Im running an essentially stock 5.7 TPI motor, ported heads and ZZ4 cam. Not wild by any stretch. But for some reason after the install the tune was vastly off. I have taken gobs and gobs out of fuel out of the car just to make it drive. With the stock tune it would just totally bog out with any throttle and leave a huge black cloud. Why should I have to cut fuel when adding a cam?

Also I cant seem to get the car to have an idle BLM of anything but 108-110. If I lean it out more it will either stop running or hit what appears to be a min MAF reading of 5 gms/sec. If I set any voltage to lower then 5gms/sec it will automatically bump it up to this, but yet even at 5gms/sec idle it reads 108 BLM and gets terrible mileage. I am using the stock spark table as well, for now.

Ill throw in a pic of my lower MAF tables for you all. These tables are "drivable" but still going through gas left and right.

Anyone know why my BLMs seem to run unchangable rich at idle?
Anyone with a similar setup have a pic of their lower MAF tables?

Injectors are stock 22lb/hr as is Inj size variable.

 

I did some more expirementing today and i found a good idle to be about 5.36gms/sec. But again my BLMs still bottom out at 108. Even if I lean it out it wont leave 108. I dont know why, and my o2 voltage at idle always seems to be around 50mv. Not even anything near right, its just nonsensical. And I even put a new o2 in today, a 4-wire heated one, same thing, idles around 50mv. It idles great, I just cant figure out why it reads so far off.

 

Sound like you might have a mechanical issue going on. My cam is smaller than yours and I'm adding fuel. I guess I would start checking fuel pressure, maybe vacuum leaks, IAC, and TPS set? I'm thinking your engine should run reasonably well as a baseline with that cam with nothing other than raising the idle 50 rpms or so. Not an expert here by any means just throwing out some ideas.
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I read somewhere here about O2 sensor position. If you have headers and welded in the bung yourself maybe it's to far away from the exhaust port and can't maintain or achieved closed loop? Is it in closed loop?

 

Minimum Air is set, TPS is set. Fuel pressure is good. I havent found any vacuum leaks.

The o2 is in the collector so it should stay warm, and in addition to that I installed a heated one yesterday in case this was the cause. Does the same thing with the heated one.

I'm going to check again tonight for vacuum leaks.

 

My current engine in my z28 is a rebuilt 350, with a zz4 cam and vortec heads. The car is an 87 (32B mask), but I recently updated to 6E mask. I used the lastest 89 mask, man, I can't think of the code (I think APYU), for a 1989 car, got it from moates.net, and it really made the car work well. I haven't touched the prom yet, other than setting the normal stuff; fan temp, and injector size.

I would also agree that there might be some mechanical problems. It might be best to start with a new bin, and go from there, too. I have not scanned my car yet, so I can't tell you where the BLM's are, but there is no hesitation, no bog, and the car smells OK (scary, work on cars long enough, you can kind of tell subtle rich/lean conditions, hah). there is a slight hesitation in transitioning from normal closed loop to PE, which I need to work out, but overall, its nothing you really notice.

so, from running a basically untouched prom on a zz4 cam, I can tell you that there is something going on there.....sorry if this isn't any help, but good luck to you....

oh, make sure your grounds are all OK, these dang MAF cars really really like the grounds to be ground.

 

what is your O2 reading?
do you have headers/no cat?

leaking injector/injectors?

 

O2 reading at idle is about 40mv. I have shorty headers with no cat.

As far as I know all injectors are good, it ran fine before heads and cam.

When I run the stock bin that im working from (AUJM) the car is *Extremely* rich. It sounds like a train because it "chugs" and wont do anything less then 1,000 rpm, if you let off the throttle it will immediately die.

 

if you O2 is reading low all the time and you can tell your running really rich,
sounds like you have an O2 sensor problem not a tuning issuse,

your ECM is going to try and make that O2 read 1 volt until it does its going to dump as much fuel as it can until that number comes up,

consider a heated O2,

you should really insure your car is mechanically /electronicly sound before you start tuning

 

It's possible you are in limp home mode on your chip. The burn didn't take. Try getting a new bin from Moates, erase your chip, and burn the new bin on to it. I'm just starting to learn how to program these and I forgot to erase the chip a few times.
That is after your sure mechanically the vehicle is good. I looked at your tables and you have made major changes to the fueling. In open loop the engine shouldn't be on the O2 and still run well enough.

One other thing if you have a stock memcal plug it in and see how things behave.

 

as far as I know if you are in limp mode engine light will be on and you'll have a code

 

Your probably right but I do know that on a few chips I programmed and for the reason I mentioned above they did not program correctly and the car idled and ran very similar to how he explains his does. I erased them and burned it again and everytime all was fine afterward. I didn't get a code/light either. Would that be a 51 or 52 code?

 

doesn't sound like your car was in limp mode,
probably running of the prom but since it wasn't programed right it was running bad,
like trying to read an 8D bin with a 6E xdf numbers are there but don't make any sence
in limp mode the car runs on predetermined numbers based on what ever isn't functioning,

stock car should run drive and idle fine for the most part,
limp mode is to get you to where it needs to be fixed,

 

I do have a heated O2, infact I thought I had a bad O2 and as previously posted I did the swap to a 4 wire heated and shielded O2 just before I made this post with no change.

I cant be in limp home mode, i am running a moates G1 adapter without the stock memcal piggybacked (no netres). It works fine, just no limp home mode. and yes I have tried it with the stock one piggybacked, it doesnt affect it when its running, just the limp since MAF cars have an external knock filter. So I left it out to clean up the ECM.

Yes I have made major changes to fueling, isnt it rediculous? And yet thats what the car wants, Ive taken it down to like 1/3 the original numbers and it seems to run great... it fires up and idles fine at 750 and drive down the road good... just gets like 12 mpg. With stock MAF tables it runns VERY rough like shaking and it wont idle at all, also smells terribly rich.

Its such a confusing situation!

BTW: Its a ZZ4 cam 1.6intake rockers, 1.5 exhaust for a total of .505/.510 lift. Ported / Bowl worked heads fed by a ported TPI with SLP runners.

MAF still has screens.

 

if your O2 is reading 40mv and you know your running rich the O2 is not working especially if its a heated O2

datalog your O2 it should fluxuate alot rich, lean, rich, lean,

if it reads lean and your running rich you have a problem, regardless of the tune, you got to be looking for another problem

 

I know the O2 is good, ive tried various ones they all do the same thing.

At cruise with a BLM of 134 the O2 will swing from 900mvs to 50mvs its not anywhere even near consistent.

 

so your O2 is working then,

134 BLM is lean so how are you runing rich?
do you foul plugs? any particular hole?

 

I get 134BLMs at cruise.

At idle I get 108 BLMs even when the plugs check out to be tan which tells me its not rich.

I have adjusted the O2 R/L threshold for low gms/sec we'll see if it helps at all.

 

Could your cold start injector be giving you problems (is it still installed and connected)?? I run AUJM with no problems, but I did see low Idle BLMs. I assumed it was the old injectors. I was able to get the MAF tables twiddled enough to bring them up though (but that also affected the cold idle some, so I tweaked the afterstart enrichment some and it works fine). I'm thinking you've got some hardware issues, though. Maybe the EGR is stuck open.

 

I got rid of the CSI and associated wiring when I got my 89+ SLP runners.

I can reach under the plenum and pull the EGR up and you can hear the motor run rough so the EGR isnt hung up.

Wouldnt a stuck open EGR cause it to run a lower gms/sec though I dont see how it would richen it up.

 

The stock bin should make that car run OK. My hotcam/lt4 intake ran good with the stock $6E ARAP bin. (after I found the vacuum leak!) Look for the problem, Make it run good with the stock bin then start burning chips to make it run better!

 

hey I just saw that you are running SLP runners on this engine. Is this the stock lower manifold? I had a problem with my Scoggin Dickey vortec manifold initally, in that the SLP runners had an interference, on the rear, drivers side. after I got it completely assembled and running, I found I had a vaccum leak on the runners, and had to trim some of the outer edge of the SLP castings to allow the runners to fully seat and seal.

just a possibility......

 

It is a stock baseplate.

 

Can any of you with a similar setup send me your .bins?

Mattodoom@GMail.com

zz4 Cam
Ported 083 heads
SLP runners
Headers & exhaust

It seems to run just fine... little lacking in power in certain rpm bands but still working on that.

Just odd that its so much leaner then a stock L98 chip everywhere in the MAF table.

I did a compression test on all 8 holes today they are all good. Plugs are all a nice tan color & gapped good.

checked for vac leaks - none.

made sure there was no exhaust leaks.

I'm also getting about 12 mpg. Does this seem right with a mild cam like a zz4 cam? Hard to believe I was getting 18-22 last year with stock cam and i go to a mild cam and get 12?

 

Thanks to Jeremy here for helping me figure out whats wrong with it.

We have it narrowed down to a bad fuel pressure regulator that is causing the extremely richness at low RPMs.

That would explain why I had to cut SO much fuel in the low MAF tables.

 

I took the ECM from my 87 project car and plugged it into the 88 with the 87s stock PROM.

Vrooom!!! started right up and idled __perfect__. It runs better then new!

Whoda thought.... all this BS was just a bad ECM.

Thank you to all who made suggestions!