2G Running very lean during idle and under acceleration

[aaparker]

I have read the heck out of current threads but they focus more on the ignition aspect when a car is sputtering badly. Mods list is on profile and updated.

This problem started while accelerating and was intermittent, it has worked its way to my idle and is present 100% of the time. Wide open throttle was never affected, no problems there. I have a narrow band o2 gauge, just for info, a wideband is on the list.

As of now when I start the car it idles fine until it gets warm, it then start putting pretty bad and will kill itself. The o2 gauge is pegged lean and the leanest L.E.D. flashes as the car sputters. I can't accelerate through it, the car falls on its face repeatedly, so it is un-drivable.

I have tested the coils (good), and have replaced the plugs and wires. Plugs are gapped at .28. I believe everything is good from the fuel pump through the rail on the fuel side. My fuel pressure is good at 34psi w/ the vacuum connected at idle, no idea under acceleration, a fuel pressure gauge for the cockpit is also on the list. My compression numbers are 145 across all four and I have fixed all boost leaks, vacuum is good.

I can only assume one of these things is going on:

I have a bad injector, I have had a cylinder 4 misfire code pop up before but it will go away for a while then come back it is not constant and currently no codes are present.

I have a bad ecu, or sensor, I am waiting to see if the problem gets better as the temperature goes up as it has been very cold, if the intake temp sensor is bad and the ecu has reverted to default temp, that could explain my lean condition when its 10 degrees outside.

Or maybe my timing is off.

Anyways I am frustrated, the car has been down for a few months and I need some help. Thanks.

 

[DougR]

Does that Narrowband guage oscilate? If it stays pegged one side or the other. That generally says you have a bad O2 sensor.. Break out that digital volt meter, and test it.
Sounds to me once the ECU shifts from closed to open and trys to use the O2 sensor is when your problems start..

Next time Break up that huge paragraph, Make it easy for us dummies to read.. I ended up cross eyed after reading it..

 

[aaparker]

I have replaced the front o2 sensor in the last five hundred miles, could it be the rear causing problems? When it was breaking up on me during acceleration the gauge would go back a forth between rich and lean, but rather than use the two or three LED's at a time it would fan out and a act really cut up and hesitant.

 

[aaparker]

Yes it will oscillate for a little while, when the car is idling fine. Then it will peg itself lean and start to kill itself.

 

[DougR]

Rear O2 just tells the ECU that your Cat is working or not.

 

[UGOT8UP]

The rear o2 would not be the issue...have you checked for air restrictions?

 

[rstchris]

You can try the "tape a fuel pressure guage to the windshield" trick. As boost goes up, fuel fressure should go up.

 

[aaparker]

I need to address the problem at idle first. Fuel pressure checks out at idle but the car still gives me a fit. I can't get the car fifty feet before its on its face pissed off at me for trying to drive it.

So i will test my o2 sensor but I think its fine being brand new and all. I reverted the AFC to nothing and reset the basic info like number of cylinders and that stuff, but am not running any correction so the ecu is on its own.

The rear o2 would not be the issue...have you checked for air restrictions?

Other than obvious obstructions, filter, intake/intercooler pipes, what do you have in mind? Filter is a K&N and I have cleaned it. I have had my intake and upper intercooler pipe off several times recently, nothing blocking those.

 

[UGOT8UP]

A rag or something that might got lost while working on the car...bent pipes, something stuck in you compressor housing, dirty or cloged air filter, maf.. just dumb stuff, I've got a rag lost in one of my pipe's before and it done the same thing you are describing..

 

[aaparker]

There is nothing obstructing any of my intake/intercooler pipes.

Would a TPS sensor cause these problems if not adjusted properly I have adjusted it a bit. My car has not idled properly since I put on the 1st Gen throttle body but the problems I am having didn't anywhere close to my adjusting the TPS to make me think it is the cause but could it be related?

 

[rbwtrans]

What year throttle body did you use? The 90 has a lot of pigtails and uses a different gasket.

 

[aaparker]

I believe it is a 92-94 it has four fittings on the top. Three side by side and a fourth angled out.

 

[aaparker]

No luck yet I was hoping there may be some more input. Has anybody ever had an o2 sensor go out within the first couple hundred miles? Besides the intake temp sensor and the coolant temp sensor are there any other sensors that could cause this problem?

 

[dsm-freak]

what size injectors are u running?

 

[aaparker]

Stock injectors, running about 14 lbs boost. But I don't have any problems really when boosting and absolutely none wide open throttle. Idle and half throttle give me problems, like I said though I haven't been able to get fifty feet without a problem lately, so right now my focus is idle.

 

[4g64fiero]

We know its fuel related so lets check fuel related things.

You mentioned it had an afc, I would check the mas wire going to the ecu, to make sure the ecu is getting a mas reading. After that I would check fuel pressure under load. I know someone already mentioned that, but its a good idea. I would also test the tps as well. You can also check the o2 sensor with a multi meter like you would the tps. This would verify whether or not its working properly.

Good luck.

 

[spyderturbo007]

Post up all of your SAFC settings, such as TPS trigger points, Ne Points and corresponding correction factors. Also, as stated above, check your wiring.

Was the SAFC recently installed? Do you have, or have access to a logger?

 

[aaparker]

Thanks for the input I will check everything mentioned. What am I looking for when testing the mas wire? How can I check fuel pressure under load, the car won't go anywhere? Like I said the problem exists at idle and the idle fuel pressure is fine, I need the idle problem solved before I can solve the problem at load, thats if they are not one in the same.

As for the AFC settings, I cleared everything. I ran out of ideas, Nothing I installed should have affected my AFC, the fuel pressure didn't change I just installed the better parts for turbo prep, and the mass and ecu should have been able to adjust for the change in air flow from the larger throttle, but it was worth a shot. I figured I should start reverting back to stock in case it was one of my mods causing the problem. I left it installed but I only reset the basics, number of cylinders, sensor type. It is currently not running any correction.

I installed it about a year and a half ago, took it to Denver had it dyno tuned, ran great for a year or so. I installed a Walbro 255lph pump, an Aeromotive fpr, and a 1g throttle body bored to 63mm by Steve Monroe. The pump and fpr went in fine no problems at first. The pump was loud but kept getting louder, sounded like it was going to explode. so I went back to the stock pump, but left the fpr.

I had a lot of trouble tuning the idle surge out, after the throttle was installed, but got it pretty steady. Shortly after that I started noticing the stutter. It would start fluttering at me, I could usually power through it and it would go away. The time in between occurrences started at a month apart, then started getting shorter and the problem started getting more severe. I replaced my plugs and wires thinking it was ignition, no luck. Tested my coil, its within specs. And now we are not moving and it has become permanent.

SO, I have no logging equipment or access to any, I hope to get it soon but until then.

 

[kenamond]

I'd get a logger or borrow one. I'd like to see your LTFT and idle O2v signal. Sounds like all of your problems are happening when in closed loop mode when the O2 is involved. I'm also suprised you haven't thrown a code for the LTFT hitting its rich limit. I don't know squat about 1g TB on a 2g, but if there is a massive vaccuum leak, that would be unmetered extra air that would lead to a lean condition. Under boost, that could turn into a boost leak and a rich condition that might cause an obvious problem.

Is your PCV system still stock-like? If your VC breather is open to atmosphere, you'd pull unmetered air at idle, but under boost or a boost leak test, the PCV would close and hide the vaccuum leak.

How did you tune out the idle surge? Are the TPS and ISC working? A logger would tell you if the TPS signal at idle is within spec. Ever consider putting the 2g TB back on?

 

[aaparker]

I had to play with TPS a little, i had to put in a screw to adjust the throttle plate, when it was shutting it would close but then would continue to close too much and then open back up the wrong direction. And then finally I had to fiddle with the biss screw to bring the idle down.

The PCV system is stock, not open. I have considered putting the 2g throttle back on.

 

[spyderturbo007]

As for the AFC settings, I cleared everything. I ran out of ideas,

Are you saying that you went through the SAFC's initialization? If so, that's your problem. When the SAFC is reset it defaults to an incorrect MAS sensor type. You need to change that back to Karmen with the arrow pointing in the north east direction.

 

[aaparker]

Yes I initialized but I also went back through and performed initial setup. I went through and set sensor type, number of cylinders, throttle sensor voltage check, throttle sensor type, re-learned throttle angle, all these things have been set properly. I am just not running any correction right now.

 

[Vincent Pandolph]

What's the fix? So tired of these forums, noone seems to care about the answers, just always rambling in. Was driving down highway all good. Normal driving, all stock aside from 255 pump and fuel lab afpr mini. Fuel pressure Gauge is reading 32 psi at idle, but does not accelerate. Barely idles. What's wrong with it. I had been driving for 30 minutes when this happened. Going good then all of a sudden, crappy, no power barely moving.

 

[1990TSIAWDTALON]

Have you checked or changed the fuel filter?
And so you know, this forum has implimented a "Resolved" feature now. We use it anytime someone posts up the answer to the questions asked. As I run across threads that are resolved, I put that header on the thread so that everyone knows it has been resolved, so there IS an answer.

 

[Vincent Pandolph]

When I bought the car it didn't run. I replaced entire fuel system, steel braided-6 walbro 255, fuel lab mini afpr, new ECU with eprom chip. My tank was rusty I cleaned as best I could with evaporust over the course of a week. Then I coated with marvel mystery oil and reinstall it and filled it up with fresh gas. Have run about 6 tanks of gas and driven about 600 miles total since getting it running. I have a Weldon racing fuel filter, if it was clogged I don't think I would see pressure at the fuel pressure gauge. I think injectors clogged up, they must be firing though because it starts with rough idle around 450 rpm