Ok, this is another post about my idle problems (sorry guys). The symptoms are an idle stumble/missfire, with occasional stalling. I hooked up a scanner (again, Snap-on ), and noted the BLM adn Integrator readings. The BLM reading cruises around 111 this is tellling me that the ECM is leaning out my mixture for some reason (even though the plugs always show signs of running lean). The Integrator readings dip as low as 108, or as high as 122 (but WHY?). If it was running rich enough to pull that much fuel out, it would at least show SOME signs on the plugs. At part throttle the BLMs dip the most, holding a steady 2000 rpm is where it hits 111. The only other odd sensor data I notice is the Timing advance numbers, they read "0" and don't change reguardless of rpm. I have no codes in the memory, the ignition checks as being fine. Balance test fails to isolate a cylinder. Vaccum reading are normal (except when it stumbles/misses, then they drop slightly).

 

You're running rich, not lean. Below 128 is rich, above is lean. The ind will always fluctuate like you are seeing when the BLM is off of 128 by much.

The timing not showing advance is a concern, maybe your ESC is shot.

 

BLM of BELOW 128 means that the computer is subtracting fuel BECAUSE it's RICH. I know this much (Snap-on told me so ). My plugs show NO sign of running rich though, they are bleach white, like they just came outta the box. Thet've been in the motor for about 5 months. WHat's this ESC you speak of (IS it "electronic spark control" ?) ANd how do I go about replacing it, I thought it was part of the ECM?

 

That is what I was referring to, you mentioned the plugs showing signs of being rich...because the BLM's do indicate rich, and yes the ECM is pulling fuel, but your int indicates that is isn't able to pull enough.

Well, on the TPI cars it is a flat black box mounted to the firewall near the relays on the driver's side. Not sure if yours is there or integrated on the calpack.

 

Bump, so I can get some opinions.

 

The Knock sensor control is on the firewall by the relays at least on my 1989 car. The Electronic Spark Control module is inside the distributor. Allen

 

Wow, you make up your own part names?

ESC is on the relay bracket for '86-89, on the MEMCAL for '90-92.
Knock sensor is threaded into the engine block.
Ignition Module is inside the distributor.

There is no such thing as a Knock sensor control...knock sensors have no actuation and therefore require no control.

 

My car has no knock sensor, so it is irrelevant. The distributor is new (A/C delco). Hitting it with a timing light shows timing advance under increased throttle, it's just not getting data to the ECM for some reason (or it is but it's not showing on the scanner).

 

The ECM may not be happy about you not having a knock sensor connected to that circuit. We know they get ticked if you run a MAF-car knock sensor on a Speed Density ECM.

Any error codes?

How old are your injectors? Your O2 sensor...how old and what brand?

 

Kev,

He mentioned no error codes. And usually, I'M the one that misses those details in the posts. It must be contagious...

Sounds like you're at the minimum INT level (as programmed) but I'm not familiar with the V-6 programming specifically.

Oddly, the lack of ignition advance could be responsible for poor/incomplete combustion, and the "fat" O² readings. Get your EST working first. You should be nearer to 20-25° BTDC at that RPM under little load.

 

Apparently people have missed the important oddity in this whole mess:
MY PLUGS SHOW A LEAN CONDITION. They are bleach white, look BRAND new, they are 5 months old. The car runs fine at part throttle, only running like garbage at idle. ALL sensors in the EFI loop are BRAND NEW (within a month, I have also checked for proper voltages with a DVM).

 

No, they didn't. If you haven't had a good tune recently (full) and the O2 is reading incorrectly, you therefore could be lean, read rich and have the ecu attempt to lean out even more. Make sense now? And as Black Helmutt intimated, you could have a slight timing issue as well.

 

By full tune are you talking tuneup? My ENTIRE ignition system is new. The O2 sensor is reading properly, and within normal parameters (tested with DVM). I changed it because I thought it was lsuggish (the old one was good too). Whatever it si, is NOT an easy solution type problem. I'm a mechanic (a young one), and the guys with more experience that i work with have no clue as well. I'm looking for ideas that are out of the box type things. I've been through all of the flow charts, I'm coming up with JACK. As for timing, reguardless of where base timing is set, it doesn't help. The Cam I'm running likes alot of time, I have it set at 10* ADV at idle with the ETC disconnected (Base timing). It will handle 24* before it even gets close to pinging (that's the timing I ran at the track a while back, no pinging under heavy load). I've been through all of the obvious stuff, I've been tracking this problem for months. Like I said, plugs are clean. Scanner shows 0 Adv. BLMs go as low as 111. Car runs good at part throttle, stumbles and occasionally dies at idle (intermittent misfire that doesn't show up on scope, nor on a balance test).

 

Does the MAF reading correspond to the O2 reading concurrently?

 

Depends what you mean? If you mean more air causes voltage to drop, then yes (or is it increase...I always get mixed up...)

 

hey Fbod, on the timing issue with the scanner, if you can try something other than the red brick, the snap-on may be having a problem with reading the timing advance right on your car.
if you don't have another brand of scanner, do you have any other cartridges for the snap-on? they claim the newer cartridges have everything the older ones have & work the same, but they lie.

on the lean/rich part, are you MAFed or SD? do you have access to a 4 or 5 gas bench?

 

In my experience, O2 mV lazy and constantly high (which causes the ECM to BLM down) and lean plugs = poisoned O2 sensor. Coolant or other silicon will poison the O2 sensor in such a way that it always reads high voltage, ECM pulls out fuel, you get what you described.

So...maybe time to pressure-test your cooling system?

 

Yup, been done. The O2 reading is going to both extremes (well not extremes, but as far as about 200mv to about 850 mv -but don't quote me). Lets just say that the O2 Mv is normal. I tried a different ECM/PROM combo today too, no difference. Still doesn't show timing advance, and it still idles crappy. I did note somthing odd too, it idles much smoother with the ETC disconnected. BASE timing is at 10* BTDC, and it even increases with ETC disconnected. BLMs are as low as 110 (that's the ceiling apparently). So...that's everything. Only thing left to do is smoke the motor and see if I can find a vac leak (there is none according to my propane tank...). I have a headache..

 

About all I can come up with is a malfunctioning injector at this point. It would probably be one on the bank that feeds the O2 sensor, which would feed a non-representative exhaust stream to the sensor and cause the ECM to adjust the fueling incorrectly.

Maybe swap injectors bank-to-bank and re-test?

 

Your using the MAF ecm with that 3.4 eh?

I'm betting your load tables are way off.

The MAF stuff is tricky to get the calibration dead on. I spent a long time trying to get mind right. I'd have a similar situation.. Plugs were white, yet the blms were around 108. wtf I said.

I'd look into a '730 personally. Redo the ve and spark table.

Theres a million reasons why your car could be doing what its doing, but honestly I can't really help you without seeing a log of the ECM. You watching a snap-on scanner is really useless. A lot of old timers think thats the best tool in the world. Thats simply because they don't have a laptop.

Hows the o2 crosscounts look?
Is it in open loop or closed loop?

Removing the knock sensor shouldn't screw things up, unless your getting knock counts. Mine is disabled BTW. I only use it for logging.

-- Joe

 

The 86 2.8L MAF ECM didn't HAVE a knock sensor. I have data logging software and a laptop, but that stuff is overrated if the problem isn't in "the program" so to speak. The car ran great for a few months after the Cam went into the 3.4L. I ran it at the track and had no odd problems untill about 4-5 months after the cam install (and NO, it isn't mechanical related problem, everything checks 100%). I do realize that the Snap-on scanner sucks for data streaming though, it's too sluggish. But data is data.

Hit's close loop, BLM's start to drop pretty quick. Car idles...decent in open loop (still slight bumps, but much better than in CL). I'm stumped.
I finally broke down and took the car to Grease onkey today (A shop my shop uses to troubleshoot crazy problems). He's gonna smoke the motor, run a scope, and use all those high tech little gadgets I don't care to touch- I really hate Computer chips in cars. If all else fails, I suppose I'll Shell out the cash for an Edelbrock 4bbl manifold and a little 400 cfm carb. Getting rid of all that PITA computer crap. I don't care for gas mileage or clean emissions, this isn't an endurance racer. Once the car hits 14's on motor, I'm buying a Nissan

 

If you want a future in automotive repair i'd get used to the computer stuff. Carbs have been done for nearly 20 years now.

Besides, EFI is faster.

-- Joe

 

That's why pro stockers/pro streeters/top fuelers and funny car guys ALL use EFI.... NAh, I know the benefits, but on my own car, I prefer somthing reliable. Oh yeah, and as for the career in Auto repair goes, I'd prefer to be in conceptual design, but I'm poor and lazy, therfore can't afford a good art school, lol.

 

Top fuelers and pro stockers don't impress me..

A 10 second street legal car that behaves just peachy in bumper to bumper traffic. That impresses me!

Im crashing. goodnight. and goodluck with the car.

-- Joe

 

Night.

 

Ok, some food for thought. First, MAF isn't hard to tune and a switch to MAP at this juncture would be unwise as you may just be putting the same problem into a system you are trying to get up and running. And for other reasons I won't go into.

Put a timing light on the car and see if the timing advances as you open the throttle. If it does then you have probably found a quirk in the scanner.

Next, O2 sensor...get a new one...heated if possible. This way you have a known good sensor in there. And check the wire for the sensor, possibly a voltage being induced in the signal wire making it report a rich condition falsely.

Next thing to look at are the injectors..the ones on the O2 sensor side specifically. I know you said the plugs look white but something is making the O2 sensor report a rich condition.

After this...I dunno
The O2 is what tells rich or lean and it is a very simple system.

 

Verify closed loop via the aldl, not the scanner.

 

Actually thats not true at all. Infact, I'm betting the problem is in his tune.

MAF is a horrible system to tune. Even Jesse eventually switched to MAP.

Quote:

Next thing to look at are the injectors..the ones on the O2 sensor side specifically. I know you said the plugs look white but something is making the O2 sensor report a rich condition.

After this...I dunno
The O2 is what tells rich or lean and it is a very simple system.

It's a very simple system, and if the calculations are just a tad off it will REPORT a super rich condition when the AFR infact could be very lean. A lot of guys with big cams see similar problems at idle.

Thats why I asked him how it was crossing.

The fact is, he is running a 3.4 motor with a completly different valvetrain timing with an ECM calibrated for a 2.8.
He needs a laptop, he needs to log a few minutes of data and get it up here for us to look at. This could be a simple problem, but him spouting out numbers from a snapshot is not helping at all.

-- Joe

 

I will always whole heartedly disagree with that, MAF is simple once you understand it. The only drawback to our MAF systems is the resolution maxing out too soon on a modified engine.

So, Jesse switched to MAP....and that means what???? I didn't and won't switch to MAP (unless I go S/C). I took the time to learn how and why the MAF works and how to tune it..within the confines of $6E code.
Nothing worthwhile is ever easy.

 

I don't want to start a fight, and if your happy with you have fine. BUt have you tuned any map calibrations?

I'm thinking maybe MAF works for you because you havn't hit any snags.

-- Joe

 

Anyhow....I'm not changing the ECM, if anything i'll ditch the computer alltogether. I tried two new O2 sensors, they din't have any effect. The car is at Grease Monkey, I will call them tommorow and see if tehy discovered anything yet (I'm hoping it's somthing easily resolved, like a cracked head or somthing ). The car needs to be chip tuned without a doubt, but I don't have the equipment to burn chips, nor do I care to learn the programing language just so I can pick up a tenth. This Engine combo has already surpassed my expectations by a long shot. It won't surprise me if it runs easily with L98 cars after the new heads and possibly a better flowing intake (2.8L intake/plenum, flows 250 cfm~). If I have to tune it to get there, I didn't do somthing right (obviously, tuning it is the RIGHT way, but I'd like to get past that).

 

Yes. I own one of each, an 85 IROC converted to 165 ECM and a 91 Formula, 350 TPI..Not to cast stones but the MAF car is definately the easier for me to tinker with and the better performer of the 2.