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Bad PCM or Bad Injectors throwing off noid light??? ...opinions wanted ..NIGHTMARE!

LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Bad PCM or Bad Injectors throwing off noid light??? ...opinions wanted ..NIGHTMARE!

Old 02-28-2019, 08:47 PM
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Re: Bad PCM or Bad Injectors throwing off noid light??? ...opinions wanted ..NIGHTMAR

squarehead, thanks for the perspective on 2 strokes and taking time to read this....bottom line is I hope it survived it and hope to find out soon. Injuneer, truthfully as I think back on that oil change last May it was probably worse than described, probably 7+ quarts came out VERY quickly. As far as I know the engine wasn't run under load, but it may have been run long enough to get hot during the so called "troubleshooting". Enough to finally blow my header gasket that had a missing bolt for years but never blew before (it did blow right there though).

I actually found several AFPR's for the LT1 and finally settled on one recommended by a competent forum member here (I think it was Shoebox). I ordered it from Advanced (Borg Warner BWD-23065) for $65 grand total. I'll start by trying to get it adjusted right for "key-on" (would that also be 43.5 PSI since there's no vacuum compensation when not running?). Got the correct Schrader core #12570619 from Rock Auto as you pointed me to Fred, thank you. Should be a week or so before both arrive. The old stocker showed some corrosion on the inside and I wasn't going to give Aeromotive $200+ after all of this! I've read many RECENT posts of failures right out of the box! Often it causes multiple gasket or ring failures. Hoping my intake and head gaskets survived, they seemed to but I won't know until I can watch it run normally.

I wanted to get injector clips that work with SVO 42# green tops so I could see if the injectors leak with the key on while at this, but see conflicting info when reading posts regarding OEM clips working with the SVO's (no data on special clips existing). I have posted in an old thread here to see if anyone learned more about it. If the clip isn't tight or proper fitting enough to seal the upper O-ring it's pointless for me to use with the key-on test. I have an easy question (next) …..

During this troubleshooting I would like to disconnect the miserable inline fuel pump that is mounted and running dry (bypassed with a metal pipe), I don't want it shorting out and blowing a fuse or whatever might happen leaving it this way too long. I do not know which fuse it's on and assume it's tied into the same fuse the intank pump uses. Can I just heat shrink and/or electrical tape the heck out of the hot wire and fold it back on itself or something? Ground wire ok to leave hooked up? I did a search on it but kept getting home electronics pages talking about using wire ties to seal the ends of live wires.

For reference to help with the FP question in this post, what should the "key-on" pressure be with an OEM FPR? Seems like it would be 43.5 PSI just like when running with the vacuum line removed and plugged (since the vacuum line is taken out of the equation when not running). However, I realize the pump isn't running continuously during "key-on" and pressure is bleeding off ….so, 35-40 PSI? Looking for some frame of reference to use as a starting point with an AFPR (I think mine was set very close to stock 43.5 PSI). I decided go with an AFPR in case my "permanent" open loop tune needs to be compensated with small FP adjustments.

Many thanks!

Last edited by canbaufo; 02-28-2019 at 09:03 PM.
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Old 03-07-2019, 10:45 AM
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Re: Bad PCM or Bad Injectors throwing off noid light??? ...opinions wanted ..NIGHTMAR

I should be going across town to work on the car again within a few days. I had a few questions in the last post I'm curious about if anyone has time. Especially with regard to the inline fuel pump wiring. In summary I would like to disconnect the power to the bypassed inline fuel pump during troubleshooting, because it's sitting there running dry and not sounding good at all. Is it safe to disconnect the positive wire to the inline pump and zip tie a chunk of rubber over it (or use heat shrink)? I think it's on the same fuse or relay as the intank pump. I don't want to chase that and only want to temporarily disconnect the inline pump. If I get the car running properly again I'll simply replace the inline pump. Thanks for the reply on the injector clips in the other thread.
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Old 03-07-2019, 11:50 PM
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Re: Bad PCM or Bad Injectors throwing off noid light??? ...opinions wanted ..NIGHTMAR

When I installed my inline pump (part of an NOS dry nitrous kit, not current setup) I added a new relay for it back inside the hatch area. Ran 12 V from the battery (w/ 20A inline fuse), to the load side of the relay. Took 12 V for the signal side of the relay by splicing into the gray stock fuel pump wire at the harness connector at the plug over the rear axle. When the stock pump turned on it also turned on the inline pump.

See where the 12 V for your pump comes from, and disconnect it at point which has minimal exposure to the under the car environment. If you end up with a bare end on a live wire, cut the exposed copper off, bend the wire back on itself and wrap it tight with high quality plastic electrical tape. Go several inches past the end of the wire to minimize the chances of water entering. Use a plastic tie to hold the end of the wire up tight to the chassis, out of direct contact with road spray. A lot of people have done that with the connector for the skip shift relay on the T56 trans, incorporating a resistor, to defeat skip shift.
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Old 03-08-2019, 09:05 AM
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Re: Bad PCM or Bad Injectors throwing off noid light??? ...opinions wanted ..NIGHTMAR

!CAGS was my very first free mod back in 1998 when I bought the car. I don't remember being that thorough, I think I just covered the connector really well and tied it back (no cutting). I won't be driving the car until I put a new pump on. Just to run it in the garage am I ok to just wrap up the end of the power wire really well with regular electrical tape and zip tie it back on itself, or will a copper end melt whatever I cover it with? I want to do it as you described but without cutting anything. I think the end of the power wire has a rubber boot if memory serves me well. Thanks for the advice.

Last edited by canbaufo; 03-08-2019 at 09:07 AM.
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Old 03-08-2019, 08:00 PM
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Re: Bad PCM or Bad Injectors throwing off noid light??? ...opinions wanted ..NIGHTMAR

You can tape the bare end. Nothing gets “hot” unless there is current flowing, and there's no current flowing when the wire isn’t connected to anything.
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Old 03-09-2019, 10:40 AM
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Re: Bad PCM or Bad Injectors throwing off noid light??? ...opinions wanted ..NIGHTMAR

Ok thanks, I thought that was probably the case but my understanding of 12v systems is limited. Well, I was planning on working with it today but have contracted the flu. Nothing like waiting longer!
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Old 03-15-2019, 07:06 PM
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Re: Bad PCM or Bad Injectors throwing off noid light??? ...opinions wanted ..NIGHTMAR

You have a lot patience, Fred!
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Old 03-15-2019, 09:04 PM
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Talking Resolved !!!

I reinstalled the rail assembly and installed a new fuel filter yesterday before starting the engine and made the following observations:

- Key on to prime the system didn't register any FP for a few tries but I reminded myself of the lost fuel during rail and filter R&R, so I kept trying

- After about five primes the FP hit 42 PSI (I left the new Borg Warner AFPR set as it was out of the box)

- Key off and the pressure would bleed down to 38 - 39 right away but then very slowly bleed down to about 30 PSI (around 20 minutes). I could not detect any fuel leaks in the engine bay or under the car, so I decided it was finally "time".

- Started the car and it fired up beautifully, making about 37 PSI. I disconnected and plugged the vacuum source for the AFPR and observed a steady 45 PSI, engine only slightly less happy idling at that pressure (normal observation) but still a good idle.

Since it ran so well I didn't tamper with the AFPR adjustment and will only do so if necessary once I begin driving the car under load again. The throttle response is crisp as ever. There was smoke from the exhaust at first but I believe it was only residual crap burning off, old fuel / water in the exhaust, carbon, etc. It was dark outside and when I shined the flashlight on the smoke it didn't appear blue. I shut it off for a few minutes while observing the engine bay again for fuel leaks. Then re-started it and no more smoke from the exhaust. I changed the oil to conventional 10W-30 yesterday just before all of this; the old oil had some gas in it, but nowhere near what I discovered last May when I changed the oil after the hack mechanic had run the car so much during "troubleshooting".

My gut tells me everything is ok, but time (and maybe more Blackstone analysis) will tell. There was a bit of nickel colored sludge on my magnetic drain plug and it was also evident in the Pure One oil filter). I have seen this with all oil changes but I think there was a bit more than usual this time. The time before, when I changed the oil the hack mechanic polluted, it came out so fast it washed the magnetic drain plug off (so much fuel in oil it was watery). Maybe the engine survived due to not being run under load with these conditions. I will change the oil again soon just to continue to flush out and dilute any remaining fuel.

I want to give everyone who's followed along and posted here a BIG THANK YOU !!!!, especially … "Injuneer (Fred)"! I had really lost most hope after all of the things that had been tried and the difficulty of driving across town to work on it in a small space. Even after discovering the bad Aeromotive AFPR I still had doubts that it was the only problem I was facing, especially since the ex mechanic had shown me the noid light issues in person. Perhaps a horribly rough running engine is enough to throw a noid light off a bit, or maybe his was on the way out. I've recently read that noid lights don't always tell the truth, unless it's just not lighting up at all from one driver but lighting up powerfully on another.

It really makes me sick that my car has seen 1.5 years of down time due to a problem that could have literally been diagnosed in a few minutes. I may have to find a way to take this up with Absolute Horsepower LLC, as I have lost a lot of time and some money (and endured great duress) due to their numerous errors and the "run around" waiting game they put me through as well. Not to mention they literally destroyed some parts (like the inline fuel pump with power left on it while bypassed of the fuel line). There's far more I could tell about how badly it all went but there's no point in it here.

It is also entirely appropriate to add that here we have yet ANOTHER utter condemnation of the infamous Aeromotive AFPR !!!!!!!!!!

Fred, thank you again so very much for all of your feedback and the very helpful highly-detailed information. It gave me the confidence to keep going!

Last edited by canbaufo; 03-15-2019 at 09:24 PM.
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