86 2.8 rebuilt. Starts quickly and easily, runs up to about 1500 rpm, then slows and then stalls. I can do this 3 or 4 times and then it will stay running or if I keep it running by playing the gas pedal for a minute or so, it runs fine - settles into an idle around 1300 rpm. No problems when driving and once I have gone through this process it runs beautifully. Injectors have been serviced, fuel pressure regulator replaced, new fuel pump and fuel filter replace, gas tank refurbished. Have checked all vacuum connects and everything appears to be in order I suspect a sensor signaling the ECM but don't know which one would cause this problem. All suggestions/help appreciated.
86 2.8 rebuilt. Starts quickly and easily, runs up to about 1500 rpm, then slows and then stalls. I can do this 3 or 4 times and then it will stay running or if I keep it running by playing the gas pedal for a minute or so, it runs fine - settles into an idle around 1300 rpm. No problems when driving and once I have gone through this process it runs beautifully. Injectors have been serviced, fuel pressure regulator replaced, new fuel pump and fuel filter replace, gas tank refurbished. Have checked all vacuum connects and everything appears to be in order I suspect a sensor signaling the ECM but don't know which one would cause this problem. All suggestions/help appreciated.
This sounds similar to a problem I (and other have had). It was resolved by changing out the CTS (Coolant Temp Sensor) and the IAC IAT Temp sensor. My 87 GT now starts easily and is ready to drive in about 15 secs or so
Edited for accuracy
[This message has been edited by 92wastheyear (edited 09-05-2013).]
86 2.8 rebuilt. Starts quickly and easily, runs up to about 1500 rpm, then slows and then stalls. I can do this 3 or 4 times and then it will stay running or if I keep it running by playing the gas pedal for a minute or so, it runs fine - settles into an idle around 1300 rpm. No problems when driving and once I have gone through this process it runs beautifully. Injectors have been serviced, fuel pressure regulator replaced, new fuel pump and fuel filter replace, gas tank refurbished. Have checked all vacuum connects and everything appears to be in order I suspect a sensor signaling the ECM but don't know which one would cause this problem. All suggestions/help appreciated.
Any codes? (start there before changing anything)
Sensor-wise, could be IAC as suggested above ------------------ Ben 87 GT / 88 GT 84 Indy #1863
[This message has been edited by benoitmalenfant (edited 09-05-2013).]
The IAC is a valve electronically controlled by the ECM, not a sensor.
If the idle speed is higher when the engine is cold and lower when the engine is warm, it most likely is not the IAC. It doesn't hurt however to remove the IAC and make sure the passage the pintle seats in is clean of carbon deposits and moves freely.
[This message has been edited by phonedawgz (edited 09-05-2013).]
The IAC is a valve electronically controlled by the ECM, not a sensor.
If the idle speed is higher when the engine is cold and lower when the engine is warm, it most likely is not the IAC. It doesn't hurt however to remove the IAC and make sure the passage the pintle seats in is clean of carbon deposits and moves freely.
I may have used the wrong acronym ....I am talking about the sensor located on the stock air cleaner
Thanks to all the respondents. About a year ago, phonedawgz provided a chart that gives the resistance across the contacts for GM coolant and air temperature sensors. I have tested both by connecting a digital multi-meter across the contacts and using a hair dryer to vary the temperature. The starting point has always been room temperature (a known number) and both the Intake Air Temp Sensor and the Coolant Temperature sensor give readings within 50 ohms of what I would anticipate and both vary appropriately as heat is applied - so I am going to say, they are OK. I actually purchased an Intake Air Temperature sensor and when I tested it with the one I removed from the car, the ohm readings were almost exactly the same (maybe out 10 to 15 ohms at room Temp. I am going to recheck the Idle Air Control valve and the pintel seat ( I had it apart and cleaned and adjusted it when I rebuilt the engine but maybe it has gone out of adjustment again)
If anyone has any other suggestions as to cures for this problem, I would appreciate hearing them.
