low throttle/load engine miss

[rich3389]

When driving my car normally around town at low throttle, the car kinda sounds like it is missing and the wideband reads real lean.
I have adjusted the TPS with no change, new rebuilt TB, and no boost leaks and the BOV is recirced.
Is there anything else I am missing to fix this problem?

 

[vol96]

Worn valve stems or seals maybe. How many miles on the motor? Have you done a compression or leak down test?

 

[DSM_PWR]

When was the last time you changed your Plugs/Wires??

The TPS must be at a certain point, so if anything you probably messed it up even more... Try getting access to a logger to correct this

 

[rich3389]

recently rebuilt engine burns no oil and has no problems, the tps is adjusted with my logger reads 0 when off pedal and 1 when just barely on it and 100 WOT. NGK wires about 1 year old and fresh ngk bpr7es.

 

[DSM_PWR]

... doesnt sound spark related...

I would assume something within the fuel system, like clogged fuel filter or even a leak...

No CELs correct?

 

[rich3389]

Let me clarify, no CEL's the car runs excellent its just at very very low throttle like 2% and lower when maintaining low speed through town, my wideband will read very lean(17ish) and it will sound like misfiring, but when i step on the throttle it is fine.
Could it be just because of my denso 660's are no good under extremely low loads? I was reading that larger injectors act a little funny when they arent flowing very much fuel(low load)?

 

[crimsondragon]

There's no way 660's will have trouble at low load. My 850's drive perfectly. I would pull the injectors and see if they're dirty.

 

[vol96]

Weak fuel pressure at low rpm...... Do you have big load on electrical system?

 

[rich3389]

Weak fuel pressure at low rpm...... Do you have big load on electrical system?

My voltage is always at 14.3ish volts at idle and 14.6ish at cruise, so that doesn't look like a problem.

Fuel filter has about 30k on her and is almost 3 years old.

I should also add that my idle fuel trims are off the wall. When warmed up I have to add 20 percent on the afc at idle to make the fuel trims zero out, but on a cold start the STFT is way in the negatives until warmed up. When the car is driven to the store and i turn it off and go inside for 10 minutes and try to start the car when it is still warmed up(coolant temps above 170 still) it will idle lean and rough for about a minute than it slowly goes back to stioch and its good to go.
dirty injectors?

 

[vol96]

Well then how about the usual TB related stuff: IAC, FIAV, EGR? Whats your vacuum at idle?

 

[rich3389]

Well then how about the usual TB related stuff: IAC, FIAV, EGR? Whats your vacuum at idle?

19 inch/lb of vac with supposed 264/272 cams, new rebuilt TB from throttlebodys.com, no egr valve, newer black top ISC that works good.

 

[the_mork]

Consider that you may be overrunning even with the 190lph pump. With whacky fuel trims you are probably jumping from your low trims to your mid trims often near idle and low throttle cruise. Low trims probably pull a fair amount of fuel to handle the overrun condition which goes away with just a bit of throttle input but still leaves you with the excessive trim adjustment cutting your IPWs down.

 

[rich3389]

Consider that you may be overrunning even with the 190lph pump. With whacky fuel trims you are probably jumping from your low trims to your mid trims often near idle and low throttle cruise. Low trims probably pull a fair amount of fuel to handle the overrun condition which goes away with just a bit of throttle input but still leaves you with the excessive trim adjustment cutting your IPWs down.

I dont think this is the case, the ecu wants to ADD fuel at idle.

 

[rich3389]

Did some experimenting today, changed FPR, oxygen sensor, maf today and it still does it, I have my AFC adding 20% at idle so i decided to bring it back to zero and now the low speed part throttle problem is better, but the idle fuel trims max out and the car idles real rough and lean...