Idle problems after engine modifications –HELP

I am having problems with idle on my 1990 5.0L Bronco. This is basically stock with heathers and I already had a Mass-Air conversion on it. The truck ran fine and idled OK before I messed with it.

After installing GT40 heads, GT40 intake and new cam on my engine, I just do not have idle control and my engine is running real hot. It is idling like it is missing a few beets.

Fiddling with the connectors and reving the engine up and down, I noticed that my forward cat was glowing red hot? The headers at the connection to the Y pipe were also glowing red hot.

I double checked my timing and all is OK. Here are the specs on my cam

Valve Lift Duration Camlift Duration Lobe Separtion
Intake 0.464 264 0.29 202 114 112
Exhaust 0.4646 264 0.29 202

There are 2 things that I suspect and need your help and input on:

1. Bad O2 sensor. It may have been ruined from the assembly lube that I used around the valve train? I pulled the plugs after running (they were new prior) and they had black carbon on them.

2. Fault in the electronics of the distributor. When the shop was pressing in a new gear, the guy dropped the distributor, breaking off the plastic piece on to. The connector is OK and I did not see anything loose or damaged inside.

Hooking up my scanner, I am not able to test because it does not get past the idle test. Stating that it cannot control idle.

Any input on what I may have done wrong?

Thank you in advance,
George
gvolosh1@san.rr.com

 

First off, if the cat is "glowing" from the heat you have a problem. Yes, it gets hotter than the rest of the exhaust system, but not that hot. Sounds to me like you have a serious backpressure problem. Perhaps a partially blocked cat. or muffler. Considering you are already running headers, has the rest of the exhaust system been upgraded to handle the increased intake capacity? Free up the exhaust and your idle will smooth out too. A hearty YES on replacing the O2 sensor as the additional heat doesn't help it either. As for the systems diagnostics, I would refer you to someone with a greater working knowledge than myself.

 

Hi, check for flooding. Vacum leaks are number one problem, fuel pressure regulator.
You may have to do a start stop cyclikng to get the computer to recognize the changes you made.
Check the throttle postion sensor, it maybe broken. You'll need to use a volt meter and a book for that info.
Bruce (Big Red Bronco)

 

it is my understanding that the purpose of a catalytic converter is to burn of the unburned fuel left after normal combustin. therfor i believe you have an overfueling problem. fuel pressure regulator controlsthe amount of fuel returning to the tank. did you disconnect the air pump? that is there to put oxogen in the exhaust to help the cats burn off the fuel. an o2 sensor controls the electonically the amount of fuel being fed to the injactors. if it senses to much fuel present in the exhaust it should lean out the mixture and if it senses to much oxegyn in the exhaust it should richen it up. carbon on the plugs suggests to me that you are running rich and that would cause the cats to get hot. glowing red cats is very dangerous from a fire stand point so please fix before you create much moe damage.
the missing you are talking about may be the lope that the cam is creating but i dont think so because it is not that hot of a cam.

 

Double check your timing.Retarded timing will cause unburnt fuel to enter the exhaust.Make sure you put #1 at TDC and check your timing marks.The inner rubber sleeve on the balancer is known to break and cause it to slip and screw up the timing marks.

Check your fuel pressure.A bad fuel presure regulator will cause high fuel pressure and a rich condition.Which can also cause a stumbling idle.

If the cats are glowing you are burning fuel in them causing them to over heat and possibly be damaged.

Good luck

Billy

 

Given the mods you stated I would be suspicious of 2 things. First is the compression on the heads. Are they new or did you buy them from someone used. High compression could cause extreme heat. The second is the cam alignment with the crank. Are you sure the cam is timed properly with the crank. If these are correct then you may have an extreme lean condition which I would start by having the fuel rail cleaned.