My cars doing it again. It lasted quite a while after the oil change and tightening the IACV. I guess its an issue with that still.

 

Well if anyones still paying attention to this.
I talked to my mechanic cuz he just did my muffler. I had him weld on a flowmaster which sounds great. But he said the issue sounds like the cat converter. I think it would also explain why my engine temp is a little high and the problem only happens when the car is hot but not necessarily when it goes into closed loop. Yet theres no CEL.

Any thoughts? Is the readiness check for the cat converter and o2 sensor readings so slow that it would not be able to pick up issues that are intermittent like that?

 

You could have an exhaust problem, I've seen this before. Sluggish power, elevated temps, wandering idle, etc. But before you jump through hoops, perform a simple Vacuum test.. (Old School troubleshooting) this may help to answer a few questions..

AutoSpeed - Using a Vacuum Gauge for Engine Diagnostics

 

Yeah, I gotta buy a vacuum gauge. Ill bookmark that guide. My theory is:

The exhaust is able to escape through the joints that need to new gaskets when the car is cold. Thats why I can accelerate well when cold. When the car and exhaust heat up the joints close up and the exhaust is forced through the partially clogged cat converter.
Perhaps I'm not getting a trouble code since the exhaust is bigger and the flow of the exhaust like it is would be comparable to that of the smaller stock exhaust?

That would explain why my engine coolant temp is rather high. Not so sure about the IM temp but it could be if the egr gases are hotter than normal. My mechanic suggested measuring the temp of the cat converter and the pipe around it to see if its heating up high.

 

You have an issue with vaccum in the system. This thread is 5 pages in length, with alot of people saying the same thing. If you want to test your exhaust, pull your o2 sensor out and run it like that. If everything is fixed you have a plugged cat.

 

I have some questions about the vacuum test though. Im going to compare my findings with what the ECU sees as well. I currently have torque for android and get 3.8psi at idle. On my computer I use Movi pro and get 25 psi at absolute manifold pressure. I think torque is off or calculating something differently. The 25 would be 25psi-14.7psi (atm) giving me 10psi or 20in/hg which seems healthy.

So I can use the gauge as a reference with the map sensor and the ecu readings, what should I look for when taking the ECU's map sensor voltages compared to what the gauge says?

 

I did a vacuum gauge test. The vacuum read 23 in/hg and was very steady, needle shaking was to 0.3 in/hg if anything. I rev'd the engine, vacuum would drop, jump a little higher, then return to 23 in/hg. Intake seems normal, no leak I can tell. Just the vacuum is a pinch too high.
Would the test results differ if I drove the car and monitored the gauge? That would be a bit harder to do but I could probably figure it out.
Its also night time so I wanna wait until day time to rev it real high to see how the gauge acts, but we're talking more about how end rpm's giving intermittent power anyways.

I may also try a fuel pressure test. Any suggestions?

 

Manifold pressure looks good in this test, I would get a second reading While the engine is Hot and messing up. A fuel pressure test is a really good idea, in fact I would rig it so that it can be observed while driving.. (Under Load) Have you noticed by chance if the CAT was glowing Cherry Hot by chance?

 

My test was done after a trip when the car was doing its thing. I'm wondering how i could rig the gauge up to see it while driving without pinching the line. Ill check.

cat converter isnt hotter than normal. I should get an exact temp. When I took it out I could shine a light through well enough. I rinsed it out anyways.

I just got back from a 140 mile highway trip. The car does great on the highway. Nice smooth acceleration. When I got off the highway it sounded great, I guess its really stop and go traffic that gets the best of it.

Dont think its the clutch again is it? It seems more engine than transmission related though.

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Maybe a valve adjustment is in order? The expanding of the engine when hot is causing some issues, especially with the increased air intake? Or am I overthinking it?

 

What about the spark plugs gap? Or would I notice a difference in the spark plug?
They're all white.