Car has an attitude..

[LwlrMk]

Ok, here is the problem. At idle and under slow acceleration car runs rough, almost like it's missing. (plugs are good) A/F guage seems to go lean when the idle drops at stop or when it misses upon acceleration. Boost is normal (procomp guage). I gutted the cat and put in the 450 cc injectors from a manual, considering mine's an auto, about 2 1/2 weeks ago; acting up just now. can hear popping in the exhaust when it misses, almost like a backfire....?

Oh, anything over 1/2 to WOT car runs great, no misses or problems, goes to the usual rich and normal boost.

clueless,
-mike

 

[LwlrMk]

anyone? any thoughts are appreciated...
could it be a bad tank of gas?

 

[TwinOptiX]

I had a similar problem after installing a new motor I rebuilt. Some thing I can suggest that help the problem:
1. Check you ignition timing. (8 BDTC)
2. Do a compression test (always a good idea on a motor with high miles.)
3. Check for intercooler and vacuum leaks.
4. Check your cam timing, meaning make sure the belt hasn't slipped a tooth.

I know that one reason you car is running rough at idle and low throttle is because of your injector upgrade. I'm going to assume that you don't have an AFC, and that the car is running too rich. The same thing happens The way you describe the A/F ratio reading confuses me. The car is supposed to go lean on deceleration, but what you want to look at is the ratio through the powerband.

Sorry I have to cut this short... I'll post more later.
Good luck!

 

[LwlrMk]

i have been meaning to do a compression test, but just haven't had the time. I am going to try and go back to the 390's and see what happens. otherwise i was thinking maybe the fuel pump, so i was going to get a guage on the line and see if it drops.
As for the a/f is does go rich when it hits boost and like you said drops to lean once off of throttle. when cruising it bounces back and forth through the stoich perfect 2 bars lean to 2 bars rich, bouncing. It only drops to lean when i am at a stop in or out of gear.
Picture it like this, a/f is bouncing perfectly, then all of a sudden it hiccups to lean. Then goes right back to perfect ratio.
I'm going to do injectors later today, keep ya posted.

thnx for your help too, thought I stumped everyone...

 

[u6t9]

did you ever figure out what was going on with your a/f gauge? mine does the exact same thing.

 

[LwlrMk]

Yeah, I figured it out. It was a boost leak out of my throttle body shaft assymbly. Was pretty bad, wouldn't hold boost at all when doing a compression test. Fixed that leak and ran great. I just upgraded the throttle body. But, Definately check for leaks if you didn't already. These cars can get pretty stubborn...let me know if any more questions.

btw: If it so happens to be your throttle body, there is a step by step rebuild for the shaft part if you don't have $$ for a new one. It's in the VFAQ site.

-mike

 

[u6t9]

excellent! thanks for that info!