Got the new eng fired up last night. See sig for mods.

When eng is goosed, it revs up ok, but then dies unless I catch it.

When I tried to set the min idle (IAC driven closed and then disconnected), eng started surging badly when RPM was lowered to abt 900 RPM. After abt 4 surges, it dies.

Had a couple of vac leaks, but I'm pretty sure I have them all fixed.. (Sprayed B12 all over the intake. Tried propane too. No more leaks found)

Could still check for an internal vac leak I suppose.

EGR valve was tested and wasn't leaking before installation.

I adjusted fuel press slowly from 40 to 50 psi while eng was surging. It had no effect.

Getting a code 33. MAF high; if I remember right. Not sure what causes that error.

Using my ancient OTC Monitor 2000 I get the following:

BLMs are 140.
INTs are 128.
Haven't got into closed loop yet.
(Can't drive it till brakes are working)

O2 voltage stays between .45 and .54 volts, and does not seem very active, although cross counts are anywhere from 5 to 25.

Didn't get a MAF reading from my scanner with eng running, but with key on, eng off, it is 015. Not sure if that's normal or not.

TPS is set to .54 volts at idle.

Batt voltage is 14.5 volts.

Water temp is 185*.

Manifold vacuum, at a steady 1000 RPM idle, is 18" and steady.

The cam (211*-219* at .050 lift, 112*LS) should idle close to a stock cam I would think.

My "custom EPROM" is a basically a stock L98 bin.
(I just cut back on the max ign advance, changed the single and double inj size to 24, and un-checked the VATS option.)

Any ideas??

Should I try decreasing the inj size to 23lbs?
Seems like increasing the fuel press should have helped, but it didn't.

 

Get the code 33 straightened out. Then if it still surges, get the idle BL to closer to 128. Then I would look at vacuum leaks, MAF cars surge badly with leaks.

 

What triggers the code 33 on a MAF system?
Seems it was something like:
over 45 g/sec airflow with less than 17% TPS and less than 2000 rpm.
Does that sound right?

 

MAF Burnoff relay
MAF Power relay
MAF itself
MAF wiring to ECM
MAF wiring to relays

BTW, I used to use an OTC scanner also. Its good because it works with tons of domestic cars, but a laptop and 8192 baud cable is great investment.

 

IF your not going closed loop then the BLs are meaningless.
If your O2 seems lazy, I'd suspect you have some gasket goo that wasn't O2 safe and it's killed the sensor.

You should get a MAF reading, try unplugging it and see if the car runs better. It may have died.

While not critical in and of it's self the TPS is kinda high, which might limit the WOT TPS voltage, you might investigate that.

 

Still having issues with code 33.
At the MAF sensor, I measured the voltage from pin "C" to pin "A" and got 5.04 volts.
Started eng, still have 5.04 volts. Goose the throttle, no change.
Replaced the MAF sensor, MAF power relay and burn-off relay; I still have 5.04 volts.

I get 5.04 volts on the pin "C" wire (dark green) with the MAF sensor unplugged. I'm assuming the the ECM is supposed to provide the 5 volts and the MAF pulls the voltage down depending on airflow.
Is this thoery correct?

Pins "A" and "B" both show very low resistance to ground.

Getting batt voltage to the red wire (pin"E") while eng is running.

What else can I check???

 

I installed a 270 ohm resistor between pins "C" and "B" of the MAF sensor connector. Pin "C" voltage dropped to ~1 volt.
Car started and SES light stayed off.

Starting to look like I got a "bad from stock" MAF sensor.
Back to Autozone.....

 

Well, here's mud in my eye..
Looks like the whole MAF issue was due to a bad connection at the MAF.

Cleaned and tweaked the pins. Now getting 2.5 volts with key on, eng off. Yeah!!

 

How's it running now?

 

I can now get a pretty smooth idle at 700 rpm. BLMs are still 108 most all the time during cruise.
I've burned abt a half dozen proms tonight. Increasing the inj size by 1lb on each burn. I'm up to 28 now and still have BLMs at 108. INTS were 80-100, but now they're 120-130. Seems like I'm moving in the right direction, but I'm a long way from 24 lbs now. Starting to get a little worried.

During light to moderate accel, INTs go up to 130-140. Once I get the cruise BLMs a little closer to 128, I'm sure I'll have to go back and crank up the PE values.
At what point should I start adjusting fuel press to nail the cruise BLMs? I was thinking I'd keep adjusting the inj size till I got the BLMs into the 120s at least.
I'm disconnecting the batt at every chip change to erase any bad habits. How long at cruise should I wait untill I can trust the new BLMs?

 

The injector code is one thing I haven't explored yet. Certainly can't wrap my head around it tonight - maybe tomorrow. Is it possible that by increasing the injector size you are leaning the motor? What would 20 give you? Might be good to check the plugs for health of the new motor and to see if you really are lean or rich. Go two or three points in other direction, then backup if necessary. Otherwise you'r lible to exceed the 5000 programming cycles on the eprom Good news on the MAF. Thanks for the report, it's always good to get feedback. I racked my brain on that and it just didn't make sense. It does now though.

Take Care

-dnult

 

Injector constant and fuel pressure changes will have the same effect, but I would only do one or the other. I would check your fuel pressure to make sure it's not crazy high causing your 24# to be 30#. When I was running MAF, setting my injector constant to their rated flow gave me closest BL numbers, so you may have another problem elsewhere.

 

plantprotection>>I'm running 43 psi on the fuel press.
The fuel press does bleed off slowly. Need to find a spec for the leakdown rate.
The fuel pump and regulator are new. The injectors have 8K miles on them. The cold-start inj however is original and there's no telling how many miles are on it.
I was thinking abt removing the cold start inj and soldering the little 1/8" line shut, then re-installing it. That should rule out any leakage getting by that goofy thing and it would look stock.

dnult>> I'm pretty sure increasing the inj size constant will lean the mixture. The ECM thinks it needs to deliver a certian amount of fuel. If it thinks the injectors are bigger, it will decrease the PW.
At least that's the way I understand it.
I'll pull a couple of plugs tomorrow evening and see what they look like.

 

ZZ: I guess I misunderstood the BLM number (108) indicating lean. So I presumed that by decreasing the injector size, the mixture would fatten up. Other than the obvious, the whole BLM issue is something something magic. By the way the test bench project is coming together. Probably won't get much more done on it this weekend though. Going to the lake this evening.

-dnult

 

The MAF issues have been resolved. The BLMs are looking a lot better, but the wierd idle thing is still there.

If car is started in park, RPMs shoot up to abt 1400, hang there a few seconds and slowly drop to abt 900.
When I shift into drive, car wants to take off. I have to increase brake press to above normal levels to keep car still.
When shifter is moved back to neutral, RPMs shoot up abt 1400 RPM again. Wait a abt 5 seconds and they drop back down to abt 900 again. This can be repeated over and over.

When crusiing at <35-40 MPH (with shifter in O-drive) I have to ride the brakes.
If I shift to neutral and let car slowly decellerate on its own, RPMs stay up at 1400.

Slowed the car to like 1 mph and coasted down a long hill (in neutral) for abt a quarter mile. RPMs stayed at 1400. As soon as car came to a complete stop, RPMs would drop down to 900.

For some reason, the ECM is driving the IAC to do this.
I've found parameters to increase idle speed in park/neutral, but can't find anything that would address this issue.

This is really driving me nuts.
Any ideas?

 

Sounds to me based on the latest post that you still have a vaccuum leak somewhere.

 

I've looked for a vacuum leak, but none have been found.
Seems like if there was a vacuum leak, my BLMs would be high instead of low (was battleing some 108 BLMs till I took drastic measures with the inj constant).

I had the scanner running just now and monitored the IAC counts.
With eng at 205 degs, in Park, IAC counts are 19. Idle speed 900.
MAF showing 11-12 g/sec.

Mashed FIRMLY on brake and shifted to Drive. IAC counts started climbing and didn't stop till they reached 145. Running stock torque converter, so that's probably what was holding the RPM to ~1000. MAF reading went to ~20.

Shifted back to neutral. RPMs rose to 1400-1500. Stayed there a sec or 2, then slowly dropped back down to 900.
AIC counts came back down to 19.


Inlight of the preceeding data, does anyone feel is really a vac leak causing the issue?
To me, it looks like like the ECM is causing the issue, but I remain open to any suggestions. Thx.

 

Made another discovery today. If I remove power from my scanner while the eng is in drive (and IAC counts are going thru the roof), the car begins to idle like a normal car.
If I start eng with scanner disconnected, it idles like normal.

How could the scanner do this?

More importantly, how can I make it stop?

I'm not in diagnostic, BUF, ALDL or road test modes.

Is it OK to have ALDL pins "E" and "M" connected together?
My 87 GTA schematic shows them connected together.