Hi everyone,
I've been fighting with an issue for a while, now. Only when the ambient temperature was cold (32F or less), my truck would have a tough or weak start-and when it would fire up, it'd lope for a second and lurch up to idle RPM. Once warm, my fuel trims were fine. It really bothered me because it sounded painful and would sometimes require 2 attempts to start it.
Last year, I replaced my fuel pump after reading on here about similar issues and how the check-valve in the pump might be bleeding off fuel rail pressure. The truck had 120,000 miles on it, sure why not.
I thought it helped some but I believed the issue was still there when it was cold enough.
I thought it could be my air intake or intake manifold gaskets (I have a K&N kit). I took off all my ducting re-tightened all the clamps. I had cleaned my MAF sensor and even replaced it a few months prior. I also cleaned my throttle body. I even checked all my grounds and wiring to the starter and battery. I sprayed a little TB cleaner around my intake mating surfaces and vacuum lines-no hesitation or anything. They're sealed pretty good. Not a vacuum leak.
I do a lot of preventative maintenance on my vehicles and would rather fix something when I feel like it on schedule than be forced to address it when I don't.
I read that some people have sometimes experienced similar issues with a cold air intake... I ordered a dealer take-off air-box to test this theory as I didn't have the original and wanted to do away with the K&N anyways. No change.
I was losing my mind... and seriously frustrated. The cold start issue was embarrassing, couldn't be helpful for the engine, and didn't help me with my confidence in the truck I only had for 2 years, now.
I started researching specifically what the ECM checks on startup and had an idea.
I had been preparing to replace my water pump and coolant... usually when I do that on any of my other vehicles, I replace the ECT sensor, too. I had a new pump, thermostat, coolant, and sensor waiting to go in when it warmed up around here. Just for the hell of it, I took the resistance of the engine's ECT, cold-sat 2 days, at 25F ambient.
Its tough to get the probes on the leads, but I was reading about 3.8kOhms (3810)... which according to the various sensor data sheets, is wrong. My ECM was thinking that it was between 15C and 20C...call it 17C and thats 62.6F. My engine computer was thinking my coolant was about 62.6F...on a bone cold start-up in 25F weather.
http://imgur.com/a/hB1YN
I already had a new ECT sensor on my shelf (ACDelco 213-4514 https://www.amazon.com/ACDelco-213-4514-Professional-Coolant-Temperature/dp/B001W0FSMM ) and had been in my unheated garage for a month or so, now. I checked it. The resistance on the new sensor and it was completely different. It was very VERY close to the correct reading for ambient temperature.
Later that night, I changed my water pump, changed my coolant, and changed the ECT. Perfect.
I can honestly say that I haven't had a hard start-up for the last month, now.
If anyone is experiencing an annoying issue like this, take a minute and check your ECT resistance. It might save you some unnecessary costs. Just thought I would share.
I've been fighting with an issue for a while, now. Only when the ambient temperature was cold (32F or less), my truck would have a tough or weak start-and when it would fire up, it'd lope for a second and lurch up to idle RPM. Once warm, my fuel trims were fine. It really bothered me because it sounded painful and would sometimes require 2 attempts to start it.
Last year, I replaced my fuel pump after reading on here about similar issues and how the check-valve in the pump might be bleeding off fuel rail pressure. The truck had 120,000 miles on it, sure why not.
I thought it helped some but I believed the issue was still there when it was cold enough.
I thought it could be my air intake or intake manifold gaskets (I have a K&N kit). I took off all my ducting re-tightened all the clamps. I had cleaned my MAF sensor and even replaced it a few months prior. I also cleaned my throttle body. I even checked all my grounds and wiring to the starter and battery. I sprayed a little TB cleaner around my intake mating surfaces and vacuum lines-no hesitation or anything. They're sealed pretty good. Not a vacuum leak.
I do a lot of preventative maintenance on my vehicles and would rather fix something when I feel like it on schedule than be forced to address it when I don't.
I read that some people have sometimes experienced similar issues with a cold air intake... I ordered a dealer take-off air-box to test this theory as I didn't have the original and wanted to do away with the K&N anyways. No change.
I was losing my mind... and seriously frustrated. The cold start issue was embarrassing, couldn't be helpful for the engine, and didn't help me with my confidence in the truck I only had for 2 years, now.
I started researching specifically what the ECM checks on startup and had an idea.
I had been preparing to replace my water pump and coolant... usually when I do that on any of my other vehicles, I replace the ECT sensor, too. I had a new pump, thermostat, coolant, and sensor waiting to go in when it warmed up around here. Just for the hell of it, I took the resistance of the engine's ECT, cold-sat 2 days, at 25F ambient.
Its tough to get the probes on the leads, but I was reading about 3.8kOhms (3810)... which according to the various sensor data sheets, is wrong. My ECM was thinking that it was between 15C and 20C...call it 17C and thats 62.6F. My engine computer was thinking my coolant was about 62.6F...on a bone cold start-up in 25F weather.
http://imgur.com/a/hB1YN
I already had a new ECT sensor on my shelf (ACDelco 213-4514 https://www.amazon.com/ACDelco-213-4514-Professional-Coolant-Temperature/dp/B001W0FSMM ) and had been in my unheated garage for a month or so, now. I checked it. The resistance on the new sensor and it was completely different. It was very VERY close to the correct reading for ambient temperature.
Later that night, I changed my water pump, changed my coolant, and changed the ECT. Perfect.
I can honestly say that I haven't had a hard start-up for the last month, now.
If anyone is experiencing an annoying issue like this, take a minute and check your ECT resistance. It might save you some unnecessary costs. Just thought I would share.
