Hi Folks. Say, my 88 GL 10 T is havin' problems. My wide band AFR is showin' some odd readings. It has run really consistantly over the last few years, under average boost (10 lbs. or less) it would run in the 12s and if I stand on it well into the 11s. Other wise it did great at keepin' it stoic. Now still running in the 12s, but when I back off the throt. it drops into the 11s, and when I stand on it, it leans into the mid 13s. I bumped the fuel pres. up 5 lbs. or so, but no change. Pulled the plugs, they show it's lean. Color me puzzled. S.

11s, 12s, 13s, referring lbs of boost?

You could be getting into an overboost condition, wastegate valve sticking, possibly a vacuum leak somewhere.

Or the fuel pump isn't able to keep up anymore. When was the last time the fuel filter was changed?

Hi. Sorry, 11-12-13 are the AFR readings. I'm running a fuel pres. gauge, so I'm sure it's got enough pres. Just replaced the filter. New plugs, wires, cap & rotor. I really feel the prob.is electronic. Questioning the MAF sensor, 'cause it seems to improve with higher rpms. Guess I'll have to run thru with the manual and check Ohm readings on MAF, TPS, etc. Thanks for your input. S.

Is your AFR at idle stoic? How about when cruising? Is the NB-O2 sensor voltage toggling at idle? You can look at the LED inside the ECU to see if the O2 is toggling.

what wideband are you using?

 

I wouldn't be surprised if the sensor is giving you false readings. I've seen these sensors die after only a few months of use. For yours to last years is a little odd.

 

A lot of times they won't throw an error code or give wildly false readings. They'll just be a little off...

It's an Inovativemotorsports unit, and this one's been in for less than a year. And, the plugs sure indicate that it's runnin' lean under boost. Still haven't had time to chase down ohm readings on other system components. Thanks for the input. S.

Could be a FPR starting to give up the ghost perhaps? Or a slight vac leak prior to the FPR.

 

Next I'd look into injectors. Are they clean, still operating effeciently, etc..

 

After injectors I'd look at the "control circuit". Airflow meter, O2's, coolant sensor, etc... to see if an erroneous reading is skewing the amount of fuel injected.

Thanks Tex. Thats where I'm goin'. I have a hood mount FP gauge, and the pressure stays nice and steady. Ohm meter next. Slightly bummed, S.

Thanks Tex. Thats where I'm goin'. I have a hood mount FP gauge, and the pressure stays nice and steady. Ohm meter next. Slightly bummed, S.

 

The fuel pressure should be relative to manifold pressure. Is that what you mean by steady? So if you get into boost you should see ~60 PSI, and at idle you'll see ~38 PSI.

 

The hose can pop off the FPR. This is a "silent killer" but it doesn't sound like your problem as it would run lean under boost.

 

You need to see if your computer has closed the loop with the NbO2 sensor. Look at the ECU LED or put a voltmeter on the O2 signal wire.

Sorry, no, I get the 10psi + under boost. But it holds steady, no flux, when the AFR gauge shows it get rich as I back out of the throt. Spose' it could be a bad O2 sensor, but it's not very old. A tech. from Inovativemotorsports said, they don't like their O2 sensor mounted so close to the turbo, because of sensor failing. They want it a min. of 12" away. When I built my dn. pipe, I put it in pretty much the stock location, so maybe. I'm gonna' pull the sensor out and recalibrate it, see if that helps. Thanks guys, S.

Hi, well I;m back at it again. Problem unchanged. Pulled the O2 sensor and recalebrated, no change, but I do feel like it's offering accurate information. Got out the multi-meter and checked the MAF, reads OK, but I think the throt. sensor is screwed up. This is the later style, with throt. switch and sensor both in the same box, rect. 3pin on top, and pig tail w/ oval 3 pin. I have 2 spare intakes complete, off of JDM swaps, but their the earlier style with just 3 pin on top. Anyway, the thing seems to be workin' backwards. My manual says, throt. sensor should read .5V @ closed throt.--5V @ WOT. I get 4.8V @ closed, and .8V @ WOT. The transition is all spikey too, this would seem to go along with my lean under boost and rich at lighter throttle problems. I guess i'll start lookin' for one. Anybody got one layin' around in your way, he he. I'd settle for opinions though, Thanks. S.