02 P5 2.0L engine missing even after plugs and coils replaced

Hey guys, so one possible result of me fixing the blower for AC on this 02 Protege5 (based on y'alls awesome advice) was to worsen the engine missing problem I've got.

Before I go further, I should state that this poor thing has probably been ragged to death/driven like it was stolen and had almost 140k miles already when I bought for cash last year off craigslist. It clearly had been in a front right collision but the guy did a decent job replacing and painting the hood. He replaced the timing belt and water pump so I was hoping to get to 200k miles. Also, it is really fun to drive as I'm sure y'all already know. I wish I had had one of these things in its prime!

The missing issue popped up a few thousand miles after and when it got worrisome, I took it to a local mechanic who said he'd start with the spark plugs, then ignition coils, then if still missing, go for the intake manifold. My research has pretty well checked out with that diagnosis. I had him replace the plugs and coils which seemed to tone it down for a while but now it's back and getting worse.

There's a weird pattern - if I drive after letting it sit overnight, then let it sit for 2 or more hours, it's fine, doesn't miss. If I make a quick grocery run, it misses once I'm on the return trip. So, it's OK for going to work for a job and back but that's it.

Now it's even worse - I think running the compressor for the AC has got it all angry and it just feels like it's about to wobble out of the dang hood.

Should I go ahead and have the intake manifold replaced? That's easily gonna be a 600$+ job that I can't do. I'll do it if there's a good chance it'll kill the missing problem.

I keep getting the OBD-II code for P033 I think, for the 3rd plug. Every time. I'm wondering if maybe I got a bad deal on the plug/coil work. I could try switching plug and/or coil around, maybe?

Well anyway thanks for reading all this and any advice is welcome. I'm at least a year out from affording another car.

kyuudou in TX

Update: I rescanned the codes and I'm not sure if I missed it before but along with P0303 (same 3rd cylinder, a "current" code) I'm getting P0660 (Intake Manifold Tuning Valve Control Circuit/Open Bank 1) which is under "pending" codes.
 
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pcb

The Diagram Dude
:
2002 MP5
Coils for our car have been a real source of problems for a lot of us.
They have been known to be bad, right out of the box, and are probably the only part that I might consider going with OEM.

They can test as fine with a bench test then fail on the car.

If your misfire code is cylinder specific, then I would swap the coils and see if the misfire follows the coil.

Hitachi coils are known to be quality coils and I think throwing a couple of quality coils at the problem is worth the price.



There is a huge list of possible causes for a random misfire and a lot less for cylinder specific and people have been chasing a misfire just to finally find out that the brand new coils are failing.





 

pcb

The Diagram Dude
:
2002 MP5
Update: I rescanned the codes and I'm not sure if I missed it before but along with P0303 (same 3rd cylinder, a "current" code) I'm getting P0660 (Intake Manifold Tuning Valve Control Circuit/Open Bank 1) which is under "pending" codes.
(I missed your update.)

You probably need a new VICS solenoid valve. Most of us have had to replace it.



Here's a thread about it.
 

pcb

The Diagram Dude
:
2002 MP5
A failing VICS valve could have something to do with your misfiring. Check the condition of your spark plugs if you swap your coils for a test. Check the condition of plug #3 specifically and make sure your plug wires are fully seated.

Most of us are using NGK V-Groove regular copper plugs. They give the strongest most reliable spark. They don't last as long as other plugs but they only cost $1-$2 each and are easy to replace.

Some injector cleaner in your gas could help with the misfiring.

You could have a fouled injector.
 

pcb

The Diagram Dude
:
2002 MP5
..., I took it to a local mechanic who said he'd start with the spark plugs, then ignition coils, then if still missing, go for the intake manifold...

Should I go ahead and have the intake manifold replaced? That's easily gonna be a 600$+ job that I can't do. I'll do it if there's a good chance it'll kill the missing problem.

I'm having a hard time seeing how the intake manifold could be "bad" unless the manifold is cracked or warped, but it may just have a bad gasket.

And you could check the intake system for leaks as well.

" MAF sensor contamination•
Excess air suction in intake-air system (between MAF sensor and dynamic chamber)"

Try replacing your air filter. It's part of regular maintenance anyway.

A dirty air filter can create suction in the air intake.
 
:
2003 P5
When you changed the coils, did you replace the plug wires too? My son's P5 developed a intermittent misfire. By intermittent it misfired most of the time and sometimes ran smoothly.

In my case it was the spark plug boot arcing directly to the head rather than through the sparkplug on #1. I managed to get a few wraps of electrical tape around it until I got the new parts in. I was able to spot it since I could slide the cover back enough to look down into the recess and see the arcing.
 

pcb

The Diagram Dude
:
2002 MP5
^^^ What he said.
I assumed that the spark plug wires were replaced.
I went with NGK for my wires.

 
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