94 2.3l 2wd Wiring issue or Pcm?

[ForzdaManger]

I hope someone can help me out on this one. Hope this post isnt too long. Recently bought a 1994 mazda b2300 4 cyl 2.3L. After about 2 weeks the check engine light came on and stayed on. The truck then started to bog down and have no power sometimes. (not always) I used my scanner and got o2 sensor, maf sensor, restricted egr flow, and failure in cid circuit. I checked the egr hoses and they were filled with powdery substance. i figure some kind of corrosion. So replaced those hoses along with the o2, Maf, egr pressure differential feedback sensor and tried to clean the egr system. Ran scanner and then only got failure in cid circuit, voltage not what expected at egr pdf sensor, and failed low rpm test. I installed Camshaft Position Sensor and the check engine light went out and she drove much better, but sometimes would still bog down. I Then cleared codes.
Then Check engine light will come on and off while i drive. I ran the scanner again and now all the same old codes o2, maf plus tps. The haynes repair manual says to check voltage of the tps should be about .5v to 1v at idle and go to 5 all the way open but i was at around 12. also the resistance was way out of parameters .
Then sometimes after turning off the engine it would not start for a while.
So I replaced the tps (old one did NOT want to come off), and the Idle air control. Because i read on this forum that the iac would cause these problems with out giving a code sometimes. Same old stuff!

two nights ago it cut off going down the road and left me stranded- (walked about 9 miles). Next morning it started up and let me get about 5 miles before cutting back off. In about 10 minutes it started back up. Drove another 5 miles or so and cut off. After about 5 minutes it started up and drove the remaining 35 miles home but with very little power. At one point i was going 25 mph going up a huge hill.

Many times when I started her up I noticed the presets & clock on the radio had been reset like the battery had died. Once with the hood open i turned the key and heard a click or spark sound and it immediately started but the clock was reset. So here is my questions. Do you think i have a pcm problem or wiring problem? What would cause the radio to reset? How can check or test to find out?

The last scan i did got - KOEO 335 CONT MEM 172 336 337 KOER 116 172 336. Are all of these sensors not within correct voltage because of Pcm or wiring or both?

I have the 1994 mazda body electrical manual but need the engine electrical manual i guess.

 

[ForzdaManger]

I Also have exhaust leak would that cause any of these probs?

 

[RonD]

Your battery posts and cables need to be cleaned, also clean where each attaches to the engine and starter relay, that is causing the Radio reset, but not your engine trouble.

I would say wiring and/or PCM issue, parts are 21 years old but all failing would be a long shot.
I would start by disconnecting battery and pulling off connector on PCM, check for moisture intrusion.
You can also pop the top on the PCM and look for problem on the circuit board.

Look here: http://www.auto-diagnostics.info/ford_eec_iv

There is also a pin out diagram/legend so you cam test some of the wires.
Pull apart connectors in the engine bay and check for corrosion.

Exhaust leak on the manifold can cause engine to run rich, O2 sees extra air from the leak, exhaust leak downstream from O2 just makes noise, won't cause engine operation problem

 

[ForzdaManger]

Thank you. When i first got this truck there was a screw driven inbetween the post and term. i replaced the the terminal. I will try the other end of the cable (or whole cable).
I will read up on the info in the link and get back working on it again. Thanks so much for the info.

 

[ForzdaManger]

Your battery posts and cables need to be cleaned, also clean where each attaches to the engine and starter relay, that is causing the Radio reset, but not your engine trouble.

I would say wiring and/or PCM issue, parts are 21 years old but all failing would be a long shot.
I would start by disconnecting battery and pulling off connector on PCM, check for moisture intrusion.
You can also pop the top on the PCM and look for problem on the circuit board.

------------------------
Now it wont start at all. engine cranks. I pulled connector no sign of moisture or broke pins. Popped the top looked ok. but dont know what to look for other than something obviously broke or leaking. Went to junkyard and got another pcm, but still wont start now. I did notice that there were little pieces paper behind some components on the wall of the pcm. Is that litmus paper? Is that so you can tell if it is bad? Some red some blue.

Also I cleaned the terminals on the starter and the batt post again, and on the starter relay. Are there any other connections?

 

[RonD]

So starter motor is working but no spark and/or no fuel so engine won't start.

PCM will have "black spots" on the circuit board 95% of the time if it is the problem.

When you turn on the key does the CEL(check engine light) come on?
If not you have a blown fuse in engine fuse box.

When you turn on the key do you hear the Fuel pump come on for 2 seconds?
It is not quiet, very easier to hear.
If not then check other fuses in the engine fuse box.

When you turn on the key, leave it on and if you have a volt meter, pull off each of the coil packs connectors and test the middle wire for 12volts.
If no volts then fuse issue.

After cranking engine pull out 1 spark plug on exhaust manifold side, check if it has fuel on the tip.
Then leave spark plug out but connect it to it's wire and put it on engine(metal) so base is grounded, have someone crank engine and watch for spark.
Also listen for a "whooosh" of good compression coming from the now open spark plug hole.

Just FYI, 2.3l Lima engine with dual coil packs ONLY uses exhaust side coil when starting engine, intake side coil will start working when engine is above 500RPMs, so you can only test for spark using exhaust side coil.

 

[ForzdaManger]

Thank you sir! Before I signed on i tried to run my scanner to a key on engine off scan but mostly to do the "wiggle test" Neither would work at all. I didnt notice of the cel light came on or not. Back to the driveway!

 

[ForzdaManger]

OK. after i put in new PCM and it wouldn't start I saw this: https://www.youtube.com/watch?v=hzSyxaZ3WAg

I figured this could be the issue and if not it wouldn't hurt any thing to try, but of course I did something wrong. The truck in the video was a 95 instead of 94 like mine so the fuse box isn't exactly in the same location. So I wasn't exactly sure what slot the ground slot so I googled relays, and found this site: http://www.teamrocs.com/technical/pages/relay_basics.htm

This site says that pin 86 on a 5 pin bosch relay is the ground so i ran 2 wires from a ground screw on the body (on driver side fender wall under hood) to pin 86 on the eec relay and the fuel pump relay. I guess that wasn't the correct way to do it because it blew the two fuses to the eec and fuel pump.
That's why the my scanner wouldn't work.
Then I saw this https://www.youtube.com/watch?v=0KN_Lbf642M&feature=youtu.be this guy had fried his fuses just like me. Im going to look at that now that I know how to lift the fuse box out.

So tomorrow i will get a ride to the store to get fuses, and continue to diagnose based on your post, but im sure its not gonna start with just the new fuses because it wouldnt start before I blew them.

One other thing: After months of diggin thru many posts, i Saw some discussion on the ICM is grounded by its screws. my ICM has 4 holes and only two screws. It has the bottom left screw and the top right screw. I went to junkyard and got screws out of their ICM. The top left screw will not go in there. I assume that someone may have broken it off changing it? The bottom right screw will go all the way in but seems to be to small. A lot of discussion in post says "make sure you have all three ground screws",but i have 4 holes. Which screw is the actual ground screw? Is there a way to ground it other wise?
This truck is so confusing because my Haynes manual says that only California emission engines have the camshaft position sensor. but I do have a cps but the emission sticker says Federal. I know that's a lot of questions at one time but any help with this is one step closer to me being able to drive to work. Thank you all so much!

 

[RonD]

In the first you tube video I don't think the guy understands the fuel pump relay, his "U" shape wire isn't Gounding anything.
The relay is controlled by the computer(PCM) by grounding the coil in the relay, what he was doing with the "U" wire was connecting fuel pump to battery.

Computer in '94 is much different than '95, 1995 was when Ranger got the EEC-V computer that is still used today, 1994 and earlier use the EEC-IV.
Anyway, the computer is Grounded via it's wiring, having case grounded is good but that won't be your issue.
Good read here for EEC_IV: http://www.auto-diagnostics.info/ford_eec_iv

Fuel pump relay or EEC relay or WOT relays are about $7, so I always have a new one in the truck as a spare.
WOT(wide open throttle) relay is just used for AC so it can be removed and put in place of a failing Fuel Pump Relay or EEC relay
EEC relay powers the computer(EEC) and also the fuel pump relay, fuel injectors and coil pack.
EEC relay is the CLICK you hear when you turn on the Key.

The EEC-IV vehicles have a Test Port, VIP Connector in the engine bay, usually drivers side by the power brake booster, but have seen them on the passenger side on some.
This test port is just hanging not mounted to anything
Look here: http://www.therangerstation.com/tech_library/OBD_I.shtml

Second drawing of test port shows "FUEL PUMP" slot, that slot can be Grounded to activate the fuel pump relay if key is on and EEC relay is working.
So turn key on
Get a short wire and stick it in that slot
Touch other end of wire to metal(ground)
You should hear the Fuel pump relay CLICK
And then hear the fuel pump run
If there is a CLICK but no fuel pump sound then either Fuel Pump Fuse is blown or fuel pump is bad.
Could be wiring but............long shot, inertia switch as well but even longer shot.
Yes the under side of the relay sockets can get corroded, so worth a look.

 

[ForzdaManger]

Replaced both of the fuses that I blew but still no check engine light when key is turned on. Used test light to test all the other fuses under hood. All fuses light up on both sides. Moved Relays around and CEL finally came on. I'm currently charging the battery, so I can go to next step.

I did notice when I took all relays out of fuse box, that the test light would light up when I probed slot for relay pin # 30 on EEC Power, and Fuel pump, but not on the WOT. Is something wrong or is that not powered unless truck is running?

 

[ForzdaManger]

Computer in '94 is much different than '95, 1995 was when Ranger got the EEC-V computer that is still used today, 1994 and earlier use the EEC-IV.
Anyway, the computer is Grounded via it's wiring, having case grounded is good but that won't be your issue.

Sorry I was talking about the screws to the Ignition Control Module. Not the computer (pcm)

 

[ForzdaManger]

Now that I got the fuse and relay problem fixed and batt charged, I finally got it started. Still runs horrible. No power. I came to complete stop, let my foot of clutch, still hardly any power, stopped did it again and it drove much better. Didn't want drive much further and risk cutting out and being stuck too far from driveway. So the problem seems not to be the pcm since junkyard pcm did no difference. Want to do the wiggle test, Do you think that would help pinpoint the wiring issue, or is that different from my problems

 

[Andy D]

what do the plugs look like? If the higher speed plugs are gassed, and not firing...

 

[ForzdaManger]

I think I'm very close to getting something else. I'm about at my limit This truck is driving me crazy! and thats the only driving it will do. When I turn the key to on position. The Check engine light does not come on, and engine will not start. So I took test light and tested each fuse under hood. all fine. What else will cause the check engine light not to come on when the key is on? Any Ideas?

 

[Mark_88]

This sounds similar to what I went through recently with my truck and it turned out to be the wiring harness to the starter/relay were corroded and/or not tightened properly along with the battery posts being loose.

My fix was, fortunately, to use a spare harness that the previous owner had left with the truck...long story but the guy swapped in a 2.5 and used the 2.3 parts...it works and runs but having CEL issues...

Anyway, before i replaced the wire harness I was getting sporadic no starts and sometimes the battery would appear to be dead...or very low voltage...and sometimes a varying voltage...

Have you tested the battery voltage at any time when you are having these problems? Does the engine still crank?

At some point I thought it was my battery...but it was the wonky harness and bad connections to the ground...there should be a ground running down to the frame and then over to the side of the engine...that one may be really wonky (as in corroded and/or loose)....

Something to check...might solve some of your problems...and by the way, I also thought my wiper/turn switch had something to do with it because it would go funny and cause the battery to appear to die when I moved the switch...only thing that worked at all was the horn...even the lights were wonky...all because of that one wire harness...

Something else to look at...there should be a black/orange stripe wire from the alternator to the relay on the fender...mine was not connected well to the relay...like it was partially broken...fixed that and it helped clear up my charging problem...

So...it all sounds like bad/loose/broken wires...check them...don't just wiggle because sometimes the connection wonkyness is inside the connector...pull them apart (gently...these are 21 year old virgins) and check for corrosion...but take your time...

Breathe deeply and focus on the fix...not the PITA that it is...since that leads to giving up...most things on these trucks are actually very simple...