94 Eldorado: Bad mpg after fuel injection service & spark plug/wires changed, why?

[RENO99DEVILLE]

94 Eldorado: Bad mpg after fuel injection service & spark plug/wires changed, why?

Service was done at jiffy lube: fuel injection service/cleaning, spark plugs and wires changed. Now the mpg is at 12 and I don't know why. What can I check or do? what is the firing order of the 94 eldorado and how can I get detailed info on that and other sensors/connections to check. And How do I check/test everything (wires/plugs/connectors/etc)..

Someone please help

[Krashed989]

Start off by checking the codes. You can do that from the dashboard by simply pressing and holding the OFF and warmer (red) buttons on the climate control panel. All of the lights on the dashboard will light up as it enters diagnostics mode. Then it will start to show you the codes. Have a pencil and paper ready to write them down. Once it reaches "PCM?" you can either press the OFF button once to have it repeat the codes or you can turn the key off to exit diagnostics mode.

After that you can post them up here and someone will help you.

Also, do you know if they changed your spark plug wires with OEM AC Delco?

[RENO99DEVILLE]

Ok I have just printed your directions.. this so far is a big help because the way I pull codes from my 99 Deville is different.

And about the plug wires, I will have to check what they are but I just bought the car (traded for it anyways..) and the prev owner told me they had just replaced plugs/wires with stock ac delco and did the fuel injection cleaning and showed me all the reciepts but I will check just to be sure. Also how can I check to see if the wires are indeed ok and connected right? And do I look out for anything un/disconnected and if yes where? I do have a snap-on volt meter so I can check for other values.. I am going to pull codes now, will get back to you in about an hour, thanks!!!

[RENO99DEVILLE]

Ok I looked and no codes..
I did have codes in the history; P032, P071, P095, P105 and S036, S060, S061, S063.

Like I said all those codes above are history but I sure would like to know what they were


Ok now what do I start checking/looking out for to find my mpg problem? I'm gonna start my fluid level checks and clean-up so I will check back for any responses, and thanks to all that are willing to take their time to help me!

[Ranger]

You can find the code definitions here.
http://myweb.accessus.net/~090/dtcobd1.html

Check to be sure that Jiffy Lube did not leave a sensor unplugged. MAF sensor ('94 may not have a MAF), IAT sensor for starters. Though they should set a DTC if left unplugged.

Might not be a bad idea to take it back to them and let them correct it. Personally, I would not have let them touch it in the first place. Especially injector cleaning. That is rarely needed and just a big money maker for them.

[RENO99DEVILLE]

Yes I know but it was not me that took the car there because I prob could have done that work myself. Well I will look for unplugged things but I think your right, there are no codes so everything is prob connected. What about the wires, I have not checked to see if indeed they are ac delco yet but would that make such a difference? Also never mentioned but the prev owner also had the fuel pump and fuel filter changed.
So can I check anything with my volt meter to see if anything fuel related is on value? I will be back in a lil, gonna go check those wires, should I check those plugs? It should be the ac delco right? Are those platinum?

[RENO99DEVILLE]

No they are carquest wires, should I can them to ac delco wires? While I'm at it I should also change the plugs to the correct ones for best mpg right?? Can you tell me what kind of plugs and wires to buy please and what else to check/change while I'm doing that please, thanks so much!!!

[submariner409]

When you finish installing the recommended ACDelco wires and plugs, make sure (use a FSM) that the correct plug wire is connected to the proper plug from each coil tower.

Look at www.rockauto.com and drill down to your car year and model for the correct wire.

There are several ACDelco double platinum Professional plugs in the late 41-9xx series, so you'll need the correct one for your engine.

(I think DELPHI, GM's parts division, has split off and is now a separate company, but still makes the various GM trademarked parts. Someone referred to them as "aftermarket" in another thread.....not quite.....---SplitFire is aftermarket; DELPHI/ACDelco is OEM.)

[RENO99DEVILLE]

Ok I will replace my plugs with oem.

[Krashed989]

WAIT!!! The ONLY reason all of your codes were in history is probably because you just went out there and without starting the engine, turned the key on and checked the codes. In doing this you would give the computer no chance at all to check the systems and set the code(s) as current again for that "current" ignition cycle.

Now let's see:
P032 ---- Open MAP Sensor Signal (Could be an unplugged MAP (Manifold Air Pressure) sensor or the MAP sensor is bad)
P071 ---- Intermittent MAP Signal (Could be a loose connection to the MAP sensor or the MAP sensor is bad)
P095 ---- Engine Stall Detected (Self Explanatory)
P105 ---- Brake Booster Vacuum too Low (Could be a vacuum leak)

What I would do is I would take off the beauty cover/plenum and I would check the connection to the MAP sensor. Do Not start the car with the plenum off as the rpms will run away unthrottled. I think the MAP is where your problem is, although it is better to have OEM AC Delco wires installed.

[RENO99DEVILLE]

No I never had any codes even driving it. I was just curious about how to check codes and that was in the history. I will have to check the map (what does that stand for anyways?) sensor one day.

[Ranger]

MAP = Manifold Absolute Pressure

[RENO99DEVILLE]

Thanks again Ranger!

[RENO99DEVILLE]

PROBLEM SOLVED. I guess I just needed to reset the system after the fuel injection service, tune-up, wire & spark plug change and new battery. Now I'm back in the 20mpg range. Thanks to everyone who helped!