ck engine light on/off

kdomingue · 11-03-2003, 03:23 PM

I bought a 95 Mustang GT about a month ago. I replaced plug wires, spark plugs, cap, rotor, coil. At any given time the ck engine light comes on and the goes off, maybe 3 or 4 times in a row. This only happens when I'm accelerate at a good rate, probably 1/2- 3/4 throttle. Is this a bad O2 sensor maybe?

Also what are the best (cheap)mods besides K&N air filter, underdrive pulleys, exhaust, advance timing and that sort of thing. It is a 302.

stanger9219 · 11-05-2003, 12:32 AM

My car had that problem, but the check engine light flashing can be soooo many different things. It could be the 02 sensors, but for me it was the EGR valve. I fixed it by trial and error but my 5.0 was runnin into quite a few problems with performance. I suggest not worrying about it until it starts to affect the way the car runs. A couple of free mods that theoretically will help is to reroute the water hose that goes into your TB (keeps air cooler) and you could take out your air silencer inside the fender well. Other than that i think you have most of the cheap mods covered. Hope thats of some help.

84LX89GT · 11-08-2003, 07:15 PM

This should probably be in the windsor forum, but here goes:

This sounds like an EGR problem. The egr system is used during part throttle situations. The EVP sensor measures the movement of the EGR valve and if something doesn't match the tables in the PCM it sends a check engine light that will often flicker/turn on-off.
My '89 GT has that problem because of a .1 volt drop from the connector to the processor, so i have to overlay a wire, but often it is just that the EGR valve is full of carbon and the pintle is stuck. The first thing i would do is take off the EGR valve and clean it out with a de-carbon fluid (lots of things work - carb clean works). Make sure to move the pintle and make sure it's free and nothing is binding.
the EVP sensor is known to go bad as well, so you can unbolt it and with a multimeter measure resistance as you move the rod. You can also use a vacuum pump on the EGR valve and measure volts and backprobe the signal wire and ground to see what the PCM sees. I believe it should read .8 or .9 volts and it can go i believe up to 4.5 volts at the far end of it's range.
If you do replace the EGR valve (usually $70 i think) it's not a bad idea to replace the EVP sensor ($30?) if you have no way to test it and it's easier to replace while the valve is off.

11-03-2003, 03:23 PM	#1
kdomingue Registered Member Join Date: Oct 2003 Location: Louisiana Posts: 12	ck engine light on/off I bought a 95 Mustang GT about a month ago. I replaced plug wires, spark plugs, cap, rotor, coil. At any given time the ck engine light comes on and the goes off, maybe 3 or 4 times in a row. This only happens when I'm accelerate at a good rate, probably 1/2- 3/4 throttle. Is this a bad O2 sensor maybe? Also what are the best (cheap)mods besides K&N air filter, underdrive pulleys, exhaust, advance timing and that sort of thing. It is a 302.

11-05-2003, 12:32 AM	#2
stanger9219 Registered Member Join Date: Sep 2003 Location: st. louis, MO Posts: 197	My car had that problem, but the check engine light flashing can be soooo many different things. It could be the 02 sensors, but for me it was the EGR valve. I fixed it by trial and error but my 5.0 was runnin into quite a few problems with performance. I suggest not worrying about it until it starts to affect the way the car runs. A couple of free mods that theoretically will help is to reroute the water hose that goes into your TB (keeps air cooler) and you could take out your air silencer inside the fender well. Other than that i think you have most of the cheap mods covered. Hope thats of some help. __________________ 98 Cobra, CAI, Flowmasters, o/r h-pipe. 4.10s, Hurst shifter.

11-08-2003, 07:15 PM	#3
84LX89GT Mustangs Join Date: Jul 2000 Posts: 1,938	This should probably be in the windsor forum, but here goes: This sounds like an EGR problem. The egr system is used during part throttle situations. The EVP sensor measures the movement of the EGR valve and if something doesn't match the tables in the PCM it sends a check engine light that will often flicker/turn on-off. My '89 GT has that problem because of a .1 volt drop from the connector to the processor, so i have to overlay a wire, but often it is just that the EGR valve is full of carbon and the pintle is stuck. The first thing i would do is take off the EGR valve and clean it out with a de-carbon fluid (lots of things work - carb clean works). Make sure to move the pintle and make sure it's free and nothing is binding. the EVP sensor is known to go bad as well, so you can unbolt it and with a multimeter measure resistance as you move the rod. You can also use a vacuum pump on the EGR valve and measure volts and backprobe the signal wire and ground to see what the PCM sees. I believe it should read .8 or .9 volts and it can go i believe up to 4.5 volts at the far end of it's range. If you do replace the EGR valve (usually $70 i think) it's not a bad idea to replace the EVP sensor ($30?) if you have no way to test it and it's easier to replace while the valve is off. __________________ 2005 Suzuki Hayabusa GSX1300-R 1980 Ford Thunderbird - 255 V8 ported heads, 5.0L ported stock headers, O.R. H-pipe and Flowmaster 2-chambers, dual roller timing chain hi-po Mack Truck hood emblem 1985 Mustang GT 5.0L T5, F-303, GT40p, headers, off-road h, flowmasters, MSD stuff, etc. Sold 02/06/04 1989 Mustang GT ET: 13.304@102.29 mph (5-24-03) Sold - 1998 Mustang Cobra coupe, 1/4 mile - street tires: 13.843@103.41 (bone stock)

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