1961ba427

iTrader: (26)

Within the last couple days my car has been acting up. First thing I noticed was it being really slow to start and smells rich when it does. By slow to start I don't mean cranking over...that is fine. It takes it awhile to fire up. Sometimes I have to press the gas pedal like in a carb'd car.
Next I noticed that when it does start it has sounds like it has a mild cam in it now so it's obviously missing.
When I drive it, it runs fine unless I drop it into a gear that brings the rpms down around 1500 - such as cruising at 60 in 6th. I get a miss then, so I have been driving it in 5th on the highway. It seems to run fine at any rpm over 2K. It also seems to run fine at WOT or just running through the gears at part throttle. I can't feel any miss or loss of power then.
I have had the car for about 4,000 miles now. It did get a miss at all rpms once after driving through a puddle about a month back, but that was only on the way home and then it was fine the farther I drove it. It didn't hiccup the next day or any since.
I did fill it up yesterday and that's about when I noticed the problem...so maybe bad gas?
Today I scanned it and the 02's seem to be working properly. I got a code #16 (IGN system Low Res Pulse Signal) and also #27 (EGR circuit) The EGR code is usual as that has been deleted, but not tuned out yet.
I also checked the fuel pressure and it is at 36# on "key on" and about 35# running at idle or giving it some throttle. The FPR is an Aeromotive Adjustable. I did notice that the FP would drop rather quickly upon key off. Shouldn't it hold pressure for awhile?
Does the Code 16 mean I definately need a new opti or opti harness?? Or is this something that could be caused by other things?
I don't remember hitting any puddles in the last few days, but did scrape/bang the y-pipe pretty good yesterday. Sounds like I may have a slight exhaust leak near the end of the Y...which is why I was hoping the 02's were reading wrong.

Car is a 97 SS M6 with 4.10's, LT's, off road Y, OBD1 PCM and knock sensor, tuned only to correct speedo so far. No EGR or AIR.

I've searched already and found several people with similar issues, but the fixes seemed to be random and anything from leaking injectors, fouled plugs, bad o2s, optis, opti harnesses, TPS, ICM, Coil, etc, etc.

Gojira94

iTrader: (4)

Sounds like you have more than one issue.

First, since you've deleted the EGR and haven't tuned it out yet, the PCM's response is to richen the mixture slightly as is normal when the SES light is triggered with a trouble code. Not so much of a problem by itself, but...

Driving with it too rich will eventually (say no longer than 6 months, probably) foul an O2 and rasie the temp inside the cat as well, since excess fuel is being burned there.

Third, low res signal (16) and high res signal failure (36) are classic opti failure. Probably rust/crud on the disk and/or getting into the encoder. The low res apertures in the wheel are the larger 8 on the inner diameter.

Feel around the regulator with your fingers with KOEO and see if you feel fuel. My Aeromotive regulator had the brass plug back out as the thread paste broke down over time. I had fuel pouring out when the rail was primed. I put the stocker back on for now. If that's dry, pull the vacuum line from the regulator off the intake and see if fuel is dripping downstream in the vacuum line. That'd be failure of the diaphragm and would cause your rapid pressure drop with the key off.

And of course a leaking header gasket will not help things- you might get additional fuel/fumes from that.

1961ba427

iTrader: (26)

Thanks for all the information. I hadn't heard (or didn't remember that check for the AFPR. I'll check that one out along with maybe pulling the injectors and rails up then priming and seeing if one or more is leaking per Shoebox's instructions.
So that code #16 definately means my opti is getting ready to crash on me? If it's rust/crud, can I take it off and clean it somehow?

Gojira94

iTrader: (4)

Start with everything else and then reset the PCM and see if the code 16 comes back; it may not. If it's persistent, then a check inside the opti may be the only way to get an answer for sure.

1961ba427

iTrader: (26)

It ended up being a bad FPR. It threw me off because the pressure seemed fine at key on and while running WITH THE VACUUM LINE CONNECTED STILL. I knew that vac affected the pressure, but didn't know it did so much at idle. When I pulled the line, gas went everywhere.
I swapped it for a stock one I already had and also changed all the plugs (my first LT1 plug change...TR55's...only bled once!!) and changed both O2 sensors. It seems to be running great now. Still need to have the EGR code tuned out. I'm hoping the Code #16 was a fluke or just related to the missfire due to gas fouling.



Is my old Aeromotive AFPR rebuildable?

01ssreda4

iTrader: (96)

Opti failure. The code will come back

RamAir95TA

iTrader: (2)

Ditch the AFPR if you aren't using it for tuning purposes. They are grossly overused and misunderstood and, in some cases, dangerous. There have been reports of both the Aeromotive and Holley leaking at random times. A stock FPR is all you'll really need until you step up fuel line sizing.

1961ba427

iTrader: (26)

Thanks for the heads up. I've already gone back to the stock FPR and planned on sticking with it. The Aeromotive was just on the car when I got it...figured if it was rebuildable, I'd have a backup.

1961ba427

iTrader: (26)

I hope not. I'm no LT1 expert, but I do know that trouble codes can be set by other things that effect the part that throws the code. Couldn't this be the case here? I mean the FPR crapping out is DEFINATELY what was causing my rich/slow starting/miss at low rpm problem I was having. Is it no possible that those missfires are what caused the code to set? Is this ABSOLUTELY a sure sign that my opti is on the way out?

Gojira94

iTrader: (4)

"Service kit" part #13003. My issue with these things is getting that brass plug to stay put without leaking. I have a machinist friend that's willing to help me make a plug with an O ring on the end to keep it from backing off and leaking. Keep the stock one on for now...

1961ba427

iTrader: (26)

Mine doesn't have a "4 bolt cover" like the pictured one in the directions, and I am not sure how to take it apart. I have taken the fuel rail side apart, but it doesn't access the diaphragm...so then I went to the other end and removed the set nut and vacuum fitting/screw....still no access. It looks like the main body may seal to the lower assembly with an internal o-ring...and possibly press or thread on...but I can't tell which. I tried some moderate pressure to unscrew it. There are no "flats" to use wrenches on it. Not coming apart so far...and I am kinda worried about breaking it.

Gojira94

iTrader: (4)

This is a 13107. If it doesn't look like this it could be another make. Pic?

1961ba427

iTrader: (26)

It's an Aeromotive regulator, but it doesn't look quite the same as the pictured one. The whole thing is red anodized and the two main halves do not bolt together. It's more rounded and not square in the middle either. Also, instead of the vacuum port coming out the side as pictured, it comes out the top and is threaded where it goes into the main body. The adjustment is made there at the vacuum port with a lock nut.

Maybe it's just an old unit from them. I'm sure it's LT1 specific since it presses directly into the fuel rail, has the attached bracket for the bolt to secure it in the correct spot/angle. O-rings were the same size. The ports both line up as stock. Etc.

I'd never messed with an LT1 regulator before and swapping back to the spare I had (from a complete spare intake) was a simple bolt off/on procedure.

I'll try to get a couple pics of it tomorrow with my phone.