94 b4000 need help

[bullfisher]

howdy folks, another noob here. I just accuired a 94 b4000 in good shape with under 10k on the short block 165k on the rest. runs strong. however after I start it and wait about 2 min. the idle will drop way off and almost die sometimes it will die. then spike up to over 1000 rpm. On the road its got some sputtering spots and hesitation in the 3/4 throttle range. but at full throttle its a bat outta hell and smooth.The cel comes on when it wants to but never stays on. I hate having a motor I know nothing about. I've replaced the maf, both coolant sensors, egr,dpfe,fuel filter,injector cleaner, the motor sat for a year and ran very little. I love the truck and this website! please help.

 

[BLUE "B"]

There are two things that you might want to try and this has happened to mine.

First at the back of the intake upper plenum on the driver side there is a fitting that goes into the plenum with many vacuume lines going off of it, check to see if any of them have come off or are loose, sometimes it doesn't show up right away. Often there will be a little fuel or oil that that will come up that way over the years and cause the rubber fittings to expand and come off or become loose and cause a vacuume leak and cause the engine to sputter and sometimes die at low idle. You will be able to hear a hissing noise comming from that area if it is leaking. The cure is just reattach the hose and put a zip tie around it as tight as you can get it so that the fitting wont slide off.

The other thing you can try if that isn't the problem, and you will have 2 of them, is change your oxygen sensors if you have not already done so. Hopes this helps. Let us Know.

Kris

 

[bullfisher]

b4000

I've checked every vacume line. even did the propane test.Been thinking about the 02 sensors but havent done them. thanks for the info i'll keep you posted.

 

[drmazda94]

I dont think its the o2 there costly. two thinks i would cheak the intake bolts they are know for coming loose for the idle. For the stumble i would cheak the tps they will get a burt spot and not make contact. Hope this helps

 

[bullfisher]

b4000

I put my meter on the tps today works fine.And the intake bolts seem fine also. I read somewhere that the 02 sensor can act this way and at full throttle the 02's are kinda bypassed by the computer and this is how my motor is acting. does that sound right to anyone

 

[redneckbl89]

try cleaning your idle air control valve. somtimes that has a tenency to cause your problems. it's located on the upper intake manifold. heres a pic of what it looks likehttp://cgi.ebay.com/ebaymotors/93-FORD-RANGER-Idle-Air-Control-Valve-MOTORCRAFT-CX1853_W0QQitemZ190305313229QQcmdZViewItem

 

[bullfisher]

b4000

I cleaned and tested the IAC and seemed fine. maybe its my injectors ?

 

[drmazda94]

i dont think its the injectors since they would be more noticable at full throttle, for the o2 i have never heard that i do know if you are getting bad milage it may help with that.
do you know if you have a cal missions or fed. the cal has a cam sensor cheak that and get back
Dirk

 

[bullfisher]

b4000

I dont think it has a cam sensor just coils and a crank position sensor (according to my chilton anyway). I think your right drmazda its probobly in the ignition system somewhere cause today on the freeway i could get it to backfire. what do u think?

 

[bullfisher]

b4000

bump

 

[Sasquatch_Ryda]

Get it scanned if there is a CEL, that will point you in the right direction and keep you from throwing money and parts at it that aren't fixing the problem at hand.

 

[Donnie strickland]

I agree with getting it scanned (or scanning it yourself), since you're flying blind without that.

However there is another thing you can check, that's free. A buddy of mine had a 94 B4000 which displayed the exact symptoms you describe. I checked his codes -- I can't remember the exact numbers -- but they were too rich and too lean, Banks 1 and 2. I checked for vacuum leaks and found none. He had had injector cleaner run through the fuel rail, so I doubted the injectors were the problem, since at WOT it ran great. Then I read on here that some people had had these same symptoms and it turned out that their oxygen sensors were crossed up. The left one was plugged into the wiring harness connector for the right O2, and vice versa.

So, I got out his wiring diagram for a 94 and looked down behind the motor with a flashlight. Lo and behold, they were crossed up. I uncrossed them, and it ran fine. He had been pulling his hair out wondering what was wrong. Turns out that when the transmission had been pulled to put in a clutch, the O2 sensors had been disconnected, and when they were reconnected they were crossed. So if the engine/trans have been removed and you have these problems, check the O2 sensors.

 

[bullfisher]

b4000

THANK YOU!!! mr. strickland that was the golden ticket. Plugged the o2 sensors into eachothers harnesses and bingo runs perfect. its somthing the previous owners must have tried to track down, I dont even think the cel could have told me that. its difficult to tell wich goes where, so failure to mark them after disconnecting them causes a guessing game. thank you all.

 

[Donnie strickland]

Great! Glad it worked out.

 

[akoutdoors]

Gosh. That just about made me a little teary eyed. That was awesome Donnie. You are a freakin Mazda guru!!!