George Posted December 22, 2014 Author Report Share Posted December 22, 2014 Thank you all for your wisdom and insight. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted December 25, 2014 Report Share Posted December 25, 2014 since this is the only LQ1 injector thread in a long time that has mentioned , I'm reminded of a mild upgrade. http://wot-tech.com/shop/gm-60v6/28-injectors/prod_283.html these are from the 4.2 DOHC Atlas L6 as would be found in a trailblazer/similar. http://60degreev6.com/forum/showthread.php/48726-Trailblazer-Fuel-injector-Info considering the 06+ got a bump in power from 275HP to 291HP, those ones might flow even more. they should certainly be able to cover almost every LQ1 unless you have a wild n/a build or start running boost. Quote Link to comment Share on other sites More sharing options...
Nicutlass_Supremacy Posted December 27, 2014 Report Share Posted December 27, 2014 Hi, how are those injectors going, I have the same problems with my lq1 and I'm thinking of buying those delphi injectors. Quote Link to comment Share on other sites More sharing options...
George Posted January 1, 2015 Author Report Share Posted January 1, 2015 They are still working well, although the other day it did surge some, but I could hear a vacuum leak only at the higher speed which made me think PCV valve. I had changed it over the summer so I didn't think it would be bad already. I'm not sure if the colder weather made it finicky. I installed a new PCV valve anyway and it runs great.So for cheap try the PCV valve. Quote Link to comment Share on other sites More sharing options...
George Posted February 13, 2015 Author Report Share Posted February 13, 2015 Ok Robert, this one is pretty much for you. Well, for almost 2 months it ran great. It started surging again a week ago or so. I've been able to borrow the portable scan tool from work (OTC genisys SPX). When started cold the ECM is in open loop, the long and short term fuel trims (LTFT & STFT) start at 128 ea. then Closed loop, cruise on, 58mph LTFT & STFT both in the 140- 150 range. Occasionally STFT will reach 180. When coming to a stop w/ LTFT & STFT approx. 140 as soon as the fuel trim cell hits 16 the engine starts surging. By stabbing the gas to keep it running, it will idle smooth when the LTFT settles at 100- 103 & STFT is at 125- 130. What does this mean? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted February 13, 2015 Report Share Posted February 13, 2015 while cruising, the ECM is seeing the O2 going extremely lean, so the fuel trims are going significantly positive(STFT of 180 alone with a 128 LTFT is 40% additional fuel). that's really hard to believe, which would lead me to believe you have a misfire or otherwise have oxygen getting sucked into the exhaust in front of/around the O2 sensor. if not, then the O2 sensor itself is junk. at an idle, the ECM is commanding noticeably less fuel due to O2 correction. Quote Link to comment Share on other sites More sharing options...
George Posted February 13, 2015 Author Report Share Posted February 13, 2015 (edited) The o2 is a fairly consistent .45v w/ quick blips to .2 and to .9. Should the o2 transition that fast or should it gradually change? Is it possibly to suck that much air through the PCV system? What other values would help? The lean/ rich flip flops and the throttle response is still crisp, seems ok. The engine coolant temp seems accurate, follows with the gauge, runs 193deg w/ 195 thermostat. Sometimes rpm will fluctuate 200- 300 rpm at cold start up (10 deg F). Edited February 13, 2015 by George Added info Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted February 13, 2015 Report Share Posted February 13, 2015 O2 sensor should be constantly switching from above ~600mV to under ~300mV when in closed loop. how quickly it switches depends on a few things, mostly the condition of the sensor itself and how hot it is, along with how quickly the PCM is commanding the fuel mixture to switch between rich/lean(it slows down transition speed considerably near idle to keep a smooth idle possible). PCV shouldn't cause that much of a deviation... you could try temporarily plugging it, but I wouldn't expect to see much of an improvement. being a MAF car and seeing the PCM remove a bunch of fuel at idle and add a bunch while cruising doesn't imply a vacuum leak(those would be reversed). how old is the MAF? cleaned recently? Quote Link to comment Share on other sites More sharing options...
Schurkey Posted February 13, 2015 Report Share Posted February 13, 2015 considering the 06+ got a bump in power from 275HP to 291HP, those ones might flow even more. First Guess: The boost in power was due to the revised SAE procedure for testing horsepower, not an actual increase due to revised/improved parts. As I recall, the revised procedure was slightly controversial as American engines tended to increase rated power, while Japanese engines didn't increase under the new testing method. Quote Link to comment Share on other sites More sharing options...
George Posted February 14, 2015 Author Report Share Posted February 14, 2015 (edited) I installed a new AC Delco O2 sensor last summer, new spark plugs a week ago. New coils and plug wires 2 yrs ago. About a year ago I got a MAF from j/y cleaned and installed it with no change, that was before I took it to the dealership where they found the bad injector. It doesn't mean the j/y MAF is working right either. I'll have to get the scan tool again and see what the MAF is doing. Last summer I tried a different ECM w/ PROM out of a '95 Monte as well with no change. I reinstalled my original PROM in the Monte ECM About the only sensors I haven't changed are the crank, temp gauge sending unit and ICM. I may buy a new MAF depending on what the scan tool says. It seems when I disassemble UIM for what ever reason it doesn't do this for a week or so. When it is in SURGE mode, stopping and putting it in park, it will die after surging 3 or4 times. Edited February 14, 2015 by George Added info Quote Link to comment Share on other sites More sharing options...
George Posted February 14, 2015 Author Report Share Posted February 14, 2015 (edited) Here is a pic of the scan tool after stabbing the throttle to keep it running, and it idling fine for 15min or so.. I guess it bothers my that the long term fuel trim is at 100, maybe that's normal for idle. While cruising, the LTFT is 140ish while the STFT spikes to 180, but is usually 145-150. What readings should I put on the screen, I can group them however. Sent from my iPhone using Tapatalk Edited February 14, 2015 by George Added readings question Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted February 15, 2015 Report Share Posted February 15, 2015 i don't know if it's normal for the 94-95 LQ1 code, but your carbon canister is being purged at idle? that might be bringing down the LTFT. TPS voltage is right on the edge of acceptable. the PCM is calculating it correctly for 0%, but the voltage seems really low to me. pulling the upper intake off for a temporary fix is weird... seems like that would imply a vacuum leak or sensor/actuator/wiring issue. you're running a normal IAC count for idle and blipping the throttle to fix it wouldn't doesn't make vacuum leak seem likely either. http://imgur.com/dFGb22f that is GM's rundown of what might be causing a surging idle, I can grab specifics if you need them. Quote Link to comment Share on other sites More sharing options...
George Posted February 20, 2015 Author Report Share Posted February 20, 2015 First off, thank you Robert for your code operations insight and everyone's suggestions. Well, I think I found the culprit of the strange running/ surging condition (although I've thought this many times before). After looking more closely at the O2 sensor numbers and noticing that it seemed to "lock up" at 450 mv, I decided to change it out. Upon removal I found that the ground tab had broken off. The heat sleeve was hiding the problem and probably holding the ground tab for an intermittent connection. Now the O2 readings vary as they should and not jump around or "lock up at 450mv (open loop mode). The fuel trims hang around the 125- 130 mark w/ the long term fuel trim dropping to 105 or so at idle. I drove the car about an hour and a half tonight w/ no hesitation or surging whatsoever and an even better throttle response, of course. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
George Posted March 3, 2015 Author Report Share Posted March 3, 2015 TPS voltage is right on the edge of acceptable. the PCM is calculating it correctly for 0%, but the voltage seems really low to me. I looked up the specs on the scan tool as I slotted the TPS for adjustment. It looks like the 0% is the important number. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
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