poor fuel economy

[Fire7]

I bought a 96 buick regal, 3.8 3800 with 197k miles. i have had several problems with the car. mostely needing to get the crank sensor replaced. when the ses light is on i get maybe 150 miles to the tank. when it is not on. i get around 200 miles to the tank. the crank sensor only acts up when im on the hwy and hit 65 mph. after getting back to town and starting the car some 40 odd times the light goes off and the car runs fine. i just cant figure out why im getting such poor gas mileage. it also has poor exceloration on a regular bases. any idea's? anyone?

[Ruley73]

Originally Posted by Fire7

I bought a 96 buick regal, 3.8 3800 with 197k miles. i have had several problems with the car. mostely needing to get the crank sensor replaced. when the ses light is on i get maybe 150 miles to the tank. when it is not on. i get around 200 miles to the tank. the crank sensor only acts up when im on the hwy and hit 65 mph. after getting back to town and starting the car some 40 odd times the light goes off and the car runs fine. i just cant figure out why im getting such poor gas mileage. it also has poor exceloration on a regular bases. any idea's? anyone?

Get the car scanned to figure out why the SES light on and go from there. Many auto parts stores perform this service for free.

When's the last time you did a tune up?
Does the SES light ever blink?
Why do you think the Crank Position Sensor needs to be replaced?

[Fire7]

I replaced the crank sensor because every time i got on the highway with it, the ses light would come on, would not blink. it would stay on. and that was the code it was sending out. i replaced both the sensor, and the harmonic ballancer. i got on the highway. and it still did the same thing, it is due for a tune up, i dont know what to do about the sensor though.

[Ruley73]

Originally Posted by Fire7

I replaced the crank sensor because every time i got on the highway with it, the ses light would come on, would not blink. it would stay on. and that was the code it was sending out. i replaced both the sensor, and the harmonic ballancer. i got on the highway. and it still did the same thing, it is due for a tune up, i dont know what to do about the sensor though.

What was the code(s)?

Nobody on here is going to be very helpful without knowing what the troublecode(s) were/are. If a certain part is mentioned in a code definition it does not mean that part needs to be replaced. So now you've spent $150 in parts and the problem remains unresolved.

Without knowing anything else, I'd say a tune up is a good start. Only 150-200 miles to the tank is absolutely pitiful. Assuming you put in about 15 gallons of gas each time you fill up that is between 10 and 13 MPG.

[richtazz]

Can you post the actual code you got before and are you getting the same code after changing the CKPS? As mentioned before by Ruley73, it's hard to offer accurate help without all the available info. Also as stated, just because a code pops up for a certain component, it doesn't mean that it is bad. It could be another seemingly unrelated component used during the test of the one that threw the code.

[Fire7]

in the beginning, it was throwing out codes p1406 emission cntrol?? and code po336 ckps.
Now, Its giving codes
p0300 Random missfire, possibly sparkplugs and/or wires, im yet to replace these since i got the car, though theres no visable wear.
p1406 emission control??
p0336 crankshaft possition sensor A circuit- range or perfomance problem
p1870 manufacturer control transmission
Light only comes on while driving on the hwy, either after so many miles, or after hitting 65 mph,
I did find an external coolant leak, its not leaking alot, not really even enough to lower my coolant lvl, but it looks like its coming out of the upper exaust manifold gasket, though i have not taken anything apart to prove thats where the leak is, but thats where the coolant is visable.

[richtazz]

P0300- Random misfire.
Do the tune-up and clear the codes, let us know if it comes back.
P0336-CKPS circuit A range/performance error
Check the wiring from both of the CKPS's to the ignition module and PCM. These wires run close to rotating and hot components (harmnic balancer, pass side CV axle, exh manifolds, etc...) and commonly chaffe and or burn causing this code.
P1406- EGR valve pintle position error.
This code indicates the EGR was not in the correct position as per PCM command. It could indicate carbon build-up on the EGR pintle, a bad EGR valve, or a restriction in the EGR feed tube.
P1870- Transmission component slipping
Pretty much self explanitory. This code is set once the car reaches steady speed and the TCC is commanded to lock-up the converter. This indicates an internal trans issue, from a sticking valve, to dirty fluid, to bad clutches. If the random misfires are bad enough, it could "confuse" the PCM and cause it to lock/unlock the TCC tripping this code. Fix the random mis-fires first and watch for this code to return. If it doesn't, then the mis-fires tripped it and it's nothing to be concerned about.

[Fire7]

well, is there any certain way i can figure out where the misfire is, or do i just use elimination to isolate the misfire?

[Fire7]

well, I changed my plugs and p-wires, fuel filter, oil, o-filter and my car still runs like crap. on the bright side I think i gained about 20 miles to the tank. unsure becouse I added fuel injector cleaner to my last full tank of gas. and exceleration is a tad better. not much though. (almost unnoticeable)
I'm havent gotten back onto the highway yet. Or scanned it for codes. Im going to do a coolant flush next week. When I see how its running after that Im going to attempt a decent distant highway trip. Ill let yall know how that goes.
My tranny is still shifting roughly right at 40mph. and tends to run 25k rpm's between everyshift then drops back down to about 13kafter I let up on the gas. Idle rpm's are are about 9k. not sure if that is relevent, or normal. figured I would through it out there. there is also a wining noise coming from around the firewall on the passenger side. almost sounds like the altanator. unsure on that one though. I did put a new serpentine on. I may need to take it off and check out the tensenor. that could be my problem. Further note egr valve was extremely sticky, I did not use anything on it. just a cloth to clean it a bit. there was no gasket on it. Im going to pick one up next time I go to the auto parts store. I did get it clean enough so that it is not sticking anymore though. screwdriver to the ear says the pintle is moving fast and doesnt hesitate. Any suggestions on anything that could couse my problems would be wonderfull.

[Fire7]

well, further annalysis of the noise sounding like its coming from the firewall has turned out to be the compressor, boy i was way off. I did not do a coolant flush, I decided to take it to a tranny shop for diagnoses after I drove on the highway and the only code that came up was transmission code. I have a bad torque converter, they also through in that i have a motor mound thats turned to mush from what they can see caused by an oil leak. Its slipping in 4th gear. they say all they can recomend is a new tranny, they also recommended against doing a transmition oil change and coolant flush for fear it could break things lose and cause the tranny to go completely.
They priced a rebuilt tranny and labor at there shop at around $2100.00, For some reason all i could do was laugh at the guy. Im going to call around and get a tranny and im sure ill start a new thread on it when i change it.
I just wanted to say THANK YOU to everyone that posted in this thread and helped me get things figured out. I did manage to clear all the rest of the codes.