well my friend has a 1988 fc and he is having problems with the engine he has made sure the firing order was right and is checking compression on the rear rotor but he said it fires up fine and will freely rev then after about 5 minutes it will only rev to 2k rpm he said with the gas to the floor it will bounce from 1500 and 2000 rpm and thats it. any ideas?

 

Is he getting a CEL?

 

Cel?

 

CEL = check engine light

 

sounds like the ecu is in "safe mode". Ground the test conector by the battery and pull codes. Note the number of times it flashes and I think Banzai racing has the chart for the number it flashes.

 

S4 doesn't really have limp mode..

Maybe a problem with the throttle body's double throttle diaphragm? Check the vacuum lines/check valve..

Not sure that's pretty weird.

 

Next time it has this problem.............disconnect the TPS plug and then it will rev normal. If that is the case most likely the TPS is sticking internally.

I've seen this twice at least on one of my cars. Basically the TPS is causing fuel cut 'cause its malfunctioning and recovers once the rpms drop below ??? 1300 rpm give or take whereupon the injectors come back online and the cycle starts all over again as long as the TPS is malfunctioning.

 

I was thinking vacuum leak somewhere, but what HAILERS2 said sounds like a good place to start.

 

You have to MAKE a test light assy to install in the six socket, green check connector up near the battery area in order to check engine codes. Thats for a series four car not a series five car.

Codes most always just indicate an electrical plug is disconnected from the item identified with the code.

Radom turning of the TPS screw could also have caused a TPS to act like I mentioned.

And...............it could also be something altogether different than what I suggested.

 

Thanks for the advice guys I'm going to have him try it all he wants to sell it because it wont run right