Holy Moly!! This is unreal!

[leonbentz]

I have just recently acquired a 1991 Metro and like driving it. For a car that has almost 180k on it, I'm amazed on how well it drives and how tight it is. Whoever had it treated it pretty good. Unfortunately........


This is the kicker. This little bugger only gets me 21 MPG!! How is that possible?? I can get an SUV twice it's size and do better. LOL

The car has a good sized soot build up, in the tailpipe, so I know it's going through the engine......(the excessive fuel loss, that is.) When I bought it, the ECM sensor (on the back of the throttle body) was unplugged, but it ran fine. I plugged it in once and noticed it ran VERY rich. OOps...this can't be right, so I decided I better fix it.

To this day, I replaced the O2 sensor, Throttle body injector, ECM sensor, MAP sensor plus I checked the adjustment, of the TP Sensor and the milage is still the same. Autozone may make me the poster boy. LOL It runs great, once it's warm. It never misses a beat. It starts good, cold or warm, but when it's warm and I let it set for a few minutes, it loads up and runs rough, for a sec.

When I start it cold, it starts right up, but soon, it starts to chug, chug, chug, like it's using twice as much fuel as it needs

My impression is: There is still something in there, that is telling it to send more fuel (than it needs) and make it run rich.....even warm! About the only thing left, that has anything to do with Throttle Body Injector duration, is the ECT sensor, which is in the Thermastat housing. If this fails to fix my problem, then I guess my only option is to take it to a .....(cough cough) technition and get his advice.

I have seen several others here, who have had trouble with bad milage, so if anyone has any input, it would be helpful to a lot here, other than myself.

Thanks guys.

[DieInterim]

Originally Posted by leonbentz

I have just recently acquired a 1991 Metro and like driving it. For a car that has almost 180k on it, I'm amazed on how well it drives and how tight it is. Whoever had it treated it pretty good. Unfortunately........


This is the kicker. This little bugger only gets me 21 MPG!! How is that possible?? I can get an SUV twice it's size and do better. LOL

The car has a good sized soot build up, in the tailpipe, so I know it's going through the engine......(the excessive fuel loss, that is.) When I bought it, the ECM sensor (on the back of the throttle body) was unplugged, but it ran fine. I plugged it in once and noticed it ran VERY rich. OOps...this can't be right, so I decided I better fix it.

To this day, I replaced the O2 sensor, Throttle body injector, ECM sensor, MAP sensor plus I checked the adjustment, of the TP Sensor and the milage is still the same. Autozone may make me the poster boy. LOL It runs great, once it's warm. It never misses a beat. It starts good, cold or warm, but when it's warm and I let it set for a few minutes, it loads up and runs rough, for a sec.

When I start it cold, it starts right up, but soon, it starts to chug, chug, chug, like it's using twice as much fuel as it needs

My impression is: There is still something in there, that is telling it to send more fuel (than it needs) and make it run rich.....even warm! About the only thing left, that has anything to do with Throttle Body Injector duration, is the ECT sensor, which is in the Thermastat housing. If this fails to fix my problem, then I guess my only option is to take it to a .....(cough cough) technition and get his advice.

I have seen several others here, who have had trouble with bad milage, so if anyone has any input, it would be helpful to a lot here, other than myself.

Thanks guys.

Change the coolant sensor and thermostat. Check for vacuum leaks with carb cleaner. Jumper service connector and set timing. Pull timing belt cover and make sure camshaft is in time. Inspect regulator diaphram for wrinkles and hardening. Press open egr valve when engine is running to see if idle changes.

You just might find the sensor is the trick, but look at the aforementioned and follow through, you'll love your car more if it runs like a top and gets 50mpg.

Blake

[BeoWolfe]

One other thing to check...

The temp sensor used to calculate fuel delivery is located on the back of the throttle body under the air cleaner - the sensor that tells your instrument cluster what temp the engine is at the thermostat housing.

You need the inspect the one on the throttle body and you need to check to see if the coolant hose that feeds the temp sensor on the back of the throttle body has a bockage. This hose is rather thin so it doesn't take much of anything to plug it up. Run the car a while and feel your front radiator hose - it should be hot. Now feel the small hose running to your throttle body - it too should be hot. If its not hot then its has a blockage and warm coolant cant reach your sensor so the car always think that the engine is cold and thus delivers too much fuel.


Good luck

[SchlockRod]

Wouldn't a check of fault codes be a novel idea?
The advice about manually/visually checking things like coolant temp. sensor definitely sounds like a good idea - coolant temp. sensor was the first thing that entered my mind. The rest is good as well (vacuum leaks, EGR valve, timing, etc.). But our poor friend has been doing a lot of parts changing when much time & $ might be saved by checking fault codes first.

This is easy on these cars. With engine at normal operating temperature, remove one of the spare fuses from the fuse block, and plug it into the "diagnostic" socket on the fuse block. Then turn on the ignition key (to the "run" position, not "start") and count the flash sequence of the "check engine" light. 1 + 3 = 13, 1 + 4 = 14, etc. Several codes may be in there, in which case it would be like: 1, 3, pause, 1, 4, pause... then starting over. Code 12 (1 + 2) means all clear.
Then would be a good time to start the other checks, after first addressing what's in the ECU.

[Metro Mighty Mouse]

of course since the ECU stores the codes the only reason to have the engine at operating temperature would be occupant comfort.

[leonbentz]

I replaced the ECT sensor tonight, so we'll see what happens. I plugged a fuse in the slot, for the diagnostics and no blinking, in the check engine light. Hmmmm. either a bad bulb, or maybe the problem is fixed. I can only hope. Thanks for all the help guys.

[seb001]

Check the light. It should of flashed that there is no code.

[leonbentz]

Well, with a new ECT sensor, I picked up a few more miles to the gallon, but it still is running too rich. I did notice one thing strange though. On Page 6-12, of the 24075 Haynes Manual, it has a chart for setting the TP Sensor. Test # 2 on the chart, where it says to test at closed position, it's supposed to read between 240 and 1140 ohms,? Mine pegs out over 1300 and starts to drop, little at a time gradually. What do you guys think? Should I replace my TP sensor? According to the maual, I should, but more oppinions would be good too.

[Vert Guy]

I would certainly take a look at your fuel preasure. If your fuel pressure is too high your car would deffinately run way too rich! If it is not working at all and fuel pressure goes unregulated you would be lucky to get 21 miles per gallon! Also your engine would suffer damage from running too rich! Smell your oil from the dipstick. Does it smell pretty gassy? Post back.

[DOCTORBILL]

What the Heck is with the posting dates on this thread?

Post #8 was December 19, 2005 from DieInterim - BTW, I miss his posts!
Why did yous guys have to have that damned fight, anyway!?

Post #9 was the 10th of this month! Today!

That is nine months between the this last post and the one before!

What is going on?

Did you ever fix this vehicle? If so, what was the problem!?

Was it a bad ECT?

Are you still there LeonBentz?.........Hellooooo!

DoctorBill