2000 Buick LeSabre - 3.8L K Fuel Mileage

[nickscarcare]

I have a new customer who just had a tune up about 2 months ago. The shop replaced plugs and wires, the plugs are Autolites, and don't know what brand the wires are. I only believe in putting in manufacturer parts for doing this. The problem is that she says it went from her normal 25mpg or so to 18 mpg overnight after the tune up. I only had about 20 minutes to look at it, but for what I can see is all is normal, fuel trim are fluctuate around 0 at an idle and about 2000 rpm. I did not get a chance to drive it as she just stopped in quick on her lunch. Firing order seems normal for what I found, all the numbers are wore of the coils and he has them written on them, and if I would go by that the firing order is off. Mitchell shows 6-3-2-5-4-1 starting at the top coil goin to the bottom with a firing order 1-6-5-4-3-2. Does anybody else think that just putting in these plugs and wires could have given her these results overnight??? The lower intake and upper plenum are leaking and she is thinking of having me do that and possibly replacing the plugs and wires with AC Delco.

[crmeyers]

Anythings possible. I too believe in sticking with the correct manufacturer of spark plugs, but did you check to see if the correct Autolite plug was even installed. I've seen shops put a totally wrong plug for the application in a vehicle and cause all kinds of problems. I think the route you're suggesting this customer to take is a good one. Start with the obvious and then reevaluate.

[brianp87]

I use autolites alot in fact the majority of the time with no issue

[liljoe]

I haven't really had any problems with autolite either, but I have seen the wrong plugs cause all kinds of problems from milage to misfires to hard starting problems....

[brianp87]

We did have a saturn yesterday that after we did a tune-up had a p1599 code. It had a slight hesitation and it ended up being the wrong firing order. No misfire codes? Wild so dont rule it out.

[crmeyers]

I'm not saying that using Autolite plugs is the issue. I'm saying he needs to make sure that the spark plug installed is actually the correct plug for that application. I had a Mitsubishi in last week that had a set of Autolite's installed. The plug was had the right thread pitch, so it screwed right in, but the reach was almost 1/2 shorter than it should have been, and it had a tapered fit rather than the double washer seat. You couldn't tell it was the wrong plug until you actually pulled it out and compared it to the correct part. Those plugs caused a check engine light, but no drivability problems.

[brianp87]

I was actually responding to the original post sorry. But yes you need to check everything dont assume someone else did it right

[fortknoxx]

check to see if all the plugs are new. is this one of them engines that have 2 plugs so hard to get at. maybe they replaced 4 plugs and 6 wires

[brianp87]

Thats neat I love to get those and point it out to the customer. well ya they did 6 of the 8 the others are original with 150k on them dang and it cost you an extra $ to fix something you already paid for.

[steven kiser]

sounds like a gap issue to me.

[fortknoxx]

sounds like a gap issue to me.

I like it when they are pre-gapped. Yeah, no need to check the gap. They came pre gapped at 30 from the factory. Yup thats right. That plug will fit 8 vehicles. Yup, and the plug gap is the same for all 8 vehicles. Yup, if not the plug wouldn'ta come pre-gapped.

[liljoe]

sounds like a gap issue to me.

I like it when they are pre-gapped. Yeah, no need to check the gap. They came pre gapped at 30 from the factory. Yup thats right. That plug will fit 8 vehicles. Yup, and the plug gap is the same for all 8 vehicles. Yup, if not the plug wouldn'ta come pre-gapped.

Tina, are you sure you are not most of my customers????

[nickscarcare]

Vehicle is coming in on 3-1-11, so I will see what happens. She is having me redo the tune up and the intake, so hopefully it fixes it. Its nice when we are the hero for a change.

[nickscarcare]

Well the intake and tune up is done. Gaskets were cracked all over, normal for this crappy design. Plugs were the correct application number according to my lookup, but the widest gap was .054. Changed them and the wires to delco, hopefully is fixes it. She watches the fuel mileage gauge like a hawk. The coolant was soo bad it ate away part of the lower intake. I think she just needs a better maintanance schedule.

[steven kiser]

good luck and i agree about you fixing the problem. just a tip here, with the gas prices sky rocketing remind her to base on miles per gallon not the cost to fill the tank.

[fortknoxx]

good luck and i agree about you fixing the problem. just a tip here, with the gas prices sky rocketing remind her to base on miles per gallon not the cost to fill the tank.

so sad, but so true. one of my female (college educated)friends bought a new car after katrina. she could not believe how much her car was using in gas. it went from 25 fill up to 55. good thing her new car had a mpg thing. I didn't have the heart to tell her.

[nickscarcare]

She watches the display on the dash which used to tell her about 24mpg with her in town and out of town driving, she lives about 4 miles out, and now it dropped to reading 18mpg. She says it happened overnight after the last shop did the tune-up. Well I just talked to her and it did not fix anything, she is still getting 18mpg. Not very surprised, when I didn't see anything real unusual with the last tun-up. I told her that I will need the car back so I can drive it longer, and watch numbers more, when I did drive it all the fuel trims, o2s all looked good. no check engine light. Just surprising that it could have happened overnight like that and not have anything showing?? Any ideas will be helpfull. I think I'm getting the car back 3-15-11.

[fortknoxx]

she might have hit the button to actual mpg and changed it from avg mpg. or she might have reset it.

[nickscarcare]

Ok anybody want a new customer, she is looking for a tech that can figure out why she is loosing fuel mileage! I had this thing down the road, fuel trims around 0, O2 S1B1 switching like crazy, S1B2 slower, looks normal to me, MAF reading looks good, cleaned anyways, swapped with different map, no change. I put it on instant fuel econ, and was getting 27-28mpg. She says her average used to be there. She did keep track of mileage and per fill and got 26mpg, with mostly highway and some in town. not bad if you ask me. Called her and told her I can find nothing, then she tells me that sometimes when going up a really big hill she looses power. Possible cat?? I have been driving it and no power loss. Remember she says this supposedly happened right after the last shop did a tune up. No brakes hanging up, torque conv. works properly.

[ricmorin]

Perhaps we're not equipped to fix what's really broken here.