Just need some input on where I should start troubleshooting plz.

Specs:
stock b18b custom turbo kit, 10psi, 248whp

car runs ok when its cold but as soon as the temp starts to rise it starts missing and stubling in partial throttle, its fine under accel. then when its hot it runs fine. help me track it dwn.

 

what plugs? is it tuned?

 

Sounds like a bad o2 sensor. Cold or full throttle it will read right from the maps, and run decent afr's. As soon as it starts correcting with the o2, it may be going pig-rich or lean, which can cause stumbling.

 

yes its tuned, been running good for 20,000+ mi. ngk plugs, gapped correctly.

just replaced o2 sensor so I dont think thats it but I will check it out, thnks

any more suggestions help.

 

Sounds like Fuel enrichment issue (when cold). Your tune is probably bad or your injectors / pump might be starting to go. In other words cold your car adds more fuel (to warm it up faster) and as soon as it hits operating temps the enrichment = 0 you are running lean

 

Throwing any codes? Have you check the distibutor for spark issues?

 

its probably not spark related if it clears up under load.

 

its throwing code 43 (if I remember right), fuel supply system..

Where should I start tracking down the problem?

 

Thanks missed that part , have you checked your fuel filter?

 

have not checked filter, replaced about 30,000 mi ago. and it runs perfect at WOT though.. Im thinking the tune... crap..

pulled the plugs and their super rich when its not quite operating temp.

 

ttt

 

come on Ht, its getting worse.. I just want to narrow it down to a component or the tune.

 

ttt

 

ttt

 

I'm curious, does it clear up after say 3k rpms and idle like a Subaru? Its a long shot, but it could be your ringlands, do a compression test.

When my ringlands went it would idle and drive rough up to 3k rpms then clear up and run fine there after.

 

yea it pretty much does exactly that, but it idles fine and runs strong when its hot

 

??

 

ok I wasnt gonna bump this again but its driving me crazy.. I need help, its been cold and I noticed its worse when its cold outside.

code 43 fuel supply
all injectors work, plugs look rich.

 

did you happen to do a compression/leakdown on the motor to narrow down any problems with the engine itself? i know its a longshot but its worth doing if you have the tools on hand to do it.

also i would change the fuel filter, how do you know the injectors are working properly? have you recently changed, added or taken anything off of the car? does your idle surge at all?

 

have not done comp/leakdwn, but it runs very strong, holds ten psi like nothing. doesnt that suggest comp/leakdwn is fine??

as far as the fuel filter is concerned im 98% sure its running pig rich so fuel supply does not seem to be the issue?

Im sure injectors are working because I pulled plugs and all are the same. Plus I listened to them with screwdriver noise trick and they are all clicking properly.

I have not done engine related maitinence, idle does not surge, it stumbles like a misfire.

 

Do you have a fuel pressure guage?

 

no, ima get one soon, im starting to think the tune has just become off over the 40,000mi its been turbo, is that common?

 

well in 40,000 miles the engine condition changes, everything is more worn, so yeah it is definately a huge possibility. if you think the condition of the motor itself is fine and the fuel supply system then a retune is definately a good idea... also i dont know about when you had your car tuned, but when i did mine ALOT more time was put into the full throttle map then into partial throttle and idle... hope this helps!

 

Also you should take a look at your turbo. If its starting to take a dump and not spinning as easily as it used too, or worse leaking oil into your intake it would obviously cause problems.

 

I would put a fuel gauge on the car and check the fuel pressure under load. It could be reg/pump related