Fixed exhaust leak engine now runs poorly

[Lunar302]

So I had a really bad exhaust manifold leak on the drivers side That I ignored for a few months I finally had the time to replace the gasket didn't do anything else just replaced that gasket besides unplugging the sparkplug wires now it stumbles at idle and shakes when in gear the only thing that I've been able to come up with is maybe the catalytic converter on that side got clogged and is causing to much back pressure since it wasnt doing this before I replaced that gasket just in a attempt at fixing it I pulled all the plugs on the drivers side and cleaned them up and checked them to see if I damaged them pulling the manifold out of the engine bay and that didn't fix my issue I've also checked the codes and the only code it's throwing is a p0118 code for my engine coolent sensor witch i got rid of so I could have a mechanic water temp gauge and I did that about a week or two ago I'm gonna try replacing the plugs on that side and see if that does anything also gonna try taking out a 02 sensor on that side to see if it's a back pressure issue also it is making a poping sound out of the exhaust which it wasnt doing before and since I have no muffler its a lot more noticeable I also run a bottle of STP zinc additive witch ive heard can clog up cats so if y'all have any ideas of what it could be send me a message

 

[SofaKing95]

Lots to unpack:

• Excess back pressure could be what blew out the gasket to begin with
• Plugs may have been damaged, may be worth replacing all of them (as you mention replacing just that side, should be replaced as full set) -- but more importantly are you sure you didn't damage the spark plugs wire when removing...hopefully you pulled by just the boot and not on the wire. Could be worth the time to check resistance/continuity on all the spark plugs wires
• Which temp sender did you disco (gauge or ECU)? You have two -- if you disconnected the ECU temp sender, that could cause poor running.
• Generally speaking, engine additives (snake oil) are almost always a bad idea

 

[Lunar302]

Lots to unpack:

• Excess back pressure could be what blew out the gasket to begin with
• Plugs may have been damaged, may be worth replacing all of them (as you mention replacing just that side, should be replaced as full set) -- but more importantly are you sure you didn't damage the spark plugs wire when removing...hopefully you pulled by just the boot and not on the wire. Could be worth the time to check resistance/continuity on all the spark plugs wires
• Which temp sender did you disco (gauge or ECU)? You have two -- if you disconnected the ECU temp sender, that could cause poor running.
• Generally speaking, engine additives (snake oil) are almost always a bad idea

Both sensors I had my gauge plugged into the ECU side but swapped it because it would only work with the heat on I already ordered a new one since I was gonna replace it anyways since I broke the connector off on the old one

 

[Lunar302]

Lots to unpack:

• Excess back pressure could be what blew out the gasket to begin with
• Plugs may have been damaged, may be worth replacing all of them (as you mention replacing just that side, should be replaced as full set) -- but more importantly are you sure you didn't damage the spark plugs wire when removing...hopefully you pulled by just the boot and not on the wire. Could be worth the time to check resistance/continuity on all the spark plugs wires
• Which temp sender did you disco (gauge or ECU)? You have two -- if you disconnected the ECU temp sender, that could cause poor running.
• Generally speaking, engine additives (snake oil) are almost always a bad idea

also about less than 10k miles ago i replaced the plugs and wires and i did pull on the boots of the wires when i was replacing the manifold gasket

 

[SofaKing95]

Both sensors I had my gauge plugged into the ECU side but swapped it because it would only work with the heat on I already ordered a new one since I was gonna replace it anyways since I broke the connector off on the old one

So is the ECU temp sender hooked up and working properly? Did you confirm using scan tool viewing live data?

 

[Lunar302]

So is the ECU temp sender hooked up and working properly? Did you confirm using scan tool viewing live data?

No I just threw it away since to connector broke on it but I've been driving it for a few months with that sensor not being hooked up at all and I haven't had any issues until I fixed the exhaust leak but I did order a new one since i was gonna replace it

 

[410Fortune]

You likely broke a spark plug wire or two
Or got the firing order wrong

There are two coolant sensors
One is for the pcm and one is for the dash

It is ok to remove the one for the dash and run your own gauge
The one for the pcm is absolutely necessary and must be in place

It is not a 02 sensor it is not a clogged
Converter… plug wires are very sensitive to being taken on and off the plugs, parts store plug wires are cheap and break easily

You must re install your cts for the pcm if you want it to run correctly and then I would re visit your work and carefully check the plug wires

 

[Lunar302]

You likely broke a spark plug wire or two
Or got the firing order wrong

There are two coolant sensors
One is for the pcm and one is for the dash

It is ok to remove the one for the dash and run your own gauge
The one for the pcm is absolutely necessary and must be in place

It is not a 02 sensor it is not a clogged
Converter… plug wires are very sensitive to being taken on and off the plugs, parts store plug wires are cheap and break easily

You must re install your cts for the pcm if you want it to run correctly and then I would re visit your work and carefully check the plug wires

i replaced the pcm cts didnt really seem to do anything also cleared the codes and the p0118 code isnt popping up anymore also replaced the plug wires that helped a little but i can still feel its down a cylinder or two but around 3000 to 4000 rpm i can feel it pick up a cylinder occasionally around that rpm also i looked on here and found the firing order and its right

 

[SofaKing95]

i replaced the pcm cts didnt really seem to do anything also cleared the codes and the p0118 code isnt popping up anymore also replaced the plug wires that helped a little but i can still feel its down a cylinder or two but around 3000 to 4000 rpm i can feel it pick up a cylinder occasionally around that rpm also i looked on here and found the firing order and its right

Take a look at link below...while you don't have coil packs, maybe needs a ignition new coil. Or pull off the cat(s) and make sure they are still good - i.e., that you can see light through the honeycomb

Feels like misfire but no codes

4.0, I seafoamed my ex a week ago. Ever since I have had issues. At idle rpms drop off and come right back sparatically. Under load and while driving, I feel like I am being rocked back and forth. Put it in N and it goes away. it feels like a misfire but I have no CEL on. What the heck did...

www.explorerforum.com

 

[Lunar302]

Take a look at link below...while you don't have coil packs, maybe needs a ignition new coil. Or pull off the cat(s) and make sure they are still good - i.e., that you can see light through the honeycomb

Feels like misfire but no codes

4.0, I seafoamed my ex a week ago. Ever since I have had issues. At idle rpms drop off and come right back sparatically. Under load and while driving, I feel like I am being rocked back and forth. Put it in N and it goes away. it feels like a misfire but I have no CEL on. What the heck did...

www.explorerforum.com

im pretty sure its fixed i replaced the ecu water temp sensor didn't do anything but fix another problem i had i replace the spark plug wires it helped but it was still down a cylinder i could feel it come back every now and then i replace the drivers side spark plugs and it runs a lot better all cylinder seem to be firing no more shaking while im accelerating and my problem i had before was my ac didn't work but i had a feeling it was the ecu water temp sensor since it was the only thing i touched from when my ac worked and when it stopped and also i didn't replace all the spark plugs because i replace all of them less then 8k ago probably a lot less my guess what happened was when i was replacing the exhaust manifold gasket a valve was slightly open allowing some pb blaster to get into the cylinder and fouled a plug when i started it up after replacing the gasket i did use a entire can of pb blaster on the manifold bolts so i wouldn't be surprised if thats what happened

 

[410Fortune]

Engine should run baby butt smooth at warm idle

Spark Plugs that run in cylinders that are not firing can easily Get fouled and then need cleaned, gapped and reset or replaced

Any miss in a 4.0 with no trouble codes is 95% of the time in the ignition plugs or wires the other 5% would be fuel pressure

Anything else usually is followed up with trouble codes

 

[allmyEXes]

When the pcm coolant temp sensor isn't functioning, the pcm will think that the engine is cold and stay in open loop.
Others may have said it, individually check the ohms of the plugs and wires, even new parts to make sure that they are good.