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Old 08-26-2014, 08:59 AM   #1
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Join Date: Aug 2014
Location: carstairs Alberta
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engine issues

To begin with some history. 88 Grand Wagoneer 4.0 400,000 km. Runs great doesn't use oil. PO had overheating issues. He changed rad, water pump,thermostat, HG, the head. He gave up and sold it to me for 100 bucks. Turns out the rad cap was buggered and the block needed to be burped.
It seemed to be running cool for me so I changed the thermostat just to be sure. In the process somehow the MAP sensor hose came off.....took a while to find that. When he changed the head he didn't get the manifold tight. With all the barking and spitting it did the manifold gasket started leaking which made it bark and spit some more.
I got a new gasket and installed it. As I was putting in the last manifold bolt I look down a d see the manifold is cracked I at least 2 places. I drove it home from my friends shop like that. Cracked manifold and no pipe on donut flange. It ran just like new except really loud and low on midrange torque. So now I pull the manifold get it properly welded get new manifold to pipe studs and install the exhaust pipe. To get the rusted mess out I had to cut the pipe about 18 inches from the donut. It's getting all new exhaust here hopefully this week.
My question here is now it starts and idles perfectly dead nuts smooth BUT as soon as rpm hits about 1400 under load it bucks and spits until about 2200. It's ok under harder acceleration but not right. You can hear where about 3000 she starts to come in tune and really pin her ears back and flat out goes. Is it just the short exhaust screwing things up or do I have something else going on. It's a second vehicle so it's not a #1 priority for money. I just don't want to dump an exhaust on it and have it still not run.

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Old 08-27-2014, 05:28 AM   #2
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If i understood correctly you have no exhaust except for 18" past the donut? it won't run right like that. The O2 sensor is picking up the undiluted air scavenging back up the pipe. Put exhaust on it and recheck it.

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Old 08-27-2014, 06:45 AM   #3
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Originally Posted by JMickey View Post
If i understood correctly you have no exhaust except for 18" past the donut? it won't run right like that. The O2 sensor is picking up the undiluted air scavenging back up the pipe. Put exhaust on it and recheck it.

Good idea. Have you checked for vacuum leaks as well? A smoke test would probably be a good idea.
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Old 08-28-2014, 07:01 AM   #4
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Location: carstairs Alberta
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Yeah I figured it might be a scavenging thing. The goofy part is it ran really sweet with just the manifold and no pipe at all. It definitely is super rpm sensitive. At 3000 you can hear it really smooth out and haul ass. I actually have it at the shop for a full exhaust right now. I knew the exhaust was totally junk but I hate to spend money on that if it still won't run and I still can't drive it. I'm thinking that exhaust is definitely part of the cure
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Old 08-28-2014, 04:14 PM   #5
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Update had the exhaust done. It's much quieter now. Still runs like crap. Neighbor who is a mechanic took a ride with me, figures it's a vacuum leak.
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Old 08-28-2014, 04:31 PM   #6
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Update had the exhaust done. It's much quieter now. Still runs like crap. Neighbor who is a mechanic took a ride with me, figures it's a vacuum leak.
I think he's right.
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Old 08-28-2014, 10:22 PM   #7
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Location: carstairs Alberta
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Found the problem. LOOSE DISTRIBUTOR HOLD DOWN BOLT. The distributor always rattled around from day 1 for me. Just a bit in each direction and then a solid stop. So I ASSUMED that was normal. Today my brother and neighbor are looking at it and noticed the distributor. They freak out and say you have to tighten that. Tightened it took it for a test drive no misfire. Never would have dreamed that was the issue

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