Runs good cold, dies warm - ZR-1 Net Registry Forums

FormulaReed · 11-09-2019

So my zr1 has got a new issue and I'm stumped....

When the car is cold, it starts right up and settles down to a smooth idle and drives good. However, as soon as it warms up (fans kick on) it will start idle hunting, misfiring and than stalls out. If I'm driving it, it will start cutting out and than die.

When I pull the codes with a paper clip, I only get a historic code 43, the DIS.

I had 2 codes previously: TPS Sensor and MAP sensor. I replaced the TPS and the MAP sensor vacuum hose. Those codes went away and the car idles and drives good when it's cold, but dies when warm.

I have replaced the crank position sensor but no change. I hooked up a fuel pressure gauge to the valve on the rail. I get 45 psi on start and 40 at idle. The pressure stays constant while the car is starting to stall out.

Any ideas on what's going on? Is the DIS box on it's way out? It's odd to me that it will run when it's cold, but right on cue when it warms up it runs bad until it dies. I was thinking that the main fuel pump is on it's way out, but the pressure is staying good so I think that it's ok.

Thanks in advance.

Reed

Ccmano · 11-09-2019

Code 43 is not the DIS, it’s the knock sensing system, knock sensor, knock control module or related wiring. Likely not related to the current issue.

The secondary fuel pump shuts down at 176F coolant temp leaving only the primary pump running. The primary pump would still be my first look. A pump amp draw test should tell you what’s going on.

Here’s the test write up.
H
http://www.zr1.net/forum/showthread.php?p=136108

FormulaReed · 11-11-2019

Tried the doing an amp draw test but I had no luck with the test port. I bet it’s on my end being an idiot...

So I got a new primary pump. I’ve already replaced the secondary pump and it was an easy job so I’m just going to change it out tomorrow and see if that fixes it.

FormulaReed · 11-16-2019

Update: I replaced the primary fuel pump and it seems to have fixed it! I let it warm up and it ran fine, went for a little drive and it ran really good. Much better than I have ever had it running. I think that it's fixed because it would not run at all as soon as it warmed up, now it runs great.

I replaced the secondary pump right after I got it and noticed that it had Precision brand pumps in it. One thing that i think is kind of odd is that it still showed fuel pressure at the rail when it was stalling out. I wonder if the secondary pump was kicking in when the idle dropped below 400 rpm and kept it sorta running as it was stalling out. Also might explain why it would cut out and than snap back to life a few times.

Thanks for the help!

11-09-2019	#1
FormulaReed Join Date: Jan 2019 Location: Seattle Posts: 62	Runs good cold, dies warm So my zr1 has got a new issue and I'm stumped.... When the car is cold, it starts right up and settles down to a smooth idle and drives good. However, as soon as it warms up (fans kick on) it will start idle hunting, misfiring and than stalls out. If I'm driving it, it will start cutting out and than die. When I pull the codes with a paper clip, I only get a historic code 43, the DIS. I had 2 codes previously: TPS Sensor and MAP sensor. I replaced the TPS and the MAP sensor vacuum hose. Those codes went away and the car idles and drives good when it's cold, but dies when warm. I have replaced the crank position sensor but no change. I hooked up a fuel pressure gauge to the valve on the rail. I get 45 psi on start and 40 at idle. The pressure stays constant while the car is starting to stall out. Any ideas on what's going on? Is the DIS box on it's way out? It's odd to me that it will run when it's cold, but right on cue when it warms up it runs bad until it dies. I was thinking that the main fuel pump is on it's way out, but the pressure is staying good so I think that it's ok. Thanks in advance. Reed

11-09-2019	#2
Ccmano Join Date: Jun 2006 Location: Sparks, NV Posts: 2,852	Re: Runs good cold, dies warm Code 43 is not the DIS, it’s the knock sensing system, knock sensor, knock control module or related wiring. Likely not related to the current issue. The secondary fuel pump shuts down at 176F coolant temp leaving only the primary pump running. The primary pump would still be my first look. A pump amp draw test should tell you what’s going on. Here’s the test write up. H http://www.zr1.net/forum/showthread.php?p=136108 __________________ 90'ZR-1 #1461 Red/Black Ported Intake, Degreed Cams, OBX Headers & Exhaust, Fidanza FW, Secondary Delete, Custom tune, C6 GS Wheels. Sold 08 C6 Z51 Crystal Red Metallic Sold Vararam Intake, Tune, Sold 05 C6 Z51 Red/Black Sold 90'ZR-1 #1723 Black/Gray Sold but not forgotten 91' Z51 L98 White Vert. My First, you always remember your first. Sold.

11-11-2019	#3
FormulaReed Join Date: Jan 2019 Location: Seattle Posts: 62	Re: Runs good cold, dies warm Tried the doing an amp draw test but I had no luck with the test port. I bet it’s on my end being an idiot... So I got a new primary pump. I’ve already replaced the secondary pump and it was an easy job so I’m just going to change it out tomorrow and see if that fixes it.

11-16-2019	#4
FormulaReed Join Date: Jan 2019 Location: Seattle Posts: 62	Re: Runs good cold, dies warm Update: I replaced the primary fuel pump and it seems to have fixed it! I let it warm up and it ran fine, went for a little drive and it ran really good. Much better than I have ever had it running. I think that it's fixed because it would not run at all as soon as it warmed up, now it runs great. I replaced the secondary pump right after I got it and noticed that it had Precision brand pumps in it. One thing that i think is kind of odd is that it still showed fuel pressure at the rail when it was stalling out. I wonder if the secondary pump was kicking in when the idle dropped below 400 rpm and kept it sorta running as it was stalling out. Also might explain why it would cut out and than snap back to life a few times. Thanks for the help!