97 Explorer 188k miles, had P1152 & P01XX (forgot already) O2 code. Had replaced plugs, wires, intake gaskets, checked for vac leaks, new MAF sensor, cleaned IAC. Ended up replacing a toasted O2 sensor, codes disappear, truck runs good, I pass inspection, LIFE IS GOOD. BUT..within a few days of passing inspection (and actually while waiting in line at the station) it starts to miss and run rough. Just a little at first but now it's like it's running on less than all cylinders. Pulled, cleaned, gapped the plugs. Removed and reinstalled the wires. New fuel filter, air cleaner is less than a month old. No change. Had a code for intermittant random misfire, cleared it, has not returned in 3 days but still runs like sh**. Have resistance on coilpack, primary and secondary all read the same, a little high to spec but consistent. I don't have a digital meter and .3 ohms is a little tough on the eyes. Runs rough and stutters all the time, at startup, when cold, when hot, in gear, in park, doing 70, doesn't matter. Shakes like bitch. Did the Seafoam thing this evening, good smoke but not much improvement. I think this is electrical or fuel related. Just for kicks I disconnected the battery last night in the hopes that some bad data had been retained from the last go round even though I cleared KAM. My luck as it is the battery decided to give up the ghost so a new one is in it now. I was hoping that a bad bat might cause some of the problems but no. Anybody have any thoughts? Jharger, you there? You followed my other posts so you have a good idea of where I've been. Any more magic up your sleeve?
Thanks guys, Vic

 

Hey Vic. 1152 is a rich O2 read. I am not sure which one. You need to get the other code too to help. You can always pull the spark plugs to look at the real situation in a cylinder. They always tell a story. If you have one side black and the other normal, brown, then we know where to start looking. The codes are just feedback from a computer program. Garbage in - garbage out. So if we have bad inputs, you can not rely on the computer's feedback. Look at the real physical conditions (spark plugs, exhaust gas color/smell...) to try and diagnos the true problem.

 

Jeff, plugs look good, no codes at this time. The misfire code I cleared was P0300, cylinder non-specific. What torques me is I did all the other stuff and got the thing running okay, albeit for a few days, and now I have no codes but it runs even worse than before. I'm gonna throw an induction timing light on the wires and see if i can tell if there is a miss in any cylinder. I'm also gonna spray ether into TB and see if it smooths out in the hopes of determining a fuel supply issue. I don't have a fuel pressure gauge so I don't know the actual pressure at the rail. I can hear the pump when key on. The lack of codes seems to eliminate rich/lean conditions since I had codes when these conditions were present before. Vac leaks should trigger lean codes too. Exhaust doesn't really tell me one way or the other, doesn't smell rich, no black smoke, actually no smoke or steam. I'll also check the alt. for voltage, don't know if it would cause these issues but wth. Thanks, Vic

 

I has a cylinder identification error or miss fire code a while back. I changed the plugs/wires and it went away as well as the missing I had. My missing was so bad you'd think it would throw all kinds of codes but no just the one. If all physical signs look OK, electrons are one thing you can't pyhsically see. Even when I ohmed out my wires they all looked OK but when changed the problem went away. Obviously,make sure you get a metal to metal contact from you good wires to the spark plugs and the coil packs are a little funky too. Make sure there's a good connection there too.

Otherwise, electronically, I think you have a cam position sensor on this year - at the back of the motor, passenger side. And the EIC - electronic ignition control - is located in front of your battery. These 2 devices commoumicate with the computer and the coil pack. You can try to trouble shoot those contacts/grounds/shorts/opens...

Finally, there is a wiggle test you can do if you have a test scanner that can accomodate such test. Here, you run the car and wiggle the suspects connects/components and try to capture a code.

 

Today I rechecked the resistance of the coil primary & secondaries. The primary should be .3 ohms, my meter has a needle, hardly moves, I say OK. The secondaries should be 6.5-11k ohms. They are all 18k ohms+/-. Higher than spec. Will this cause a problem? The plug wires shoukd be 5k ohms/ft, some were good, others lower than spec. I threw the timing light on and bank 1 sparks were steady but with numerous "misses". Bank 2 were very rapid, much more so than bank 1 and had numerous misses also. I call it "V-FIB" like in a heart attack. I'm thinking that the missing spark from bank 1 is on bank 2. Is it possible? TPS volts w/KOEO are 5, good to spec. Still no codes present. Exhaust doesn't smell unusually rich or lean. Still misses terribly, runs very rough. I'm thinking coil pack and another set of new wires. (wires first) What say you guys? Thanks, Vic

 

It does sound electrical. So far you have done everything I would have done - well I think the intake manifolds were overkill but you probably wanted to be sure since the earlier model 91-94 had issues.

I'm not sure how you tested the spark with the timing light. I was going to suggest this actually so you beat me to it. What I would look for would be a steady rate of flash from the light. Sounds like you might have seen some differences from cylinder to cylinder.

One thing on a test like this that could be a bit misleading is that you have only 3 coils in the pack. Plug leads from 2 cylinders hook up on to the same coil. It goes 2,2,2 front to back, pairs being side to side. So electricity takes the path of least resistance. This is usually to the cylinder at TDC of the power stroke. Since this cylinder is packed full of nice juicy fuel mixture, it conducts a lot better than the other cylinder at BDC of the exhaust stroke with just a little exahust fumes left in it before th intake valve opens up again. So it's the "usually" part of this that can be tricky. You might be getting a spark to both leads at the same time, or maybe not. The engine doesn't care but it may skew your test perception/results.

I can't remember from high school auto shop if it was primary or secondary in the coil that goes high resistance when a coil is bad. Like I said, I checked my wires and they seemed OK, maybe a little higher than the 5 ohms/ft you mentioned. But when I cahnged them, it made all the difference in the world and removed all the missing.

Take a gamble on a new coil.

Also, if TPS or MAF or EGR...all those other control devices were not reading within spec, the PCM will give a code. It watches that given the value of 1 sensor, another sensor or actuator should be within a certain range.

 

Well here I am to update the progess, or lack of as it may be. I did buy new Autolite wires to replace the other "new" ones, no change. I boughta new coil pack, checked the resistance right out of the box, was good so I installed it. Made no difference. I'm stumped guys...If this was a pre-computer engine I would have checked cap, wires, plugs, rotor, points,and timing. The only thing from that list I haven't done is check the timing. Right now I just want to see if the timing is stable, not jumping around. To me that would indicate the timing chain is good. As it is I can not hear a rattle indicating a loose or worn chain. I do hear a tick, one, very rarely from the engine. Still have no codes, still runs like crap, misses all the time, at idle, in park, in drive, on the hiway,..catches for a sec or two, then misses alot, and on & on.
What are the timing sensors, if any. Cam Position Sensor I would think, what about crank sensor? Any others? I'll have all new sensors soon.
And vac leaks should show up all the time and pop some codes, yes?
Thanks guys.......

 

Are you using Motorcraft spark plugs? I've known several Fords that don't run very well unless the factory motocraft plugs are used. Haven't heard of any situation that bad being caused by using non-oem plugs though

 

Give the engine and engine compression test.

 

Installed autolite plugs and wires. I went back to the IAC, tried to see if it is moving at all. Removed it from intake plenum but left the wires hooked up. Had a helper start the car while I was plugging the holes with my thumbs. I was trying to act as the valve by metering air into the plenum much the way the IAC would and watching to see if the IAC would move in response to my metering. I did not see any action. I put an ohm meter on it per Wolfmeister article. Pins to case did not move needle- okay; pin to pin was wide open circuit- not good per Wolfie. Before I plunk down more $ on this I have a question: when driving on the hiway isn't an inoperative IAC a moot issue? All the air is thru the TB while cruising, yes? If so, and I still have the miss/surge/hunting, how does this point to the IAC?
I'm gonna hunt down a compression tester and a fuel pressure gauge to borrow.

 

Did you try to acctuate the IAC by itself? Try hooking it up to a 5 VDC power source. From what you say so far, it seems like the soleniod is bad. If so, I would think the car wouldn't even idle on its own - unless it is stuck open.

From what I've read, the IAC is basically full open all the time except at idle or decelarating. Turn key to "on" and IAC goes full open to give the engine the air it needs to start - this way you don't need the gas pedal to start it.

Mash the pedal down for full throttle and IAC goes full open. This is where the debate comes in - do you really get more air into the manifold through the relatviely restrictive IAC orifice compared to the big open throttle plate? In the least though, with the IAC wide open, if you let your foot off the gas, the engine wont stall out.

When decellerating, IAC goes closed so you get full engine braking. Then when you hit 1,500-1,300 RPM, it goes full open again so the engine wont stall. I have a manual trans and obviously down shift to stop (so I get 65K miles out of a set of brakes). I can feel it when the IAC opens back up - get much less engine braking.

So the IAC does work all the time, not just at idle. But the point is to what affect? Why would it cause such severe issues? The O2 sensors are controlling the A/F mixture and the IAC has no computer control over the A/F mixture.

Which makes me have to ask you this - are the O2 sensors connected to the right leads off the wiring harness? You said they were changed right? I ask this because another poster had this error and we finally tracked it down. Of course he was getting rich/lean codes so we focused on the O2's but I thought I'd ask just in case.

One thing that does affect A/F ration is the EGR if you have one. I have heard the DPFE switch causing erradic engine performance. Since this sensor senses how much exhaust is flowing back into the intake, if it is wrong, the computer will be reducing fuel through the injectors by the wrong amount. You could be going too lean sporadically but not long enough to throw a O2 lean or not switching code.

 

Jeff, I hooked up the O2 sensors 1 at a time, and I have 3 total on opposite sides of the tranny (each exhaust pipe). Since I did them individually the chance of hooking them up wrong is basicall nil.
The diaphragm is just slightly open straight off the engine, I guess that's why it will start although it runs badly. I did just try to operate the IAC from a battery charger. It's a 12 volt charger and I ran it at 2 amps hoping not to fry the thing. I did hear it trying to move but it did not. I would think that at 12v and 2 amps it would zip in and out. I really don't want to try it a 6 amps.
I believe I have both an EGR valve and a DPFE. And thinking about it< if I did have a coolant leak thru the intake before I replace the gakets it could have buggered up the DPFE. I did notice white, crusty stuff where the hoses attach. I scraped whatI could reach from inside the tubes on the DPFE but don't know if it's clear inside or not. Supppose I could remove it and try to blow it out. The EGR, well I've been ignoring it. You know, for 189k a couple a hundred bucks (forgetting the 4 ball joints) ain't terrible but I hate "fixin" things that ain't broke, know what I mean? The wifey's starting to complain about the $$ I'm chunkin out, and it's HER car! I'm just PO'd that I'm still dinking with it. I don't want to take it to a mechanic if I can help it. As always i appreciate your comments....Vic

 

Make sure your spark plug wires are not crossed. Recheck your spark plug wires and make sure that they follow the firing order for your engine.

 

If you follow the fuel line from the fuel tank. Sometimes you'll find a fuel distribution that look like blackcanister, the top portion has the inlet and outlet for the fuel, the lower portion of this canister is shaped round. If you remove the round lower portion lid of this black canister (Not sure of the technical name of this canister) there you will find a round fuel filter in the canister. Every time I find this filter (looks like 2 inch to 3 inch air filter) it is usuall very dirty.

When I come upon one of these filters, I toss it away and don't replace it. I use the other filter mounted on the frame as the filter to filter the gasoline.

 

News Flash: It's running good! I bit the bullet today and bought a new IAC but before I got home the cel came on. Threw the scanner on it and got P304 cyl 4 misfire. WTF! I check the wire, got flame so I yank the plug. Damn insulator is cracked and damn near broke off! Only 2 months on the plugs. I did pull'em when I got the random misfire code but I didn't see anything, musta had a hairline crack or was just plain bad. Anyway I popped a new one in (and put the new IAC on for kicks) and it runs smooth. I'll keep my fingers crossed....Many thanks to all who chipped in their 2 cents, the forum at it's best. Vic