Help me please!!

[Climb over it]

Hey everybody this is my first post and I'm a jeep newbie but if I could get some help from the veterans it would be greatly appreciated! Ok so recently inquired 1986 comanche with the 2.5 TBI with a 5 speed manual and after replacing the gas tank, fuel pump and fuel sending unit along with plugs, wires distributor cap and rotor and the coil my jeep starts up just fine and idles fine BUT when I let off the clutch and hit the gas it bogs and dies out almost immediately....I've replaced every vacuum line I could find along with egr valve and map sensor and the o2 sensor but to no avail....I've checked for intake leaks and I don't see anything and the fuel injector IS working...I've done everything I can think of except maybe tps sensor and nothing is working! Please help me out!

[jdog]

Does it bog when the clutch is left in?

1988 swb 4.0 ax15 np 231 red with gray interior.

[Climb over it]

Yes even if I push the clutch back in it stalls....the clutch feels good and grabs good...the pedal itself is a little iffy (kind of sticks) but i can let off the clutch all the way and the truck is rolling and feels good,  no signs of dying out....and then I push the gas and it chokes and misfires and sputters until it dies or just dies immediately....I checked the firing order and all plugs to make they were snug and it just seems like it can't breathe or something

[Eagle]

Does the TBI have a throttle position sensor? I imagine it must -- I'd start by checking that.

 

What happens if you leave it in neutral and try to rev the engine?

[Climb over it]

Yes it has a tps sensor and I haven't messed with that yet. I can tach the engine out in neutral no problem. It will rev all day long and idle all day long without choking in neutral....only when I put it in gear and hit the gas is when it chokes.

[eaglescout526]

Hmm. You’ve checked just about every box for this problem. Course I’m curious about your sending unit, not that that is the issue. Check your TPS and make sure it’s voltage output is around 4.5-4.8(or 85% something like that) volts if I remember correctly from my TBI service manual(there’s a whole adjustment procedure, it is in Cruisers tips).  Make sure the TPS is receiving 5 volts as well. You can also play with the TPS as the engine is running and see what it does. It should bog down as you push on the sensor’s lever as the engine is idle. 

[jdog]

In any gear?

1988 swb 4.0 ax15 np 231 red with gray interior.

[Climb over it]

13 minutes ago, eaglescout526 said:

Thanks eagle I'll check that out when I get home...also I should check the wot switch out as well and make sure that's not stuck 

 

 

[Climb over it]

13 minutes ago, eaglescout526 said:

Thanks eagle I'll check that out when I get home...also I should check the wot switch out as well and make sure that's not stuck 

 

 

[Eagle]

Also check the O2 sensor, but I'd look first at the TPS.

[Cheapamanche]

Could this issue be caused by the fuel pump? Maybe it's not flowing enough fuel so its starving once put in gear. Did you replace the fuel filter?

[eaglescout526]

If it was, revving it while at idle would starve for fuel in the same manner you would putting it in gear and driving. 

[Climb over it]

Ok guys I've been messing around with it and found the wide open throttle switch was wired shut so I undid all of that and tinkered with the tps sensor and the lever and the only difference when I was messing around with the lever at the tps sensor was that when i pushed it down the engine would idle a little more rough so I unplugged the sensor and did it again and nothing happened so I plugged it back up and left it alone until I can get a new if necessary.

[eaglescout526]

Progress. Your TPS works as designed. 

[Ωhm]

You also have a Closed Throttle Switch (CTS) located on the tip of the Idle Speed Control Motor (ISCM). Check this circuit for continuity and no continuity (open or closed circuit) by pushing the tip in and out. Connect ohmmeter between pins D2-7 and D2-13 for this test. KEY OFF.

 

[Climb over it]

Awesome! I really didnt want to have to buy that lol...I took the fuel filter out to check it ( brand new by the way) and gas poured everywhere so I put it back...it doesn't seem to have a fuel delivery problem....I also put the truck on Jack stands and put it in gear...it doesn't stall in the air...in fact I shifted to 3rd before letting off....it only seems to be "underload" if u will.

 

[omega_rugal]

loss of compression? clogged inyector?

[Climb over it]

Not sure if it's a loss of compression and as far as I can tell the injector is working and spray pattern is fine....timing maybe? Or chain? 

[jdog]

bad motor mounts? its a long shot, but maybe when its under load and torquing the motor its pinching a fuel line closed.

[Climb over it]

Possibility for sure..I can check on those later today.

[cruiser54]

"I've checked for intake leaks and I don't see anything"

 

Did you put a wrench on the fasteners?  

[Money_Pits]

Another long shot might be a plugged catalytic converter if it has one? My dads Ram did some weird things (bucking/stalling) under load (ie hauling/pulling trailer) when his plugged up, but idled fine.

[Eagle]

On 8/2/2019 at 11:17 AM, Money_Pits said:

Another long shot might be a plugged catalytic converter if it has one? My dads Ram did some weird things (bucking/stalling) under load (ie hauling/pulling trailer) when his plugged up, but idled fine.

 

I was about to offer this suggestion.

[Climb over it]

Ok guys thanks so much for everything...I know it's been a minute or two since I've posted but I swapped out the ole cheapo fuel pump for a bosch and now I can drive it! But it does hesitate if I hit gas HARD for a few seconds and then it will back fire and TRY to accelerate but if I ease on the gas it accelerates almost normally...I drove it through my neighborhood and didnt stall it once...I'm pretty sure if I'm easy on the gas i could take it a little further....any suggestions?? oh and I don't have a cat on it...the exhaust is missing from the catalytic converter all the way back....

[JMO413]

Have you checked fuel pressure? My 4.0 did the same thing with a bad fuel pressure regulator.