deleted and un subscribed to this thread
I don't know when the stations switch over around here, but last fall I took a 250 mile road trip and got 26 according to the display. About a month later, I did the exact same drive and got 22.Do you live in a cold climate with winter gas? My 92 got around 20 in the summer and around 15 in the winter. Some of the winter loss is caused my longer warm up times, colder temps, and riding through snow and some due to the winter gas.
==========================Resurrecting old thread (to keep history together). .
Actions taken got the mpg up to 14/22. Not quite the oem, but good enough for a dd.
Early 2018, noticed a significant power problem and odd stumble.
- Did the hunt on normal tuneup, no change.
- ran power test, and found bad injector. Picked available injector from local summittracing (it was only one in stock in Dfw) for $45. Installed, power returned. Good.
Late Summer 2018, mpg dropped off significantly to 10/13. Spent the next 2.5 months digging through statistics with the car via diagnostics:
- mpg at the pump did not match mpg calculated at fdc. I would have 11, it would say 15.
- fuel used would not match fuel remaining
- fuel pumped did match fuel remaining (implying fuel guage in the tank was working)
- old problem returned of fuel remaining after driving would not be close to fuel remaining when started the next day
- significant powerful start on cold start.
Ran power test and found 2 injectors were misbehaving. Assumed one or both was leaking and likely leaking the built up fuel pressure left when engine was shut off. The extra fuel apparently accumulated in 1-2 cylinders giving the powerful start, odd fuel remaining, and low mpg.
- after the last injector replacement experience, I decided to go the Bosch upgraded or gen III replacement. Found a upgrade set for $95. Ordered and installed.
- one odd note on the install, had plugged the coolant hose located on top of the engine. Turns out, the plug ended up being a wick, dripping coolant into the #8 injector hole during the gap of remove/install. I had vacuumed the injector holes and found nothing unusual. Tried to start the car and engine locked. Remembering my old hydrolock days, decided to pull the #8 plug, cranked, replaced, started with a lot of white smoke - hoping I didn't break anything)
Ran numbers, mpg still off with. . .
- the fdc numbers now match my numbers
- fuel remaining at end and start match
- so, leaking injector assumption was correct and solved that part of the problem.
With new injectors, new set of symptoms
- rough idle, related to hydrolock? Uhoh
- First did a idle learn procedure and eliminated about 80% of the rough idle
- slight hesitation from stop, but runs great during normal cruising/acceleration.
Diagnostics numbers turned up some odd numbers
- MAT is running real hot, almost as though the wiring is broken
- o2 sensor was pegged at .9v when the FSM stated that .45v was average. Cross overs are 0, so engine is running rich
- MAP showed kpas in 90 while FSM suggested <38 is normal idle. Ah ha. High pressure talks ecm to add more fuel.
- picked up o2, MAT sensor, MAP sensor and a FPR and figured I would try one at a time with likely to less likely
Installed new MAP sensor (cheap local brand).
- cold idle starts at 56, and then drops and increases per spec on cruise (lower), accelerating (56 ish), pegged at high end for deacceleration.
- o2 sensor, after warming up, now cycles voltage and I get cross overs from 0-16 depending on driving.
- lost another 5-10% of the rough idle, but a little still there, and still have the slight hesitation
But new problem, under open loop (car is cold), o2 voltage is .9 and no cross over - expected. Close Loop - I get proper voltages etc. BUT,
- the car might stay in Open loop for a long time
- it might go close loop, then switch back to open loop (poorer gas mileage)
Will run a coupe of tanks to see what mpg is with new MAP, additional actions to do:
- will check timing. I had been using a jumper at the ALDL to put the engine into timing mode. Find a switch setting in the diagnostics that allows for the setting. I'm thinking I may have screwed up the ALDL and this can't trust my timing, especially since I replaced the injectors
- will double check fpr to see if I need a new one
- might replace o2 sensor anyway as it might be polluted with all of the old richness.
- not sure of the MAT, figured out that it is located on the opposite side of the intake manifold and may not get proper air flow. Odd design, and would explain the hot air that accumulates above the engine. Probably has minimal effect on ecm calculation on injector pulse width anyway.
Any ideas on why I would drop out of close loop?