Strange bucking

[Cheapamanche]

Hello everyone, first post. Happy to join! I recently acquired a 1988 comanche eliminator with the ba10/5 transmission, dana 35. As far as I can tell, everything is stock except the wheels.

I have been scouring the internet for a couple of weeks now trying to figure out why I am having this slight bucking directly related to my speed. It is most noticable at slow speeds. For example rolling through parking lots or taking off from stops. The only way I can describe it is it feels like when someone releases the clutch too quickly. When it's happening my rpm stays steady and I will plant my foot on the floor just incase and it will continue to happen. It also happens when rolling without any gas being applied but seems to smooth out as I build speed or rpm. 

A little more info on the transmission, the 3rd and 4th synchro is nearly gone and sometimes clunky when shifting into first at a stop. Reverse is also hard to get into SOMETIMES. I can put it in 2 and then it will go into reverse normally. I have a brand new clutch, slave, master and flywheel. All LUK brand. Could this be a symptom of the transmission? The mount is good as are my engine mounts. New fluid in tranny and rear differential and the engine has no vacuum leaks. TPS was set and I cleaned my IAC and throttle body. Any suggestions would be very appreciated. I plan on keeping this truck for the next 200 years so I want to get everything buttoned up on it.

[Jeep Driver]

Your grille is upside down, that'll maker her buck every time. 

 

Those wheels could be original. 

 

 

As to your problem..........wild hair guess.............O2 sensor? 

[Cheapamanche]

I have since flipped the grill right side up. The grill was my first guess too hehe. I didnt think to check the o2 sensor. Interesting. I'll have to check how to test them if possible. Thanks for your suggestion. So you think it sounds like an engine related symptom? It does look new from outward appearance. I'll check it this weekend.

[87MJTIM]

In order to see what the computer sees, you should purchase a Renix Engine Monitor (REM) from www.nickintimedesign.com. This will let see how all the sensors are functioning/ or not functioning. 

 

Also, check out Cruiser’s Renix Tips at www.cruiser54.com.  

 

As for the bucking issues, does yours have a cat?  How old is it?  A clogged cat caused similar issues for me (although across the whole RPM range. 

 

Welcome to the addiction.  Beautiful MJ. 

 

complete your signature: year, engine, transmission, any modifications made to it and your location. That way when people read your posts they can see what you have and where you are. 

[mjeff87]

Quick check, just unplug it and see if the bucking goes away.  My old 2.5L had the same symptoms once (happened at the same spot on the way to work every day, like clockwork) and it was the O2 sensor.  While it was acting up, I got out and unplugged it and it cleared up immediately.  New sensor, never had the problem again.

[89 MJ]

Slughtly unrelated, and correct me if I am wrong, but I throught all Eliminators has D44s and I thought the Eliminator package started in 89. 

[cruiser54]

Before anything else, go to www.cruiser54.com and complete tips 1 through 5. 

 

Plugs, wires, cap and rotor should be replaced every 30,000 miles. How are they?

 

With the engine cold, check the intake manifold bolts to be sure they are snug. 

[Cheapamanche]

1 hour ago, cruiser54 said:

Before anything else, go to www.cruiser54.com and complete tips 1 through 5. 

 

Plugs, wires, cap and rotor should be replaced every 30,000 miles. How are they?

 

With the engine cold, check the intake manifold bolts to be sure they are snug. 

I replaced the plugs, cap and rotor but not the wires yet. I'll do that this evening. I went through and snugged the intake bolts down a couple of days ago.

 

3 hours ago, mjeff87 said:

Quick check, just unplug it and see if the bucking goes away.  My old 2.5L had the same symptoms once (happened at the same spot on the way to work every day, like clockwork) and it was the O2 sensor.  While it was acting up, I got out and unplugged it and it cleared up immediately.  New sensor, never had the problem again.

I'll try unplugging it and let everyone know what it does.

3 hours ago, 87MJTIM said:

In order to see what the computer sees, you should purchase a Renix Engine Monitor (REM) from www.nickintimedesign.com. This will let see how all the sensors are functioning/ or not functioning. 

 

Also, check out Cruiser’s Renix Tips at www.cruiser54.com.  

 

As for the bucking issues, does yours have a cat?  How old is it?  A clogged cat caused similar issues for me (although across the whole RPM range. 

 

Welcome to the addiction.  Beautiful MJ. 

 

complete your signature: year, engine, transmission, any modifications made to it and your location. That way when people read your posts they can see what you have and where you are. 

I have seen some YouTube videos of nickinthetimes and I saw his scan tool. That's pretty sweet. I will definitely lately check it out. I just wasnt sure about it but if people here have tried it with success I will give it a whirl. I'll check out the 1-5 tips and re post after I start digging into it.

[Cheapamanche]

Hey guys, I was doing some digging around and the topic of the egr valve came up and it remi ded me that I forgot to mention that I had capped the vacuum lines running to the egr valve a while back. I read somewhere that you don't have to use a block off plate by just blocking the vacuum lines to the egr. Is this true or do I need to block it off with a plate?

 

I did complete steps 1-4 so far. Also while inspecting I noticed the both hoses to my canister look very rough. I'm not exactly sure what the purpose of the canister is. Is that just venting for the gas tank or can I be a source of vacuum leak?

 

I hope that some day I can be as helpful as everyone on here is.

[Cheapamanche]

Well it turns out the bogging ended up being 2 vacuum leaks that I missed. Doh! The first one was the underside of a vacuum hose attached to the egr valve. The second was my throttle body gasket. Apparently I had ripped the gasket when removing it to clean. It never showed up in my smoke test. I guess I don't have enough lung power with the cigars anymore.

   Thanks everyone for all the suggestions.