Wont idle after HG swap.
06-03-2014, 03:33 PM
#1
Wont idle after HG swap. So, I changed the head gasket on my 97 formula and now it wont stay idling when it's hot. It will idle for about a minute, then start slowly dieing. If I hold the gas open, it will stay running, but the RPMs will surge. It wasn't doing this before the HG swap. Any ideas?
MAF is clean
No codes
No vacuum leaks that I can find
Plugs and wires are new.
Fuel trims try like hell to lean it out when this starts.
Next up on my to do list is checking EGR function and IAC.
MAF is clean
No codes
No vacuum leaks that I can find
Plugs and wires are new.
Fuel trims try like hell to lean it out when this starts.
Next up on my to do list is checking EGR function and IAC.
06-03-2014, 06:15 PM
#3
TECH Addict
Have you checked you EGR and IAC yet? It sounds EGR related. Does your scanner show open loop closed loop? Also, does this happen in gear at idle? Or while cruising at 55-65mph level ground?
Your EGR makes the engine think it's smaller than it really is by pumping exhaust gases back into the intake manifold. The exhaust gases take up space and therefore less oxygen will be in the chamber. The computer compensates this by removing fuel. If the EGR isn't letting the exhaust gases in and the engine thinks it is it'll run like this.
I don't remember all the perameters the EGR opens, but I do remember that it will open on cold start up (to warm the engine up faster) and while cruising (improves fuel economy and burns any gases that were otherwise not burned in the first cycle that actually make it back into the intake through the EGR valve). I think (and I could be wrong here) it also opens at normal warm idle to reduce fuel consumption also (it's a steady state low load situation like cruising along the highway at 65mph); it makes sense for the EGR to open at that point.
In any case, you could, if you have a tuner available, turn off the EGR system and see if the problem goes away. If it does it's the EGR, if not look elsewhere. You probably could also just unplug the EGR solenoid and see if that removes the idle problem (you will get an SES light).
Your EGR makes the engine think it's smaller than it really is by pumping exhaust gases back into the intake manifold. The exhaust gases take up space and therefore less oxygen will be in the chamber. The computer compensates this by removing fuel. If the EGR isn't letting the exhaust gases in and the engine thinks it is it'll run like this.
I don't remember all the perameters the EGR opens, but I do remember that it will open on cold start up (to warm the engine up faster) and while cruising (improves fuel economy and burns any gases that were otherwise not burned in the first cycle that actually make it back into the intake through the EGR valve). I think (and I could be wrong here) it also opens at normal warm idle to reduce fuel consumption also (it's a steady state low load situation like cruising along the highway at 65mph); it makes sense for the EGR to open at that point.
In any case, you could, if you have a tuner available, turn off the EGR system and see if the problem goes away. If it does it's the EGR, if not look elsewhere. You probably could also just unplug the EGR solenoid and see if that removes the idle problem (you will get an SES light).
06-03-2014, 06:47 PM
#4
Have you checked you EGR and IAC yet? It sounds EGR related. Does your scanner show open loop closed loop? Also, does this happen in gear at idle? Or while cruising at 55-65mph level ground?
Your EGR makes the engine think it's smaller than it really is by pumping exhaust gases back into the intake manifold. The exhaust gases take up space and therefore less oxygen will be in the chamber. The computer compensates this by removing fuel. If the EGR isn't letting the exhaust gases in and the engine thinks it is it'll run like this.
I don't remember all the perameters the EGR opens, but I do remember that it will open on cold start up (to warm the engine up faster) and while cruising (improves fuel economy and burns any gases that were otherwise not burned in the first cycle that actually make it back into the intake through the EGR valve). I think (and I could be wrong here) it also opens at normal warm idle to reduce fuel consumption also (it's a steady state low load situation like cruising along the highway at 65mph); it makes sense for the EGR to open at that point.
In any case, you could, if you have a tuner available, turn off the EGR system and see if the problem goes away. If it does it's the EGR, if not look elsewhere. You probably could also just unplug the EGR solenoid and see if that removes the idle problem (you will get an SES light).
Your EGR makes the engine think it's smaller than it really is by pumping exhaust gases back into the intake manifold. The exhaust gases take up space and therefore less oxygen will be in the chamber. The computer compensates this by removing fuel. If the EGR isn't letting the exhaust gases in and the engine thinks it is it'll run like this.
I don't remember all the perameters the EGR opens, but I do remember that it will open on cold start up (to warm the engine up faster) and while cruising (improves fuel economy and burns any gases that were otherwise not burned in the first cycle that actually make it back into the intake through the EGR valve). I think (and I could be wrong here) it also opens at normal warm idle to reduce fuel consumption also (it's a steady state low load situation like cruising along the highway at 65mph); it makes sense for the EGR to open at that point.
In any case, you could, if you have a tuner available, turn off the EGR system and see if the problem goes away. If it does it's the EGR, if not look elsewhere. You probably could also just unplug the EGR solenoid and see if that removes the idle problem (you will get an SES light).
06-03-2014, 06:53 PM
#5
TECH Addict
Popping the vacuum line off the EGR valve wont disable it in the ECM. Pulling the plug will though.
If it's not the EGR (I'm think not now though as it doesn't happen during cold start), then look into the ICM. Have it checked while it's hot though or check it more than 4 times in a row with out any failures. Our ICM's do tend to have heat soak failures.
If it's not the EGR (I'm think not now though as it doesn't happen during cold start), then look into the ICM. Have it checked while it's hot though or check it more than 4 times in a row with out any failures. Our ICM's do tend to have heat soak failures.
06-03-2014, 07:38 PM
#6
Popped the IAC out, it was dirty so I cleaned it up, new TB gasket. Zero effect. But, I finally got the rat bastard to spit out a code. O2 sensor, bank 1, sensor 1 high voltage. Makes sense because it starts have the issue the second it goes into closed loop.
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06-04-2014, 12:49 AM
#9
TECH Addict
06-04-2014, 02:06 PM
#10
Well, bank 1 sensor 1 fixed the idle issue and bank 1's fuel trims. Now bank 2 has lost it's mind, causing misfires. Guess my original theory was correct, 02's shat the bed, leaned it out causing detonation, which burned through the head gaskets. Going to get the next one, looks like it's going to be FUN to replace.
It's nice when things are fixed farely easily. 