Explorer Bucks really bad under acceleration

[Ferox]

After letting it set for about a month my explorer has some new problems that have come out of the closet. Other than the tranny pan gasket leaking all over..

When im driving, under normal or hard acceleration the engine will buck and seem to want to die, then jump back up to the current rpms and run fine again.. it will do it every 40 seconds or so.. sometimes less often sometimes more. When it does this the check engine light comes on, then after it drives normal sometimes it will go off or after it bucks again it will shut off..

I would put it on a reader to check codes but the computer does not store them. It hasn't for about a year now. once the key is shut off it forgets all the CEL's that have been thrown.

Ive checked the plugs which happen to be about a month old as well as the wires, they seem to be running rich and covered with gas. I belive one of my 02 sensors is bad.

so any ideas would really help

thanks

 

[410Fortune]

The computer does store hard codes, or should. If it does not I would suspect my PCM itself, or the constant power to it (fuse under hood, EEC power)

 

[Ferox]

re

I checked the fuse and the relay. They are both good.

Time to buy a new pcm?

 

[MrShorty]

Did you check grounds? Everything electrical (including a computer) needs a complete circuit from B+ to B-.

When you say it doesn't store codes, are you getting no codes at all from it, or all pass codes?

 

[Ferox]

When you drive down the road for about 30 miles.. the check engine light will come on. im assuming from an 02 sensor. once you shut the engine off and turn the key back on. The light goes off till you drive for another 30 miles.

When put on a reader it will not give any codes because it doesnt not store them. It sort of has amnesia..

 

[94Blue302GT]

under normal or hard acceleration the engine will buck and seem to want to die, then jump back up to the current rpms and run fine again.. it will do it every 40 seconds or so.. sometimes less often sometimes more. When it does this the check engine light comes on, then after it drives normal sometimes it will go off or after it bucks again it will shut off..

once the key is shut off it forgets all the CEL's that have been thrown.

Ive checked the plugs which happen to be about a month old as well as the wires, they seem to be running rich and covered with gas. I belive one of my 02 sensors is bad.

Like they said, it might be your PCM. Check all the wires. I would def. check your negative batt.
Also, you might want to get one of those "carchip" deals from autozone or something, which will store the codes as it's bucking, even though your PCM might not retain them.
Are ALL of your plugs covered or just some? If just some, you might want to run a compression test (buy the gauge and turn the motor over a few times for each cyl, not a big deal) on each cyl, you might have a bad head gasket.
Also, check your belt, make sure it's tight. I had a problem with my engine giving out a bit on top end, which was due to the belt slipping because of my tensioner being busted, NOT a cool thing.
I"d also consider checking over your WHOLE ignition system. If you have DIS, maybe pick up yourself a new coil. If you have a dizzy, check all those electronics. I know on my stang 5.0 i had to replace the electronics INSIDE the dist. in order to get rid of a starting and bucking problem.

LASTLY, check ALL your wires, sparkplug, to the coil, etc. make sure NOTHING is shorted out. You might want to get a multimeter or something to check some of the more important things.
Lata
Lee

 

[Ferox]

re

all the plugs were the same, i know one of the 02 sensors was bad so it was just running rich.. none of them were really that bad. just dark and a little wet from running rich.

As for the coil pack.. dont think thats the problem but could be. Either way im getting a new Computer for the damn thing since i would like to know what codes its trying to give me. That will give me a better idea of whats wrong.

Im only fixing it to sell.. so i dont want to put much money into it.

If anyone on here wants to buy it as is let me know ill give more details on it.

checked belts they seem tights but ill check again.. Dont think its a head gasket but then agian ill check to make sure. maybe tomorrow ill borrow my friends snap on compression tester.. comes in handy. If i test it ill dry test it if the compression is low ill shoot some oil in each cyl, and test it.. hopefully the rings arent shot. It has been pretty well taken care of and doesnt smoke so i dont think thats a problem.

By the way.. would a clogged Cat cause any of this?

 

[94Blue302GT]

Doubt the cat. But you could check. I"ve got 128,000 and mine's fine.

 

[Ferox]

yea.. but there is almost 200k on this.

 

[MrShorty]

When you drive down the road for about 30 miles.. the check engine light will come on. im assuming from an 02 sensor. once you shut the engine off and turn the key back on. The light goes off till you drive for another 30 miles.

When put on a reader it will not give any codes because it doesnt not store them. It sort of has amnesia..

I'm going to assume at this point that the computer doesn't respond to the test at all. If it were simply forgetting codes, you would be getting a pass code (111) in continuous memory (after separator pulse during KOEO test).

have you tried the test with a jumper wire instead of a code reader, to see if the reader is having a problem? Have you verified the computer's main power (2 or 3 connections at the computer)? Have you checked the three ground connections? Double checked the wiring between the self-test connector and the PCM? The usual process of diagnosing a bad computer is to check all possible external causes of the fault (in this case a "no codes - computer doesn't respond to self-test). Then, if everything checks out, the computer itself must be at fault by process of elimination.

Good luck. let us know how it turns out.

 

[Ferox]

I'm going to assume at this point that the computer doesn't respond to the test at all. If it were simply forgetting codes, you would be getting a pass code (111) in continuous memory (after separator pulse during KOEO test).

have you tried the test with a jumper wire instead of a code reader, to see if the reader is having a problem? Have you verified the computer's main power (2 or 3 connections at the computer)? Have you checked the three ground connections? Double checked the wiring between the self-test connector and the PCM? The usual process of diagnosing a bad computer is to check all possible external causes of the fault (in this case a "no codes - computer doesn't respond to self-test). Then, if everything checks out, the computer itself must be at fault by process of elimination.

Good luck. let us know how it turns out.

Where can i check with a jumper? Are there any Faq or sticky post's on this subject? i havent found any.

 

[MrShorty]

Instructions for the EEC-IV self-tests are all over the internet. The easiest to read (and perhaps the most verbose) is at www.fordfuelinjection.com Try that, google "Ford EEC-IV self-test", and check in your favorite repair manual and you should find all the instruction you need.

 

[Ferox]

Instructions for the EEC-IV self-tests are all over the internet. The easiest to read (and perhaps the most verbose) is at www.fordfuelinjection.com Try that, google "Ford EEC-IV self-test", and check in your favorite repair manual and you should find all the instruction you need.

Okay.. just one last question.. does anyone know where that one pin STI connector is? or do i have to jump a wire in the bigger 6 pin port? That site says i need to ground the STI Wire.. but i cant find it..

 

[Ferox]

okay here is what i got..

KOEO i get 111

KOER i get 998 Which is hard fault present.. after 998 i get 157 but fordfuelinjection.com says that 157 shouldnt show up during KOER?? so umm yea im lost.. would the MAF actually cause this problem?

The maf needs to be cleaned? Or bad?

 

[94Blue302GT]

okay here is what i got..

KOEO i get 111

KOER i get 998 Which is hard fault present.. after 998 i get 157 but fordfuelinjection.com says that 157 shouldnt show up during KOER?? so umm yea im lost.. would the MAF actually cause this problem?

The maf needs to be cleaned? Or bad?

try cleaning it, the cleaner is only a couple of bucks.
Otherwise, see if a junk yard has one to swap on there, but you'll still have to clean that up.

 

[Rhett]

Hmm having read this thread, I don't really agree with all of this talk of replacing/testing the PCM right off the bat. I would start by buying a new set of spark plug wires ($30) and plugs ($<12) and go from there, because it seems like 90% of bucking while accelerating issues are a wire problem.

 

[Ferox]

Hmm having read this thread, I don't really agree with all of this talk of replacing/testing the PCM right off the bat. I would start by buying a new set of spark plug wires ($30) and plugs ($<12) and go from there, because it seems like 90% of bucking while accelerating issues are a wire problem.

Well i got the pcm to work obviously. So thats not the problem.

Its not the plugs or wires because they are all brand new.
Im getting a 998 then a 157 which means that my maf is pretty much junk. Im going to try cleaning it again in the morning if it doesnt work ill get a new one from a junkyard and see what happens from there.

 

[MrShorty]

Does that "KOEO 111" mean you got 111 for both the KOEO codes and the CM codes, or did you cut the test off after the KOEO codes and not let it run long enough to output memory codes?

A KOER 157 doesn't, by itself doesn't mean your MAF is junk. The computer can't see past the end of its proverbial nose. It can't tell the difference between a bad sensor or a bad connection in the wiring to that sensor. Also remember that the computer is measuring voltages -- there's no such thing as an absolute voltage; all voltages are measured "in reference to" something -- in this case the negative battery post. A bad computer ground can wreak havoc on the computer's measurements.

I would start diagnosing this by checking the power supply to the MAF, then hook up a voltmeter to the signal wire and see what the MAF signal is.

 

[Rhett]

Its not the plugs or wires because they are all brand new.

You said they were "about a month old" before. But that they were "covered in gas", which could mean they're ruined, even after 1 month. Here is what you said before:

Ive checked the plugs which happen to be about a month old as well as the wires, they seem to be running rich and covered with gas.

I assume you mean that your spark plugs were sooty and dark, meaning the engine is running rich. And also I assume from your statement that the plug wires are, "covered with gas", which is not good. They may be new, but if they're "covered in gas" that sounds pretty dangerous. Do you have any leaks on the fuel rail or around the fuel pressure regulator?

You may have 6 fouled spark plugs; an engine running that rich can foul them in a hurry.

 

[Ferox]

Well i cleaned the plugs up and it didnt make much difference. The wires them selves dont have any oil or gas on them. I guess you just miss took what i said.

the plugs were kind of dark. but ive seen plugs twice as bad that still functioned. Ill start by cleaning the MAF tonight then checking some other things. If i dead end and cant find a solution ill buy another set of plugs but that seems to be the least likely of causes.