gen 1 running lean after mods UPDATE

[sharkey]

ive done a few things on my 86 cavalier 2.8 gen 1 motor. ive put on a complete msd ignition (coil, 6al, plug wires, ect), changed the horribly restrictive stock air intake pipe (it turns a complete 90 degrees before the throttle body) to alumuminum tubing mandrel bent with a k&n filter, and bukped the timing from 10-12 degrees (it realy like that). ever since ive done that (mainly the ignition stuff) it has started running lean. most of the time when im stomping it, my air fuel gauge shows it around the first bar of stoich and lean, and the spark plugs show lean as well. now this is concerning me a bit, so i decided to throw on an adjustable fpr to bump the fuel pressure up a bit. i threw 2lb more in and it seems to help a bit, but not as much as i want. i have also changed my fuel filter and been running injector cleaner through my car every 5 tanks for the past 8 months. i have tried what i can and it still runs lean. i find if i back the timing back down to 8 degrees, its not as lean (high side of stoich) but i do lose power.

im figuring my stock, old 16lb/h injectors just arent up to snuff of what im doing (and plan to do), so im looking for an upgrade. now i know there are a few choices (i know accel makes some) that fit our motors. ive also heard about 5.0l mustang injectors will work. now i know they are 19lb/h, so it would be about right. now are these a direct fit??? i know were i can get several sets for cheap (lots of boosted mustangs in my area), so if they are a direct fit, i may as well try.

any thoughts on this???

[sharkey]

another thought, what about dohc 3.4 injectors??? will the work ok and what is the rating on them.

i also know were a 3100 is from a 94 grand am, what are the specs on those injectors??? are they sfi injectors in that year???

[donk_316]

Seriously if all you have done is an ignition upgrade and a CAI then your stock injectors are fine. Grab a set of #17s if it will make you feel better. But i think a new fresh set of #15s will be just fine. Pay no attention to your AF meter. they are for show. I have one. It impresses the chicks to see flashing lights.

FYI #19's drowned my 3.4 with H272 cam, headers, full porting, MSD, 255 fuel pump and bumped compression. Im running factory 3.1 injectors and she is perfect.

[XLR8ING]

He's right. Stay away from the big injectors unless you do a reprogram. I did the same thing with 19# injectors to my 3.1.

[dbtk2]

19lb. injectors are definately too much. I only have 22lb. injectors and I'm making ~240hp. I think your 15lb. injectors should be fine for you...maybe it wouldn't hurt to replace them, but going much bigger than 15 is gonna give you problems.

Shawn

[sharkey]

ok iu guess ill just grab another set of injectors to throw at it for now. afteri do a bunch more mods, i know im gonna need bigger.

and im using my air/fuel gauge as a refferance, 99% of what im going by is the plugs, and they all show its running a bit lean.

[Guest]

I say hit a dyno with a wideband to get true readings of your ratio. I am running a modified 2.8 with stock injectors and I am stupid rich.

I have headers and a dual tb intake and I am still around 11:1 a/f at WOT. The stock programming on these cars makes them run rich from the factory. So unless your injectors arent' spraying well then you are probably fine.

What is your fuel pressure set to? it should be around 38 psi or so

Also are you running the correct plug heat range? A hotter plug will make it look like it is running leaner

[LA1 Z24]

I say hit a dyno with a wideband to get true readings of your ratio. I am running a modified 2.8 with stock injectors and I am stupid rich.

I have headers and a dual tb intake and I am still around 11:1 a/f at WOT. The stock programming on these cars makes them run rich from the factory. So unless your injectors arent' spraying well then you are probably fine.

What is your fuel pressure set to? it should be around 38 psi or so

Also are you running the correct plug heat range? A hotter plug will make it look like it is running leaner

I replaced the plugs in my LA1 Z24 with Denso plugs and now I throw lean exhaust codes...Could that be part of my problem? (sorry for the hijacking)

[sharkey]

im running the right plugs. my fuel pressure with the stock regulator was at 43psi with the vacume line unhooked. right now its at 46.

must just be dirty, 370,000km injectors. i can get another set of injectors from my buddies 90 3.1l.

[sharkey]

ok i thew the 3.1l injectors in. they had just been cleaned and flowed. it made no difference. the plugs are snow white (lean) and my air/fuel gauge reads in the middle of lean. i tried putting the timing back down, but it didnt make a difference. i played with the fuel pressure, had it as high as 49lbs, didnt help.

this is starting to drive me nuts. i replaced everything when i put the car on the road 9 months ago. fuel pump, o2 sensor, tps, maf, iat, temp sensors, ecm, prom, due to electrical issues frying everything, so i know its all good. i just replaced my fuel filter, there are also no restrictions in the fuel lines. i even put the car in limp mode (unplug the timing conector) to make it run rich (supposed to go full rich) and it did richen it up, but not a lot (read the first bar of rich, were when i first put the a/f gauge in it read at the top of the gauge).

any idea on what next???

[XLR8ING]

vacuum leak?

[ProjectMM]

could posibly be an intake leak? or a bypassing fuel prossure regulator

[sharkey]

there arent any vacume leaks to my knoledge (the pcv line has been fixed in so many places i cant could, and i cant find another one to replace it with).

the intake has new gaskets, i installed my other fuel rail with the new injectors, but no change.

i took my complete cai off and put it all back stock, put the stock coil on, and it did richen up a bit, it now sits about the middle of stoich. i havent driven it much yet, but im driving it to work tomorow so ill check the plugs to see what they are like.all i know is it is noticably slower with everything stock again.

[sharkey]

another thing to note, it doent idle high, stumble on pick up or do anything else related to a vacume leak

[Corpse]

For a vacuum leak in one of these engines it may not idle high if it is a small leak. the Idle Air Control valve and the throttle plate rest screw (adjustable on some TB's) could be correcting the problem. Ie: if the plate-stop screw was far down, the IAC would normally be very open at times to idle. If there was a small leak it would just be adjusted to be less open.

The only way to actually tell would be to probe the manifold vacuum with a vacuum guage and see. Although, realistically, I would not consider this to be a vac-leak situation as so much work was just done to the engine. If it was done correctly, it should not leak..

"running injector cleaner through my car " - If you have Multec Port Injection certain types of cleaners will destroy the metering function of the injector. It is due to a certain type of alcohol being incompatible with the injector, GM still states that Multec fuel injectors should not be cleaned (GM TSB).

Also, you may want to measure the resistance of the injector coils (make sure to do it HOT). At least it is a quick way to tell if the coils are hurtin or not.

"ive also heard about 5.0l mustang injectors will work. now i know they are 19lb/h" - Any normal injector will work, the only difference will be that the electrical plug may be different. The only other thing than fitment is the type of injector. Peak and Hold vs. Saturation. Pintle vs Multec vs Disc, etc.. Low resistance vs high resistance...

"Pay no attention to your AF meter. they are for show." - That is somewhat of a correct answer to adhere to. If the engine and meter were setup correctly they would be useful. Unfortunately, on the 660 engines the O2 sensor isn't exactly placed in a good spot, nor are the manifolds designed with any kind of tune behind them. The Gen 1 and especially gen II motors were poorly designed as, the cylinders really aren't going to be putting out the same numbers. Look at the runners on a Gen II, they are sickly and, I don't know how then engines last so long with such a horrible setup. inconsitent.

Also, the stock injectors should be good for a bit below 200HP if they are working 100%. if you change the injectors and the computer is not set for what you are using, you are just trying to create yourself a good tuning headache.

"A hotter plug will make it look like it is running leaner" - A hotter plug will cause detonation also. It may function as a glow plug if it is too hot, no good. the only reason to go higher than stock plug temperature is if you are running more power as in, higher octane fuels, cylinder pressures or a richer mixture. Also, in a poorly running engine, it may be done to reduce fouling, although, that is the "band-aid" approach to a bigger problem.

If you get over 200HP, then you may have a reason to up the temp, otherwise, stock should be perfect.


"to make it run rich (supposed to go full rich) and it did richen it up" more than likely, you did not richen up the mixture whatsoever. Al you did was remove advaces so the fuel did not have the proper amount of time to ignite, causing more unburnt fuel to hit the sensor.

It sound though, like you may be having a air metering problem, unless there is an injection issue. but, what is your car MAF or IAT? I will assume MAF, you may want to test the MAF or remove the wire to the MAF and step on the pedal a few times, see if perhaps you can get it to go super-rich, which will tell you that the fuel system is capable of more than enough.

Just to let you know, I think I remember correclty but, the gen 1 Multiport fuel pressure regulator is the same as used on some 350's, I believe it would be the same as the L98 (I think) which was used in late 80's F-bodies and 80's Vettes... Just to let ya know..

I need more info..

-Dave