HOW DO I GET MY RUNNING RIGHT??

1992 GMC Typhoon

Tiny

mrmarkbrody

February, 26, 2012 AT 11:39 PM

Ok so here we go. I bought this truck 3 years ago and I havent started working on it until recently. This truck suffers from a series of problems but I just want to get the engine squared away. I cannot keep this thing running. It has a very rough idle upon the start and it doest go away. The truck is loading up with fuel and it will not stay running for any amount of time. Ive tried adjusting the regulator and lowering pressure on the rail but no results. We have tested the map and it seems to be up to spec. The turbo is fine as well and we have cleaned out the cac on next to the intake. New plugs, wires, distributor cap and rotor, air filter and oil. Gas is standard 93. We found that the ECM is remanufactured and I think that it might have something to do. When we disconnect the different sensors it will not throw any codes. There was a intermitent code for 02 sensor but a new one was placed in it and its testing fine. Map sensor voltage is up to par and fuels system is clean. I need some help or ideas where to go from here. There are no leaks anywhere that can be seen on intake but there is a small knock coming from the passenger side head (lifter I assume). This thing is running rich and it will not stop its like injectors are stuck open. Please any suggestions let me know I will sing at your wedding if you help me fix this problem!

thanks!
~mark

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17 Answers

Tiny

billymac

February, 27, 2012 AT 1:02 AM

Hi mark
the fact that ecm will not store any codes is a problem possible prom failure in the ecm. The simpleist thing to try is a coolant temp sensor this could be bad since your ecm is not working right you would never know. If it were mine I would replace the cts. And try and get ecm to reset. Another possible is base gasket or intake leak check really good for vac leaks. Let me know we are just getting started.

Tiny

mrmarkbrody

February, 27, 2012 AT 1:40 AM

Will check the cts tomorrow. If it is a ecm problem or a problem with the prom can you suggest a way to flash it or reset it to factory standard. This truck has had some hands in it before I got it thats for sure im just trying to get it back to stock. Also the lower mounter cooler for the cold air charge system is dinged up and I was wondering if you knew of something I could use that wouldnt break the bank

Tiny

mrmarkbrody

February, 27, 2012 AT 1:43 AM

Just fyi I have an OBD1 to usb2.0 cable just dont know what to use as far as a program to read ecm from it. Thank you for your time I ran into a wall before I got on here!

Tiny

billymac

February, 27, 2012 AT 1:50 AM

Well the prom and ecm are both predet at the factory so reflashing without a very expensive gm scanner is not possible. Maybe try and locate a ecm from a salvage. The air charge? Are you referring to the air conditioning or a charged air system for the engine. Or eng oil cooler?

Tiny

dethinc

February, 29, 2012 AT 3:29 AM

I am working on the car for mrmarkbrody. Ok here is where the car is. Rich running tend to flood starting. Must pull fuse to ecm to get started again, shutting fuel system down.
O2 sensor is all over the chart from a steady 800 down to 30 on the datamaster software. No leaks anywhere all tested. Injectors when running look like they bounce once in awhile average is 1.5 but for a brief moment it jumps to 30 or so, nutts Is this a voltage problem never seen this before. When started goes into openloop correctly then when it closes loop it tweaks, runs rich eratic idle somtimes wont start back up. Any idea on maybe a bad ecm? Checked prom it is the right chip. Fuel pressure is good I have a adjustable regulator on the vehicle with a gauge. Good ignition/spark all the time. Any ideas would help

Tiny

mrmarkbrody

February, 29, 2012 AT 5:50 AM

Please refer to previous statement. We are also getting a coolant temp sensor code getting another one tomorrow for 20$ but dont think it will fix please any suggestions?

Tiny

billymac

February, 29, 2012 AT 11:51 PM

HI I NOTICED YOU DID NOT POST MAP VOLTAGE OR FUEL TRIM STATS. THIS REALLY SOUNDS LIKE A CTS PROB PLEASE LET ME KNOW IF CTS SOLVES THIS PROB. ALSO CRANK SENSOR AND CAM SENSOR WOULD HELP THANKS.

Tiny

dethinc

March, 1, 2012 AT 3:05 AM

Tonight we replaced the cts that code is now gone. All good as far a codes. I did record the truck running with datamaster but have no real way of showing the data here. The map voltage was at 5v. Have not gotten to crank sensor yet. But tonight the truck still up and down on idle pretty hard. We have verified that the pprom is right but it has a remanufactured ecm. I'm just hoping the previous owner was not trying to mod the prom or anything. Also notice when running at idle the ignition is at 24 or so for advancement. How bad would this vehicle run if the previous owner did not time the car properly. Would this early system run rich and idle this badly? This is one thing I have not checked yet. Will have to check tomorrow.

Tiny

billymac

March, 1, 2012 AT 3:42 AM

Yes if not timed corectly you could see these problems and prob a fuel trim concern and even a extended pulse width. Good place to go next. Kinda looking like a wrong or malfunctioned ecm

Tiny

dethinc

March, 2, 2012 AT 12:22 AM

OK here we go, Retimed tonight to oem specs. Runs and idles better but still rich. I really should have started here but with all the problems we have found I dont think it would have mattered. I am still getting a well to put it simple the timing mark I noticed jumps once in awhile almost a skip, I can hear the rpms drop down. Dont know if pickup sensor/crank sensor is going bad or ignition control unit in dist. But I can say the truck is a long way from what it was. What is killing me im a ford man. Lol but the principles are the same.

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