So far all I have done is changed the plugs and air filter. I've been thinking I should do the fuel filter soon, also heard that changing the O2 sensors at XXX miles is a good idea. What about injector service? Or maybe I should just take it to a shop and have it put on an analyser to know for sure that everything is working OK and if so not do anything?

Anyone have any thoughts. Everything is running fine, just wondering if there is something I should do.

Thanks,
Ken

I'd definitely change the fuel filter, and probably the O2 sensors. I'd probably not bother with the injectors, myself.

"brave new world" - yeah insn't that the truth!

Looks like I will stick with what you suggested - I guess I can call these items the 'basics'.

I would just change the plugs, air filter, and fuel filter. The fuel injector flush is problaby not a bad idea, but not absolutely necessary at your mileage, especially if you have been running premium gas.

You could buy some throttle body cleaner and clean the throttle body. Don't use carb cleaner. If you replace the filter with a K&N or other oiled filter, be careful and don't use too much oil, the oil can ruin your MAF sensor.

Started the car in the evening to head home and the idle kind of jumped around (seemed like firing out of time as the engine shook a bit). Check engine light came on and stays on and the idle is a bit rough now. Power when cruising and accelerating seems fine. Idle was fine before so I don't suspect injectors, I drove the car about 40 miles, shut it off, then started it about 10 hours later and this occurred. Put about 100 miles on since filling the tank so don't suspect problem with bad gas.

Any recommendations for a scan tool that a guy should have so that I can read the error codes to begin fixing the problem. Any other info would help.

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Sub Stanger/1990 LX 5.0 convertible.

Past Mustangs: '84 GT 5-speed; '91 GT auto; '70 M-code Mach 1, grabber yellow; 2 '95 GT 5 speeds, totalled first one; '94 6-banger, wifes; '89 LX 5.0 vert, '90 LX 5.0 hatch, '69 M-code Mach 1, 4 speed.

First things first though, check for vacuum leaks, cheak to make sure you got the intake tubing tight (a leak after the MAF can cause rough running). Open your hood at night!

Submariner: not to question your experience but am just curious that if the ford plug wires are so good how come they fail in 6-7 years? I agree that Ford seems to have a pretty good quality plug wire from what I have seen in the past but I would expect them to last longer than is. However someone else did suggest bad wires also. How about something like MSD or Taylor wires? I have Taylor on my Cleveland, I don't mind spending the extra money in this area.

Still hoping to get suggestions on a code reader, are there not units around that will do the job for $50-$100? I may have a chance to shop around for a code reader this weekend. In the meantime I will look at the wires to see if something is amiss.

Have you had the code pulled yet?? You're driving me crazy wondering what's wrong with your car. When a car comes into me with the check engine light on, I play a little "mental diagnosis" in my head, depending on the model and year the car is. The longer I do this job, the better I get at "guessing" the code before I actually pull it.

Let us know what it is when you get it read.

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Sub Stanger/1990 LX 5.0 convertible;
2003 Mach 1 (on order!!)

I've been too busy to look into this but tonight will be the night to get the codes. I am picking up an Actron (sunpro) code reader tonight for about CAN$300 that will work on this car - the car is OBDII compliant.

I checked plug wires the other night, they look like a good heavy wire as I am used to seeing (8.8mm I think) and no signs of damage. Ran the car in the dark and looked under the hood and saw no signs or sounds of spark jumping.

I will hopefully post in the next day or so as to what the code reader tells me.

According the code reader manual this code says "exhaust gas recirculation flow excessive detected".

I don't know what to make of this, EGR or something stuck momentarily perhaps. This fault came at moment of start up when the motor felt like it back fired when cranking over. I cleared the code and the "check engine" light went out but I haven't driven the car to see if it comes back. Car still has a rough idle, not terrible by any means but there is a noticeable shudder where as to the best of my memory the engine used to be rock steady at idle. Maybe just coincidently my fuel injectors need a bottle of cleaner in the tank to clean them up, I will have to try this and drive the car for a while to see if the code comes back.

I'll post here if something developes,

This is exactly what I was talking about earlier as far as my "mental diagnosis", but I always back up the mental diagnosis with the proper tests. There are a couple of ways to check the EGR system depending on which sensor you have, but both checks require some additional test equipment, one being our NGS or WDS scan tools, and the other being a simple vacuum pump. I hook the vacuum pump up to the EGR valves vacuum nipple, start the engine, operate the EGR valve with the vacuum pump, and monitor the signal being sent to the PCM via either the NGS or WDS that I mentioned earlier to see if the EGR valve is opening or not, and check for a voltage change being sent to the PCM from the EGR's sensor. This test checks the operation of the EGR valve see if it opens and closes, stays open, or stays closed, and the sensor associated with it. It sounds more complicated than it actually is.

Well, at least you know your wires are okay, and you don't have a misfire. Keep me posted on what you have done, and let me know if I can help out parts wise. Sorry I couln't help out with a "gnats *** " diagnosis, I just don't want to steer you in the wrong direction, and have you upset that you went out and bought parts before you actually knew what the bad part was. Good luck with it.

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Sub Stanger/1990 LX 5.0 convertible;
2003 Mach 1 (on order!!)

Past Mustangs: '84 GT 5-speed; '91 GT auto; '70 M-code Mach 1, grabber yellow; 2 '95 GT 5 speeds, totalled first one; '94 6-banger, wifes; '89 LX 5.0 vert, '90 LX 5.0 hatch, '69 M-code Mach 1, 4 speed.

I looked at my EGR valve yesterday and disconnected the vacuum line to the valve, noted that there is no vacuum to the valve at idle which seems correct to me.

I had the code show up a few times yesterday when I ran out: once on intial startup with the engine cold, once when coasting to a stop light, once at some point while driving. Idle is rough, around 5-600 in drive, about 800 in N, idle is smooth in drive is if pick it up to about 800. Seems likely the EGR is stuck open dumping exhaust into the intake and messing up the idle mixture.

I was also thinking that I could use a vacuum pump to operate the EGR (open it) but I don't know how I could monitor it to know it is working. Can I check this with a multimeter? I am Electrical Tech and have a good knowledge of testing three phase/single phase and DC systems, and have some test equipment that will work on electronics (scope meter for instance). If the test of the EGR operation can be performed with a multimeter then let me know. Otherwise I am thinking that this is something that I could let a garage handle.

Basically, the EGR valve has a sensor that monitors EGR flow, and that sensor is what tells the PCM that the EGR valve is opening/closing ect. Since you have the P0402 code as well as the rough idle, it's most likely a stuck EGR valve. Those things can get pretty carboned up inside. When I replace an EGR valve, I usually replace the sensor along with it. I'm not sure which sensor you've got with your's, either a DPFE sensor, which is separate from the EGR valve, or the sensor that's bolted right to it, and then plugs into the harness.

Whatever you decide to do, you're most likely not doing any harm to the engine right now, it's just a little inconvenient with the rough idle, and your fuel mileage may be affected a little. In any case, I'm sure you want to get that 4.6 running smooth again as the smoothness is one of the best characteristics of that engine.

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Sub Stanger/1990 LX 5.0 convertible;
2003 Mach 1 (on order!!)

I'll book the car into a shop one of these days to get this problem looked into and likely have them make the repairs. When done then I will know that the engine is running the way it should be, if it isn't the shop will let me know what else I need to do which essentially gives the answers to my original question of what to do for a tune-up at 60,000 miles.

Thanks for all your input, its been a big help

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Sub Stanger/1990 LX 5.0 convertible;
2003 Mach 1 (on order!!)

Here's the CP test

Unplug the EGR vacuum line and attach a length of hose.

Attach a multi-meter to the return wire of the DPFE sensor (middle wire, usually Brown /green stripe)

Start the engine, and suck on the hose. Yep, you are the best vacuum tool ever made It doesn't take much to open the EGR. Voltage should change. I can't remember which way, but usually if the DPFE is bad then it sticks at a fixed voltage (close to 5V seems to stick in my mind). Also, the engine should stumble and want to stall. If it doesn't the EGR is either stuck open or closed.

If the engine stumbles a bit and the DPFe does change, then your EGR is likely carboned. Take it off and clean/inspect it.

Hope this helps

I guess I could also use engine vacuum routed directly to the EGR, but as you say sucking on the valve should operate it - I'll give that a try and see if I can monitor the DPFE.