'89 SHO, will not idle correctly, really bad bucking and misfire under any load

[Jon]

Hey guys, so my newly aquired 89 SHO started to have rough start ups where it wouldn't idle, misfire and die. Would go away for the most part when warm. Now I left the car sitting for a month, tried to start it up, and the problem is now constant.

It bucks and misfires and backfires under any load, AND under idle probably half the time. I'm thinking the Cam Position Sensor could be the culprit? The car leaks lots of oil on the belt side of the motor. I replaced the spark plugs and it ran a little better for about 3 minutes, then started to buck and not run well again.

Any experience with these symptoms?

Thanks all!

 

[zoomlater]

sounds like a cam position sensor, but pull your codes to see if that is really the issue. my car would buck when driving when the cam position sensor failed

 

[luigisho]

Did the oil leak into the spark plug tubes? That can cause a misfire not just with fouled plugs but also foul the wires. The cam sensor is easily removable to check for oil leakage. That is very common. You should pull the codes and see what is registering in the computer.

here is a guide to pull the codes with a paperclip or jumper wire
https://web.archive.org/web/20080617184612mp_/http://www.shophoenixproject.com/eec/eec.htm

 

[Irish Pride]

Make sure you have the plug wires routed correctly. It's very common to get a wire crossed or use a manual that has the wires routed wrong.

Engine
1 2 3
4 5 6

Coil
5 1
6 2
4 3

 

[Jon]

Did the oil leak into the spark plug tubes? That can cause a misfire not just with fouled plugs but also foul the wires. The cam sensor is easily removable to check for oil leakage. That is very common. You should pull the codes and see what is registering in the computer.

here is a guide to pull the codes with a paperclip or jumper wire
https://web.archive.org/web/20080617184612mp_/http://www.shophoenixproject.com/eec/eec.htm

Thanks for the guide! I pulled the plugs again and there is definitely no major oil in the tubes, the threads of a few of the plugs were a tiny bit damp at most, but nothing of major concern. Valve covers are on the list, they seep a little bit. I'll go ahead and check those codes.

 

[luigisho]

Pull those. Rechecking plug wire config is a good idea as posted above. go from there.

 

[FastCAD]

Definitely check the plug wire sequence at the coil (an easy mistake). The (round) cam sensor cap; passenger side left of cam cover near the firewall is an easy check for oil leakage and fouling. If you don't get any codes then go to the
(I )dle (A)ir (B)ypass (behind the throttle body). IAB does not throw a code. "Delphi- CV10140-11B1" Summit Racing $55.
It is not likely that oil will foul the crank position sensor. A leaking water pump is another story. Valve cover gaskets-with plug well seals, manifold gasket set, cam seals and sensor gaskets (3 pieces) - RockAuto. Don't forget valve cover bolt gaskets "ShoSource".
The SHO might burn a little oil like all ohc engines but oil leaks are not acceptable.

 

[rubydist]

we need to know what the codes are or we are just providing wild speculation. please pull the codes and report what they are.

 

[shorage]

THIS

sounds like a cam position sensor, but pull your codes to see if that is really the issue. my car would buck when driving when the cam position sensor failed