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Discussion Starter #1
First and foremost: thanks for any and all help. I've been reading/piddling but I'm not making too much progress. Remember: I'm not a professional mechanic by any means, I do have factory service manuals for most of my cars though so I can follow those procedures.

I will be providing logs of whatever I can scan with this OBD2 scanner/torque as soon as I can but I'm not sure what exactly to log in this case, so I'll just report what I've been observing.

Ok so here's the run down:

1. P1133, P0133 and P0301 codes
2. Stalls intermittently after being warmed up and usually when going downhill
3. Ridiculous LTFT (-22.6 :icon_redf), mid-low teens when WOT with STFT avging ~-10 at idle and normal (+/- 5) when WOT
4. Weird O2 sensor voltages (0mV at times with the rear O2 sensor, ~700-900mV on the front at all times, clogged cat? it sounded normal when I got under it and tapped it a good bit)

It has Bosch 42.5# injectors, a thrasher intake, ported 3rd gen M90 (~13.5psi max observed when it was running better, I'm hesitant to flog it right now), SLP headers, walbro fuel pump (I'm starting to suspect this, walbro pumps are loud but this sounds BAD at times) and a fuel filter that's about to be replaced (running GM fuel system treatment through it first before dropping/cleaning the tank to see if this pump is semi-faulty, didn't these have bad check valves for a while or something?). It *may* be cammed but the previous owner was not sure (and it probably is a milder cam) .

I have checked the FPR and no gas came out of the vac, spark plugs look okay (#1 cyl was pretty clean, still replacing wires/plugs anyway as they're AL104s), ignition module contacts were cleaned along with coil pack contacts. Wiring seems OK on the O2 sensor extension previous owner installed, did not test the sensor via the procedure someone outlined here. Intake gaskets have been replaced at some point but I'll test again with a multimeter as per a procedure I saw on here, I doubt they're too bad but I'll replace them if necessary.

Before I throw money at the problem hopefully someone can chime in, I'll log whatever one likes with one of these cheap scanners while I wait for my HPT to show up. I do have O2 sensors coming but I'd like to stop this thing from running hog rich, if I can, before I possibly destroy another set of them. This weekend I intend on cleaning the TB/IAC/MAF but the MAF has been reading somewhat normally as far as I can tell, it's just been too damn hot to work anywhere other than a climate controlled garage :icon_redf.
 

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So, what model car is it? I was gonna look at my ALLDATA and SHOP KEY for better definitions of those codes but need specific model/engine.

Jake
 

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Discussion Starter #3
1997.5 Regal GS, L67 engine, thanks for your help!

As far as I know the P0301 is a misfire (cyl 1), the P1133 and P0133 are O2 sensor codes (slow switching, slow response)
 

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After checking some tech info and REMEMBERING my GTP has SLP headers also, the codes are just as you mentioned. I can tell you first hand my GTP does the same thing on occasion. The problem is the O2 sensor on SLP headers is TOO FAR AWAY FROM THE EXHAUST PORTS. These headers work great except for the questionable primary O2 sensor position. Being that far away from the exhaust ports the primary O2 doesn't get hot enough for good operation.

On my car I have noticed while at cruse or steady speeds, this is when it may set this code. So in my case and knowing the issue, I sort of ignored the light until I take the time to delete that code. I have not noticed any drivability issues.

The later models of similar cars use a "heated" O2 sensor where as the later models have a "heater circuit" and a 4 wire connection. I suppose one could try using a late model O2 sensor and wire in a power circuit to power up the internal heater of the O2. OR, just understand why it's doing this and live with it. You could also drive it a little harder(maybe drive it in 3rd gear at slower speeds to keep the O2 hot.

I have never experienced any side affects with my car.....just the "check engine light".

Hope this sheds some light on your issue.......... Jake

PS.... If you really need to stop that code from popping up, you probably could relocate the primary O2 closer to the exhaust ports. OR, reprogram the PCM to eliminate that particular code.......
 

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Discussion Starter #7
That's what I was thinking, PO seemed to know a good bit about the car but I couldn't get an answer out of him with respect to that. I might try swapping on a set of OEM injectors from a complete engine that came out of a C-Body to test that this weekend after I clean the MAF/TB/IAC and run a few fuel pressure tests to ensure it isn't the FPR.
 

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Discussion Starter #8 (Edited)
Also this forum is slow enough that double/triple posts are probably not too bad. I am replacing all plugs and wires with AL104s (maybe 103s if I can't address the misfire after checking everything else) and good Delphi wires (I've had a lot of luck with Delphi/Denso stuff and this forum echoes that experience), but the wires are relatively new and check out resistance-wise as far as I can tell. I didn't log the resistance but I did give them a good twist to see if I could create a short. Overall this is really frustrating but at least it pans out so far compression-wise (and I have a complete engine here obviously that was going to go in another car but I could just rip off the heads for later and use the shortblock in this)

E so I don't triple post: Do you think a local muffler shop would create an O2 bung closer to the exhaust manifolds so I don't need to try newer sensors?
 

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I have SLP HEADERS on my 2003 GTP 3800 and I don't think there's enough room on the back side where the header pipe goes down to install a different O2 sensor BUNG. But, maybe a local good exhaust shop may be able to deal with that. OR, if you have time on your hands, remove the rear header and then have a new O2 sensor BUNG(the part that has a threaded hole for an O2 sensor). I my case I understand what's going on with the O2 sensor location and just live with it.

Get back and let us know how it all works out....... Jake
 

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My rear oxygen sensor also reported zero sometimes. Other times it would show 0.1 or 0.2, other times it reported 0.4 volts when the engine was cold. I removed the heat shield covering the rear O2 sensor and found frayed wires. I replaced the O2 sensor and now see the rear O2 sensor respond correctly. I suggest you too look at the wiring of therear oxygen sensor.
 

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That rear sensor issue is not a good thing. Glad you were able to track that down.

Another thing to remember is.... The rear O2 sensor(at the convertor) is a monitor for cat efficiency. It doesn't control fuel delivery like the front O2 sensor does. Jake

PS, I don't run a rear O2 sensor any more (and no cat) and the front O2 controls/shows valid data and there are no side effects or codes.....those codes were probably removed from the reprogramming process...I think... There is probably default
data in the PCM reprogramming....
 
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