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Need advice from starquest veterans.


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#1 Spooled_Starion

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Posted 01 April 2019 - 06:17 PM

To all the starquest veterans: what can cause extreme over fueling on a stock fuel system in my 1987? I've gone through multiple sets of oem and aftermarket injectors all of them dump to much fuel under boost. I currently have 4 sets of oem injectors and every single combination of primary and secondary injectors dumps to much fuel. I find it unlikely, but possible that they are all bad. I'm leaning towards my issue being elsewhere in my fuel system. I still have the oem fuel pump, replaced fuel filter in bay, and have tried swapping my fpr for one of the 4 others I have. When I swap my fpr out for a different one my car runs to lean and wont boost because of not enough fuel. I do have an air/fuel gauge, dont worry I'm not running it lean or pushing it when she tries to run lean. I do also have the hks pfc fcon, but it is set at 0, which is stock. I also have the hks fcd and was almost wondering if the signal from that could possibly be causing an overwhelming situation because of how it modifies the injector signals. I also have 4 or 5 maf sensors I've swapped between and the current one in my car has made it run the best. I'm hoping someone might be able to help with this situation. Any advice is appreciated. Yes, all basic maintenance has been done, correct plugs, correct timing, tps is .5v, no vac leaks. The second issue I am having is while I'm cruising or at part throttle my car misses and it's very obnoxious. It doesnt run rich or lean when it misses the afrs are still good so I assume that it's a spark miss, but with new plugs, new plug wires, new H.O msd coil, new cap I'm not sure what it's happening. Any input on wither of these is very much appreciated. Thanks

Edited by Spooled_Starion, 01 April 2019 - 06:44 PM.

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#2 croquest87

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Posted 01 April 2019 - 06:34 PM

How much boost?  Plug gap?

Edited by croquest87, 01 April 2019 - 06:35 PM.


#3 Spooled_Starion

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Posted 01 April 2019 - 06:40 PM

14psi on a td05h 14g. Plugs are the correct ngk 7031 with the gap they came with, which worked perfect with the 12a. I pulled them out and gapped them down thinking I was experiencing spark blow out but even at .32 it still misses while cruising and part throttle only.

Edited by Spooled_Starion, 01 April 2019 - 06:43 PM.

Hks Downpipe, hks exhaust, hks intake, hks camshaft, hks pfc-fcon, hks fcd, hks turbo timer, trilogy injectors, mk1 short shifter, GReddy traditional shift knob, 89 ecu, Hks Boost gauge, innovative wideband A/F gauge.

#4 81zfan

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Posted 01 April 2019 - 06:42 PM

Following...
88 conquest, .30 over block,Bs eliminated, M28 head ,17c turbo,Ottowerks shifter bushing, Lower Shores Braided lines and TB parts, Boostinmini TPS conversion kit,Optional Methanol Kit "when hooked up",Custom 2.5 Intercooler Piping,3 inch Downpipe, Gasket Ported Intake and Exhaust Manifold, Manual steering conversion,ACT HD clutch, Ebay knock off GReedy BOV,put car on a diet "lost between 590-620 lbs", Super AFC, AEM wideband, Glowshift Boost,Fuel Pressure, and Coolant Temp gauges, ARP Head and Rod bolts/Studs, Walbro 255.... In the process of adding more !

#5 aknorthstar

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Posted 01 April 2019 - 06:59 PM

You dont need a HKS FCD on a 87 first of all. FCD is for cars with a external pressure sensor (MAP) . The 87 and up have a internal pressure sensor in the maf. The istructions on the HKS site goes over this. Never ran a FCD on a 87

Edited by aknorthstar, 01 April 2019 - 07:00 PM.


#6 Spooled_Starion

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Posted 01 April 2019 - 07:53 PM

This car was built by hks in the 90s so I'd trust what and why they did what they did. The thing is she used to run perfect and now she doesn't so whatever my issue is has cam about long after hks modded this car.

Edited by Spooled_Starion, 01 April 2019 - 07:56 PM.

Hks Downpipe, hks exhaust, hks intake, hks camshaft, hks pfc-fcon, hks fcd, hks turbo timer, trilogy injectors, mk1 short shifter, GReddy traditional shift knob, 89 ecu, Hks Boost gauge, innovative wideband A/F gauge.

#7 87redcat

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Posted 01 April 2019 - 08:21 PM

Water temp sensor that has 2 prongs. Located on intake mani between #1 and #2 runners.
Mine has been running rich, fouling plugs, ie. Running in closed loop. Switched it out and BAM. Runs like new.
Good luck buddy. Keep us updated
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#8 Spooled_Starion

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Posted 01 April 2019 - 08:55 PM

Yeah I already replaced the cts a few months back with no difference in run ability or drivability
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#9 ucw458

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Posted 02 April 2019 - 12:21 AM

Well start with the simple stuff that usually goes wrong, grounds and fuseable links.

What's your fuel pressure?


Also like previously stated, ditch the FCD.  Just because HKS put it in doesn't mean it's correct.  The FCD was for 83-86 cars that had a MAP sensor.  87-89 do not have a map sensor.  They cannot sense boost in any way.  The FCD was to clamp the map sensor voltage below 5v to prevent fuel cut.  They might have wired it to the baro sensor which would be stupid.  That reads atmospheric pressure not manifold pressure.  The baro sensor is used to compensate for altitude.  The FCD is likely old, miswired, and may be failing causing weird issues.  It's a potential failure point that can't be ruled out until removed.
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#10 jinx

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Posted 02 April 2019 - 02:23 AM

did u boost-test your plumbing ? any fuel in vacuum line to 'this good' fpr ?
my throttle body hose deteriorated/had a puncture that leaked only under boost.... black smoke, car fell on its face
this is wierd tho.... can't see 4 bad fpr, plus they all make the car run that lean:

Quote

tried swapping my fpr for one of the 4 others I have. When I swap my fpr out for a different one my car runs to lean and wont boost because of not enough fuel.
part throttle miss could be distributor cannister diaphram

#11 Spooled_Starion

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Posted 02 April 2019 - 04:59 AM

View Postjinx, on 02 April 2019 - 02:23 AM, said:

did u boost-test your plumbing ? any fuel in vacuum line to 'this good' fpr ?
my throttle body hose deteriorated/had a puncture that leaked only under boost.... black smoke, car fell on its face
this is wierd tho.... can't see 4 bad fpr, plus they all make the car run that lean:

part throttle miss could be distributor cannister diaphram

If by boost testing my plumbing, are you referring to boost/vac leaks? If so then, no I dont have a boost or a vac leak. The vacuum line going to my fpr does not get fuel in it. Always dry, I've checked multiple times as that indicates a bad FPR. Not sure what a distributer diaphragm is exactly but if that is the vacuum advance then yes it is new and passed the holding vacuum and smooth rod movement test.
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#12 Turbo Cary

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Posted 02 April 2019 - 07:30 AM

Check your engine coolant temp sensor. When mine failed it basically pegged full rich.

#13 scott87star

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Posted 02 April 2019 - 08:23 AM

Has to be your fuel pressure, you answered it yourself when you replaced it and the symptoms changed.  Now it may be a compound problem, meaning the FPR itself and something else in the fuel system such as any one of the additional filters in the system, fuel pump or obstructions in the feed or return lines.  Get a fuel pressure gauge in the system on the throttle body to aid in troubleshooting.

You say you have an AFR gauge but I doubt it's accurate and I assume its a narrow band gauge.  The clue is misfiring in cruise, you say it isn't running rich or lean but a misfire means a cylinder didn't fire, didn't burn its load of fuel and oxygen.  Wide band (or narrow) sensors measure the amount of oxygen in the exhaust so when you get a misfire it always reads huge lean from the unconsumed oxygen getting pushed through the exhaust.
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#14 speedyquest

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Posted 02 April 2019 - 08:32 AM

I'd have to agree with Scott on this. I'd also heed the point several people have made about your HKS FCD, its not needed and only adding more confusion and variables to your problem.

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#15 Spooled_Starion

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Posted 02 April 2019 - 11:56 AM

View PostTurbo Cary, on 02 April 2019 - 07:30 AM, said:

Check your engine coolant temp sensor. When mine failed it basically pegged full rich.

I replaced it last year, I suppose maybe it could have failed already but I will have to ohm it out and see.

View Postscott87star, on 02 April 2019 - 08:23 AM, said:

You say you have an AFR gauge but I doubt it's accurate and I assume its a narrow band gauge.  The clue is misfiring in cruise, you say it isn't running rich or lean but a misfire means a cylinder didn't fire, didn't burn its load of fuel and oxygen.  Wide band (or narrow) sensors measure the amount of oxygen in the exhaust so when you get a misfire it always reads huge lean from the unconsumed oxygen getting pushed through the exhaust.

My air fuel gauge is actually brand new with maybe 100 miles on it. Why would you assume it was a narrowband air fuel gauge? I actually run the Aem x series wideband with the bosch 4.9 LSU sensor for monitoring purposes. As for my standard o2 sensor it utilizes the factory style sensor setup in the downpipe. When it misses under cruise and part throttle it doesnt register any change on the wideband gauge, nothing rich or lean, and with the 4.9 LSU sensor, which is the fastest responding wideband sensor on the market, and if that sensor cant detect any change in afrs when it happens I dont know what else to say.

View Postucw458, on 02 April 2019 - 12:21 AM, said:

Well start with the simple stuff that usually goes wrong, grounds and fuseable links.

What's your fuel pressure?


Also like previously stated, ditch the FCD.  Just because HKS put it in doesn't mean it's correct.  The FCD was for 83-86 cars that had a MAP sensor.  87-89 do not have a map sensor.  They cannot sense boost in any way.  The FCD was to clamp the map sensor voltage below 5v to prevent fuel cut.  They might have wired it to the baro sensor which would be stupid.  That reads atmospheric pressure not manifold pressure.  The baro sensor is used to compensate for altitude.  The FCD is likely old, miswired, and may be failing causing weird issues.  It's a potential failure point that can't be ruled out until removed.

View Postspeedyquest, on 02 April 2019 - 08:32 AM, said:

I'd have to agree with Scott on this. I'd also heed the point several people have made about your HKS FCD, its not needed and only adding more confusion and variables to your problem.

I have cleaned a few of the grounds already I could go back and redo it though. My fusible links have been replaced about 6 months back as well and they still appear to be in like new condition. I even cleaned up the contact points inside the link housing for better contact. I will attempt to mess with the settings on the FCD but since the HKS PFC FCON utilizes a MAP sensor I am thinking that the fcd is in place for that. I will attempt to either pull the FCD completely or try adjusting the settings on it to see if anything changes and will reply back after that. I should have mentioned that the miss under part throttle and cruise has started only after I changed out my 12a for a 14g. Thinking I was experiencing spark blow out from more air i tried gapping my plugs down some to no avail. It's weird because this car has had a 14g on it for years up until it blew up and was demoted to a 12a until either a rebuild or replacement 14g could be found.  Once a suitable 14g replacement was found and installed only then did it start the miss at part throttle and cruise.

Edited by Spooled_Starion, 02 April 2019 - 12:36 PM.

Hks Downpipe, hks exhaust, hks intake, hks camshaft, hks pfc-fcon, hks fcd, hks turbo timer, trilogy injectors, mk1 short shifter, GReddy traditional shift knob, 89 ecu, Hks Boost gauge, innovative wideband A/F gauge.

#16 Spooled_Starion

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Posted 02 April 2019 - 12:02 PM

Thanks for all the help so far guys I do appreciate it! I did happen to adjust my fcd to no avail on any setting it just seems to dump fuel the same. I'm gonna try to get a fuel pressure gauge installed soon and will post some updates after I'm able to see what my fuel pressure looks like. I wonder if I have a compounding issue of possibly a weak fuel pump with a bad fpr. Because of how the fpr made my car run lean when I changed it out to different ones I'm wondering if my pump is barely keeping up and having a blown fpr is letting it get as much fuel as it can, and when I put a functional fpr on her the fuel pump just couldn't get enough pressure to the injectors or for to run right.

Edited by Spooled_Starion, 03 April 2019 - 07:22 PM.

Hks Downpipe, hks exhaust, hks intake, hks camshaft, hks pfc-fcon, hks fcd, hks turbo timer, trilogy injectors, mk1 short shifter, GReddy traditional shift knob, 89 ecu, Hks Boost gauge, innovative wideband A/F gauge.

#17 87redcat

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Posted 04 April 2019 - 09:33 AM

If you have the original fuel pump, you probably have the original filters as well. Go big and get a bosch 044 and change the filter in the tank, remove the cone filter at the inlet side of the pump replace the filter in the engine bay clean and blow out the hard lines.
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#18 81zfan

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Posted 04 April 2019 - 09:59 AM

Have you removed the inspection plate in the rear and checked the filters and pump?
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#19 Spooled_Starion

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Posted 04 April 2019 - 03:12 PM

View Post87redcat, on 04 April 2019 - 09:33 AM, said:

If you have the original fuel pump, you probably have the original filters as well. Go big and get a bosch 044 and change the filter in the tank, remove the cone filter at the inlet side of the pump replace the filter in the engine bay clean and blow out the hard lines.

Is that a good pump? I've never actually had to replace the fuel pump on a single starquest I have owned. I have the fuel filter that DAD sells on his website and i also replaced the one in the bay already about 10k miles ago. My pump is definetly getting loud and whining a lot lately. So i assume she is either getting clogged or a filter is getting plugged up causing this pump whine I'm now getting.

View Post81zfan, on 04 April 2019 - 09:59 AM, said:

Have you removed the inspection plate in the rear and checked the filters and pump?

I did pull the inspection plate this morning and I wasnt really sure what to check in there. Everything was dirty as hell, looks to be the original pump because how how filthy everything was and how undisturbed all the dirt and debris buildup looked. Not a lot of room in there to change the pump is there. Looks like I'd have to cut the access hole a lot bigger to change out the pump.

Edited by Spooled_Starion, 04 April 2019 - 03:14 PM.

Hks Downpipe, hks exhaust, hks intake, hks camshaft, hks pfc-fcon, hks fcd, hks turbo timer, trilogy injectors, mk1 short shifter, GReddy traditional shift knob, 89 ecu, Hks Boost gauge, innovative wideband A/F gauge.

#20 ucw458

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Posted 04 April 2019 - 03:22 PM

Unless you're MPI and pushing big power an 044 pump is overkill.  That pump supports 600-700 HP.  You will need a bigger FPR and a 10ga wire to support that pump.  Not to mention they are loud.
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