I've been very curious about a problem with my MAF TPI system. I've installed an auto-meter air/fuel ratio meter so I can monitor my fuel on the go. Here's what happens. I'll start up cold, let the engine warm up and drive around just fine. Everything's normal. At cruise and part throttle the meter bounces between lean and the edge of rich, right where I think it should be, and when you mash it, it goes a few lights green. Sound good so far?

Here's the tricky part, I stop, shut off the engine, and wait a few minutes. Re-start engine and start driving. As soon as it goes into closed loop again the engine is starved for fuel at cruise and part throttle. The meter will show maybe 2 bars lean, otherwise it's off the chart lean. Sometimes the display will go completely blank. During this time the engine is sluggish and not very responsive which would make sense since the meter is showing lack of fuel. After about 5-10 minutes of driving this clears up. But while this is happening if it falls lean, I can mash it and it'll go open loop and pour the fuel to 'er. I thought maybe a sensor was acting up after the engine is hot. This didn't happen overnight either, it's been progressive over the last few weeks. It didn't used to do this when I first installed the TPI.

I did use winaldl and view the sensor readings during the lean condition and everything appears normal as far as MAF and TPS goes. Nothing out of the ordinary.

Any ideas as to what I should do next? Is my fuel pressure regulator acting up? Do I have a sensor going bad? What else should I be looking for on my scanner?

Oh, and here's another problem. When I start up cold my engine will idle at about 900 rpm with an IAC count of 125. After the engine is hot it'll idle at 750 with an IAC count of 40. That seems a little suspect to me, or is that normal? Occasionally when the engine is idling, it'll suddenly idle up to about 1100~1200 rpm for a bit, then calm back down to 750. Also when cold starting the engine will idle much too low (400~600) for about 30 seconds before it picks up rpm. I've set IAC with this method: engine off, jump diagnostic pins, key on, wait 30 seconds, disconnect IAC motor, start engine, set rpm at 550 rpm, engine off, re-connect IAC, remove diagnostic jumper, key on, reset TPS to .054V, start engine.

Thanks,

-HD

 

[Remove jumper after IAC has been disconnected but before you start engine and set minimum air.

 

Also can you post a CSV file of your datalog???? If you can it should take some of the guessing out of it. Try to include as much data as possible, not just the MAF and TPS. Your O2 readings, CTS and a few others might be nice to see.

 

What is a CSV file? I can send the log files from WinALDL. Or is there another program I should be logging with?

Thanks

HD

 

A CSV file is a just a nice way of gathering your info and orgainizing it into something that others will have no trouble viewing. CSV files can be opened by Excel and thus allows your info to be orderly placed into columns when opened by Excel, ect. Save your datalog as a CSV file.

As for WinALDL its fine. I can't say as I am familiar with it at all but I have a friend that uses it and it gets the job done. I am sure if you can get something posted that someone can help eliminate some possible causes for the lean condition. In the meantime try to reset your IAC properly to see if it fixes your idle issues.

 

Alright, I'll make another run and log the lean condition again. I'll try re-setting the IAC again. I know that spec is to set the idle at 450 rpm in drive for a stock engine, but mine is far from stock. What should my target min air rpm be with my engine?

Comp magnum 280 cam, 280 adv duration, 230 @.050, .480 lift
trick flow aluminum heads

Those are the biggest mods anyway.

I'm worried that if I have to increase the min air setting any more, and I have the tps reset to .540, I'll run out of throttle travel to get over 4 volts at full throttle. How do I get around this?

-HD

 

Nah you will have lots of room on the TPS adjustment. Might try bringing your idle up to 550-600ish before IAC has control. Just remember to remove the jumper before you turn the key back on to start the car.