Lance_S Posted March 18, 2012 Report Share Posted March 18, 2012 So i got the rocket back on the road and when I hit about 15 lbs of boost on the s16g It goes lean into the 13's and 14's and the power cuts out like a fuel cut. I am guessing the knock sensor is kicking in. I keep adding fuel with the MAFT but it doesn't make a difference. If I turn the boost down to 12 or 13 its fine. I have to check the pump, it's pretty new bit I don't believe it's a high volume pump. On a stock pump, at 13 psi am I out of fuel??? Link to comment Share on other sites More sharing options...
StarquestRescue Posted March 18, 2012 Report Share Posted March 18, 2012 (edited) A healthy stock pump should keep up fine. How fast does it go from say 11.00 afr to 13-14 than cut? Say in terms of rpms? or maybe its happens in a blink and the 13-14 is the last you see before it "cuts"? If it stuttering, bucking hesitating but still trying to run, it may be misfiring, which can give a false leaner reading. You can either put a fuel pressure gauge in the car besides the af meter, or buy a pump you may not need. Edited March 18, 2012 by StarquestRescue Link to comment Share on other sites More sharing options...
Lance_S Posted March 18, 2012 Author Report Share Posted March 18, 2012 Yeah, I Jane a gauge on the tb, i will have to just get a line to extend it. It bucks, like I pulls the fuel for a second the. Brings it back in. It's not rpm related as much as boost. As soon as I hit 15 lbs I hit the cut. Like someone turning a switch off the. Back on real quick. Of I stay in the throttle it wI'll do I every 5 or 6 seconds. I had an 87 ecu in it and it happened last summer, I figured it was the ecu. Urging fuel. So I swapped it out with an 88/89 thinking I would fix he problem but it didnt so now I am thinking fuel. Link to comment Share on other sites More sharing options...
ucw458 Posted March 18, 2012 Report Share Posted March 18, 2012 New pump huh, did you remove the cone filter? The cone filter blocks 2/3 of the pump inlet on aftermarket pumps. Just enough so you can idle and cruise but not boost. I bought a SQ with the same problem. Turned out to be a new pump with the cone filter installed. Link to comment Share on other sites More sharing options...
StarquestRescue Posted March 18, 2012 Report Share Posted March 18, 2012 (edited) If I turn the boost down to 12 or 13 its fine. What is the afr at 12-13 psi? A fuel pump does not just cut out and back on. I think you need to back off on your wot setting and work the boost up real slow. On the other hand if you are trying to compensate for a lack of fuel flow with the maft, you may be sending the ecu a airflow signal that is off the top of the map. In which case the "cut" is a secondary symptom. Edited March 18, 2012 by StarquestRescue Link to comment Share on other sites More sharing options...
wrngwae Posted March 19, 2012 Report Share Posted March 19, 2012 (edited) Lance,,,,,my car had a similar issue...... when the PO replaced pump with im assuming a used stocker... they had a cone filter in the replacement and somehow the original was stuck in the hose when they removed it....so there were 2 cone filters and both were nasty...... just a thought... also....when i was running maft at 20psi on a tdo5h 16g. i had a secondary injector "get weak",,,,,,, but if i turned the boost down it was fine.....you have a spare secondary to swap with???? if not i got one for ya.. Edited March 19, 2012 by wrngwae Link to comment Share on other sites More sharing options...
Lance_S Posted March 19, 2012 Author Report Share Posted March 19, 2012 Thks guys. I will first check the filters. Then back it down and start fresh from around 12 psi and worlmy way up. Link to comment Share on other sites More sharing options...
Indiana Posted March 19, 2012 Report Share Posted March 19, 2012 What rpms does this "cut" happen at 15psi? Do you see the air/fuel go lean after this or before? If you lean out it will keep going, if something is causing this then it hesitates is the result the air/fuel number you see? What is the air/fuel prior to this, at what boost, rpm? I usually don't comment on MAFT modified cars because I don't run them but aren't they adjustable by rpm windows? Are those modified by throttle position? They are on SAFC is why I ask and if have the setup wrong it will run like crap and do what you are describing. Link to comment Share on other sites More sharing options...
Lance_S Posted March 19, 2012 Author Report Share Posted March 19, 2012 I backed the boost off and set the maft settings back to where I had them before. I am running 13 to 14 lbs. No hickups. For the maft settings, Base = 2, Idle = 2, mid = 2 and WOT = 0. I am at high 11's at WOT, 14.5 at idle, 14.5 at cruise, midrange throttle will drop down around 11 to 12 depending or rpm and boost. So the numbers are pretty good as far as I can tell. Car pulls pretty hard. I will slowly inch it up and see where it goes. Probably an additional 1lb or two of boost and maybe one click up on the WOT? I haven't had a chance to check the fuel pump yet. I will do that soon. Thanks, L Link to comment Share on other sites More sharing options...
scott87star Posted March 19, 2012 Report Share Posted March 19, 2012 All misfires look lean because a cylinder didn't fire hence didn't burn the oxygen that now gets dumped into the exhaust manifold and is read by the wide band. So don't rule out too rich or ignition issues either, watch the wide band very carefully prior to the misfire to see if its dropping or rising. Scott Link to comment Share on other sites More sharing options...
Lance_S Posted March 19, 2012 Author Report Share Posted March 19, 2012 When it does it there is no pre-warning on the AFR, it just cuts. Hard to tell if it's a fuel or ignition cut. It's a buck. Like a flick of the switch. I backed it down, reset everything back to normal and am currently running 13 lbs. I will creep it up slowly. I also have a take a look at the fuel pump and check the cone filter. Link to comment Share on other sites More sharing options...
Indiana Posted March 19, 2012 Report Share Posted March 19, 2012 I'd get rid of that greasy air filter and get some MAS cleaner. Link to comment Share on other sites More sharing options...
Lance_S Posted March 19, 2012 Author Report Share Posted March 19, 2012 I'd get rid of that greasy air filter and get some MAS cleaner. I actually cleaned the MAS when I reinstalled it. As far as the K and N filter, I don't really know what to replace it with. Any ideas? I doubt that's my fuel cut problem but if it's a crap filter I will look to replace it. I am working my way up in boost. I am at 15 right now, had to bump the base one and add one to WOT but it's not bucking currently. Still have a ways to go but it's getting there, it's actually pretty quick right now. I am a little rich on mid range with light to medium throttle I dip down into the 10's on my AFR but if I pull back on the mids I go lean at WOT, even when bumping the WOT 3 positions. So there is a pretty close relationship between the mid setting and the WOT setting. Mid seems to have as much effect on WOT as WOT does. They must overlap a bit. Link to comment Share on other sites More sharing options...
StarquestRescue Posted March 20, 2012 Report Share Posted March 20, 2012 I will slowly inch it up and see where it goes. Probably an additional 1lb or two of boost and maybe one click up on the WOT.Thanks,Assuming a healthy fuel system, you do not necessary add fuel with the maft as the boost is raised. The airflow meter will send a higher hz signal to the ecu as boost increases and the ecu will add the extra fuel based on that higher air flow signal. What a maft does is modified the air flow signal before it gets to the ecu. Link to comment Share on other sites More sharing options...
StarquestRescue Posted March 20, 2012 Report Share Posted March 20, 2012 (edited) I am a little rich on mid range with light to medium throttle I dip down into the 10's on my AFR but if I pull back on the mids I go lean at WOT, even when bumping the WOT 3 positions. So there is a pretty close relationship between the mid setting and the WOT setting. Mid seems to have as much effect on WOT as WOT does. They must overlap a bit.That is not the way it is supposed to work. Is the #4 dip switch off? I would not ruel out a bad gm mas. They are noted for fequent failure and there have been several documet cases of bad gm mas in the last couple of years on here. I posted right before your last post, in case you missed it. Edited March 20, 2012 by StarquestRescue Link to comment Share on other sites More sharing options...
StarquestRescue Posted March 20, 2012 Report Share Posted March 20, 2012 (edited) I usually don't comment on MAFT modified cars because I don't run them but aren't they adjustable by rpm windows? Are those modified by throttle position? They are on SAFC is why I ask and if have the setup wrong it will run like crap and do what you are describing.This model maft does not have a tps input. So there is just one setting, no high or low setting.In base mode, switch 4 off. the idle knob modifies the airflow signal at 25Hz (these cars idle around 50), the mid knob at 500 hz (the secondary kicks in at 390 or sooner), and the wot at 1000 hz. (which is likely reached by 12-13 psi depending or rpms.) It can run in rpm mode (switch 4 on)if you have msd, but the rpm points do not match up well with a conquest.. If switch 4 is on with out a rpm signal, the knobs give additional fine tune adjustment. As the base knob is turned for larger injectors t actally leans out the base setting. IE base 2 is leaner than 0. It gets confusing and the instructions are crap. Especially if you try and go beyond the base mode settings. The commet "the knobs are useless" is common in the dsm world" That why they just use the base setting for the appropriate injector size and do the real tuning with an afc. Edited March 20, 2012 by StarquestRescue Link to comment Share on other sites More sharing options...
Caliber308 Posted March 20, 2012 Report Share Posted March 20, 2012 (edited) What is your Fuel Pressure reading? Have you upgraded the ECU ? You don't need to screw around with any switches except these: setting the MAF size, Idle, Midrange and Wide Open Throttle switches. Do you have a MAF- Translator installation Instruction Manual? If your Fuel Injectors are not operating properly, or if your fuel filters are clogged up you will be at it, trying to get the proper AFR setting....... FOREVER. Everything in your Fuel System has to be in pristine condition prior to introducing a MAF-Translator into it. Want to find out? Remove the MAF-T and go back to what you ran prior to it. Does it run fine?If so, you need to do some fuel system work. Members who install the MAF-T (Rev 2.02) set up need to know this: This system was NEVER meant for a Starquest. It was designed for a 1990-1993 DSM Four Injector set up. We can make it work by reading how others in the past did it. You and others might want to do some searching in the Engine and Performance mod Forum. That is where I found the information to set mine up, properly. Up and running correctly in less than 20 minutes by following the information in the Engine and Performance Mod Forum. Bill Edited March 20, 2012 by Caliber308 Link to comment Share on other sites More sharing options...
Lance_S Posted March 20, 2012 Author Report Share Posted March 20, 2012 SQR, Yeah, I was actually just reading through the great MAFT thread and read about the base leaning it out. I check the hypothesis and sure enough. So here is the interesting thing. When it's lean, it doesn't buck. At WOT around 13 to 14 AFR is doesn't buck at all and pulls hard. I know it's lean so I can't keep it there. But when i add fuel, it bucks. I had the base at 4 and it was lean but it didn't buck and pulled hard and clean. I dropped the base to 3 and it was still lean but better. I dropped it to 2 and it fattened up to 12 at WOT but it started bucking again. Frustrating. I can get it to pull like a champ and melt my motor or buck and be safe. Something I am missing. It only does this at 14 psi or above. When I drop the psi down to 12, I can get it to run at WOT in the 11's and it won't buck. Link to comment Share on other sites More sharing options...
Lance_S Posted March 20, 2012 Author Report Share Posted March 20, 2012 What is your Fuel Pressure reading? Have you upgraded the ECU ? You don't need to screw around with any switches except these: setting the MAF size, Idle, Midrange and Wide Open Throttle switches. Do you have a MAF- Translator installation Instruction Manual? If your Fuel Injectors are not operating properly, or if your fuel filters are clogged up you will be at it, trying to get the proper AFR setting....... FOREVER. Everything in your Fuel System has to be in pristine condition prior to introducing a MAF-Translator into it. Want to find out? Remove the MAF-T and go back to what you ran prior to it. Does it run fine?If so, you need to do some fuel system work. Bill I have 38 to 40 lbs at idle. I need to get an extension hose and tape it to the windshield. The pump, lines and filter were replace just before I got the car. I just upgraded the ECU this past weekend. I actually thought it was an 89 ECU but I popped the top and found out it was the 87. I was sure that was my problem because I ran into this before. So I put a new ECU in it and it didn't solve it. But yes, it's an upgraded ECU. So are are saying set the base switch back to zero and just adjust the idle, mid and WOT? I have the instruction manual and just got done reading it. As far as putting back to stock. I have the original stuff but never ran it with it on. When I got the car I switched it to the MAS and MAFT setup right away. I then just kept it under 14 lbs because I had bad head seals and wanted to replace them before bumping the boost. Link to comment Share on other sites More sharing options...
bha280 Posted March 20, 2012 Report Share Posted March 20, 2012 I am having a similar problem and have pretty much the same mods as you. Please, keep posting what you find. Only difference is my cam. Link to comment Share on other sites More sharing options...
StarquestRescue Posted March 20, 2012 Report Share Posted March 20, 2012 (edited) What injectors are in this car? If they are oem, pull them out and look at the letters on them.The evidence points to fuel pressure dropping off or ithe injectors are to small ( in this case smaller than the 650/959 you think you have) or not flowing what they are rated for. Edited March 20, 2012 by StarquestRescue Link to comment Share on other sites More sharing options...
Lance_S Posted March 20, 2012 Author Report Share Posted March 20, 2012 650/950 trilogys Link to comment Share on other sites More sharing options...
Caliber308 Posted March 20, 2012 Report Share Posted March 20, 2012 So are are saying set the base switch back to zero and just adjust the idle, mid and WOT? Yep. I run mine sometimes to 20 psi boost without any problems. If you have the Installation Instructions, read what the BASE knob does. It actually has nothing to do with a Starquest. Remember, this system was meant for a FOUR INJECTOR DSM set up with all four of the injectors the same size, not a two injector set up with a different Primary and Secondary size The information is under controls on page 4. AUX Knob, the same thing: We don't run a Trigger Wire on a Starquest. So, that leaves four switches: 1. Mode Switch.2. Idle Switch.3. Midrange Switch.4. Wide Open Throttle Switch. Set it up using only those four, and you will be fine. Bill Link to comment Share on other sites More sharing options...
Lance_S Posted March 20, 2012 Author Report Share Posted March 20, 2012 might be right SQR. I was reading the maft thread and someone posted that they had the same problem at 15 psi until he switched to twin 950's, then it went away. Thus the thread topic, lol, "I might be out of fuel". Link to comment Share on other sites More sharing options...
Lance_S Posted March 20, 2012 Author Report Share Posted March 20, 2012 Yep. I run mine sometimes to 20 psi boost without any problems. If you have the Installation Instructions, read what the BASE knob does. It actually has nothing to do with a Starquest. Remember, this system was meant for a FOUR INJECTOR DSM set up with all four of the injectors the same size, not a two injector set up with a different Primary and Secondary size The information is under controls on page 4. AUX Knob, the same thing: We don't run a Trigger Wire on a Starquest. So, that leaves four switches: 1. Mode Switch.2. Idle Switch.3. Midrange Switch.4. Wide Open Throttle Switch. Set it up using only those four, and you will be fine. Bill The mode switch is just suppose to be set with the 4 switches off correct? That is the way I currently have it for the 3 inch mas. L Link to comment Share on other sites More sharing options...
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