flaming-ford

iTrader: (7)

All right guys this has been a problem i've kinda lived with over the past few months i've had the car (1992 camaro rs tbi 305 lo3), i'm not getting that great of gas milage at all.... It's 15mpg and i don't go over 2,000 rpm in steady driving ever other than the ocassional wot tire spin for a sec or 2 going around a corner every day or 2 (dunno why i do this i just do...)

I do about 70% highway driving and about 50% of the time the rpms are 1,500 and lower.

Heres what i know, i'm getting no codes in the computer, and 02 sensor seems to be functioning properly (keeps changing from lean to rich with our snap on computer and shows itself in the correct voltage range.

As of today i used our snap on exhaust gas anylyzer tool to check and was getting about 800 hydro carbons at idle, but, when revved out to about 2500 rpms for about a minute straight it drops down to about 38 ..... I also have the other values it spit out which were way overly excessive while at idle also if they help. (i've removed the air pump which i would expect could be causing some of this).

I also know my injecters on my tbi unit are fairly dirty, being that it's not port injection i didn't figure this would make a huge difference (could be wrong here). Btw if theres some cheap injecter cleaner you guys have used thats worked well throw me the name and i'll go buy it (i've used stp's and it didn't seem to do jack), i'd like to get them clean without removing them.

I also noticed that i developed a miss at 2500rpms when held down after about a minute or 2 (engine have 140k on it but, seems to run well always this was sorta a mysterty i hope to figure out tomorow)..... Realy wierd because, it doesn't do it at first just after you've held it down for quite a while. Maybe this has something to do with the crappy splitfire plugs installed along with the possibly plugged cat????

I'll be using our snap on scope analyzer to hopefully figure this out tomorow.

Any info/ advice on the subject is appreciated i'm still going over it in my head trying to figure out what's most likely.....

ShiftyCapone

iTrader: (7)

There could be a lot of factors contributing to your mileage. What is the condition of the ignition components? I would ditch the splifires and put in a set of properly gapped AC delcos. That could be a problem right there. These cars don't like "fancy plugs". Check the resistance of your plugs wires and make sure that they are within spec. Is your airfilter clean and free of debris? Are your tires properly inflated? Do you let your car run awhile before you drive it? Are the injector screens clogged? Does the EGR work properly? What is your base timing set at?

I would look into a TBI rebuild kit and a little more diagnostic work.

Don't base too much on your exhaust gas analyzer. Those readings are post cat and won't give you a true reading of what the motor is doing.

flaming-ford

iTrader: (7)

yah i'm aware of that my instructor informed me that the afr readings would be off and all, i just figured with readings as bad as they were that it may be clogged.

Any more info. i'd appreciate it. Still kinda scratching my head on this 1. If i got 20+ i'd be happy but, i'm not unfortunately......

flaming-ford

iTrader: (7)

anymore advice would be greatly appreciated i'd like to get this taken care of soon (mostly figure out what's with my *miss*). Any comments on if your think the cat is plugged or why my exhaust gas values are so bad feel free to throw at me.

Need anymore information on it just ask.

I'll be replacing the plugs real soon then complete the rest of the tuneup hopefully within the next week or 2. When i do that i'd like to try my luck with some good injecter cleaner if any1 has been lucky with 1 of them. I'm going to put a little marvel mirace oil in the gas to see if it does anything (doubtful but, you never know).

zipfast

iTrader: (2)

I like SEA FOAM fuel injector cleaner (Put in the tank and or some in the TB).
There is also a BG two part kit that you put in the tank and in the TB. The stuff you put in the TB will clean the junk (carbon) off the back of the valves and piston tops.
If you have a valve starting to hang open because of carbon that could give you a miss.
Just my 3 cents worth. (inflation)

flaming-ford

iTrader: (7)

i appreciate it, i'll post up my findings about the scope readings later tonight and hopefully that can lead me/us in the right direction.

Alrighty well the mystery get's deeper. I did a cylinder power balance test and mechanically the engine seems fine, the rpm drop fluctuations are very close to one another (i did remember to unplug the iac). After this i tried some more things on the scope like revving it out and watching it hoping it would drop a cylinder or show an abnormal difference but, i wasn't able to get it to miss at all today...

The computer still hasn't stored any codes. I also squirted where the iac draws air in with some carb clewaner which brought my idle down a little (it does idle abnormally high according to our scanner about 1025 rpms. According to my tach more like 750. I'll stick to the scanner though.

Only thing i was able to find that was out of range is my map sensor! So i'll be checking for vaccum leaks and or checking wiring to and from it tonight.

If it not that it's gotta be plugs/wires/cap or rotor.

vorgath

Bosch O2 sensor ?

flaming-ford

iTrader: (7)

it just dawned on me why my map readings are off and a good reason why i'm not getting great gas milage.

I have a coolant leek on my intake manifold that's a pretty decent size, i've just learned to ignore it considering i have a new motor that will be in it before to long. With the coolant leak it probably won't be able to hold manifold pressure correctly therefore it's giving me a low voltage reading because, of the *high load factor* which for me means bad gas milage and overall performance. Am i correct in thinking this?

I know that the map reads the engines load pretty much and the higher the load the less the vaccum... So is the voltage higher when at high load or lower like i'm thinking? It showed up as .92 volts on my scan tool and it should have showed between 3-5volts i beleive.

Anyways i'll be investigating this a little more at school today and hopefully i can talk to my instructor on it for a bit in lab, he was pretty busy helping other people yesterday so i was limited to my own very limited knowledge unfortunately...

T/y for the 02 sensor idea but, i'm 99.9% sure that mine is functioning properly (we'll see after i cut the cat off and weld a test pipe in (i'll test it on the exhaust gas analyzer for afr readings. The computer shows it keeps switching from lean to rich constantly which i assume would be because, the 02 sensor is trying to compensate for the perfect afr reading. It also was reading in range for the voltage that the manafacturer specify's.

Anyways thanks for the ideas guys keep them coming plz, because, i'm getting in to unknown terriotory and would like to know if i'm chasing my tail or heading in the right direction.

RBob

iTrader: (1)

The .92 v MAP reading is 28 KPA, which at idle is correct. MAP reads absolute pressure, not vacuum. Your sig mentions 95% stock, does the engine still have the stock 195° thermostat, and stock air cleaner with pre-heat?

With the scan tool on a warmed up engine, make sure the scan tool is in 'open' mode. Check the engine temperature (CTS), idle speed and the IAC counts. If the engine temperature is over 190° F, and the idle is higher then 550 RPM, check the IAC counts. If the IAC counts are 0 then there is a vacuum leak (or someone messed with the TB air setting).

RBob.

SB406

If you have a known problem with the intake gasket, I'd be inclined to look for vacuum leaks. Shoot some ether around the manufold at idle and see if the engine changes RPM at all.

Have you put a timing light on it? 140K......original timing chain?....They stretch.......

Aside from that, sounds like it needs a tune up with some better plugs. Try running the engine at night with the hood open and NO lights on. Can you see any spark plug wires arking?

Also, doing a "Turn & Burn" every other day is definately not fuel efficient.

If it were a plugged cat, the car would probobly not go over 40 MPH when hot, but be ok cold.

flaming-ford

iTrader: (7)

I Didn't mean a completely plugged cat, was thinking along the lines of a plugging cat. I'll chop it off over the weekend that way i'll be sure it's that.

Yah i also found out that my m.a.p. was reading correctly according to what the scanner was telling me, our computer program (mitchell on demand shows me 3.5-5 volts or so at idle) slowly dropping off as vaccum drops. Maybe i looked under a different engine option or something while using it on accident....

I'll probably put some new plugs in it over the weekend most likely and have new wires in it real soon too.

Btw as for the turn and burn thing i was overexaggerating with the everyday thing, this is usually a once a week thing or less.... Just figured i'd be honest and not act like i always drive like an old grandma.

it mis fired on me while i revved it in the parking lot to see if it would do it again today too (hate these intermittent problems).

sb 406 i have put a timing light on it when i first got it and adjusted it back to factory 0* and found it to be undrivable so i set it back to how it was (10*) and it's seemed fine since. Monday i'll drop it down to 6* where i had it for a bit to see if it makes any + difference.

Anyways i'll let you know how ripping the cat off and adding new plugs turns out.

Any more suggestions feel free to post i appreciate it.

flaming-ford

iTrader: (7)

well unfortunately i've been lazy lately and haven't done anything to it, i've come to the conclusion that it has a slight misfire all the time and am planning on hooking it up to a scanner again tomorow to see which cylinder it is and maybe pulling the plug and wire off to see if they may be the problem... I should have the cat delete done soon along iwth a different set of plugs maybe wires/cap and rotor very soon, sooner the better.....

I need some brain power here men (or women) , any other ideas?

flaming-ford

iTrader: (7)

I must have missed reading your post somewhere along the line very informative i'll print it off and take it to school with me tomorow sorry i didn't catch this response sooner, not sure how i missed it.

The motor still has a stock 195 t-stat which is in good working order and newer (month old or so), the whole cooling system has been replaced not to long ago except possibly the heater core and coolant temp sensor/sending unit.

The engine doesn't have the stock aircleaner it has a cheapy mr gasket open element on it. Not sure what's meant by *the stock aircleaner with preheat*, i've got the stock aircleaner in my garage but, i don't see what you mean by preheat, are you thinking manifold preheater type thing, if so i have no idea but, i would expect it does if it did from factory.

Not sure what you mean by *open* mode either with the scan tool, i made sure it was in closed loop and checked codes before after and during and found none stored other then when doing my component tests.

I'll reset the timing to 8* tomorow , it's about about 10.5* now which is super high i suppose but, seems to run best around here, it barely even runs at factory 0*. I've ran it at 6* and it was fairly decent but, didn't have the snappiest throttle response.

Btw i've been warming up the car for 20 minutes in the morning before i drive it so i'm sure this isn't helping but, i still think i should be getting better milage imo.

flaming-ford

iTrader: (7)

slight update i've got the timing set at 6-8* and it seems to idle down a little better and sound *crisper* while revved but, is much more lacking in throttle response than it was. I can always live with that though.


I pulled out a pos splitfire plug and looked at it closer and they are junk! The points over top of the electrode are unevenly gapped and the plugs that were put in just about 2,000 miles ago almost look shot to me. I'll be replacing these over the weekend 1 way or another and hopefully getting a cap and rotor and peice of pipe to put in place of the cat.

flaming-ford

iTrader: (7)

alright guys heres the newest update:

I have the timing set at 8*advanced and it's pretty doggy compares to how it was and i'm sick of having to use my throttle so much (feel like i'm driving an escort with 50hp v8). I plan to change it back to 10-12* base tomorow and yes i do run premium so i should be alright (it's ran with this much timing since before i ever bought it so i'm sure it's ok).

Heres the deal i'm still not sure why my car likes so much timing, it idles like a stock cam and doesn't show any signs of being torn down at any time.... So i beleive it's not someone adding a cam as an issue.

What i've found leads me to another mystery so here it go's, i rotated my engine clocking wise to tdc after pulling the cap and indexed where my rotor was pointing on the dizzy (shows about 20* after where # 1 spark plug would be it seems). I then had someone slowly rotate my crank counterclockwise until i saw the rotor turn, what i found was the timing chain shows about 4* stretch give or take 2*. So in my opinion that isn't the reason why it likes all the timing it's showing.....

When i pulled the cap i did notice that the cap and rotor were pretty much shot, all terminals were nasty and corroded like crazy and the rotor was due for replacement, i scraped off all the corrosion andsprayed both with wd40 and dried them thoroughly, this was not my misfire issue though it seems, although it does seem to move slightly better, not necessarily faster or more efficiently but, it could be in my head. only real noticable difference i saw after doing this was it's off idle stumble that it has a lot of times has pretty much gone away (only stumbled on me sorta once at 1 light outa about 10).

So heres the deal, i should be able to have enough money to give this a complete tuneup, cap,rotor, plugs,wires, and possibly a msd coil just for ****t's and giggles along with the testpipe in place of my cat at the end of this week i hope so i'll let everyone know how that go's.

I plan to run it on the scope today and me to watch the readings instead of a friend to check and see which cylinder(s) it's dropping when it misfires, also plan to set my timing back, and possibly start to figure out what's up with that cylinder.

Realy could use some brain power guys/girls, any opinions throw them out, i'm starting to run out of my own thoughts and frankly my instructor is almost at his wits end lol.

Fast355

iTrader: (2)

Have you ever considered that maybe the balancer has slipped, and 0* is really -20*??? Check it REALLY close for signs of slippage, you can usually tell because the outer ring will move either forward or backwards in most cases.

flaming-ford

iTrader: (7)

yah that's about the only thing i can think of that would cause this sorta timing issue, I did check yesterday but, i didn't look super close i'll look real close today at it and tell you my findings.

Well i didn't get to do as much as i hoiped today but, i did get some stuff done. We've definetly determined that it does have a intermittent mis-fire for sure.

Cylinder power balance tests show 150-180 on all cylinders except #2 which was 80 (after rechecking these with my eyes) instead of a friends, not sure what he was looking at last time.

Looking at the wave pulses and comparing them to the proper hei ignition i came up with just what i should see. My secondary waveform was very close on all cylinders and my coil tested fine as i figured.

I did fix a blowby problem though, found the pcv line and tb where it plugged in was super super clogged. After about 1/2 hour of chiseling at the junk inside it and constant carb cleaner spraying it was good to go. Now i have a good sized vaccum leak lol (cheap pcv that doesn't seal for ****t).

I'll do a compression test before i recplace my spark plugs when i buy them, hopefully tonight and have all the stuff here for friday through summit (if not monday most likely).

Well i'm going to set my timing back to where my balancer says 10-12* are, and do a compression test wet and dry on #2 cylinder (the low one) to see where that gets me.

Any1 on here ever have valve seating problems due to a worn valve seal(s). I know mine just gives the slightest puff on startup after it's sat for a few days. Anyways i'll look in to it and see what i can diagnose with that cylinder today.

flaming-ford

iTrader: (7)

well i broke my wire off where my spark timing connecter thing is at (that's the technical term hehe). Didn't get to reset my timing and checked compression on my bad cylinder and found it to be just as good as my others....... So once again i'm stuck but, i'll see what i can do tomorow.

I plan to reset the timing tomorow and fix the connecter tonight (damn gm engineers smallest thinnest little wire that broke. Now i have to buy a special little set of wire strippers lol.

flaming-ford

iTrader: (7)

well the est wire is now fixed, i don't like how i fixed it but, it works and i'll be pulling the old harness and such competely to check it out and maybe modify some things before the new motor go's in.

It definetly liked the extra degree or 2 of timing i gave it for sure. So last thing i'll do to it unless i or you guys have any good ideas, is check my wires to see if they are bad. The compression test shows the cylinders all very close with none that are realy out of whack so i'm not realy sure why it's misfiring.

Btw the spark plug wires don't arc across anything at night.

BMmonteSS

You should really see if your balancer has slipped, I've found lots of stock balancers that have moved over the years. I finally got a TDC locater that just screws into your spark plug hole, this allows you to double check your balancer. Your timing chain can also stretch over time, which will cause all kinds of wierd timing problems.

flaming-ford

iTrader: (7)

yah i checked my timing chain stretch and ended up with 4* stretch, i'll be looking over the balancer again but, it doesn't look like it's slipped to my eyes. I think i'm just going to leave this engine alone the more i think about it..... Not realy worth putting money in to since i have another 1 that should be ready to drop in by mid summer most likely.

flaming-ford

iTrader: (7)

well i got rid of my misfire finally, replaced my ****tfire plugs with some ac delcos. I also bought the pipe to go in place of the cat finally

should have it on tomorow.

flaming-ford

iTrader: (7)

guess i lied, it's running like complete crap now......... Got me why. Misfiring and shaking like crazy.

I've got the converter out of the picture now which seemed to be in fine shape after i pulled it.

New ac delco plugs are in and correctly gapped to .035. I replaced the cap and rotor with a good brass terminal set (made a slight difference but, not a lot.

I Also hosed the throttle body down with some carb cleaner.

I'll pull the plugs again tomorow and double check my firing order and such. Hopefully i just didn't get a plug tightened down enough or something.

I realy should buy new wires for it too but, money went byby so they will have to wait unless it runs this bad even after i play with the timing and tweak some things tomorow....

flaming-ford

iTrader: (7)

well it was an unhooked plug wire, i fuess it popped off, i crimped the end down and the rest are good to go. it's running like a champ with no misfire or stutter anymore finally. Hopefully this should help the high fuel consumption issue again.

Moral of the story is don't buy fancy plugs they are a waste of money and ****y overall quality.