I'm talking diesel rich, the pipes are black and you can visually see it rolling out the pipe with every spike of the throttle. I have seen my fuel trims at -17. Once it's warm it surges and wants to stall. I have replaced the o2, iac, maf and map sensors. I noticed a small header leak at cylinder #2 because the header wrap was getting sooty. It wasn't something that I could feel but I welded it up. The spark plugsan o2 were sooty. MThe idle seems normal. I doubt I have a vacuum leak as its all new hoses. I did spray the engine with carb cleaner ad seafoamed it and didn't turn up anything.
------------------ 86 SE Convertible 3800sc 4t65e HD.
Check out what the ECM is seeing on Tunerpro or whatever if you have a scanner, maybe you have some bad wiring from sensor to ECM... The O2 sensor operates in a relatively small range ( I think if I remember correctly the voltages I have seen are between 200mv and 800mv). Have you checked fuel pressure? Possible bad regulator? I doubt injectors would go bad enough to cause that... Would the wrong type of injectors cause that? (impedance-wise)... maybe your cold start injector is stuck open.
Edit to say saw 3800 in signature so disregard if you are not referring to a 2.8
[This message has been edited by zkhennings (edited 10-10-2013).]
Check out what the ECM is seeing on Tunerpro or whatever if you have a scanner, maybe you have some bad wiring from sensor to ECM... The O2 sensor operates in a relatively small range ( I think if I remember correctly the voltages I have seen are between 200mv and 800mv). Have you checked fuel pressure? Possible bad regulator? I doubt injectors would go bad enough to cause that... Would the wrong type of injectors cause that? (impedance-wise)... maybe your cold start injector is stuck open.
Edit to say saw 3800 in signature so disregard if you are not referring to a 2.8
Yeah it's a 3800sc. I will have to scan the new o2 and see. My fuel pressure is 40+.
------------------ 86 SE Convertible 3800sc 4t65e HD.
What's the MAP sensor reading ? An EGR valve stuck open or a bad intake gasket could cause a low vacuum problem making the map sensor add too much fuel. I used to see this all the time on S10 4.3's, they make an egr gasket with a built-in screen to keep carbon pieces out of the valves.
If the MAF sensor readings look wrong try unpluging it (engine will use it's default values) & see if it runs better - this usually works more for MAF caused hesitation problems.
[This message has been edited by AL68 (edited 10-10-2013).]
What's the MAP sensor reading ? An EGR valve stuck open or a bad intake gasket could cause a low vacuum problem making the map sensor add too much fuel. I used to see this all the time on S10 4.3's, they make an egr gasket with a built-in screen to keep carbon pieces out of the valves.
If the MAF sensor readings look wrong try unpluging it (engine will use it's default values) & see if it runs better - this usually works more for MAF caused hesitation problems.
I will have to log a new tune tomorrow to see what the map readings are. I have no egr. I hope the maf is correct as its new.
------------------ 86 SE Convertible 3800sc 4t65e HD.
Does your setup use a Coolant Temperature Sensor? The symptoms sound similar to what a 2.8 would suffer if the sensor suddenly defaulted to the cold side. Mine happened from one stop light to the next. Stopped at one light and everything was fine. At the next one, it was like I'd done a diesel engine swap. Black smoke everywhere.
Does your setup use a Coolant Temperature Sensor? The symptoms sound similar to what a 2.8 would suffer if the sensor suddenly defaulted to the cold side. Mine happened from one stop light to the next. Stopped at one light and everything was fine. At the next one, it was like I'd done a diesel engine swap. Black smoke everywhere.
Yeah it does, is there any way to test the sensor? Or can I get a reading in hptuners? I do see the temp guage move.
------------------ 86 SE Convertible 3800sc 4t65e HD.
Yeah it does, is there any way to test the sensor? Or can I get a reading in hptuners? I do see the temp guage move.
In the 2.8 the Coolant Temp Sensor data is strictly for the computer to adjust fuel mixture. The gauge uses a different sensor/sender....and the fan uses another .....third one
In the 2.8 the Coolant Temp Sensor data is strictly for the computer to adjust fuel mixture. The gauge uses a different sensor/sender....and the fan uses another .....third one
I'm running the 3800sc as in my sig but if the sensor controls the fuel mixture the same in both engines the it's possible mine is nfg.
------------------ 86 SE Convertible 3800sc 4t65e HD.
A bad temp sensor is a good possibility, it works the same on both motors. It could stay at a low temp reading & run the engine rich. Check the temp reading & see if it matches the actual engine temp cold and hot. I had a 2.8 with a corroded temp sensor plug, would read -19 degrees and run rich but no code, -19 was within it's normal operating range.
To test the wiring and PCM unplug the sensor, it should read -40 degrees, connect the plug's two black/yellow wires & should read 250+ degrees.
A bad temp sensor is a good possibility, it works the same on both motors. It could stay at a low temp reading & run the engine rich. Check the temp reading & see if it matches the actual engine temp cold and hot. I had a 2.8 with a corroded temp sensor plug, would read -19 degrees and run rich but no code, -19 was within it's normal operating range.
To test the wiring and PCM unplug the sensor, it should read -40 degrees, connect the plug's two black/yellow wires & should read 250+ degrees.
Awesome thanks
------------------ 86 SE Convertible 3800sc 4t65e HD.
Tweeder, go to the Georgia Fiero website at www.gafiero.org then click on message board. Do a search for temperature sensor chart and you'll find a chart that applies to all GM temperature sensors. It will tell you if the CTS is reasonably accurate. All you need is an ohmmeter.
Well I believe you have a scanner. Rather than checking part of it (just the sensor) check all of it by reading the temperature reported by the scanner. Then that includes the wiring and the PCM receiving it. If the scanner doesn't check out to be reading the correct temp then drill down into it by examining the sensor itself, the wiring, the PCM...
I went out and really doused the upper manifold gasket with two cans of carb cleaner and I seem to have a leak in the manifold next to the thermostat so I have a new gasket ordered and will be in on Wednesday. Anything I should take care of easily as I have the blower off?
------------------ 86 SE Convertible 3800sc 4t65e HD.
[This message has been edited by Tweeder (edited 10-28-2013).]
I reseated the intake gasket and I think I got it but I'm still running rich and surging when warm. I made a contraption to pressurize the intake through the throttle body and I was leaking from the map so I took it out and siliconed it and that helped, now it leaked down from 20 or so psi very slowly, I soaped the engine and I didn't' see any. Mabey the purge solenoid? I'm thinking of taking off the throttle body and making a block off plate and then pressurize it from the octopus. I'm just wondering if if possibly be leaking from the brake boost port? I'll have to make a smoke test and see if that shows something
------------------ 86 SE Convertible 3800sc 4t65e HD.
Not sure if this is it but I sprayed a soapy solution in the injector holes and sure enough injector number three is bubblin, so I have a set of o rings on order.
------------------ 86 SE Convertible 3800sc 4t65e HD.
Got the new o rings in and now a new problem, I swear I get a new problem every time in fix something else. Now it won't start, I checked and I am getting fuel and spark but it backfires really powerful and loud. So powerful that it blows the rubber exhaust tubing right off the pipes.
------------------ 86 SE Convertible 3800sc 4t65e HD.
Distributor moved (loose clamp)? Spark at the wrong time is usually the only cause of a backfire like that. Could the coil wire and another wire on the cap be switched around? I bought a Formula that the guy couldn't get started after working on it - he had the coil wire going to a plug wire terminal on the cap - it did backfire once every time the motor rotated.
Distributor moved (loose clamp)? Spark at the wrong time is usually the only cause of a backfire like that. Could the coil wire and another wire on the cap be switched around? I bought a Formula that the guy couldn't get started after working on it - he had the coil wire going to a plug wire terminal on the cap - it did backfire once every time the motor rotated.
Nope, 3800sc.
------------------ 86 SE Convertible 3800sc 4t65e HD.
Forgot which post I was in - not sure if no distributor - sounds like an ignition problem but just pulling the fuel rail shouldn't cause that. Injector connectors on the wrong Injectors? I don't think it makes a difference but I remember seeing injector harnesses with numbers 1-6 on the plugs, may have been an earlier 3800.
Forgot which post I was in - not sure if no distributor - sounds like an ignition problem but just pulling the fuel rail shouldn't cause that. Injector connectors on the wrong Injectors? I don't think it makes a difference but I remember seeing injector harnesses with numbers 1-6 on the plugs, may have been an earlier 3800.
Injectors correct, the way I have the wired run it can't be screwed up. The only think that I did before was pump smoke inside the motor to text for the leak, is it possible the smoke put a coating that's causing thinks to not work properly? I highly doubt it though.
------------------ 86 SE Convertible 3800sc 4t65e HD.
I was thinking there might be a bad ground for the crank sensor or ignition module making it fire at the wrong time, couldn't remember if some of the wires went through the large connector for the injectors & intake sensors, been a while since wiring my 3800sc.
I finally got time to do a log and I'll be damned, she fired up. Albeit it took a few times with it backfiring and stalling but then it stayed running. But I don't think I got that corner next to the thermostat housing sealed as when it was running I sprayed carb cleaner it stumbled. So I pressurized the intake and sprayed soapy water there and I couldn't get no bubbles? I don't know how it could be leaking as I put a good 1/4" bead of silicone around the whole intake, mabey I should put a few more layers all the way to the rotors.
------------------ 86 SE Convertible 3800sc 4t65e HD.
- not sure if no distributor - sounds like an ignition problem but just pulling the fuel rail shouldn't cause that. 
