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I am the proud owner of a 1990 Buick Le-Sabre custom that is equipped with the bullet proof 3.8 liter LN3 Natural Aspirated 3800 tuned multi port engine. It is equipped with a 4 speed automatic transmission.
The reason why I have come to you all today is that pesky, invasive check engine light! At first I thought my issues may have stemmed from an exhaust leak. I had a buddy plug the tail pipe, and the first time my car stalled out. I did it again, and then I heard a hissing, and saw exhaust coming out of my EGR valve.
I have experience doing my own repairs, so I thought this would be a simple fix. It turns out troubleshooting this mess has been a nightmare. Before I proceeded any further I plugged in an el-cheapo OBD 1&2 scanner into my trusty Buick. The scanner then began spewing out error code, after error code, after error code. Those 13 error codes are as follows:
DTC 21 -TPS voltage was above 0.8 volts for 5 seconds when engine was running and air flow was less than 15 gm/sec, or the TPS voltage was over 4.8 volts at any time.
DTC 22 -TPS voltage was under 0.2 volts for 4 seconds when the ignition was on. On Bonneville, Le Sabre and Park Avenue the TPS voltage was between 0.48 and 1.3 volts for 30 seconds with engine speed between 1300 and 2100 RPM and vehicle speed between 50 and 60 MPH.
DTC 24 -Vehicle speed sensor signal showed less than 3 MPH for 2 seconds when engine speed was greater than 3000 RPM and transmission has not been in park or neutral for more than 4 seconds. Or vehicle speed goes from above 18 MPH to 0 in less than 2 seconds without applying brake.
DTC 25 -Inlet air temperature sensor signal showed an air temperature of over 218° F for 5 seconds when vehicle speed was greater than 35 MPH.
DTC 26 -Quad-Driver sense voltage shows a low voltage when battery voltage should be present, or if the sense voltage shows battery voltage when a low voltage should be present for at least 5 seconds when the engine was running.
DTC 32 -EGR system failure
DTC 35 -IAC problem or idle error
DTC 41 -Ignition control error
DTC 43 -Knock sensor error
DTC 66 – A/C pressure sensor circuit error (low pressure indicated)
As for symptoms my vehicle seems just fine. On a cold start it starts shivering a little bit when it is idling. I would not even call it a rough idle. The problem goes away as the engine gets warmer (again it doesn’t really idle rough, just a bit of a shiver) I also get a bit of a lag when I really laid into the gas. Transmission did shift a bit clunky, and sometimes when I threw it into reverse the car would die. Occasionally it stalls when coming to a stop. Sometimes when I start accelerating the vehicle won’t respond, it will push jerk forward a few times then everything will be business as usual.
The caveat here is I replaced the ECU with a junkyard unit and many of these issues have disappeared. My transmission shifts A LOT smoother, the hesitation/lag on the acceleration has disappeared, my car hasn’t stalled since I replaced the ECU, even the idle is a bit better.
My car really feels almost like a new vehicle, but the problem is I cannot pass emissions with my check engine light on making it a mute point. I’m sure my EGR valve needs to be replaced, but nothing else looks looks out of place, as my car is running very smoothly. Unfortunately I still have the same exact error codes.
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Sounds like the first order of business is finding the exact leak of the EGR. Gasket or the valve itself? Should not be too hard to find. It is the electronic EGR yes? Rock Auto shows mostly electronic but also one vacuum controlled one. Weird.
Disconnect the battery for a few minutes to erase codes.
After it has some miles on it (maybe a couple hundred) then see what codes came back.Keep in mind that ONE problem can set off several codes, since many systems work together. Once you fix the actual problem, the rest of the codes will quit showing up.
What is happening with the EGR leak is it is allowing unmetered air to enter the engine. Engines HATE unmetered air. It throws off several other things and since the ECM is trying to calculate for precise fuel delivery, it just cannot and assumes everything is messed up, not just the EGR.
It would be like say you took a big swig of milk and THEN found out it was rotten. You flinch, gag, spit, make an ugly face, possibly puke, and maybe get pissed off.
All that because your body and brain were expecting one thing and your taste buds started screaming “OH F*** OH F*** OH F***! DANGER!”Your engine is pissed off and freaking out about too much extra air and it doesn’t know what the heck to do.
[quote=”Summer_Night” post=118944]Sounds like the first order of business is finding the exact leak of the EGR. Gasket or the valve itself? Should not be too hard to find. It is the electronic EGR yes? Rock Auto shows mostly electronic but also one vacuum controlled one. Weird.
Disconnect the battery for a few minutes to erase codes.
After it has some miles on it (maybe a couple hundred) then see what codes came back.Keep in mind that ONE problem can set off several codes, since many systems work together. Once you fix the actual problem, the rest of the codes will quit showing up.
What is happening with the EGR leak is it is allowing unmetered air to enter the engine. Engines HATE unmetered air. It throws off several other things the ECM is trying to calculate for precise fuel delivery.
It would be like say you took a big swig of milk and THEN found out it was rotten. You flinch, gag, spit, make an ugly face, and maybe get pissed off.[/quote]
Hmm, so you think the EGR valve is to blame for most of those codes? That was going to be my next order of business (because its obviously a problem). I know that something is causing all of those codes, probably one or two things. Anyways, thanks for the response.I don’t know for fact that it is causing ALL those codes but since it is obviously messed up (leaking) then there is your starting point.
BTW as I said – try the gasket first. Do the leak test as you did before.
The caveat here is I replaced the ECU with a junkyard
Your PCM contains a PROM (Programmable Read-Only Memory) that must be transferred from the old unit to the new unit. It has all the info that’s needed for your vehicle. Was that transferred? If not I think that’s your problem… It under a flap (held in by a small bolt) on the side of the PCM.
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