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Author Topic: 5.2 popping through intake?  (Read 210 times)

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Offline WagoneerXJ

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5.2 popping through intake?
« on: September 09, 2017, 10:22:50 PM »
So I've recently completed (almost!) a 5.2 EFI Magnum swap in my 97 TJ. I'm having an issue however. It seems to not be running on all 8 cylinders.

Starts up perfectly fine, but it's not smooth like it should be. Give it some throttle and it pops and farts through the intake. Was gettin a CEL for an open injector circuit for a while. Swapped out that injector and code went away.

 I'm not sure what's going on with it  :'(. I changed out the timing chain, did head gaskets, new intake and plenum gasket etc. New plugs and wires, and I did not touch the distributor at all.

Anyone have any thoughts? Thanks!
« Last Edit: September 09, 2017, 10:24:28 PM by WagoneerXJ »
98 XJ Sport 2 Dr, 3", 33's and Bushwacker Flat Flares
87 XJ Wagoneer 5", Dana 44, 34" Swamper TSL's
97 TJ 5.2 Magnum V8 swap, 4" and 33" MTZ's- GF's Jeep
84 Mustang GT-Built 351W 5spd
97 XJ - 3.5", 31" BFG. 370,000 KMS and counting!

Offline Pookapotamus

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Re: 5.2 popping through intake?
« Reply #1 on: September 10, 2017, 10:46:03 AM »
Sounds like a timing issue, you might have to check all the timing components, recheck everything to see if you are off by a bit, check the timing chain vs the old one, check the install procedure. Also check the firing order, it sometimes is very easy to mix up two wires. Now you say you did not touch the distributor, it is possible that the timing was messed up before you got it, and installing the new chain in the correct position now means the distributor is now out.

Also do you hear any vacuum leaks at the intake? 

Start from scratch and double check everything!

Good luck!


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Offline WagoneerXJ

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Re: 5.2 popping through intake?
« Reply #2 on: September 11, 2017, 12:45:03 PM »
Thanks for the advice, I've got some investigating to do!
98 XJ Sport 2 Dr, 3", 33's and Bushwacker Flat Flares
87 XJ Wagoneer 5", Dana 44, 34" Swamper TSL's
97 TJ 5.2 Magnum V8 swap, 4" and 33" MTZ's- GF's Jeep
84 Mustang GT-Built 351W 5spd
97 XJ - 3.5", 31" BFG. 370,000 KMS and counting!

Offline cLAY

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Re: 5.2 popping through intake?
« Reply #3 on: September 11, 2017, 02:21:25 PM »
Did you pull the motor? If not are you sure that whoever did pull the motor didn't pull the dist and then drop it back in? Those Magnum motors are pretty tight to the firewall and I cann't see getting one out of a ZJ without atleast popping the cap off, it still might be tight. Maybe a truck has enough room...You also need a scan tool to set the timing.

Did you change the timing chain before putting motor in or after thinking the problem was the chain? If you did it before then I suspect you got it a tooth out. They can be a PITA to line up.

Mark the lower body of the distributor where the #1 post is. Remove cap so you can see rotor. Rotate engine so that crank mark lines up with the TDC mark. Rotor should be at or just before the #1 mark. If its pointed 180* away then roll the crankshaft over another 360* and see if it lines up. If it doesn't line up properly either your distributor is off or the timing chain is out. If it does line up then pull the valve cover and check #1 cylinder to make sure both valves are loose, this confirms the valves are both closed and are on overlap and you are on TDC compression.

I have had a bad coil cause poor running/backfiring as well.
Incompetence - When you earnestly believe you can compensate for a lack of skill by doubling your efforts, there's no end to what you can't do.
The only work I've done on a Rubi involved a chainsaw....

'93 ZJ, 5.2L, lifted/locked/36s..<gone>
'98 5.9e

Offline WagoneerXJ

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Re: 5.2 popping through intake?
« Reply #4 on: September 14, 2017, 09:59:44 PM »
Did you pull the motor? If not are you sure that whoever did pull the motor didn't pull the dist and then drop it back in? Those Magnum motors are pretty tight to the firewall and I cann't see getting one out of a ZJ without atleast popping the cap off, it still might be tight. Maybe a truck has enough room...You also need a scan tool to set the timing.

Did you change the timing chain before putting motor in or after thinking the problem was the chain? If you did it before then I suspect you got it a tooth out. They can be a PITA to line up.

Mark the lower body of the distributor where the #1 post is. Remove cap so you can see rotor. Rotate engine so that crank mark lines up with the TDC mark. Rotor should be at or just before the #1 mark. If its pointed 180* away then roll the crankshaft over another 360* and see if it lines up. If it doesn't line up properly either your distributor is off or the timing chain is out. If it does line up then pull the valve cover and check #1 cylinder to make sure both valves are loose, this confirms the valves are both closed and are on overlap and you are on TDC compression.

I have had a bad coil cause poor running/backfiring as well.

Thanks for the insight, Clay. My donor for this swap was a 98 ZJ. I pull the engine myself, it did come out, but was a pain in the arse. Never did remove the cap. I did purchase a new cap and rotor today, just in case.
 Distributor was never removed, I've never actually messed with it. I replaced the timing chain back when it was out on the stand. I made sure the marks lines up when I took off the old chain, and installed the new one
the same way. Hopefully I did this correctly!

I'll pull the cap and check to see if it's 180 out. I'm also going to check the firing order again. I'm used to Small Block Fords, new to the Mopar thing. I have a couple spare coils, I'll try one of those, just for fun
 
98 XJ Sport 2 Dr, 3", 33's and Bushwacker Flat Flares
87 XJ Wagoneer 5", Dana 44, 34" Swamper TSL's
97 TJ 5.2 Magnum V8 swap, 4" and 33" MTZ's- GF's Jeep
84 Mustang GT-Built 351W 5spd
97 XJ - 3.5", 31" BFG. 370,000 KMS and counting!

Offline cLAY

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Re: 5.2 popping through intake?
« Reply #5 on: September 22, 2017, 11:19:43 AM »
Figure it out yet?
Incompetence - When you earnestly believe you can compensate for a lack of skill by doubling your efforts, there's no end to what you can't do.
The only work I've done on a Rubi involved a chainsaw....

'93 ZJ, 5.2L, lifted/locked/36s..<gone>
'98 5.9e

Offline WagoneerXJ

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Re: 5.2 popping through intake?
« Reply #6 on: September 23, 2017, 08:22:23 AM »
Yes I did, the rocker arms were set wrong completely. Now it runs great and has lots of pull through all 5 gears.

This swap was well worth it!
98 XJ Sport 2 Dr, 3", 33's and Bushwacker Flat Flares
87 XJ Wagoneer 5", Dana 44, 34" Swamper TSL's
97 TJ 5.2 Magnum V8 swap, 4" and 33" MTZ's- GF's Jeep
84 Mustang GT-Built 351W 5spd
97 XJ - 3.5", 31" BFG. 370,000 KMS and counting!

Offline cLAY

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Re: 5.2 popping through intake?
« Reply #7 on: September 25, 2017, 08:35:13 AM »
Rocker arm setting? Aren't they non adjustable/hydraulic lifters? How did that get messed up?
Incompetence - When you earnestly believe you can compensate for a lack of skill by doubling your efforts, there's no end to what you can't do.
The only work I've done on a Rubi involved a chainsaw....

'93 ZJ, 5.2L, lifted/locked/36s..<gone>
'98 5.9e

Offline WagoneerXJ

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  • Posts: 1358
  • Bagon Wagon!
Re: 5.2 popping through intake?
« Reply #8 on: September 29, 2017, 06:39:46 AM »
Rocker arm setting? Aren't they non adjustable/hydraulic lifters? How did that get messed up?

Well, I had the cylinder heads off
for new gaskets, so upon re-assembly i did not install the rocker arms correctly. Once I was
Told how to do it ( by a very nice Chrysler dealer Tech) the engine runs great!
98 XJ Sport 2 Dr, 3", 33's and Bushwacker Flat Flares
87 XJ Wagoneer 5", Dana 44, 34" Swamper TSL's
97 TJ 5.2 Magnum V8 swap, 4" and 33" MTZ's- GF's Jeep
84 Mustang GT-Built 351W 5spd
97 XJ - 3.5", 31" BFG. 370,000 KMS and counting!