Rough Idle

[BlackStang00]

Alright guys, I have a similar topic on another site but I thought more input was needed. Here it goes.

I recently picked up a 00 Gt. It’s in pretty good shape for what it is but has some running issues. Around idle it’s rough and shakes the car. I’ve been datalogging with Forscan but it’s not showing anything out of the ordinary. I’m getting egr codes (it has an egr delete) and P1152. The long term fuel trim in around -25% on bank 2, bank 1 is around -14 or so. So I know it’s running rich. It has 30# injectors, I had a canned tune to at least get a baseline to see if it wasn’t tuned for them. It didn’t really help. I swapped the accel coils for stickers I had lying around and that made the idle worse. I noticed that sometimes when I hit the gas the tps voltage won’t budge so I unplugged it and it idles a little lower and smoother. I’m sure that I’m missing something.

Can anyone give any advice on what to check or has a similar experience?


Sent from my iPhone using Tapatalk

 

[BlackStang00]

I think I’ve narrowed it down to the fuel injectors. It seems the coils on cylinders 5 and 6 were not part of the 8 I had from my old 00 Gt that I swapped so I swapped 2 accels in their place and not much change. But I unplugged a few injectors on bank 2 and see now that 5 and 6 do make a difference unlike before. Also I pulled the plug from cylinder 5 and it looks fine. Even though it’s running really rich the plug didn’t have a lot of carbon on it. In fact it was relatively clean and had some tannish coloring on the ground strap. Maybe the o2 sensor signal isn’t right. I’m at a loss right now.


Sent from my iPhone using Tapatalk

 

[Blkkbgt]

I think I’ve narrowed it down to the fuel injectors. It seems the coils on cylinders 5 and 6 were not part of the 8 I had from my old 00 Gt that I swapped so I swapped 2 accels in their place and not much change. But I unplugged a few injectors on bank 2 and see now that 5 and 6 do make a difference unlike before. Also I pulled the plug from cylinder 5 and it looks fine. Even though it’s running really rich the plug didn’t have a lot of carbon on it. In fact it was relatively clean and had some tannish coloring on the ground strap. Maybe the o2 sensor signal isn’t right. I’m at a loss right now.


Sent from my iPhone using Tapatalk

I think you're on a good path with the fuel injectors. You may have one or more leaking injectors considering your trims are off on both banks.

Being that both banks are off it sounds like you have a problem that is common to both banks.

Have you tried the easy things like cleaning the MAF or double checking the EGR delete?

You stated the TPS voltage doesn't move when you hit the throttle. I know they are cheap, have you replaced it?

One cheap easy thing you can do is clean your fuel injectors. There a few videos on YouTube that will help. If you clean them and get a significant change I'd either replace them or send them out for a proper cleaning and flow check.

Hopefully this helps and someone with more experience will chime in.

 

[BlackStang00]

I think you're on a good path with the fuel injectors. You may have one or more leaking injectors considering your trims are off on both banks.

Being that both banks are off it sounds like you have a problem that is common to both banks.

Have you tried the easy things like cleaning the MAF or double checking the EGR delete?

You stated the TPS voltage doesn't move when you hit the throttle. I know they are cheap, have you replaced it?

One cheap easy thing you can do is clean your fuel injectors. There a few videos on YouTube that will help. If you clean them and get a significant change I'd either replace them or send them out for a proper cleaning and flow check.

Hopefully this helps and someone with more experience will chime in.

I appreciate any help. I got a set of oem 24# injectors from an s197 cheap that I’ll try out.

A few things I’ll mention, there don’t seem to be any vacuum leaks. They’d show up as adding fuel in the fuel trims anyway. I noticed while revving that the rpms will fluctuate but the tps voltage stays the same so I know it’s not that. But the temp will drop to -40*, which may explain the fluctuation. I’m wondering if it’s a bad sensor or an air pocket in the cooling system though. I tried burping it but nothing came out.

I’m going to swap in new plugs next. Maybe get another iac and clean the maf on my next day off. Thanks.


Sent from my iPhone using Tapatalk

 

[BlackStang00]

Swapped the injectors and loaded a new tune. It’s running better but there still is a slight stumble at idle that can be felt. Not a huge deal but it’s not perfect. Sounds stupid but I’m thinking it’s the pcv valve stuck open. The strange thing is it almost seems like a vacuum leak but the fuel trims would be positive if that were the case. And it drives fine otherwise, it’s just at idle.


Sent from my iPhone using Tapatalk