engine codes 42 and 44

[Bones]

89 TBI motor, painless wiring...

CODE 42 - Elect Spark Timing Circuit

CODE 44- o2 senser (lean)

Replace o2, coolant and MAP sensors....

It cycles at idle, from almost stalling up to about 2500 rpm then back down, for about 1 minute. Then if I give it gas and let off, the idle will level out like normal. After that, if I give it throttle, it just kind of chokes itself out.... I can rev the engine fine, all the way to WOT, but if I leave it at 1/2 throttle for more than 1/2 sec, it chokes itself out....

guesses? Suggestions?

Would a bad IAC do this??

[Bones]

updates, replace the whole TBI with a spare (that includes TPS, IAC, injectors), also replaced the EGR (had a spare).

I now get code 22 and 42

22-TPS voltage was under 0.2 volts for 2 seconds when the engine was running.

42-The EST signal did not change when the ECM applied bypass voltage to the ignition module.

what the f fixes code 42

[GreaseMonkey]

Check you wiring, connections and grounds. I'm assuming the codes in your first post went away?

Both codes sound like wiring problems. I've never seen a TPS go bad for 2 seconds then be fine from there on out.

[Bones]

ok, I went back to the original TPS and that code went away.

I started it, it would hardly idle and now has codes 33 and 42

33-MAP sensor signal voltage was too high (low vacuum) for 5 seconds when throttle opening was under 4%.

and still code 42
42-The EST signal did not change when the ECM applied bypass voltage to the ignition module.

The wiring is a painless kit so it is really really simple.

I have a feeling it is a vacuum leak, but I can't find one....

[GreaseMonkey]

I know it's 1 am now, and I'm operating at 50%, but what's an EST again?

As far as the vacuum leak, start disconnecting all vacuum hoses, and they should effect idle. If you pull one off and it doesn't, that's probably the source of your vacuum leak.

[Bones]

it hardly idles right now, so it is hard to check that way....

[GreaseMonkey]

Yea, that's gonna be a PITA.

[MuddyPaws]

EST = Electronic Spark Timing

[MuddyPaws]

When system is running on ignition module (no voltage on by-pass line), the ignition module grounds the EST signal line. The ECM expects to see no voltage on the EST signal line during this condition. If the ECM sees voltage on this line, Code 42 will be set and the system will not go into "EST" mode.

When engine RPM for EST is reached (about 400 RPM), and by-pass voltage is applied, EST should no longer be grounded in ignition module, so EST voltage should be varying.

If the by-pass line is open or grounded, the ignition module will not switch to "EST" mode. EST voltage will be low and Code 42 will be set.

If the EST line is grounded, the ignition module will switch to EST, but because the line is grounded, no EST signal will be present. Code 42 will be set.

Code 42 sets if there is an open, or a short to ground, in the EST or by-pass circuit.

Test It

1. Code 42 means the ECM has seen an open, or short to ground, in EST or by-pass circuit. This confirms Code 42, and confirms that fault causing the code is also present.

2. Checks for normal EST ground path through ignition module. An EST circuit No. 423 shorted to ground will also read less than 500 ohms (will be checked later).

3. As test light voltage touches circuit No. 424, module should switch, causing ohmmeter to "overrange" if meter is in the 100-200 ohms position. Selecting 10-20,000 ohms position will indicate above 5000 ohms. The important thing is that the module "switched".

4. The module did not switch and this step checks for:
a) EST circuit No. 423 shorted to ground.
b) By-pass circuit No. 424 open.
c) Faulty ignition module connection or module.

5. Confirms that Code 42 is a faulty ECM and not an intermittent in circuit No. 423 or circuit No.
424.

[MuddyPaws]

Usually it's the ignition module under the cap. But you coulda pinched the wire...prolly not though.

[Bones]

well after help from Shawn and a tech from Painless it runs pretty good, but still throws code 42....

[MuddyPaws]

Swap module...

[Bones]

Originally Posted by MuddyPaws

Usually it's the ignition module under the cap. But you coulda pinched the wire...prolly not though.

is that this thing?

[MuddyPaws]

Yea, it's that thing...

[Bones]

I'll try it tonight.

If that isn't it, which wires should I trace for pinching?

[Bones]

replaced the ign module, not it

replaced the ESC, not it....

[MuddyPaws]

Sorry about the big pic...makes it easier to read though.

[Bones]

cool, which pins are ckt 423 and 424?

I talked to Painless again, it really just doesn't make sense...

[MuddyPaws]

Umm...is your "set timing" connector plugged in?

Yellow = 423
Pink = 424

Again, large pic...might need to zoom if you have "resize images" enabled on your computer.

[Bones]

Originally Posted by MuddyPaws

Umm...is your "set timing" connector plugged in?

Yellow = 423
Pink = 424

Again, large pic...might need to zoom if you have "resize images" enabled on your computer.

WOW! I owe you a beer, or maybe 6.

I went out and traced wire 423. It aparently had been rubbing on the sheetmetal on the firewall and must have been shorting itself out, or atleast loosing some signal (my own fault for not using a grommet on the firewall). Wrapped some elect tape around it, fired it up and holy crap, its back to perfect. No code, high rvving, etc....

Thanks, I owe you.... I had about 10-12 hours in troubleshooting different sensors, etc, going to junkyards, etc and it turns out it was just shorting out on the tub.