Still won't idle properly (1 Viewer)

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Joined
Oct 14, 2013
Threads
27
Messages
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Location
Milan, IL
Well after replacing my old dissy with one that has working advance, resetting baseline timing, and lean drop adjusting the idle mixture, I'm still having issues with idling. It idles great on start up, but when I clutch in after driving down the road it dies. It's bad enough that if I don't pull the choke or hand throttle out I have to run start it around turns. If I pull the choke out about 1/3 it'll stay running when I clutch in, then after 20-30 seconds I can let the choke off and it'll run rough but won't die, after 1-2 more minutes it'll smooth out and idle normally.
Any ideas?
I'm about out of patience with this truck. Every time I fix something, something else goes wrong.
 
I also got 12.5 mpg on the last two tanks when I used to get 14-15. Not sure if that's related or a different issue.
 
I just did some testing with a vac gauge. On startup it sits at 19inHg. After driving for 3 minutes or so I pulled over and got the vac gauge as soon as I could while it was still idling bad. It started at at about 10 and slowly creeped up to 18 as the idle smoothed out. There was never any jumping or fluttering.
Is low vacuum causing my idling problem, or is it the other way round?
 
I haven't messed with the EGR system before. How would be best to check it?
 
Disconnect the vacuum hose that connects to the top of it. Put a plug in the hose. Connect a longer length of hose to the valve and let it dangle.

Start the engine and apply both a little vacuum to the valve, ( the engine will stumble) and then blow hard on the hose with your mouth to make sure the valve is closed. If the engine idles smooth, the valve is closed.

Once the engine is idling smooth (with hi vacuum), take it for a SHORT test drive with the EGR DISCONNECTED. See if the problem goes away. If it does, the the EGR valve was intermittently sticking open a bit. If the problem persists, look elsewhere.

You can't drive the engine w/o the EGR like that permanently though, as it will ping at higher rpm.
 
I just dealt with similar issues with my truck, it ended up being the intake manifold gasket. Something else you may want to look at. Good luck.
 
Disconnect the vacuum hose that connects to the top of it. Put a plug in the hose. Connect a longer length of hose to the valve and let it dangle.

Start the engine and apply both a little vacuum to the valve, ( the engine will stumble) and then blow hard on the hose with your mouth to make sure the valve is closed. If the engine idles smooth, the valve is closed.

Once the engine is idling smooth (with hi vacuum), take it for a SHORT test drive with the EGR DISCONNECTED. See if the problem goes away. If it does, the the EGR valve was intermittently sticking open a bit. If the problem persists, look elsewhere.

You can't drive the engine w/o the EGR like that permanently though, as it will ping at higher rpm.
I will try that tomorrow. Found a similar recommendation from Jim C in an older thread.
As a testing method, I suggest completely disabling the EGR vacuum system.
simply pull the hoses off the EGR modulator, BVSV and VSV, then plug them w/ golf tees. Now test drive the vehicle.

If it runs good, then the problem is in the EGR system.

If it still runs like poo, then the problem lies elsewhere in the engine management systems.
 
I just dealt with similar issues with my truck, it ended up being the intake manifold gasket. Something else you may want to look at. Good luck.
What was wrong with the gasket, and how did you diagnose the problem?
 
It is either a manifold vacuum leak or a lack of idle fuel. The most common problems are an EGR valve stuck open and a bad manifold gasket seal. Whack the top of the EGR valve with the handle of a screw driver and see if the problem goes away. Tighten up the intake manifold nuts/screws and see if the problem goes away.
If neither of these help, keep checking for manifold vacuum leaks with carb cleaner spray.
 
So I can understand the EGR valve sticking and then eventually opening allowing the motor to idle properly, but I don't understand why a vac leak at the manifold would only present itself after running.

I'm not doubting that you're right, just curious as to why.
 
The EGR valve is supposed to be closed at idle and if it is stuck open it creates a vacuum leak.

Any air entering the manifold via a leak bypsses the carb and has no fuel, so it can't combust and the engine won't run at idle.
 
When the manifold heats up, it expands. Sometimes manifold leaks are worse when it is hot or cold. It depends.

If the manifold gasket is older than 10 years, it's probably sealing the manifold with hair of its chinny chin chin. On the 2F, they don't last forever. ( not to say that that is the current problem).
 
The manifold gasket is less than a year old, but I'll try retorquing it tomorrow in addition to checking EGR
 
So when I went to disable the EGR for testing today but when I opened the hood up I could hear a whistling sound that had not been there before. Sure enoughthe manifold bolts had gotten loose and there was substantial vac leak around the gasket. Torqued them back to spec, checked timing, readjusted idle, and took her for a test drive. She doesn't die anymore! Hopefully this will fix the fuel economy issue as well.

Thanks so much guys!
 

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