay too much money as is. If a timing chain solves most of my problems, yay, if not, i'll do the cam next payday.

So, do I buy a roller timing set? Double roller? This is the stuff I'm a bit confused about.. I dunno where a roller block is important, I just know I don't have one.