runs great / random rough idle

[CrazySupra]

I just installed a new intercooler and it ran great. I then swapped out AFM with a lexus one. It still runs great or even better but when I slow down or stop it idles really low and sometimes idles up and down. Also the check engine light came on tonight so I pulled the codes and it was 31 and 34. I replaced the AFM about 6 months ago but it would not go down the road without spitting and sputtering. This is only when its idling. Any help from some of you experienced guys would be great.

Thanks

 

[Zrain25]

Do u have 550 injectors

 

[chrisisg77]

^+1
To do the lex mod you need 550s thats the whole point with the lex AFM

 

[hvyman]

Check for boost leaks as well.

 

[CrazySupra]

found it. it was a boost leak. I have not changed to 550s but it runs great no fuel cut

 

[OfnaRcR4]

Hey you're going to blow that engine without the 550's... Do not boost until you get 550's and a walbro 255 in there. Or better yet, put the stock afm in.

 

[CrazySupra]

I thought as long as no fuel cut the engine could handle it?? It only boosts to about 8. Pulls hard with no fuel cut and sputtering. I already have a 255 but have not installed it yet. Looking for 550s now.

 

[Zrain25]

No the Lexus afm let's more air in 25% more then the 550s are 25% more fuel so it keeps the air fuel ratios the same as stock because it turns up the air and fuel 25% so if u only letting more air in you will be running lean...


That's no bueno!!!!

 

[hvyman]

Fuel cut is there to safe the engine

 

[CrazySupra]

I'm gonna change it out till I get the 550s. Will the stock fuel pump handle the 550s or will I need to go ahead and change both out? Thanks for the info...

 

[OfnaRcR4]

I don't know from experience but I've always been under the impression that you'll still run lean with the lex without fuel?
CrazySupra, you need to do more reading about the lex 550 mod if you're asking that kind of question.

 

[87suprat]

I just did the mod you want to do. 550cc high impediance injectors on ebay for $260, Running 18lbs of boost, 40psi fuel pressure, runns awsome!

 

[hvyman]

Low imp and you don't have to bypass anything.

 

[OfnaRcR4]

Also if you can find a set of stock mitsubishi evo 8 injectors those literally bolt right in and are 560cc. Just make sure to get them flow tested prior to installing.

BTW the absolute minimum are: Lex AFM, injectors and fuel pump but many would advise a FPR, wideband and some sort of tuning. I went with the first three for a few years and had a blast but i was one case that was successful, others wont be though. These cars are too old and poorly maintained for each car to be the same.