93 Grand Marquis runs rough on statup

[kevin23]

93 GM 126,000

Runs very rough on cold start up, backfires, smooths out after a couple of minutes and runs pretty good. Will also sometimes surge at idle, stop lights and such. Gas mileage is down 3-5 mpg

Local shop with a great reputation kept it 4 days, called me to come pick it up. No charge, so I know he didn't check any thing. Just told me it was a very old car and it was hard to get codes out of them. His business was booming so I assume he was picking his jobs.

I have only replaced plugs.

Any help is appreciated.

[miamibob]

Sounds VERY much like you need a new shop! Issue sounds like an IAC problem. The Idle Air Control, if you are "handy" can easily be replaced. Getting to it may not be (plenty of wires in the way so be careful) but the replacements is two bolts and an electrical connector. It is located on the Driver's side under the throtle body near the firewall. Get a Factory Manual (EBAY?) and I would STRONGLY suggest an OEM part. Clean the ports, when you get it out, and don't forget the gasket. Hope this helps!! MB

[kevin23]

Still runs rough on startup, have to keep it at high idle, bogs down, backfires sometimes, after 3 to 5 minutes it runs pretty good. Will idle without foot on gas pedal. but shakes or surges abit.

Have new plugs, wires, IAC without improvement. Have not cleaned throttle body yet.
Any suggestions? I am at a loss of what to do
Thanks

[miamibob]

Originally Posted by kevin23

Still runs rough on startup, have to keep it at high idle, bogs down, backfires sometimes, after 3 to 5 minutes it runs pretty good. Will idle without foot on gas pedal. but shakes or surges abit.

Have new plugs, wires, IAC without improvement. Have not cleaned throttle body yet.
Any suggestions? I am at a loss of what to do
Thanks

WOW! Almost 2 years and STILL having this issue? Any codes when the car is scanned? Could be EGR related. Many times the part is ok but need to clean out the EGR ports. The codes will tell you that. Let us know!!

[kevin23]

Obviously not my daily driver, just tinkering with it when I have time.
Mechanics tell me that on this older model it don't give many codes like newer models do and I really don't know. Will Auto Zone, etc check for codes?

Thanks for the reply.

[miamibob]

Contrary to your mechanic the '93's DO give EGR codes (among others) so he needs to go back to school. It may or not be that but they can scan for codes. Some auto parts places do so you'll just have to check it out. "Insufficient EGR" usually means to clean out the EGR ports. See wha codes you get and if any look them up online to see the fix. Good luck!!

[way2old]

Check this site out. It tells how to get codes with a test light. Parts stores will not read OBD1 codes.

http://www.extreme-check-engine-ligh...%20Decoder.htm

[miamibob]

Good catch, Tom! Guess I am spoiled as I still have an OBD 1 Scanner and forgot that starting around 1995 Ford went to OBD II!!

[kevin23]

Thanks to everyone, special thanks to way2old, great information, I will use it next chance I get to tinker with the car again.

[way2old]

Hello again Bobby. Long time between posts. Hope things are OK. No problem kevin23. Glad to help anyway we can.

[miamibob]

Thanks for the thoughts, Tom. Haven't been here, recently, or anywhere else for that matter. EMAIL me if you wish and I can get you caught up on recent events.....

[kevin23]

Finally ran the codes with a test light as Way2old suggested.

Results:
32 egr position sensor below closed limit
42 oxygen sensor circuit indicates system always rich
43 oxygen sensor out of self test range
45 coil 1 primary circuit failure

I have replaced the IAC valve with no improvement. Still haven't cleaned the the egr ports, a bit difficult to get to on this model.

More help please, Thanks

[miamibob]

I would clean the EGR port COMPLETELY and change the O2 Sensors (not sure if you have 2 or 4). See where you are at then and let us know.

[kevin23]

Solution : Mass Air Flow sensor

I had this replaced at the beginning of my problems with no change, Apperantly it was a bad one. Runs great now.