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1994 Ford Ranger misfire and hesitation - really need help

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Old 03-09-2012, 07:38 PM   #1
danmm7
San Jose, CA
1994 Mazda B4000 RWD
 
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Question 1994 Ford Ranger misfire and hesitation - really need help

I have been dealing with this problem for a few months now. I received a lot of useful advices on other forums, i tried most of them, but i am still dealing with the same issue. I did replace a lot of parts and i did a lot of testing. I feel really stuck!! I've sunk a lot of money into this old truck buying new/used parts, swapping one part for another and i still have the same problem with very little improvement. Here is the latest.... i would appreciate any feedback, advices, tips, etc.

I have a 1994 Mazda B4000 truck which is essentially a Ford Ranger with 4.0L V6 and 5-speed M/T, 2WD. Truck has 101k miles. California edition (emission)

Here is the problem:
My truck feels as if it’s misfiring/hesitating and shaking/vibrating during acceleration and it feels underpowered. Almost as if I am in the wrong gear at a low speed. Also, quite often, while I am accelerating and I press on the gas harder, I can hear/feel some sort of loud “detonations” (for lack of better word) happening somewhere under the hood, in addition to feeling the lack of power. It sounds like “knocks” inside the engine or inside the exhaust. It's hard to describe but it is very obvious inside the truck and i am sure people outside can also hear it. If i am gentle with the acceleration - the detonations/knocks are not happening.

The problem seems to be more obvious when the truck is warm. Only sometimes, even though for only a short time, it just starts to run fine without any issues and then all of a sudden the misfires and lack of power are back. Feels like something is making a bad contact and as soon as it makes a good connection – the truck is back to normal.

** Currently, the OBD scanner shows NO error codes in the system. I used to have code 216 for a long time but I just fixed it a week ago with a new Camshaft sensor. **

Here is what I have done/checked and replaced so far with no results:

- New spark plugs (autolite) -2nd set because one plug was cracked from the new set I installed 3 months ago.
- New generic brand spark plug cables (2-mo old)
- New coil pack (2-mo old). I tried with a used one before from a junk yard – got same behavior.
- New crankshaft sensor (I was getting “CID error“ code – OBD 216 for a looong time but truck drove fine)
- New camshaft sensor (this fixed the OBD 216 code finally but it did not fix the misfire/detonations/lack of power)
- Newer fuel filter (2-3k miles old)
- Newer air filter
- Cleaned MAF sensor with MAF sensor cleaner twice – made no difference at all
- Ran SeaFoam cleaner thru intake – lots of smoke out of exhaust but made no difference
- New injectors – installed 6 rebuilt OEM injectors and new intake manifold gaskets – made no difference at all
- New CAT converters installed a month ago – made no difference
- I measured the fuel pressure using a pressure gauge and it showed pretty much everything in spec. A bit border line low, but within spec.
- I tested for spark at each plug, using a $10 spark plug tester and I got spark on all 6-cyl @ idle.
- Truck starts easily - every time. No need for excessive cranking.
- My idle seems to be very stable and healthy at all times. If i rev the engine RPM in "neutral", there are no issues or hesitation!!
- ** The misfire/hesitation starts to happen once I start accelerating, especially between 2nd to 3rd and 3rd to 4th gear, etc. Sometimes i even hear the detonations/shaking leaving from a stop light. **
- After driving the truck for awhile, when I stop at a light, I can feel the engine idling fine but vibrating/shaking more than it used to. Occasionally - it will become smooth and then start shaking again. Feels like a cylinder may be off...on...off.
- Something interesting: last week, after I replaced the Camshaft sensor (it required removing of the intake, fuel rail, etc to get to it) I took the truck for a test drive and for the first 5-7 minutes of driving it drove 95% fine!!! There was very little engine vibration under acceleration but I did not feel any misfiring, any detonations or lack of power. The truck was much smoothers and quicker. Took it on the freeway, accelerated to 75-80mph with almost no issue (slight vibration under load)…drove for 1-2 minutes in 5th gear fine, …. I Stepped on the gas to take it to 85mph and I started to feel the hesitation again. I felt and heard a few very obvious “detonations” under the hood too when pressing the gas. The truck went back to the old behavior. My hope that the new Camshaft sensor fixed everything disappeared. The problem must be somewhere else and I don’t know where to look. Something did fix it for a few minutes. Not sure what.

Like i said - i am really stuck!!! Not sure where to look next.

Sorry for making this so long. If you can give me any pointers or ideas, I will be very thankful.
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Old 03-09-2012, 08:58 PM   #2
nexis
Cedar Rapids, IA
93 Limited
 
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You said that you checked the fuel pressure, I assume this was checked at idle?

When you pulled the plugs to change them out, how did they look, was there any glazing or deposits. Was the insulator white, grey or black??

If you still have the fuel pressure gauge, see if you can rig it up so you can see it while driving, you stated that the pressure was a little on the low side when you checked it. If your fuel pump is on its last leg and having problems keeping up at idle. When your at speed it may be dropping out and not proving enough fuel.
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Old 03-10-2012, 02:03 AM   #3
danmm7
San Jose, CA
1994 Mazda B4000 RWD
 
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Originally Posted by nexis View Post
You said that you checked the fuel pressure, I assume this was checked at idle?

....

If your fuel pump is on its last leg and having problems keeping up at idle. When your at speed it may be dropping out and not proving enough fuel.
Yes, i did the fuel pressure at idle, following a procedure in the manual.

Just curious, if my fuel pump is on its last leg, wouldn't there be ANY other symptoms? Like... during starting the car? Or during idle?
When i rev up the engine at a stop light, i can rev it as high as i want...and it does NOT hesitate at all. Issue is there only when truck is moving and i am accelerating.

Ideas?
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Old 03-10-2012, 06:03 AM   #4
wantdeath
NW Ohio
1992 Mazda Navajo
 
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you dont use very much gas to rev it up with no load. the motor spins up so fast that any pressure you built up by idling would be enough to rev it like that. my ranger ran the exact same way your describing when i first bought it. changed the fuel filter and it was gone instantly. maybe change your pump. or fuel regulator. have you done a vacuum check on it? i know nobody does that anymore but it will tell you if you have a vacuum or manifold leak. my fuel pressure tester has a vacuum side on the gauge.
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Old 03-10-2012, 11:27 AM   #5
nexis
Cedar Rapids, IA
93 Limited
 
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Agree very much with wantdeath, Its an issue of delivery, seeing as you said you already replaced the fuel filter i would again suggest trying to record pressure under load. It could be the pump about to crap out, or the sock on the pump could be gumed up. Im sure that somone else will throw in their ideas soon enough, but thats my 2c
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Old 03-13-2012, 12:37 AM   #6
danmm7
San Jose, CA
1994 Mazda B4000 RWD
 
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Smile Update - Fixed!!!

Wow!!! I am VERY happy to report that the problem was fixed.

I replaced the spark plugs again and i put new Bosch ignition cables. The 'old' plugs were less than 6 months old with less than 2k miles on them. They were Autolite Platinums. The 'old' cables were some generic cheap brand, but also only 2-3 months old.

I installed brand new, properly gapped NGK Platinums and new cables.... and miracle - now the truck runs like new. Smooth and fast. No hesitation at all. I drove it for 20-30 miles.... in the city, on the freeway, under load, gently, fast - it just runs and runs the way it is supposed to do. I am 100% sure that whatever the problem was - it was related to the spark plugs or the cables or both. I can't really explain to myself what was wrong with the 'old' parts given that they were pretty much new too. I would never find out, i guess.

I had hesitation issues before i replaced the original plugs/cables and i know that the problems did not start when i installed those Autolites. MY original coil pack had one of the 6 connectors kind of burned out/damaged, so when i replaced it, this was when i put the new Autolites and cables. Since I still had the hesitation, i moved to fixing other stuff and sensors, ruling out the plugs. Looks like i was wrong the whole time.

Either way - problem fixed! Hopefully it won't return ever again.
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Old 12-10-2014, 07:16 PM   #7
djmauricio
1994 - Ford Ranger 2.3L
 
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orange

Just bought a similar truck 2 months ago, i did change everything and still had same problem with it...
So i decided to remove the PCM and open it completely..
And I found some signs of water and corrosion on some elements and on the other side I had to solder some components that looked weak due to corrosion..


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Old 12-10-2014, 07:39 PM   #8
larrydd999
Elite Explorer
Port Angeles, WA
92 XLT, 94 Limited
 
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Glad to hear you fixed the long-term problem. It's always satisfying to get to the end, and great to have you report your findings. Dj, the lower side of some of the IC's look bad compared to the upper (in the photo). Is that the corrosion that you saw? Was the processor unit giving trouble? (Don't mean to start a new thread, just curious.)
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Old 12-11-2014, 12:29 PM   #9
djmauricio
1994 - Ford Ranger 2.3L
 
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Lightbulb

Yes its the processor unit that was giving trouble..all symptomps mention on this thread are complete gone after PCM repair...I don't really know how long its going to last on working conditions due to once corrosion its on something you can't never get it to work as before..But if problem comes back Ill just buy a used PCM to solve the problem..
Lot of mechanics and people will never believe that PCM was the problem of the truck and its always the last resort they go after they have spent so much money changing parts..
Also PCM was not giving any codes on scanners and if it gave me some it was CRAZY CODES I was getting & over 15 codes and different all the time..LOL..And now I got clean codes 111..
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Old 12-14-2014, 10:17 AM   #10
shamal
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Victoria, BC
 
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good post, good fix !




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