lean out at 2600-2700

[7mgt45r]

Ok...that's good

You have your fuel pump running directly off battery 12V, triggered by the stock wiring through a relay in the trunk now...correct?

How old is the fuel pump and is it a "real" (not a Chinese copy) Walbro?

Have you tried to increase fuel pressure on the AFPR?

How are AFR's outside (both sides) the 2600-2700 RPM stumble you are experiencing?

yes, my fuel pump is running off 12v relay in trunk and 4yrs old and i order frm suprastore, so i guess its real but just did 12v mod. yes adjusted fuel pressure to 28 psi> afr's are fine on both sides. after 2700 rpms the car runs like at bat frm hell. just between 2600-2700 goes lean on wide band and stumbles and if you easy on gas it doesn't do it as bad. just when your trying to accelerate kind hard. tryed to add more fuel at rpms but no good.

 

[jdub]

What are the AFR's (numbers) before the stumble and after?

Have you tried to add fuel via the AFPR...say to 35 psi?

 

[7mgt45r]

What are the AFR's (numbers) before the stumble and after?

Have you tried to add fuel via the AFPR...say to 35 psi?

the afr's 14.5 and after they they jump to 10.0 if on gas hard. no i haven't tryed to adjust fuel pressure to 35psi. Do you think it might be tps not set correctly and its telling the computer to hit fuel cut at 2600-2700 rpm?

 

[gixxer750]

removing EGR is FTW if you have a standalone... damn thing is in the way of getting to stuff when working on the engine. Stock computer, EGR stays.

 

[jdub]

Give the AFPR increase a try.

Fuel cut is not based on the TPS...it is based on what the AFM is reading for ingested air.

However, you may have a flat spot in your TPS (specifically VTA)...fairly common on an old TPS at that RPM range due to it being a normal highway cruise. The RPM increase for heavy acceleration is not being matched by ECU command to increase injector volume till you pass the flat spot.

 

[7mgt45r]

Give the AFPR increase a try.

Fuel cut is not based on the TPS...it is based on what the AFM is reading for ingested air.

However, you may have a flat spot in your TPS (specifically VTA)...fairly common on an old TPS at that RPM range due to it being a normal highway cruise. The RPM increase for heavy acceleration is not being matched by ECU command to increase injector volume till you pass the flat spot.

jdub, i'll try to turn up afpr to 35psi and if that don't wrk i'll chg afpr. i'll get bck with you tomorrow on update and thanks again for all your help.

 

[7mgt45r]

jdub, i'll try to turn up afpr to 35psi and if that don't wrk i'll chg afpr. i'll get bck with you tomorrow on update and thanks again for all your help.

jdub, hey man turned the fuel pressure up to 35psi and that didn't wrk. chg tps that didn't wrk either. man i don't know whats going on it run fine before and after 2600-2700 rpm's. car runs strong until and after that point adjusted timing it was off a little. still not fix.

 

[7mgt45r]

jdub, hey man turned the fuel pressure up to 35psi and that didn't wrk. chg tps that didn't wrk either. man i don't know whats going on it run fine before and after 2600-2700 rpm's. car runs strong until and after that point adjusted timing it was off a little. still not fix.

jdubb i needed a responce man.

 

[jdub]

Sorry man, but I'm in China...I was flying when you posted above

Was the TPS used? If so, it's pretty likely it has the same flat spot as your original...that RPM is right where highway cruise is. If you can, test VTA for a smooth voltage rise as the TPS is turned.

I suspect the ECU inputs to power enrichment...my TCCS book is at home.

The stock FP relay is gone, correct?

Does the lean situation lasts about 3 sec still...and, if you let off the gas at that spot, it still "bucks"?

 

[figgie]

Col.,

China? You turning them into a giant parking lot hehe

ontopic: that lean spot, I wonder.........

I know there has been cases where if you run too rich the O2 sensor starts to actually read lean. That can also happen during a misfire too.

7mgt45r

You coil packs. Are they grounded to the engine or battery? There should be a wire that connects from the coil pack mounting plate to the either the engine or, sometimes if modified, directly to the batt.

That lean spot, I know the MKIV are notorious for that just a bit higher in the RPM range.

 

[Poodles]

I still think it has to do with the FPD delete...

 

[jdub]

China? You turning them into a giant parking lot hehe.

Just got back...nah, hung out in Beijing for a couple days. Did get a little shopping done...LOL.

Poodles - I know what you're saying, but I don't think a FPD would do this...it would manifest itself over a larger portion of the power band.

It's either:
Power Enrichment - looks at VTA, engine speed (Ne) and coolant temp (THW)
This happens when the engine is under heavy load...injector volume is increased 10-30%

Or, as figgie alluded to:
AFR correction during transition - Looks at Ne, vehicle speed (SPD), IDL, and THW
The injector volume correction is much less than power enrichment...this is primarily a fuel economy thing. I don't think this is the problem.

AFR feedback correction is inop during power enrichment...the engine goes to closed loop. Also happens if the O2 sensor sees a lean or rich condition longer than a predetermined interval.

You could pull the EFI fuse to erase the AFR learned values...it wouldn't hurt.

 

[7mgt45r]

Sorry man, but I'm in China...I was flying when you posted above

Was the TPS used? If so, it's pretty likely it has the same flat spot as your original...that RPM is right where highway cruise is. If you can, test VTA for a smooth voltage rise as the TPS is turned.

I suspect the ECU inputs to power enrichment...my TCCS book is at home.

The stock FP relay is gone, correct?

Does the lean situation lasts about 3 sec still...and, if you let off the gas at that spot, it still "bucks"?

jdubb, i've chg ecu too, still have same problem. yes stock fp is gone. when i'm barely on the gas when i reach that certain rpm its okay, nut if i'm about 5% of the throttle depressed it does it. tryed to add fuel doesn't clear up.

 

[7mgt45r]

Col.,

China? You turning them into a giant parking lot hehe

ontopic: that lean spot, I wonder.........

I know there has been cases where if you run too rich the O2 sensor starts to actually read lean. That can also happen during a misfire too.

7mgt45r

You coil packs. Are they grounded to the engine or battery? There should be a wire that connects from the coil pack mounting plate to the either the engine or, sometimes if modified, directly to the batt.

That lean spot, I know the MKIV are notorious for that just a bit higher in the RPM range.

grounded to the engine, to the stud right by the throttle.

 

[7mgt45r]

Just got back...nah, hung out in Beijing for a couple days. Did get a little shopping done...LOL.

Poodles - I know what you're saying, but I don't think a FPD would do this...it would manifest itself over a larger portion of the power band.

It's either:
Power Enrichment - looks at VTA, engine speed (Ne) and coolant temp (THW)
This happens when the engine is under heavy load...injector volume is increased 10-30%

Or, as figgie alluded to:
AFR correction during transition - Looks at Ne, vehicle speed (SPD), IDL, and THW
The injector volume correction is much less than power enrichment...this is primarily a fuel economy thing. I don't think this is the problem.

AFR feedback correction is inop during power enrichment...the engine goes to closed loop. Also happens if the O2 sensor sees a lean or rich condition longer than a predetermined interval.

You could pull the EFI fuse to erase the AFR learned values...it wouldn't hurt.

already pulled efi fuse.

 

[jdub]

Have you tried it without the SAFC in the loop? (i.e...disconnected and run straight with the ECU)

What kind of wideband are you using.

What brand/model AFPR?

 

[7mgt45r]

Have you tried it without the SAFC in the loop? (i.e...disconnected and run straight with the ECU)

What kind of wideband are you using.

What brand/model AFPR?

no haven't tried without safc out of the loop. do you really think it could be the safc. i'm using aem wideband

 

[Poodles]

Yes, BUT, the issue happened after he removed the FPD. As the general ruel applies if something is fucked up, what's the last thing you did that might have caused it...

Up to the OP, bit I would think about going back to the way it was to single it out...

 

[jdub]

Poodles - it wouldn't hurt to try it.

7M - I would check the TPS for a smooth, linear VTA output from 0-5 volts moving the throttle from closed to WOT. The ignition has to be on to test this with a multimeter...you want to be a smooth as possible.

The SAFC could also be the issue...taking it out of the loop will confirm.

After increasing fuel pressure, did the lean condition last ~3 sec as before at the same RPM?


Edit: another question...what kind of AFPR are you using? Is it the Chinese Aeromotive knockoff?

 

[7mgt45r]

Yes, BUT, the issue happened after he removed the FPD. As the general ruel applies if something is fucked up, what's the last thing you did that might have caused it...

Up to the OP, bit I would think about going back to the way it was to single it out...

poodles, if i put the fuel pressure reg. bck on it will shoot fuel out the top of it and i tried two of them.