Damn thing is running rich now...

derangedsheep · Post by **derangedsheep** » Sat Dec 03, 2005 11:48 am

It's always something. My gas mileage absolutly fucking sucks. My last tank I got like, 17ish and the tank before that I got 18.25. Now Its a V6 Auto, so its not like im expecting 30 out of it, but I really dont think I should be getting 18. I've been driving it rather nicely, I was expecting around 20-23.

Then, the other day I got out of the car and I went around to get something out of the trunk. The exhaust smelled like gas. Not really heavily, but heavy enough.

The O2 sensor was replaced with a Bosch OE type around 2 years ago. It only has maybe 3000 miles on it. The following has been replaced, TPS, NGK plugs, Bosch premium wires, cap, rotor, ign module, pickup coil, distributor, and coil.

I was thinking maybe the ECM coolant sensor? I had read that they can read wrong but still be within spec so the SES light won't go off but the ECM isn't recieving the correct signal. I have also heard of people having problems with the Bosch O2 sensors being faulty or something and that the Delco sensors are much better.

Any help would be great.

Thanks,
Steve

allWorkNoPlay · Post by **allWorkNoPlay** » Sat Dec 03, 2005 2:06 pm

Unless those are highway miles, that's really not that bad.

crzyone · Post by **crzyone** » Sat Dec 03, 2005 3:00 pm

Yeah, its not bad. A fiero 5 speed was only rated at 27mpg on the highway. So an auto with mixed driving would probibly be low 20s at best.

There could be a few things to check though. You could have a leaky cold start injector. This would cause you to run pretty rich.

derangedsheep · Post by **derangedsheep** » Sat Dec 03, 2005 3:58 pm

The cold start injector has been replaced with a known good one. So I'm pretty sure that's not it. Any other ideas?

Like I said, I know the V6 auto isn't known for gas mileage, but I'm not even breaking into the 20s.

TurboGT · Post by **TurboGT** » Sat Dec 03, 2005 4:10 pm

My v6 only gets 23 or so mpg, and I have a 5 speed. I know that the o2 sensor can cause bad gas mileage and being only like 30 bucks or so it would be a cheep guess. Mabe you got a difective one????

crzyone · Post by **crzyone** » Sat Dec 03, 2005 4:12 pm

How many miles on the engine?

You could have leaky injectors or they could have a bad spray pattern. Could get them rebuilt.

The O2 sensor could be the culprit.

Is this 17mpg city miles?

Shaun41178(2) · Post by **Shaun41178(2)** » Sat Dec 03, 2005 5:29 pm

I have an 88 formula with the v6 88k miles or so and around town it gets like 18 or so. on the highway it does around 27ish at 80 mph. I have a 5 spd getrag.

derangedsheep · Post by **derangedsheep** » Sat Dec 03, 2005 11:15 pm

I just rolled 131k. I would say the miles are mixed driving.

z.MacK · Post by **z.MacK** » Wed Dec 14, 2005 11:13 pm

My 2.8 with the slush-o-matic gets about the same mileage... Its the trannie. The 2.8 is a gas pig, add on a non overdrive trannie and 20mpg is about the tops

Funny thing, I watched robocop las nite.. They have the "6000sux commercial" in the movie, at the bottom it says, 8.6 mpg.
Guess what engine and trannie most of the 6000's came with ? lol

Weponhead · Post by **Weponhead** » Thu Dec 15, 2005 12:13 am

I get on average 24 mpg out of my slushy boat anchor combo meal .. and have gotten 29 on the highway at 70mph meh.. its getting tired tho lol starting to lose its superior gas mileage.. soon it'll jump to about 30mpg, that is if i ever get the 3800 in there with the 5 spd "and keep my foot out of it"

derangedsheep · Post by **derangedsheep** » Thu Dec 15, 2005 1:08 pm

Well, I guess its mostly the engine/tranny combo then. Who puts a tranny with three gears in a commuter car? Wasnt the 4 speed auto out by 87 or 88? Anyway, if this tranny dies (which I have a sneaking suspicion that it is on its way out) I'll put a 4t40 in. Power is nice, but I just dont feel like doing an engine swap.

Weponhead wrote:... "and keep my foot out of it"

Like that will ever happen. Haha.

Kohburn · Post by **Kohburn** » Thu Dec 15, 2005 1:10 pm

the coolant temp sensor can also slowly go bad making the engine run rich - eventually to the point that it will run for 20 seconds after pulling the pump fuse from all the fuel puddled in the intake

Series8217 · Post by **Series8217** » Thu Dec 15, 2005 1:32 pm

Isn't that only going to happen if BLM hits the minimum? While cruising the computer operates in closed loop. Or does it go to open loop because it thinks its too cold?

Kohburn · Post by **Kohburn** » Thu Dec 15, 2005 2:29 pm

Series8217 wrote:Isn't that only going to happen if BLM hits the minimum? While cruising the computer operates in closed loop. Or does it go to open loop because it thinks its too cold?

nah it will adjust the fuel to match what it thinks the tempurature is as long as the temp is within its regular operating range it won't realize anything is wrong except from the O2 - running rich will slowly kill the O2 and then its all down hill very rapidly

had it happen on the blue 2.8 turbo i fixed up and sold to my dad

whipped · Post by **whipped** » Thu Dec 15, 2005 4:20 pm

Series8217 wrote:Or does it go to open loop because it thinks its too cold?

Yes, there is a minimum coolant temperature to be in closed loop. Normally this is around 110 degrees F. An open temp sensor, or a bad connector can make it read -32F or so. It will not enter closed loop in that instance. Some corrosion can cause it to read about 0F, or 40 degrees F, or something like that, and it would never set a code.

Series8217 · Post by **Series8217** » Thu Dec 15, 2005 5:03 pm

Yeah.. not watching the O2 sensor since it thinks it should be in open loop.

derangedsheep · Post by **derangedsheep** » Fri Dec 16, 2005 9:45 pm

I picked up a new coolant temp sensor to put in. Just to verify, this is the correct one, right?

http://www.partsamerica.com/ProductDeta ... 90&ptset=A

Now, when I put it in, should I do anything special? Wire brush the sensing end, brush the threads, teflon tape? I was thinking that wire brushing it might be good to get any oxidation or anything off of it. And I had heard that teflon tape is bad from one source, and that its good from another.

Let me know.

crzyone · Post by **crzyone** » Fri Dec 16, 2005 10:16 pm

I use teflon tape on alot of glycol service pipes. Use a little bit to help seal the sensor.

BigRedDeckSpoiler · Post by **BigRedDeckSpoiler** » Sat Dec 17, 2005 4:24 am

If the sensor just has one wire, which means it gets its ground through the engine, DON'T use teflon tape. The threads might be sharp enough to cut through it, but I've heard many instances of it causing problems.
I use pipe joint compound on all my sensors that ground through the block.

crzyone · Post by **crzyone** » Sat Dec 17, 2005 7:27 am

I usually don't cover all the threads with teflon tape, only the top half to seal.