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2005 Suzuki Forenza - Mysterious Misfire, with a side of overheating!

I have a 2005 Suzuki Forenza Wagon - 2.0L L4.

First off I apologize for the TL;DR.

In the beginning there was only a slight problem with heating, It would never get as hot as I always thought it should get. But it did get hot enough so I ignored it as the ignorant frequently do.

Then I began noticing a slight misfire every once in a while and only when I first turn on the engine. So, having never done the Plugs and wires on this car, I decide to take care of it. Ordered the parts and waited for them to come in.

As I was waiting, the engine began overheating all of a sudden, seeing this now, I deduced that my thermostat must be gone, and before when it was only slightly hot it was broken in the slightly open position, and something happened, and now it was closed and began my over heating problem.

So I ventured to replace my thermostat, and long story short, I have to get one off eBay. So I am currently waiting for that one to come in.

The wires came in so I got the plugs and set out to replace the whole set.

After I replaced the plugs and wires, the misfire became vividly more apparent. highly noticeable. I double checked the firing order and that was all correct. I made sure they contacted the coil pack and each wire was getting spark from the coil, and it was. very strong. I pulled the plugs and wires, and double checked that the plugs themselves were still OK, and they were.

So, Having eliminated spark, I moved on to fuel, I decided to pull the fuel injector connectors one at a time while the engine was running.

only one fuel injector did not effect the engine, the other 3 I barely had it off before the engine began to stutter and shut down.

Cylinder 2 Fuel Injector.

I Have another Fuel Injector on order, and while I was waiting, I tried throwing in some Fuel Injector Cleaner and try out the coolant issue, perhaps running the engine would work a blockage free, so far it has not.

My main problem that I have noticed, when I put the radiator cap back on the coolant reservoir when the pressure builds up, either the misfire starts back up, or it gets more pronounced. I don’t understand how the two correlate.

I am probably over thinking it, but What I was thinking is maybe the thermostat being closed was not allowing fluid through, and so the water pump couldn’t push the coolant freely, so it would bog down and maybe stretch the timing belt slightly, enough to adjust the timing and cause the Cylinder 2 Misfire.

I realize it’s kind of a “Rube Goldberg” explanation, but there it is.

Help me CarTalk Community, you are my only hope.

Unfortunately, it sounds like it may be a head gasket issue.

When the pressure builds up, coolant is being forced past the head gasket into the cylinders, causing it to run rough.

To determine for certain, you will need to have a block test done to test for the presence of hydrocarbons (i.e., exhaust gases) in the coolant.

I was thinking of head gasket too. You must have error codes in there. What are they? (exact codes like “P0123”).

Before you go too far check the compression. For your sake, I’m hoping that’s not it - but I’d want to eliminate that first as its not too hard to check out and can save a lot of tail chasing.

According to the poster named “ladybri” in the thread below, she had a similar problem with her 2005 Forenza and it turned out to be a cracked head. She was told cracked heads are a common problem with Daewoo-engined Forenzas. So if your head is cracked too, a new head gasket won’t help.