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Old 05-01-2010, 06:30 AM   #1
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Default A/F is getting leaner and leaner...?

At the dyno 10 months ago I had a solid air/fuel ratio in the 11:6-11:7 range throughout the pull, and it remained that way for some time.
Since then, I turned the boost **** up a hair to hit 12 psi - about 1 or 2 psi more than at the dyno, but I made sure fuel was good when I did.
A couple months ago, I started to hear a little pinging under boost, so I pulled some timing out of that row and that solved that, but I noticed I was leaner than I wanted, so I ran the autotune and added a bit of fuel.
Thinking about all this, I wondered why my tune that worked fine for months was leaning out...
I explored further tonight, and compared the fuel table I used at the dyno that had given me 11.6:1 in boost and the table I was at now and in some cells I had as much as 4 or 5 more points than the old table..
I went out tonight and logged and I am still too lean - in some places almost 12.2 - so I added some fuel in the boosted cells again.. did another log and it didn't seem to help - still lean.

The current setup is:
stock fuel pump
stock FPR
Rx-7 460cc injectors cleaned/flowed by Injector Rehab 14 months ago
duty cycles according to MS are about 75-80%

Should I be running injector cleaner through the fuel system periodically to keep the injectors from getting gunked up?
Does it sound like the fuel pump is at its limit? Is this level of power nearing the end of the stock fuel pump's ability or could mine be getting old and tired? This is a 20 year old car after all...
Could the FPR be going?

My theory is fuel pump.... but I don't know! Are there ways to check these things or should I just go buy a 190 high pressure Walbro??

Talk to me
-Ryan

Last edited by ThePass; 05-01-2010 at 06:56 AM.
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Old 05-01-2010, 12:02 PM   #2
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This is what my Lc-1 did to me before it died. I was actually so rich it would backfire if I went WOT by the time I caught on.

or you have an exhaust leak.
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Old 05-01-2010, 01:09 PM   #3
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I think Brain is right with suspecting your wideband, but it's sort of concerning that you were getting pinging. The fuel pump on my 1990 failed in 2003, so I would also say you should replace that fuel pump. It could be getting weak. Mine pretty much fell apart in my hand when I took it out...
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Old 05-01-2010, 02:16 PM   #4
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Not to knock Brain's diagnosis, but when was the last time you changed the fuel filter?

Yes you can check the pump if you have a fuel pressure gauge. hook the gauge up to the feed line, check pressure. If you have a gauge inline, pinch the return line and note the pressure. This is good to check max pressure but flow is a different story.The engine has to be under load to check flow, I think. That I don't know.
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Old 05-01-2010, 03:27 PM   #5
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Originally Posted by lordrigamus View Post
Not to knock Brain's diagnosis, but when was the last time you changed the fuel filter?
I can't believe I forgot about this. I haven't. Will do this asap, I think I even have a brand new one laying around somewhere. Will report back after that.
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Old 05-01-2010, 03:58 PM   #6
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If it's old I would change it just for the peace of mind.
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Old 05-01-2010, 07:36 PM   #7
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Well, to add to the confusion, I added a few more points of fuel to the boosted range and went for a spin and now it sits at a solid 11.4 - which I didn't expect to be possible if the fuel system was getting maxed out at some point like if the filter or pump or fpr were dying,...
So, now I'm even more confused, but I will change out the filter and see how things feel.

I need water injection, if only for the peace of mind...
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Old 04-14-2011, 10:51 AM   #8
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Did you resolve this? I noticed my tune getting leaner and leaner throughout the week and my tune hasnt been touched in a month.

First noticed it Monday when a hot restart had me idling at 17:1. Then on Tuesday I was seeing 16-17:1 in certain areas around 2500RPM.

Yesterday I autotuned into work and I was happy with how it added fuel, jus tin certain spots...but it had me scratching my head. Drove home no issue.

This morning the car for the first time ever, started then died. Had to try it a second time, where it ran but even with all my warmup enrichments that usually have me seeing 12.5:1 at idle, was closer to 14.0:1.

Driving into work I was seeing more spots that were hitting 16-17:1.


Like I said, the tune hasn't been touched. I'm thinking the 140K mile OEM pump might be on its way out. Fuel filter was replaced last year.
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Old 04-15-2011, 11:35 PM   #9
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Perhaps its because temps are getting hotter and your intake temp enrichment's are off a bit? I had that problem with mine however the other way as it was before the winter. It was tuned during the summer with a violent enrichment so as intake temps dropped 20 degrees afrs went down to 12-13 where before they were at stoich, likewise with traffic. As the intake temp raised it would start leaning out.

If its fuel pump or fuel filter you wouldnt have issues at low volumes.
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Old 04-15-2011, 11:57 PM   #10
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I had the same thing happen when the sensor on my lc1 was giving up. At first I just richened things up. Eventually when it was saying I was running 17 afr in boost I replaced the sensor. After putting a new sensor in it said I was running 10 in boost. A re tune later and its been solid more or less.
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Old 04-16-2011, 12:04 AM   #11
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From memory the LC1 sensor can be purchased from vatozone for a PT cruiser turbo.

When my sensor died it died almost instantly. Was running in the mourning, started it up after work and it was either max rich or max lean with few jumps in between.
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Old 04-16-2011, 12:06 AM   #12
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I am having the same problem just recently. It will stumble sometimes then run smoothly. When it's running smooth, the AFR's are lean. I used to have low 10's in boost at WOT. Now it climbs down to the 12's and then shoots up over 17. I'm going to replace the fuel filter as I don't know how long it's been since it was replaced. But could the UEGO sensor cause this? All my plugs are white, not good.
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Old 04-16-2011, 12:34 AM   #13
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Speaking of the wideband and accuracy . . . how often do you guys do free air calibrations?
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Old 04-16-2011, 12:51 AM   #14
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You guys are making me paranoid about my lc1.
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Old 04-16-2011, 11:21 AM   #15
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This happened to my LC1 about 5 years ago. This is not the case, when it says 17:1 it was hesitant and really lean.

Car has been fine for the rest of the week. I think I fooled with the fuel map offline, I thought I just had it ready for a new firmware I was going to load but I simply can't remember if I loaded it on my controller or not.

Anyways, once I added a touch of fuel in the bad zone it was fine.

The reason it stalled on start up was because I'm on a new firmware and my autotune filters didn't save over, so it leaned out the zone just above idle...this caused issues.

All has been well for the last few days. Regardless, I have a 255LPH going in tomorrow just in case
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Old 04-16-2011, 01:25 PM   #16
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Quote:
Originally Posted by hornetball View Post
Speaking of the wideband and accuracy . . . how often do you guys do free air calibrations?
Not very often really...I've gone through 3 sensors in a year and a half. I never had a problem with AFRs until the sensor was fucked, and calibrations did nothing. That was usually the sign that I needed a new sensor.

I had to reflash firmware once, it may or may not have helped a problem I had with inaccurate numbers and signal noise.

My tune seems to change every day. Idle and cruise is steady most of the time but WOT, I can be anywhere from 11.8 to 13.2. Its never the same.
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Old 04-16-2011, 01:41 PM   #17
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you shouldn't need to go through them that fast...I'm on my second in 4 years, and I don't think I needed it.
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Old 04-16-2011, 02:15 PM   #18
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You're right, I shouldn't. I'm not sure why they go bad either, I've been N/A this entire time. They always fail the same way though, they start reading full rich to full lean while I'm cruising. No amount of calibrations does anything for them.
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