Acceleration hesitation

[Vineyard86manch]

I’ve now had my 86 2.5 for 6 months and I’ve put about 4K miles on it. It has developed a rough idle, to the point where it has stalled a half dozen times at stop signs (usually when my wife is with me of course). It also tends to have a hesitation or complete lack of acceleration when in gear, I’ll apply the gas and nothing appears to happen. I did plugs, wires, distributor cap and rotor, fuel filter, as well as cleaned the throttle body and done seafoam as well. What’s the next step for this novice? Thanks!

[Manche757]

42 minutes ago, Vineyard86manch said:

I’ve now had my 86 2.5 for 6 months and I’ve put about 4K miles on it. It has developed a rough idle, to the point where it has stalled a half dozen times at stop signs (usually when my wife is with me of course). It also tends to have a hesitation or complete lack of acceleration when in gear, I’ll apply the gas and nothing appears to happen. I did plugs, wires, distributor cap and rotor, fuel filter, as well as cleaned the throttle body and done seafoam as well. What’s the next step for this novice? Thanks!

Is your muffler/cat converter very old? If the inside is full of rust and collapses, it will cause big time loss of power

[cruiser54]

This^^, And clean the ground at the firewall to bare metal and re-secure.

 

Also, inspect these hoses and put a wrench on all the intake manifold bolts. they are famous for loosening up.

 

 

[Vineyard86manch]

Thanks so much for the quick replies and advice! 

 

@Manche757  I replaced the muffler a couple months ago but I’m not sure about the cat converter I’ll check it out.

 

@cruiser54 I’ll give this stuff a try. Thanks for the pic it’s helpful for a noob!

 

[Manche757]

On 11/10/2018 at 8:19 AM, Vineyard86manch said:

Thanks so much for the quick replies and advice! 

 

@Manche757  I replaced the muffler a couple months ago but I’m not sure about the cat converter I’ll check it out.

 

@cruiser54 I’ll give this stuff a try. Thanks for the pic it’s helpful for a noob!

 

Did you solve the mystery and the hesitation?

[Vineyard86manch]

I haven’t yet, I’ve been busy with other stuff at the moment. I’ve driven it a couple times in the last week and for the most part it drives real smooth but it will have these hesitations for brief periods then it goes away. Is there a way to  test the catalytic converter? Thanks for your help @manche757!

[bigmistake]

1 hour ago, Vineyard86manch said:

I haven’t yet, I’ve been busy with other stuff at the moment. I’ve driven it a couple times in the last week and for the most part it drives real smooth but it will have these hesitations for brief periods then it goes away. Is there a way to  test the catalytic converter? Thanks for your help @manche757!

 

I had the exact symptoms of "driving fine then stops accelerating, then randomly starts accelerating again."  It ended up being an early indicator that my fuel pump was going bad.  

[Vineyard86manch]

@bigmistake that was definitely another thing I was considering. With having driven my mj a lot more in the last few months than it had been driven by the previous owner in the past few years I’m thinking that the tank has had a lot of other crap in it other than fuel://

[Manche757]

7 hours ago, Vineyard86manch said:

I haven’t yet, I’ve been busy with other stuff at the moment. I’ve driven it a couple times in the last week and for the most part it drives real smooth but it will have these hesitations for brief periods then it goes away. Is there a way to  test the catalytic converter? 

Glad to know the truck is running better for you.  Most likely it is some fueling problem that Cruiser and others indicate.  I bought an 89 MJ a couple years ago with 57K miles on it. I don't usually venture further than an hour and half from home in it because of the  truck's age. Four  months after I bought it I drove it to a family reunion that was 3 to 4 hours away.  On he way, something not at all subtle happened to cause a big time loss of power. I had no idea what was wrong with it and thought the engine was doomed. I drove on to the reunion not knowing if I was likely to be stranded or not.  Then back home.  About 4 hours or so driving time after something went very wrong.   I took it to a mechanic that has worked on the truck and waited for his call.  He said rust had collapsed in the muffler and cat converter blocking the exhaust.  He started speaking about replacing those. I asked if the Y pipe was good and it was. I told him to replace everything that came after that. The heat build up under the hood had melted a few things.  He chuckled and said when he was in high school, which based on his age,  would have been 40 or so years ago, they would put a potato in the exhaust pipe of others and it would cause the same loss of power.

[Vineyard86manch]

@Manche757 It kind of feels like something is stuck in there and then it fixes itself, I wish it was just a potato:/ my mechanic says it may be a timing issue but I’m not sure. The exhaust isn’t a normal smell either. I don’t quite know how to describe it but it’s got a funk to it.