ok, I have a thread on the mpg issue, but this one has me baffled.
my tips and rear bumper are black. everyone who smells the exhaust agrees it is definately rich.
so I decided to change out the ngk platimun plugs for some std ngk plugs, just cause I've read some people have had issues.
I expected the plugs to be black/grey. nope. they are almost as white as the new plugs, after almost 2k miles.
Actually, almost too white.
there is the conundrum. exhaust tips say rich,mpg says rich, plugs say lean. must be magic.
butt-o-meter says it is running rich too, feels sluggish.
no vac leaks, o2 is new. no cat installed atm. idle is perfect, stable at about 950 - 1k on the tach (which may be off a tad).
timing is at 11 degrees. full rebuild motor. pistons, cam, valves etc...
any thoughts on why the plugs are lying?

Are you sure they're the right temperature plugs?
I know everyone likes to use different plugs, but I still say stay with the factory AC plugs.
I know you say it runs smooth, any chance you might have a cyl. misfiring?
Have you checked your fuel pressure at idle and higher rpm, maybe the pressure is jumping higher at idle but is better at higher rpm. (possible FP reg.)
Do you have Winaldl etc. and check your map sensor. Might be staying higher than it should and keeping it richer at idle.
Are you running a lower temp stat? Might cause it to go open loop if it stays to cool.

Just spit balling to give you ideas.

[This message has been edited by Dodgerunner (edited 04-06-2006).]

well, you;ve seen my aldl runs. fixed the tstat. running at 195.
fuel pressure: turn to start, hits 40#...start the car, at idle it is about 30#, racing it drops to around 20#.
that sounds a little low to me.
leak down: from 40 to 25# in about 10 minutes.
. thing is I pulled the plugs after local driving all day, they shoulda been their worst.
these are stock ngk equivs no change in heat range.. (acdelco absolutely suck, you couldn;t pay me to put them in any of my engines). I haven;t gotten it to the point I would be playing with spark plug heat ranges. even if they were too hot a plug, they should have still shown black. in one week, you need to use degreaser to get the black off the bumper reliefs around the tips.
o2 is new bosch. maybe time for a map sensor....
I know this is gonna be something stupid when I find it.

quote Originally posted by tjm4fun: well, you;ve seen my aldl runs. fixed the tstat. running at 195. fuel pressure: turn to start, hits 40#...start the car, at idle it is about 30#, racing it drops to around 20#. that sounds a little low to me. leak down: from 40 to 25# in about 10 minutes. . thing is I pulled the plugs after local driving all day, they shoulda been their worst. these are stock ngk equivs no change in heat range.. (acdelco absolutely suck, you couldn;t pay me to put them in any of my engines). I haven;t gotten it to the point I would be playing with spark plug heat ranges. even if they were too hot a plug, they should have still shown black. in one week, you need to use degreaser to get the black off the bumper reliefs around the tips. o2 is new bosch. maybe time for a map sensor.... I know this is gonna be something stupid when I find it.

Some things going on with your fuel pressure, it should be idling around 36-38lbs slightly lower when blipped. 20 --just doesn`t sound right ? Remember I said your iac looked funny --and wasn`t sure on the map----so I shipped it out to dodgerunner to get 2nd opinion. My other Gt does that --I need to replace 02 first , then what ever you find --will probally be what I need next ..LOL..

quote Originally posted by tjm4fun: ...no cat installed...

When I removed my cat, the exhaust was so rich that it would make your eyes burn just by backing it into the garage. You could almost smell raw gas.
I didn't pay a great deal of attention to whether I sooted up my bumper, though.
3.4, BTW.

Does the 2.8/V6 have a problem with Bosch O2 sensors? I recall a thread concerning this with a 4.9 build? Basically someone replaced an old sensor on a 4.9 and was having a lot of issues with the new Bosch O2. They replaced the new Bosch with a new Delco O2 and all problems were solved. My 88 GT runs rich and I get thick black tips also. I replaced the old and cracked oem O2 with a new Bosch O2 and I cant tell any difference. Just wondering if anyone else had experience with the Bosch O2's on the 2.8/V6

quote Originally posted by CCB33: Does the 2.8/V6 have a problem with Bosch O2 sensors? I recall a thread concerning this with a 4.9 build? Basically someone replaced an old sensor on a 4.9 and was having a lot of issues with the new Bosch O2. They replaced the new Bosch with a new Delco O2 and all problems were solved. My 88 GT runs rich and I get thick black tips also. I replaced the old and cracked oem O2 with a new Bosch O2 and I cant tell any difference. Just wondering if anyone else had experience with the Bosch O2's on the 2.8/V6

Hi, I saw that thread also---I`m guessing its a 4.9 problem, most have had good luck with the bosch & the 2.8`s....

I have a stock 2.8l 4spd.

Mine was running rich like that. changed out the ECM temp sensor and put a Bosch O2 sensor in, cleared it up.

Man I'm sorry didn't pay any attention to who the post was from. Bad habit!

That fuel pressure is really low for running speed. Can't recall, have you changed the fuel filter?

Do you have any logs of the engine at idle. The logs 3800SF passed onto me where all mostly running at 45-55 mph. Went back and looked at them and like was said, we never understood why your IAC was flate lined.
Another reason would like to see a idle log again. Do the idle rpm's change during warmup? IE is your IAC moving. Sorry if these where answered before, guess I should dig back in the post and look again...

DR

quote Originally posted by Dodgerunner: Man I'm sorry didn't pay any attention to who the post was from. Bad habit! That fuel pressure is really low for running speed. Can't recall, have you changed the fuel filter? Do you have any logs of the engine at idle. The logs 3800SF passed onto me where all mostly running at 45-55 mph. Went back and looked at them and like was said, we never understood why your IAC was flate lined. Another reason would like to see a idle log again. Do the idle rpm's change during warmup? IE is your IAC moving. Sorry if these where answered before, guess I should dig back in the post and look again... DR

I think I still have it--but he has changed a few thing since then, as I remember the iac just stayed at a low value through the run--until the cars operating temp came up to some what normal, wasn`t alot if any flucuation in it, started very low then slowly rose to acceptable value. This is one of the reasons I needed you to double check what I was seeing, I`ll try to dig it back up & email..

quote Originally posted by tjm4fun: (acdelco absolutely suck, you couldn;t pay me to put them in any of my engines). I know this is gonna be something stupid when I find it.

I feel the same way about NGK plugs. They rate the same as Autolite, abloulte TRASH! (just my opinion, no offense meant)

If your fuel pressure is that low I suspect the plugs are telling the story true. The engine is running lean. Your soot may be the result of the EGR and PCV system working as they should which allows more hydrocarbons into the engine. These are not being burned properly due to the lean condition (not enought heat from combustion) creating soot out of the exhaust. It has been asked about the fuel filter change, if it hasn't been changed then change it and recheck the fuel pressure. If there is no change you may wish to change the pump to get the pressure range into the acceptable operating pressures.
Also if you have a cat convertor still attached to the system it will only be a matter of time before it gets clogged up from the soot.

Fuel filter is new. o2 is new bosch unit.
As far as the winaldl runs, the last ones with the finally working thermostat is adecent one. an resend it, but there is not alot of idle time. the runs is mostly the 60-70 mph run to work on the hiway. trying to hold 55 mph going to work at 2300 is really risky, since most traffic is running 75+mph.
idle is perfect. cold start sits at 1500 and drops to 1000 in about 1-2 minutes depending on how cold it is, we had some unusually cool days here.
Vacuum at the manifold is solid at idle, forget the exact number, I think 28 hg.
Interesting thought about the egr system leaning out the mix. easy test, I'll plug the egr.(I usually block them off, didn't this time.)
Cat was not installed for 2 reasons: (I have my exhaust flanged, it is a bolt in, as is the straight pipe).1. didn't install it as I expected a new motor to run rich til break in finished. 2. I drive it daily, and past experience with both this car and my previous showed the cat only lasted 18 months before it broke apart and clogged. so I only install it for the inspection, then drive home and drop it out.
Strange thing is I tracked the mpg form initial firing, and the best gas mileage I got was around 500 mile point, with the 180 thermostat and hypertech chip hitting 19 mpg. then it dropped to 13, and has been slowly coming back up as I throw more money at it.

AFA the fuel pressure, I am going to drop the tank to fix 2 problems: sending unit is way off. and the evap system is unable to pull a vacumm on the tank, a requirement for the inspection emmisions test. as a side ? can you pull the filler neck without removing the rear clip? after seeing that pic on the archie thread with the rusted thru filler neck pipe, I am suspicious. also since I think this is still original tank with 150k mile, the sock on the FP is likely fairly mucked up. I will be ordering a new fp to put in there while it;s down, as I;ve dropped the tank before and really don;t cherish getting my big hands in there to reconnect the hoses again. any suggestions on the pump?
after I launch the boat next week, I'll have time to really tear this apart. it is really starting to irk me.

well, this might be too early to tell, but I plugged the egr vac line to basically disable it without the codes. since doing that, the usually visably moving gas gauge has stopped dropping like a rock, and my butt-o-meter is feeling a noticabley better kick in the rear.will need a few days to verify mpg is better.

the filter is new as I said, but if I'm gonna drop the tank anyway for other issues, what is the recommended fuel pump? recommendations should be based on reliability over all else, this is my daily driver!!!
I'll likely replace the filter anyway as the car did sit for almost 3 years, and it may be loaded up with crap from the tank.

if new motor, old ext pipe maybe the old soot is getting blowout
by the new hot/lean ext flow

btw I agree lean is hot
and plug reading is good indication of current state

------------------
Question wonder and be wierd
are you kind?

actually, the exhaust was clean for the first 3 weeks or so. this started after about 700miles. I mean the mpg nose dived from 18 local to 13 with hiway miles. every thing I change since then yields only minor improvement.

Bump....

what;s the fuel pump of choice for a 2.8 motor? reliability is the most important factor, this is my daily driver...

AFAIk, after going thru the receipts for everything the formor owner had done, this is the stock original 1988 pump...

Hi, I sent a pm to you--but mise well post it--get a Delphi --made by GM ---same as ac/delco products, that way you won`t have to fool with dropping the tank again & again..

okey dokey time.
Couldn;t locate a delphi pump, so got an ac delco. what';s another $100??? (tho my wife didn;t htink it was the best birthday present she's gotten from me, it was her bday, so I celebrated taking a gas bath under the car)
Dropped the tank, looked clean inside, cause all the crap was sucked up in the sock, which you could not see thru . yuk.
So, I put in the new pump, the old pulsator looked fine, and will continue to look fine in my junk bin, hooked up with clamps and fuel line.
Installed with new sock.
Fixed the fuel sender unit (I hope). What a stupid way to connect things. shoulda fixed that, but next time....
Verified that the tank holds pressure, the expansion tank holds pressure, the filler asm holds pressure. (so I still have to figure out what's whacked with the evap system, which is now all happily plugged off.
Put it all back. Felt good. hooked up pressure guage. key on, 40 psi.
start car, 35 -38 psi. race motor, drops to 32 then climbes up to 40, when back off throttle, back to 35-38. maybe regulator is funky. or the vac to it cracked after re-assembly on the build, all tubes where vacumm checked before they went back in.
when I have time will clamp off return line and retest, also will check the calibtation on the guage first.
Fuel filter is/was new, less than 2500 miles on it.

Only positive thing is my butt-o-meter seems to feel it pulls a bit harder, but maybe it's just sensitized from layin on the ground.

[This message has been edited by tjm4fun (edited 04-22-2006).]

quote Originally posted by tjm4fun: Dropped the tank, looked clean inside, cause all the crap was sucked up in the sock, which you could not see thru . yuk. Fuel filter is/was new, less than 2500 miles on it.