Hi guys, recently my mt coupe has been having a strange issue that I need help diagnosing. Last Thursday I went to a car meet and let my buddy drive the G around the corner because I wanted to hear what my car sounded like from the outside. Sadly, he is not used to car clutches since he drives a wrangler, and proceeded to burn my clutch all the way around the corner. On the way home from that meet is when I began to get this problem.
Here's the issue: When accelerating, my car will accelerate as normal in 1st and 2nd gear, but when I get to 3rd and all gears afterward it sharply cuts fuel when accelerating to where the rpm goes up and then immediately drops as if the car is bogging out, and then goes up again.
At first I thought the issue was the clutch, but with my limited understanding, I would think if the clutch were going that that would mean that it would slip in the gears with more torque like first and second, and not the higher gears. Also the rpms go down when it bogs, and if the clutch were to slip, they would go up, no?
I previously had gone to change my spark plugs for my 100k service, and the boot ripped slightly on the way out. I assumed this was causing the issue. I went in and found that the 6th spark plug well was full of oil. I thought this was the issue, so I replaced the valve covers and all gaskets up to and including the area, whilst also cleaning out the plenum. After putting everything back together last night and doing all the pedal dances, the issue still persisted.
I think it's safe to say that I have no idea what to do. If anyone has any ideas as to what might be causing this, I would really appreciate the help.
Thanks,
Mitch

2005 6mt coupe, 113k, previous owner claims clutch replaced at 90k.
Not sure if actually limp mode, this just sucks. After posting I really I can't change the title.
No check engine lights either

PS If this is in the improper section, feel free to move it. I've never actually asked a technical question on the forums, as normally as issues are solved with a search.

 

Does your service engine light turn on during the lamp test when you turn the ignition to ON? Can you rev the engine normally in neutral?

 

@cleric Yes and yes. I went and spoke with my mechanic today and went for a bit of a drive. On the way over I filled my gas tank, and by the time we went and tried to replicate the issue, it had already decreased significantly. I'm thinking a good amount of the issue is that I got a bad batch of gas. Perhaps I got the bottom of the barrel bit of gas with some deposits in it. My mechanic suggests that the issue is most likely just some gooked up valves or injectors, since no electronic problems seem to be happening which would throw codes. I put in some Chevron Techron upon his recommendation and it has been improving.
He also checked out the AFRs and they seem to be off, but that could be due to the fact that it's only been 34 miles since a hard reset and it's trying to relearn everything. They are all skewed though, so the issue has to be some kind of common denominator.
If the problem persists, we're going to move down the line of troubleshooting and do some tests and check out the reading of the maf and see if the results are skewed.
Luckily my mechanic is my uncle.
From what I understand, VQs can actually have sensors be the fault and not throw codes, unlike most other cars?

My car is also burning some oil out the tailpipes, but at this point I'm just going to see if the changes I made are going to sort that out. It could also be my new set of valve covers' pcv valve is louder hissing when going to my catch can, so maybe it's messing with the oil since the car isn't used to it yet? The catch can didn't have that effect before (aka it wasn't as loud)

 

Take off the PCV valve and shake it to make sure it rattles, could be seized in the open position and screwing up air flow. Hopefully that's the reason for your smoke out the tailpipe, also check your oil dipstick to make sure the gasket is intact on it, funny thing is THAT can cause the engine to smoke also...

You didn't suck deposits in your fuel, there is a pre-filter on the pump that keeps debris out but you can have degraded fuel that doesn't have the proper octane. The computer doesn't need time to relearn anything, it literally makes those necessary changes dozens of times per second and it uses that data to determine a baseline threshold called "long term fuel trim" which doesn't affect performance whatsoever, it's more of a reference tool for technicians to use to determine potential problems.

 

Thanks man, I'll have to check it out later and see if either of those are the issue.
As for the weird fuel cuts, I'm still trying to figure that out. Currently thinking the maf is probably the problem but I'm going to test it this week with my mechanic and see what the verdict is on that.

 

Were you able to figure this out? Something very similar to this just happened to me yesterday. Was driving on the fwy at about 70mph, then the car suddenly started to slow down. Pressed the gas and nothing happened, downshifted and the RPMs went up, but still no throttle/very laggy throttle response. I pulled over and restarted and it seemed ok after that, but I don't want it to happen again. I'm not throwing any codes either.

 

I haven't found the solution quite yet. It appears we might have a pretty different issue though. I'd clean your maf and see if that helps