Boggy starts after engine is warmed up

[Murphy]

I don't remember how long this has been going on for, a week or two. I start the engine and it idles around 300rpm while sputtering for two seconds then it jumps back up to the 750 range and idles completely fine afterwards. This only happens when I'm starting the car while the engine is warm.

Recent things I've done to the engine, new spark plugs NGK platinum a same ones I used before, tightened the valves to spec, bled and refilled the cooling system a few times, and changed the oil.

There's no air in the cooling system and there is exactly 4 quarts of oil in the crankcase. The fuel filter has 20-30k miles on it, I thought they were suppose to last 50k miles, but that's the only thing I can think of.

There's no cel.

 

[Swerve]

Slightly low compression in one cylinder? How's your gas mileage been?

 

[Mikeinteg]

Clean your IACV and FTIV to start, those might be clogged. Also check for vacuum leaks.

 

[Muckman]

Boggy?

 

[96LSteg]

Im going with primary o2 sensor. Let me explain.....

I had this same issue. When the car is cold it bases its AFR off of the MAP sensor ( i believe its called open loop?). Once the primary o2 sensor is heated up to operating temp, the ecu then bases its AFR off of that sensor (I believe this is called closed loop?). If the heating coil in the o2 sensor is bad (which you will not always throw a code for) your ecu is stuck in open loop, and when you accelerate adding more air, your ecu is not compensating with fuel. This is what causes the bogging.

I am willing to bet that if you replace your primary (upstream) o2 sensor, you will fix your issue.

 

[Murphy]

I replaced the O2 sensor in May, but I fucked up. I put anti seize grease in the electrical connections thinking it was dielectric grease. I cleaned the connections out a few times, but they are definitely still dirty I'll try again.

I'll try cleaning air control valves as well. As for low compression, if that's the case I'm pretty much fucked right, can't do anything about that.

 

[Murphy]

And my gas mileage sucks, around 260 miles for 10.5-11 gallons.

 

[Swerve]

Compression test it and go from there. Fuel pressure regulator, clogged injectors

 

[Murphy]

So I cleaned out the iacv and the electrical connection for my O2 sensor and now the problem is slightly worse lol. My cold start idle is only around 1.2k rpm and my hot idle is down to 500rpm. I don't see how it's possible for idle to drop after cleaning haha.

Tomorrow I have a 9 hour drive so I only have time to play with the idle screw. I'll have to do a compression test when I get back from Florida.

 

[Swerve]

Coolant temp sensor is a cheap thing to replace real quick

 

[Nick_C78]

Coolant temp sensor is a cheap thing to replace real quick

I would do this too, since a bad one can cause bad fuel mileage and idle issues. Also, why did you replace the O2 last time and what brand? I have seen bosche ones die pretty fast, also if you are burning oil it will kill O2 sensors quick.

 

[96LSteg]

I would do this too, since a bad one can cause bad fuel mileage and idle issues. Also, why did you replace the O2 last time and what brand? I have seen bosche ones die pretty fast, also if you are burning oil it will kill O2 sensors quick.

This. I want to know the brand as well. Those universal ones are shitty to. Denso is the way to go. waaaay more expensive but worth it.

 

[Murphy]

I got an oem fit Denso I had an O2 sensor code. Like I said though that anti seize grease I put in the electrical connections could have fucked it up. I cleaned it out completely with CRC electric parts cleaner and put in dielectric grease after.

I'll do the coolant temp sensor next. I turned in the idle screw and that's fixed my idle and my boggy start so far.

 

[ArmyIntegra]

Mine does that. I need new piston rings though. I'm getting some oil in the cylinders. It does it for a lot longer than yours though.


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[Murphy]

Mine doesn't burn a drop of oil, but my gas mileage has been pitiful for a while. I used to get 31 on the highway now I'm down to 28 and 24 combined.

I just hate to spend money on parts and still have these problems. I'll see if I can rent a compression test kit and do that first before throwing parts at it.

Opening up the idle screw definitely helped, sometimes the warm starts are a little boggy.