Flames in tbi!

[f85gtron]

I'm trying to diagnose a rough idle on an 84 duke (which also had bogging on throttle tip-in).  I fitted a fuel pressure tester to it last night (it was dark out), and fired it up to check running pressure. Well, I noticed light coming from the intake cover wing nut holes and took a look through the space.  There was flame coming up through the iac and getting sucked down into the intake. I could smell fuel burning and I shut it down. I've smelled that smell before, so I know of one other occasion it's happened. I've never seen this before. What causes it?  How do I correct it?

[GTRS Fiero]

Just to be clear: flames were coming from the IAC?  It's basically a stepper motor with a rod on it.

[f85gtron]

Yes, flames where coming up or down THROUGH the iac, so does that mean there's too much fuel in the intake manifold?  How did it get ignited?

[Fierofool]

That rough idle may be due to a burned intake valve that's igniting fuel in the intake?  But it seems that if that were the case, the whole intake system would explode or the fire wouldn't go out when the engine is shut down. 

[Fierofool]

I've had my second cup of coffee and am thinking a little better now.  I'm not really familiar with the 4 cylinder, but I know the EGR valve is sitting right in front of the throttle body.  Is there any possibility that it might be defective and allowing exhaust gases to enter the intake? 

[GTRS Fiero]

I don't know about the L4, but the gases that come out of the EGR to the intake on the V6 are not hot.  If the EGR is releasing hot gases to the intake, it'd be easy to test.

[f85gtron]

I guess i could block it off to test. Also, looks like a compression test is in order!  I might try the compression test first.

[Raydar]

Burned or sticking intake valve or bad EGR valve could both cause bad running.
(Are the exhaust valves usually the ones that burn?)

[TopNotch]

You could have a leaking injector or injector o-ring. Disconnect the wire from the injector while the car is running, and see if it stops immediately, or runs on for a bit.

[Fierofool]

I don't know about the L4, but the gases that come out of the EGR to the intake on the V6 are not hot.  If the EGR is releasing hot gases to the intake, it'd be easy to test.

Are you sure?  The V6 EGR tube is wrapped in a heat blanket from the factory.  Rodney's replacement has a tube shield around it. 

The L4 allows exhaust gases to pass directly into the intake manifold when it's open, being as there's no tube.  I just checked in a Chilton's manual and it has a cross-section diagram of the EGR gas flow. 

[GTRS Fiero]

Well, I thought it was hot for exactly those reasons, but I grabbed it while the engine was hot and running, and it wasn't hot.  That may be symptomatic of an EGR issue, but I've had several people tell me that the tube doesn't get hot. I have no idea how hot exhaust gas could be cool.

[GTRS Fiero]

After reading this, I believe my EGR is not working, and that the tube should be hot, at least 178 degrees.

[Fierofool]

It probably won't get hot if just sitting and idling since the EGR system only works at road speeds, then it pulls hot gases into the intake. 

[TopNotch]

You could take the EGR off, make a plate out of a piece of aluminum from a drink can, put it over the hole, and put the EGR back on. The see how the engine idles.

[GTXVette]

 If like the Old school egr's you can slip a couple fingers into the diaphram (from the underside of the Valve and raise it up) thus stalling it at Idle or Hold a finger against it and raise the RPM to road speed and feel it raise up like it should if operating correctly. If it doesn't stall at Idle it's plugged up and needs to have the port Cleaned or the Valve replaced.
 if not raising up above idle the same will be true. We used a speedo cable cut about a foot long chucked up in a drill motor to spin it and ream out the port. use the end that has a square on it where it fits into the gear or speedo to chuck up into drill motor. 
these ports get a carbon build up in them.
caution they DO get HOT