EST and ESC diagnostics for TBI

[bp71k5]

So I took my new TBI motor out for a test drive today. It seemed to do pretty well at first except for a stumble every once and a while when the engine was under a bit of load and I had just shifted to a higher gear. The longer I'd drive it the more it would stumble. Enough so that I had to idle it back to the house in second gear. It idles consistantly with no trouble at all.

I found one possible cause was before my test drive I changed the base timing from 4 BTDC to 0 BTDC by just twisting the distributer a bit to what I thought was close enough. After it was running like crap, I checked it again and discovered it was at 4 ATDC. (retarded). So I reset it back to 0 with the timing gun, but I didn't pull the fuse for the ECM after I made this adjustment. In fact the ECM has been connected to power since the motor was first started and I was tuning it.

After I went for second test drive, I noticed it doing the same thing and found the SES light was on and it's reporting 3 codes. These could have been set from the earlier problems I had:
1. 24 -No VSS signal (because I haven't hooked it up yet)
2. 42 and 43 which are the ESC and EST functions. I've double checked the wiring and they appear correct.

One additional bit of info is that the park\neutral switch wire is not hooked up to anything. Since I have a manual tranny, I wasn't sure what to do with it until I got a new chip burned.

So the big question I have is:
Is there way to test the ESC module or the EST (in the distributer) to determine if they are working correctly. The distributer is brand new, but the ESC is used.

I've reset the ECM and will try a test drive in the morning after the neighbors have left.

 

[Jason4x4]

IIRC, the esc code sets when you unplug the wire to set the timing. you would have to clear it and see if it comes back.

 

[eagle mark]

So I took my new TBI motor out for a test drive today. It seemed to do pretty well at first except for a stumble every once and a while when the engine was under a bit of load and I had just shifted to a higher gear. The longer I'd drive it the more it would stumble. Enough so that I had to idle it back to the house in second gear. It idles consistantly with no trouble at all.

Check your fuel presure! Sounds like the filter may be pluging up.

The EST can be checked at an auto parts store. Check it three times, if it fails any? It's defective.

 

[bigblock72]

The stumble is likely getting worse because the computer has leaned out the mixture to where it's supposed to be and uncovered a lean acceleration enrichment setting on the chip. TBIs are very sensitive to A.E settings compared to a port injection. The best way to tell is get yourself WINALDL and the cable and log data, this will also help whoever burned your chip to get it corrected. Sometimes a little more timing will help with these types of problems.

Code 42 should have set when you disconnected the bypass to set base timing. Code 43 is a little unusual, and could be causing your stumble if the module is sending a knock signal to the computer all of the time and the computer is retarding the timing.Double check you have power and ground at the esc (knock) module, check the wire to the knock sensor and verify continuity to the computer. Beyond that will require datastream info. Just as a side note for those who don't know what the knock module does. It simply takes the signal from the knock sensor cleans and filters it then sends that to the computer. The modules are tuned to specific powetrain combinations so they can filter out normal operating noises to help prevent false signals from getting through. Speed density TPI and newer PCMs (trans controlling ECMs) all have the knock module built into the CALPACK (a fancy PROM).

To tell if the computer is in control of the timing just simply make sure the timing changes when the bypass is connected and the SES is off.

 

[bp71k5]

Check your fuel presure! Sounds like the filter may be pluging up.

I have not yet checked the pressure, but the tank, pump, gas, fuel lines, fuel filter, and sending unit sock are all brand new. I'm pretty sure their clean. This problem feels just like it did before I set the base timing and it was far too retarded.

Code 42 should have set when you disconnected the bypass to set base timing.

That clears up (for now) the code 42. The SES light is way under the dash for now so I probably didn't see it come on.

this will also help whoever burned your chip to get it corrected.

Don't really know, but I'd guess it's the stock chip still. I have to get the EGR, TCC, and whatever else I don't need removed from it still. I was going to wait until the oxy sensor and everything else was working as best as possible.

Code 43 is a little unusual, and could be causing your stumble if the module is sending a knock signal to the computer all of the time and the computer is retarding the timing

I can verify that it's at least controlling the timing a little bit because when I hooked up the timing test wire again, the idle advance goes from 0 degrees to about 10 degrees BTDC. I should check what it does with some throttle.

I can turn the motor on in about 40 minutes and see what happens. The neighbors are still sleeping...

 

[dyeager535]

Hmm, don't the TBI motors advance to somewhere around 20* at idle, normally?

One of GM knock sensor tests is to watch the timing, and tap the block near the knock sensor with a hammer. If timing retards, it's working.

 

[bp71k5]

Hmm, don't the TBI motors advance to somewhere around 20* at idle, normally

Actually you seem to be right. I was reading the marker incorrectly. It's idling at about 14* with everything hooked up.

All the SES lights are gone except for the VSS which is expected.

When I watch the timing mark while giving it some gas, the timing advances just a tad up to 18* and off the scale to about 20* as engine rpm increases and then when it misses\stumbles\etc the timing drops back 4-6 degrees. I'm not totally sure, but I think I can hear some pinging when it does that. I'm usually inside the car when I've heard pinging in other cars so I'm not totally sure.

In any case, it doesn't seem to advance the timing all that much as the engine speed increases. But maybe this normal?

 

[dyeager535]

I'd have to look at timing maps, but since timing starts off so high from idle, I suspect more isn't added until the RPM's get a bit higher.

 

[4X4HIGH]

I think most of your problem is from not having the VSS working. I ran into the same issues years ago when i forgot to hook it up. Before you try to diagnose anything you need to get ALL the sensors hooked up and working. It's kinda like trying to make an engine run smooth with one or more plug wires off, sure it will run but not very good.

 

[bp71k5]

Before you try to diagnose anything you need to get ALL the sensors hooked up and working.

I agree. I just dropped it off at the exhaust shop so they can weld a bung in there and give me a quieter muffler. Then I can hookup the oxy sensor and will hookup the vss when it's back.

After several test drives, it seems to work ok before the engine comes up to temp. Once it's at full temp, it stumbles under light throttle but recovers if I give it more gas. It doesn't seem to have any trouble over about 2200rpm. Thanks for all the help! The new 4.10 gears in the back are also much nicer than my old 3.07's.

 

[4X4HIGH]

When you get it back and are not afraid to drive it too far bring it over and we can throw my scanner on it or even the winALDL program, i have the cable. (i have the cable for this crappy laptop that is serial port, still need to buy a cable for USB port to use with my new laptop).

 

[eagle mark]

You didn't even have the O2 hooked up? IIRC that will really back off timing when warm... being in open loop...

There are bin files for whatever your doing! When you get the O2 and ? hooked up maybe start with some more information like: engine, transmission, axle ratio, ECM #, chip code, what sensors are not hooked up, fuel pressure, error codes etc...

I have seen problems with VSS not hooked up and others have said they were fine. If you have it? Use it! There is a way to turn off VSS then burn a chip. But I have never tried and then driven the vehicle looking for drive-ability issues. It may just turn off the diagnostic code.

 

[bp71k5]

You didn't even have the O2 hooked up? IIRC that will really back off timing when warm... being in open loop...

I thought I mentioned it. I needed to get it running well enough to make it 5 miles to the exhaust shop. I seemed to be stalling out pretty bad just a block away so I wasn't ready to chance it. It seems to be running well enough now that it was worth taking it over. Hopefully that is all it is. I have a painless vss adaptor ready to install.

 

[bp71k5]

When you get it back and are not afraid to drive it too far bring it over and we can throw my scanner on it or even the winALDL program

I'll probably take you up on that sometime next week. I'll give you a ring when I think I'm ready to venture out that far.

 

[bp71k5]

Thanks for all the help guys, it looks like the O2 sensor took care of it. I'll still hookup the vss to get rid of my ses light anway. It seems to be running pretty well now.

 

[bp71k5]

Update: Code 43

This might be a little long and wordy...

So now that I've been able to drive it for a while under different conditions, I discovered something.

Almost every time I would drive the k5 for more than 10 minutes, I'd get a code 43 after the engine warmed up. I was suspecting the ESC was detecting a knock too frequently since the timing was set correctly and the engine seems to run fine otherwise.

I suspected I was shifting a little too early because if I shift when the engine reaches 2600-2800 rpm the engine RPM would drop to around 1500 rpm after the shift. I don't know what the optimal rpm is, but 1500 RPM seems too low to me during acceleration.

So on way home from work, instead of shifting into overdrive on the freeway, I made an effort to keep the engine rpm's above 2000 if my foot was on the gas. I didn't shift until the motor reached 3000 rpm, and made extra sure to downshift whenever I could to keep the rpms's between 2000-3000 rpm.

I can't hear any noticable difference in the engine noise (knocking, etc) so I'm not sure what the difference was, but when I got home, the SES light was still not on. Cool!

I just ordered a ALDL cable and will try to see what's really going on, but I find it hard to believe the small difference in engine rpm would make a difference. It's not like I was lugging it or anything. It had plenty of power even at 1500-1700rpm.

Any clues on what I should look for?

PS:
The 7747 ECM is setup for an auto tranny and EGR, but I have none of those. I wanted to get it datalogged before having any chip mods done.

 

[dyeager535]

EGR shouldn't matter, pretty narrow parameters for its operation. The main one is consistent low engine load. Sounds like this isn't when the problem occurs.

Auto tranny I suppose could do it, but plenty of people run them and don't experience a problem. Brian could probably tell you if it's likely the issue.

ALDL logging is certainly the way to go with this. I didn't re-read the whole thread, is your park neutral setup correct? (not jumpered so it thinks it's in Park all the time?)

 

[bp71k5]

Park/Neutral wire is not connected to anything.

I'd like to make sure everything possible is setup right before datalogging and swapping chips in\out.

 

[dyeager535]

So not connected, I believe that means it thinks its in park/neutral all the time, which changes a few things, to include how much load the ECM expects is on the engine at X RPM.

Man it's been a long time...I *think* you can jumper the P/N wires and it will be "correct". Other option if you didn't change the column, is to manually shift the bowl after starting, with the P/N wires hooked to the switch, so the ECM thinks that the vehicle is in gear.

 

[bp71k5]

So not connected, I believe that means it thinks its in park/neutral all the time,

I'll have to check as well, but I thought disconnected would make it think it's NOT in P/N.

I did change the column out otherwise I would have hooked those up. Maybe I should give Brian at TBIchips a call\email about ordering a new chip and see if he thinks I should do something differently with that before datalogging and actually ordering the chip.