Can't get rid of lean condition, part throttle low rpm

EDIT: finally back at this after contaminating my tank, replacing it, installing correct injectors and throttle body kit. Story picks up again at post #36.

I've started tuning VE on my AMC 360 and am running into problems.

ECM is 7747, $42 mask bin based on ASDU. It's a stock motor with 3" exhaust. The truck weighs probably 5500# give or take and has 33" tires and 3.73:1 gears. I originally had a mini fuel pressure gauge showing between 14-15 psi.

I've started by tuning idle and working at exploring cells in lower rpms and progressively higher loads. I've been having a hard time getting the BLM numbers to indicate anything but lean. There's a definite power loss as I get into the throttle, sort of like a lean bog--but I'm in closed loop?

I thought I'd try increasing BPW a little at a time and see what would happen. While it has improved a little as BPW increases, the high load cells (let's say 50-70 kPA, 1200-2000 rpm range) in the history table continue to read lean -- 135-145 range. I'm at BPW of 175. VE1 table (I've added VE1/2) is maxing out in those areas, too.

Suspecting fuel pressure I swapped on a different (better?) gauge which reads 14.5 at idle.

PE is not disabled. Is that the reason for the wonky numbers? I don't see how because I can feel the lean and it gets better as I increase BPW.

I could swear I was running the appropriate-sized 5.7L injectors but will double check when I get a few minutes. I haven't checked fuel flow out of the pump.

What other things should I be looking at?

I've not touched spark advance. Is there any way that might come into play? Maybe that's where the power loss is coming from.

My catalytic converter is suspect. How likely is that to cause trouble? Some honeycomb chunks blew out the tailpipe. I like to troubleshoot by testing and trying the cheap stuff first, rather than throwing expensive parts at problems hoping the next one is the fix. :)

I should mention I had run across this post by EagleMark that may be a lead for me here: "All my testing of BPW changes from stock without factoring fuel pressure have resulted in raising BPW and low end goes rich and high end goes lean." More research and reading to do...

I started again with the ASDU, disabled EGR, disabled PE, zeroed knock retard, physically disabled EGR, and used a calculated BPW. I hit most of the cells in the 800-2000 rpm and 20-70 kpa range. I was able to tune most of the cells but...

It's really difficult to richen the higher kpa cells, particularly in the 1600-2000 range, 60-80kpa. Numbers are reading in the 140-150 range and I'm nearly tapped out on VE1--I've added A LOT to VE1. I've even added some to VE2. Can that be right?!?

Something MUST be wrong ...

I will keep at it and see if I can get those numbers to budge at all. But there must be something wrong.

I wonder if timing would help improve the burn and thus the numbers.

Post your bin and log file and I'll see if I can help.

ASDU VE1 and VE2 added together is already over 100% from factory! So you can't add fuel.

Timing will effect fueling...

Fuel pressure is a major issue, so many times we have gone through this and found fuel pressure gauges that are off! But if you have used 2 and both are the same at idle, can you use one to see fuel pressure during drive? Here's one I made that has found so many issues!
http://www.gearhead-efi.com/Fuel-Inj...1&d=1348450328

If you have blown out chunks of CAT... remove or replace. It could be causing some restriction but it's not your fuel issue.

Maybe one of the injectors is not working correctly? One of the independent parts stores near me sells rebuilt 350 injectors for $34 (exchange).

dave w

Always a possibility! I avoid by having injectors serviced before a tune...

Read this:
http://www.gearhead-efi.com/Fuel-Inj...4-7747-ve1-ve2

Ok, I will chase down a fuel pressure gauge that I can watch while I drive. Will post up the results and go from there.

Thanks!!

Michael

I got this TBI kit from CustomEFIs several years ago, assuming correct injectors. They are actually GM5235270*RPD, front injectors for Crossfire 5.7L camaro, corvette, and some sites claim these alternate P/Ns: OEM # 17078846, 5235270, 5233775, 17111547, 11547

One site says these can be replaced with 535206. One forum lists these flow rates in ml/cycle

350 CFI Rear: 114
350 CFI Front: 111 <--
350 2bbl truck: 103
454 2bbl early: 124
454 2bbl late: 129
305 F-body: 91
305 CFI Rear: 101
305 CFI Front: 100

So it seems they flow slighly more than the truck 2bbl injectors? If this is to be believed then it probably doesn't explain the extremely lean condition under power. I'm working on getting a gauge to measure from in the cab while driving. Need to check connections/ground/voltages at the pump, may try a different pump I have that came with the kit.

Man this is frustrating. I guess it could be worse tho.

Michael

Differant injectors could have differant settings? I'm not familar with old crossfire injectors. They are OLD! Did you have them serviced? I get between 6 and 18% increase flow with service.

Fuel pressure is a usuaul cause for issues like this but you still have over 100% with VE 1 and 2 so your not getting more fuel without more pressure. Or could add some to injector bias... check fuel pressure when gauge is available.

Supposedly they were rebuilt before being sent to me 10 years ago... so... with them sitting on a dry shelf in colorado maybe they need servicing in a bad way?

Seems I'm out of fuel. I can't get it to run right unless I jack up VE. So, yeah, fuel pressure. Something seems horribly amiss here... hopefully I can find out what very soon...

If...... IF......... they were serviced and properly they would have been oiled and fine.

If you do the VE1 and 2 combine, and increase injector bias you might get the little fuel you need.

If you post a bin and log I would look...

Have you pulled plugs to see how it is really running? Od one side richer then other?

look at the power enrich fuel ratio table, some are off a long ways

Quote:

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Originally Posted by EagleMark

If...... IF......... they were serviced and properly they would have been oiled and fine.

If you do the VE1 and 2 combine, and increase injector bias you might get the little fuel you need.

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Tried combining VE1/2. Didn't try mucking with injector bias. By how much might I increase it?

Quote:

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If you post a bin and log I would look...

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Seems like things are just too much of a disaster to waste your time :)

Quote:

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Have you pulled plugs to see how it is really running? Od one side richer then other?

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No, good idea.

It acts like it's lean when BLM says its lean. Lean die out when BLM is in the 150-160 range. Lesser at 140. As part of a process of elimination I swapped fuel pumps ... now getting only 12psi... went back to ASDU stock bin... running severely lean in the same areas as before.

I figure the following possibilities that I need to eliminate one by one

- fuel pump not flowing enough <-- swapped pumps to see if there was a major problem with old pump; unfortunately I'm down 2.5 psi with new pump
X voltage at fuel pump / bad ground <-- was seeing 14V at fuel pump
- injectors are bad
- fuel pressure "T" fitting/gauge isn't big enough
- fuel line isn't big enough (I'm running 5/16" stock line up and the smaller stuff back)
- fuel filter is restricting flow (it's brand new but maybe it's a type that's causing problems)
- bad ecm?
- o2 sensor not getting hot enough (it's a 1-wire and located at the Y and sometimes ECM goes out of closed loop at idle, but not always)
- something else wrong with o2? Does it need to be grounded? how well?
- insufficient fuel pressure at high load <-- swapped pump see above
- not sure what else?

Michael

have you tried spraying throtle body cleaner around the intake an brake boster to check for a vacuam leak?

if you are useing tuner pro to tune, try droping the syn air fuel ratio down to 18.1, then you might go up or down from there.