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92 Fleetwood mpg search begun
92 with 110k on a 4.9. I've been taking care of it while the boys drive it at various universities and first jobs.
Had the chance/need to drive it a bit, a couple of tankfuls, and realize that it's getting 16/17 mpg when it had been over 20 in the past. So, figured I would post on my diagnostics and search.
Note, car has been maintained, but coming up in some regular maintenance.
Symptoms noticed:
- mpg down, filled with premium (not sure what the boys were using) and turned off climate control. No change.
- I'd swear, I'd park the car at night with at 8 gallons, and find 6 gallons the next day. No gas smell, no ground leak, nothing around the tank.
Went through maintenance records:
- fuel tank, pump replaced 15 k ago
- plugs replaced 20k
- oil at 7k, need a change, but dip stick shows clean
- timing and other tuneup done 20k
- 92 sensor never replaced - hhmm
Ran diagnostics (p codes), most are as expected, barometric, mass air, temp sensors etc. Yet:
- throttle angle less than expected
- no o2 cross overs
- short term fuel trim at 128
- LTFT at 95.
So, running rich due to bad o2
Replaced o2 fit proper voltages, cross overs. Ran another tank. Just as bad mpg
- Checked for vacuum leaks, first pulling each to verify rpm change and then sprayed all around with cleaner - nothing.
- Ran diagnostics will driving. Noticed o2 voltage running at .97 (rich) with 0 cross overs. Hymn - leaking fuel injector?
- Ran power test - turning off injectors one at a time and verify rpm drop. All injectors ran fine (ie, they shutoff correctly)
- when I first ran the power test, at idle if 650 rpm, the o2 voltage was cycling from .25-.8. Ran the power test successfully. I then ran the engine speed up to 2-3k and found the o2 voltage climbed to a steady .97. When I left it idle down, it would hold the.97 for a couple of minutes. I ran the power test during these .97 periods and found all injectors operating correctly.
Will start with plug replacement over the weekend. Keep ya posted - and let me know if anyone has similar problem/solution.
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Had the chance/need to drive it a bit, a couple of tankfuls, and realize that it's getting 16/17 mpg when it had been over 20 in the past. So, figured I would post on my diagnostics and search.
Note, car has been maintained, but coming up in some regular maintenance.
Symptoms noticed:
- mpg down, filled with premium (not sure what the boys were using) and turned off climate control. No change.
- I'd swear, I'd park the car at night with at 8 gallons, and find 6 gallons the next day. No gas smell, no ground leak, nothing around the tank.
Went through maintenance records:
- fuel tank, pump replaced 15 k ago
- plugs replaced 20k
- oil at 7k, need a change, but dip stick shows clean
- timing and other tuneup done 20k
- 92 sensor never replaced - hhmm
Ran diagnostics (p codes), most are as expected, barometric, mass air, temp sensors etc. Yet:
- throttle angle less than expected
- no o2 cross overs
- short term fuel trim at 128
- LTFT at 95.
So, running rich due to bad o2
Replaced o2 fit proper voltages, cross overs. Ran another tank. Just as bad mpg
- Checked for vacuum leaks, first pulling each to verify rpm change and then sprayed all around with cleaner - nothing.
- Ran diagnostics will driving. Noticed o2 voltage running at .97 (rich) with 0 cross overs. Hymn - leaking fuel injector?
- Ran power test - turning off injectors one at a time and verify rpm drop. All injectors ran fine (ie, they shutoff correctly)
- when I first ran the power test, at idle if 650 rpm, the o2 voltage was cycling from .25-.8. Ran the power test successfully. I then ran the engine speed up to 2-3k and found the o2 voltage climbed to a steady .97. When I left it idle down, it would hold the.97 for a couple of minutes. I ran the power test during these .97 periods and found all injectors operating correctly.
Will start with plug replacement over the weekend. Keep ya posted - and let me know if anyone has similar problem/solution.
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1 - 20 of 33 Posts
Hobby car, boys enjoy driving it around town when home as everyone recognizes them
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Sent from my XT1053 using Tapatalk
deleted and un subscribed to this thread.
you might have leaking fuel injectors -
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.
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.
I noticed you did not mention the FPR. Might want to check that as well.
Answers:
- power test turns off each injector and measures rpm change. All injectors passed with equal rpm drop
- texas car, we do have winter fuel mixes down here and are in the process of changing over , will watch for impact
- FPR was replace 18 months ago. Pulled vacuum hose to confirm no leak, and confirmed that pressure jumped from 38 to 44 at idle.
Did some more research
- pulled a random set of plugs, all clean (at 20k) with no sign of excessive fuel
- decided to check timing, tps and idle throttle control. Tps and idle were at spec (I had checked/adjusted some 2 years ago). Found the timing at 14 which might explain the clean plugs - excess fuel being burned off? (Yes, I am running premium). Changed it back to 10 - but did find in the FSM that it could be set to 6 if running regular.
- the minimum idle test confirmed no vacuum leaks. It consists of getting the throttle to minimum and measuring against stock if 525. Anything higher would indicate a vacuum leak - no leak confirming my original test.
While doing the above, I had noticed an odd, very faint, not quite gasoline smell but closer to gasoline than any other fluid (clean or burned). This smell had been noticed once in a while when driving. I found the source to be the charcoal canister area. Pulled and tested the purge valve and found it to be leaking. I also suspect the vapor lines are dry and likely porous. Ordered new valve and will replace hoses then. Could this also be the source of my other symptoms namely running rich (per o2 voltage reading) and the perception that I'm losing gas when parked long term (could it be venting through possible porous vent hoses)
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- power test turns off each injector and measures rpm change. All injectors passed with equal rpm drop
- texas car, we do have winter fuel mixes down here and are in the process of changing over , will watch for impact
- FPR was replace 18 months ago. Pulled vacuum hose to confirm no leak, and confirmed that pressure jumped from 38 to 44 at idle.
Did some more research
- pulled a random set of plugs, all clean (at 20k) with no sign of excessive fuel
- decided to check timing, tps and idle throttle control. Tps and idle were at spec (I had checked/adjusted some 2 years ago). Found the timing at 14 which might explain the clean plugs - excess fuel being burned off? (Yes, I am running premium). Changed it back to 10 - but did find in the FSM that it could be set to 6 if running regular.
- the minimum idle test confirmed no vacuum leaks. It consists of getting the throttle to minimum and measuring against stock if 525. Anything higher would indicate a vacuum leak - no leak confirming my original test.
While doing the above, I had noticed an odd, very faint, not quite gasoline smell but closer to gasoline than any other fluid (clean or burned). This smell had been noticed once in a while when driving. I found the source to be the charcoal canister area. Pulled and tested the purge valve and found it to be leaking. I also suspect the vapor lines are dry and likely porous. Ordered new valve and will replace hoses then. Could this also be the source of my other symptoms namely running rich (per o2 voltage reading) and the perception that I'm losing gas when parked long term (could it be venting through possible porous vent hoses)
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Hah.. mine's been getting slightly worse mileage than that even. Of course I tend to make use of the 4.9's excellent torque but this car should really be getting realistically about 19 or 20 miles to the gallon average.
Is the cat and muffler original? I'm probably going to be replacing mine soon.
Yep, original. Smog tests had been getting worse but with some finagling of early registration for a 2 year college car in Denver, I was able to get to 25 year mark - which in texas means only safety tests are done.
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Sent from my XT1053 using Tapatalk
Maybe there's broken material inside the cat and muffler that isn't allowing the engine to run at maximum efficiency. I've been surprised with all the crap I've seen fall out of old cats and mufflers. Might be a good excuse to look into a new exhaust; I'll go for dual stock looking pipes if I have to replace mine.
Replaced the tank and pump some 2 years ago. Had it up on a friend's lift then and had pulled the whole exhaust from cat back - little to nothing in it then. Might have changed since then - but I'm not noticing any drop off since then.
Buttoning it and taking it on a couple of 4hr rt's to ref some HS soccer playoff games. Will see what my fiddling has accomplished.
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Buttoning it and taking it on a couple of 4hr rt's to ref some HS soccer playoff games. Will see what my fiddling has accomplished.
Sent from my XT1053 using Tapatalk
Took a short trip before the long trip. Good news, fuel trim/o2 readings are back at spec. Guess I'll have to look into old school tuneup info as to why running advanced timing would cause a rich condition in a fuel injected system.
On another note, the distributor hold down bolt is a royal PITA. Had to set it to 9 to end up with 10 when tightening up.
Now, the interesting question is why did it end up at 14? owner manual says 91 octane, FSM says regular can be run (87?). Could it be that since we can't get 91 around here (only 89 or 93), that I had advanced it to adapt to 93? I remember the tests we ran with the boys, noting that 87 $/g savings did not make up for the mpg loss. But I wonder now, if I had set the timing to 6 and ran regular, would I get close to oem mpg, or at least a mpg that would make up the cost savings. Experiences?
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On another note, the distributor hold down bolt is a royal PITA. Had to set it to 9 to end up with 10 when tightening up.
Now, the interesting question is why did it end up at 14? owner manual says 91 octane, FSM says regular can be run (87?). Could it be that since we can't get 91 around here (only 89 or 93), that I had advanced it to adapt to 93? I remember the tests we ran with the boys, noting that 87 $/g savings did not make up for the mpg loss. But I wonder now, if I had set the timing to 6 and ran regular, would I get close to oem mpg, or at least a mpg that would make up the cost savings. Experiences?
Sent from my XT1053 using Tapatalk
Not sure but if it works I'd do it myself.
I backed my 4.5 off to 6 degrees to try to run regular. Ran like shit. Total dog off idle. Well worth the few extra bucks for the driveability with stock timing and premium.
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?
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?
==========================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?
check reported temp with actual temp -
are the EGR tubes in the TP clean and open?
Tubes are cleaned 18 months ago
Water temp 175, air temp 170 (cruising at 55)
Temps climb to 200 at idle
Goes open loop typically on Hwy. On city driving, it goes closed loop
FSM says
- closed loop should occur when o2 and coolant reach operating temp.
- MAT and MAP used to calculate injector pulse width
Sure coolant temp appears correct, that leaves the o2 sensor. However, it's a question of cause vs symptom. My understanding of a 2-wire o2 sensor is that the sensor needs to warm up before it would generate voltages. So, does the PCM, by sensing voltage then decide that the O2 sensor is at temp and if coolant is hot then close loop. That gets back to what is causing the PCM drop out of close loop. Monitoring o2 voltages, the following is observed:
- when open loop, it's pegged at .9v
- when closed loop, it's bunching around .18-.8 except
- that slight hesitancy shows.02v indicating real lean , a lack of fuel
. . . . Hunt continues
Water temp 175, air temp 170 (cruising at 55)
Temps climb to 200 at idle
Goes open loop typically on Hwy. On city driving, it goes closed loop
FSM says
- closed loop should occur when o2 and coolant reach operating temp.
- MAT and MAP used to calculate injector pulse width
Sure coolant temp appears correct, that leaves the o2 sensor. However, it's a question of cause vs symptom. My understanding of a 2-wire o2 sensor is that the sensor needs to warm up before it would generate voltages. So, does the PCM, by sensing voltage then decide that the O2 sensor is at temp and if coolant is hot then close loop. That gets back to what is causing the PCM drop out of close loop. Monitoring o2 voltages, the following is observed:
- when open loop, it's pegged at .9v
- when closed loop, it's bunching around .18-.8 except
- that slight hesitancy shows.02v indicating real lean , a lack of fuel
. . . . Hunt continues
1 - 20 of 33 Posts
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