Will HG leak affect AFR???

[rob21a48422]

I'm pretty new to the site and had a few Q's. I just bought a '87 Turbo 5-Speed with 60tCT26, LIPP Elbow, RC DP, 3" custom no cats from there, K&N FIPK, stock i.c., i.c. hardpipes, Lexus AFM, 550 injectors (They're Venoms but prev. owner said they were flowcharted), AFPR, walbro, Greddy Profec A BC, SAFC, TechTom Board w/ 550 chip, TechEdge 2A0 Wideband unit w/ LDo2 display, and the sensor is about 1' in front of where the cat used to be. I drove the car home from GA to MI and it ran fine the whole time but the AFR was all over the place. It would stay steady @ 14.8-14.9 (which I thought was a little high) but would periodically run to LEAN (30+) and stay there for hours at a time. When it did so the car acted normal and just motored on unchanged. I already have a new AEM setup on the way (30-4100). I do think I have the beginning of a BHG. The temp gauge stayed right at about 1/3 the whole way home but I can hear an occasional gurgling sound from the engine bay and the exhaust smells like AF. I don't really want to do a new HG and hoped to limp her by for a while. I have a complete engine gasket kit and Ross forged pistons for a complete rebuild next summer. I assume the wideband sensor is either bad or the unit but don't want to put the AEM in if the head leak will affect the sensor. I also don't want to play with the SAFC until I know the AFR#'s I'm working with are accurate. Will a leaking HG affect the AFR# on the wideband??? Thanks for any help and I apologize if this has been covered. I looked for about an hour and couldn't find anything.

 

[robbo185]

check to see if there is coolant in your oil thats a sure sign of a bhg. also do a compression check. I had the sound behind the dash but no bhg. I burped the system and it went away. Also get rid of your venoms. If they are faulty then you would get bad a/f ratios if they arent working right.

not sure about the hg throwing off the a/f ratio though. someone else can chime in on that

 

[rob21a48422]

I did a compression check and had between 147-152psi across the board. The previous owner said he had the Venoms flowcharted and considering how much he put into the engine, I believe him. Even if they are flowcharted are they known to become faulty later down the road?? I changed the oil yesterday and it was thin and smelled a little like gas but wasn't milky at all.

 

[spoolint78]

check those injectors.
i wouldn;'t trust them at all.

they probably are flooding out the engine, and washing down the cylinder walls if they are stuck open.

 

[rob21a48422]

I know I must get different injectors soon but can't afford them right now. The car isn't running bad at all, it's running smoothly around town and the few times I've gotten into the boost it's been strong as hell. I just want to know if a HG leak will alter my AFR readings before I put the new AEM UEGO in and start fine tuning. I'm not trying to make big numbers or anything and I've got the Profec set at a modest 10psi. I just want to be able to monitor what's going on with the wideband until I get the time and money to completely rebuild her from the oil pan to the valve covers. Also, if anyone lives in MI and is very knowledgable with Supra's I'd love to bring the car to them and let them drive her just to make sure everything's ok. I'm new to Supra's and don't know what to expect from everything. The engine makes the "turkey" noises I've read about and I want to make sure it's the BOV and not compressor surge. Little things like that worry me sometimes as I'm not as familiar with the car as I'd like to be yet. I live in the Thumb of MI but I'm going to be in Troy on Saturday night and all day Sunday. Thanks for everything guys. Without Supramania I'd be lost.

 

[hellraiser456]

i would check the injectors....venoms are not very good. you could probably find a set of rc's on the forums for a decent price...

a leaking head gasket wouldn't effect the afr readings. a failing injector can... when the afr goes wacky...does the car still drive fine...how does the engine sound. i think if your afr was actually at 30...you would be putting pistons through your hood. keep in mind when diagnosing...the o2 only sees o2...not fuel. so when it says 30.0 afr...that means it sees a whole load of oxygen.

does the car backfire at anytime..especially when the afrs go all over the place...it could be a problem with ignition

do you have any codes

for the record venom injectors are crap. people are going to tell you it could be a problem with the injectors because they have been proven to be bad numerous times by people on these forums...i think there is a sticky about them somewhere as well.

 

[rob21a48422]

When the AFR goes wacky the car runs fine. If I weren't looking at the display and looking at the road I'd never know anything different. There's no change in RPM's, sound, or anything else. The car hasn't backfired once. I know the injectors have to go but can't afford the RC's right now. With all the mods the car has if I put some stock injectors back in, raise the fuel pressure, and tune with the SAFC, would I be able to run it reliably or would there not be enough fuel to keep it from being lean. I'm not looking for big #'s right now, just to be able to get through the winter. What kind of prices would I be looking at for good used RC's or any other reputable 550?? I've got a little money to work with but not much until I sell my SHO.

 

[Poodles]

find someone with a stock AFM housing and stock injectors and slap em in until you can afford decent injectors...

it's far better to be down on power than to blow the engine from those injectors!!

 

[rob21a48422]

I've heard that stock MKIV injectors are 550s. Is this true? Are they direct fit for our MKIII's? The reason I'm asking is because I work at a NAPA branch part-time but get the employee discount (10% over cost). I was just wondering if I ordered replacement injectors for a MKIV whether or not they'd work. I have a feeling they are pretty cheap for me, maybe even in the $60 range. I'll have to check tomorrow at work.

 

[hellraiser456]

if you know what you are doing..yes...you can downsize the injectors. however..you will probably need to turn down the boost as well. you don't want to push the stockers too much...or any injector for that matter.

you may be able to find a set of rc's for a good price in the classifieds here and on sf

 

[robbo185]

miv injectors will not work in our cars