Runs rich until hot

raporter1 · 07-22-2008, 09:01 PM

I have a 1995 truck with a 350 FI engine that ran great until the plastic clip broke one of the oil coolers line at 65 MPH, wasted the engine. I got a 1988 Chevy van 350 F engine and put all the sensors from my engine on the 88 engine. To start the engine you have to go wide-open throttle and then the engine runs rich. At a point when the engine warms up to close to operating temperature its like a sensor or relay shifts and the engine smoothes out and runs fine. When the engine is running rich, if you crack the throttle just a little the engine tries to die. I have replaced the coolant temp sensor, no change. I check for engine codes and received code 15 "Coolant temperature sensor". Any suggestions?

leolkfrm · 07-23-2008, 06:04 AM

Don't uou have 2 coolant temp switches on the 95? one on the intake for the ecm and one in the head for the guage Which one did you change? Also a good scan tool will show the readings off all sensors and you can confirm that the sensors are working correctly

raporter1 · 07-23-2008, 06:58 AM

Yes, the 1995 has two temp sensors; I change the one for the ecm. I also checked to ensure I did not pinch any wiring when I installed the new engine.

Case 7230 · 07-23-2008, 10:45 AM

Did you reattach all grounds on the wiring harness on top of the engine? Did you clear the error code and it reappeared? Did you check the fuel pressure, may be a faulty fuel pressure regulator?

raporter1 · 07-23-2008, 12:18 PM

Yes, all ground straps were re-connected. All codes were cleared and the code came back, tonight I will put a meter on the temp sensor to see if it's reading correctly. No, I have not checked fuel PSI, because when engine warms up to about operating temp the engine changes and runs and drives without any problem. This is a open loop problem, it just finding the problem that's the problem.

leolkfrm · 07-24-2008, 05:23 AM

Did you use the injection system from the 88 or 95?

raporter1 · 07-24-2008, 07:02 AM

I used the 95 injectors and I replaced them 3 months ago.

leolkfrm · 07-24-2008, 07:19 AM

I gues I should have been more general. Did u use the intake off the 95 so it included the injection system throttle pos sensor etc?

raporter1 · 07-24-2008, 11:02 AM

Yes, I used the complete throttle body assembly from the 1995 engine.

leolkfrm · 07-24-2008, 11:25 AM

Did you get a chance to get it on a scan tool when cold to check sensor readings?

07-22-2008, 09:01 PM	#1
raporter1 Junior Member Join Date: Jul 2008 Location: WA Posts: 9	Runs rich until hot I have a 1995 truck with a 350 FI engine that ran great until the plastic clip broke one of the oil coolers line at 65 MPH, wasted the engine. I got a 1988 Chevy van 350 F engine and put all the sensors from my engine on the 88 engine. To start the engine you have to go wide-open throttle and then the engine runs rich. At a point when the engine warms up to close to operating temperature its like a sensor or relay shifts and the engine smoothes out and runs fine. When the engine is running rich, if you crack the throttle just a little the engine tries to die. I have replaced the coolant temp sensor, no change. I check for engine codes and received code 15 "Coolant temperature sensor". Any suggestions?

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07-23-2008, 06:04 AM	#2
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 1,456	Don't uou have 2 coolant temp switches on the 95? one on the intake for the ecm and one in the head for the guage Which one did you change? Also a good scan tool will show the readings off all sensors and you can confirm that the sensors are working correctly

07-23-2008, 06:58 AM	#3
raporter1 Junior Member Join Date: Jul 2008 Location: WA Posts: 9	Yes, the 1995 has two temp sensors; I change the one for the ecm. I also checked to ensure I did not pinch any wiring when I installed the new engine.

07-23-2008, 10:45 AM	#4
Case 7230 Senior Member Join Date: Dec 2007 Posts: 253	Did you reattach all grounds on the wiring harness on top of the engine? Did you clear the error code and it reappeared? Did you check the fuel pressure, may be a faulty fuel pressure regulator?

07-23-2008, 12:18 PM	#5
raporter1 Junior Member Join Date: Jul 2008 Location: WA Posts: 9	Yes, all ground straps were re-connected. All codes were cleared and the code came back, tonight I will put a meter on the temp sensor to see if it's reading correctly. No, I have not checked fuel PSI, because when engine warms up to about operating temp the engine changes and runs and drives without any problem. This is a open loop problem, it just finding the problem that's the problem.

07-24-2008, 05:23 AM	#6
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 1,456	Did you use the injection system from the 88 or 95?

07-24-2008, 07:02 AM	#7
raporter1 Junior Member Join Date: Jul 2008 Location: WA Posts: 9	I used the 95 injectors and I replaced them 3 months ago.

07-24-2008, 07:19 AM	#8
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 1,456	I gues I should have been more general. Did u use the intake off the 95 so it included the injection system throttle pos sensor etc?

07-24-2008, 11:02 AM	#9
raporter1 Junior Member Join Date: Jul 2008 Location: WA Posts: 9	Yes, I used the complete throttle body assembly from the 1995 engine.

07-24-2008, 11:25 AM	#10
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 1,456	Did you get a chance to get it on a scan tool when cold to check sensor readings?