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code 76 on my '94.

$700later

NAXJA Forum User
Location
Jacksboro TN
well, i may have narrowed my problems down to the code 76. correct me if i'm wrong but code 76 is something like "fuel pump resistor bypass relay circuit" i've searched and found few results.

my jeep is a '94 4.0 5 speed, running extremly rich and won't run smooth enough to be driven. fuel pressure is 45-50.

i've replaced:
1.spark plug wires
2. spark plugs
3. o2 sensor
4. coil
5. dist. cap & rotor button
6. coil pickup
7. cps sensor
8. map sensor
9. ecu/computer

so whats next??? thanks! :laugh3:
 
Is that 45-50 psi at idle? If it is, then check the vacumn line to the fuel regulator as that's too high. Should be more like 31 psi idling with the vac line hookup up. Idling without the vac line hooked up should be around 39 psi per the FSM.
 
The FSM also says the 94 does not have a ballast resistor, so the 76 code might actually mean something else.

"For the 1994 model year, the ballast resistor and
ballast resistor bypass relay are no longer used to
control the fuel pump circuit."
 
yes at idle, i'll have to check it again to make sure, vacumn line at the fuel regulator? i thought the filter doubled as the regulator...shows what i know. i'll go look for it.

and i thought i didn't have a ballast resistor, that must be why i couldn't find it!

thanks for the help.

and hello from a Lawson in Tennessee. i doubt we're related though.
 
add fuel pressure regulator to the list, problem didn't change.

You changed the regulator and it is still reading 45-50 psi??

That pressure needs to be at 31/39 as posted earlier.
 
i checked the pressure myself just now and it stayed between 37-40 with me working the throttle to keep it around idle. the first time it was checked by a mech. so i'm just going by what i saw on the gauge with my own eyes now.

also, if i unplug any vacuum lines on the intake manifold, it will idle on its own and CAN be driven, maybe that is some kind of clue. doesn't run perfect but has decant power.

for some reason the motor limits at 4k also. that ain't right!
 
could something be choking the motor of air? especially at idle aka when i don't have my foot on the gas?

i'm starting to believe it isn't a fuel issue, but i'm still unsure what code 76 even means.
 
Were the 14 and 24 codes from trying to run with those sensors unplugged? Have you tried unbolting the exhaust at the exhaust header to see if maybe its a plugged cat?
 
Were the 14 and 24 codes from trying to run with those sensors unplugged? Have you tried unbolting the exhaust at the exhaust header to see if maybe its a plugged cat?
as far as the codes go, 14 relates to the map sens. and i replaced it with no change so i put my old map sensor back in so i could return the new one. i think today was the first time it threw the 24 which is "Intake air temp. sensor voltage high" according to about.com..

and as far as the cat goes, yeah i thought the same thing a couple of months ago so i just did it the redneck way and drilled a couple of holes right at the front of the cat. i didn't mind doing that cause it needs exhaust work anyway...there doesn't seem to be excessive pressure at the holes anything weird. but i still wonder about the cat, i mean it has 200,000 miles on it....yeah i'll drill some more holes, its free so nothing to lose there.

thanks for the help!!:wave:

does anyone know the symptoms of bad fuel injectors, bad mass air flow, or a bad tps??

those keep coming to mind, esp sense i have normal fuel pressure at idle but rich exhaust smell.
 
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If you have a meter, you could double check that the tps and map sensors have a decent ground and +5 volts. Could be a bad ground in the sensor circuits and adding a new ground might help. Not sure what you should see for a signal on the map, but you've replaced that with no change. The TPS you can check that it changes smoothly with the throttle (analog meter is much easier for this). It should run without the tps connected, but stumble trying to accelerate and no shift worth a damn.
 
You've replaced a lot of parts already not to know the mechanical condition.

you're right. i don't have the tools to check compression, the jeep has normal power when i mash down on the gas, i've drove plenty of xj's and this 4.0 has the same power as any other renix or H.O. also the throttle is very responsive, if it was a compression problem i would expect to notice it being sluggish or smoking.

should i check compression in spite of the motor running like a top?

i had a 2.8v6 xj 4 years ago so i do know how a motor drives when compression is less than great, that jeep was a "check the gas and add some oil" kind of jeep.
 
well i could be getting closer to a fix, today i took the idle air control valve off and it was covered in carbon/black gunk. i cleaned it and put it back in, started the jeep and after a couple of start and stalls it started and idled on its own at around 400rpm. took he around the block and it ran much better than before, it sat in the driveway off for 10 minutes then took it back out and drove about 10 miles, the CEL was still on so i decided to pull over, un hook the ground (take a pee on the side of the road) so to hopefully reset the computer. then i go to start it and it won't start. turns over about twice, fires for a split second then dies. (which is what its been doing) so i unplug a couple of vacuum lines on the intake manifold to maybe give it some air, i try again 3 or 4 times to start, no luck. i let it sit a couple of minutes and try and BAM it starts! i rev it a couple of times before i take off. then i drop the clutch, cut half a dougnut in the gravel to turn it around to head back home. after i drive a couple of miles i noticed it started to idle high, which is normal with a vacuum leak, so i pull over and fix the vac lines, idle drops to 500-700. i drive home.
 
No, I don't believe it would prevent starting.

With the run rich problem your engine may just be full of carbon. Maybe grab some Seafoam or similar product, follow the directions for running it into the intake through the vacuum booster line.

Might consider pulling the plugs and cleaning them, maybe a couple of times until they stay normal.
 
yeah i am dieing to seafoam it, it only cost $10 but i spent around $200 on parts this weekend so i'm going to try to wait til next weekend for seafoam. the plugs are new but i'm sure they're dirty from me tinkering with it all the time.

an iac valve is on next weekends list too, i have an extra computer that i could trade at my local pull-part for a complete TB though, but its about 70 miles away so i need to factor the cost of that in too. a new IAC is about $40.

eveything in this jeep seems to be all carboned up.

hey joe, i read somewhere that i bad pcv valve could cause carbon build up. you know anything about that??

hope everyone had a good safe 4th of july...

i blew up 2 5 gallon buckets, each one into atleast 15 pieces!
 
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