Poor fuel economy - hard start - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 11-14-2007, 03:16 PM   #1
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Default Poor fuel economy - hard start

Iím still trying to get my 93 SSEi running well. It has gone back to a bit of a hard start and gets 10mpg. It misses occasionally when idle or driving. No codes.

The following items have been changed
Plugs and wires changed
FPR had leaking diaphragm causing a previous hard start earlier.
New O2 sensor, Fuel filter
New coil packs and swapped ICM. (Iíve got 2 both bench test good)
Cleaned IAC, MAF, TPS
Had exhaust system check
Canít find any vacuum leaks, fuel pressure 43psi.
Scan tool shows vehicle goes to closed loop with good O2 cross counts.

Iím thinking from other posts that a flaky crank sensor could be issue. Any suggestions. Thanks
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Old 11-14-2007, 05:16 PM   #2
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Default mpg

10 mpg you have to be dumping fuel. Remove the 02 and look at the tip. Let us know what color it is, it could be defective.
Also have you run fuel injector cleaner lately? Set the voltage on the TPS?
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Old 11-14-2007, 05:19 PM   #3
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check for fuel leaks? sounds like alot of fuel is being lost somewhere
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Old 11-15-2007, 03:10 AM   #4
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Check for a fuel leak somewhere - I currently have a slight fuel leak (still getting ~22mpg though, so not that bad) and on occasion I get to my car and a small puddle of fuel is by the back right tire...

Every time I start it when the puddle is there, it takes a second to turn over. I'm assuming you have a similar issue - but much more severe.

Next time you let your car sit for a while, check under the car for a fuel spot...that'* probably the problem.
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Old 11-15-2007, 12:19 PM   #5
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Never drive a car with a fuel leak, its just too dangerous.
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Old 11-15-2007, 01:45 PM   #6
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I donít have a fuel leak but thanks for the concern. Iím still learning my new scan tool and I recorded the readings from the other day and with the typical scan values mentioned in FSM I saw my MAF reading is around 2200. So I missed that!
I remember ití* not dirty but Iím going to check the wiring and sensor tonight. Iíll keep yah posted.
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Old 11-25-2007, 11:36 AM   #7
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I replaced the MAF after both a voltage and Actron 9190 Scan Tool readout showing high numbers (1800-1900 gm/sec at idle). This was not the issue. I must assume that the Actron doesnít put the MAF numbers in the right range. I noticed another post where someone had similar MAF numbers http://www.bonnevilleclub.com/forum/...af+scan+actron

WOT is showing >15000 gm/sec. The FSM says 6 typ (0 -255.9). I had about 3.2 V instead of 2.5 V when measured with DVM but I donít know if thatí* what it should be http://www.wellsmfgcorp.com/pdf/Counterpoint3_2.pdf At least it is linear. I will get some accurate MPG numbers soon (see below).
By the way GM genuine only sells remanufactured MAFí* for this year (93) and the part I got had OEM # AFH50M-02C (the 92 units) so it appears they consider the two yrs the same part#88961002

I now have a working dash. United Radio is a doing a great job remanufacturing these early dashes. They got mine on Wed and it came back on Friday. They reprogram your mileage as well. I didnít ask but I think the reasonable price ($155 with shipping included) is a result of the high failure rate (I actually had a remanufactured unit in my car when NEW!) which I believe was caused by the 3 layer circuit board technology of the early 90í*. I believe a large percentage of intermittent problems that get posted about the cluster are traceable to this issue. So donít delay and get it done.
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Old 11-25-2007, 06:26 PM   #8
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Well the hard start was the Fuel Pressure Regulator again. Same thing as before Ė leaky diaphragm getting gas in vacuum line. I had 2 days left on 1 yr warranty (AutoZone GP Sorenson 800-272). I hate changing that thing. Also it seems to be running better since I gave the battery cables a good cleaning (especially between the + split section).
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