First Off, Tons of great reading here on Thirdren.org. I have read alot of articles with a wealth of information. Months of reading is more like it. Grumpy's final answers is worth GOLD! My situation is an engine swap on a tired stock 350 for a home built 350 / board 40 over / RV2 cam / factory 350 horse 350 valve springs / Alot of port work to stock heads/ stock intake,exhaust,TBI, and all smog and sensors switched over to match original engine on 1227747 ecm running a 29c256 stacked switching adaptor. I am using a pocket programmer and romulator and have other software available as well. I have weeded through a string of hang ups and shorts and finally it seems ready to tune. I will be the first to admit I am a bit scared of the whole thing but I have to get this engine up and running. (engine only has approx. 15k on it before swap) I have a backgroung of wrenching and enjoy it. I have studied the posts and read alot of great input and hence my question: With the above in mind is a code 33 (Map High) and rich condition a normal occurance with this type of swap running the stock bin for first start ups? Is the error code a problem "persay" or should I go on with the tune and it will go away as the tuning progresses? Everything attached to the ecm is new, EVERYTHING! Thanks for your time and hope I didn't get to winded. Any knowledge or advice on this will be appreciated and thanks again in advance! KUTGW! Any Questions will be answered gladly and my machine is on. LOL!

 

It may be normal, but it is hard to say. My undersatnding of an RV cam is that the overlap is minimal. So a high MAP shouldn't be an issue.

However, you didn't mention what you are using for injectors. If they are larger and causing a rich idle, then yes, I can see that this would cause a high MAP error. A high MAP error is usually at idle and caused by a higher then normal MAP reading (low vacuum) at idle.

If rich lean it out, but watch for the MAP 33 error. If that occures then the MAP value is being created via the ECM, not the sensor.

RBob.

 

I am not sure if the 747 MAP ground ties to the back of the block. If it does and it is accidentally not connected then that might cause it. It would be worth disconnecting the MAP sensor and do an ohm check from the sensor to ground.

 

To RBob, I am running the stock injectors and my engine does pull a low vacuum at idle. I just finished reseating the intake and fixing a vacuum leak that was present there this evening. I also checked the codes after a short startup (Between the stalls) and now a 42 is present after a battery clear before run. I am going to check the Map vacuum hose to make sure it is good and if need be replace it by in the morning. First thing in the morning I am going to do some logging and see what happens and I will get back here with info on the log. Thanks for your time.

To junkcltr I have not seen a ground to the block but your advice will be well taken. I will ohm check for ground because an open would be a welcome find at this point. Thank you to for your reply.

I will be back in the morning with more info and logging hopefully with some good news. Thank you very much.!

 

If you do have low vacuum at idle, that would be a trigger of code 33. The factory ECM will go bonkers if it see's less than about 7 in/hg of vacuum at idle and in gear. Sometimes it will set the code at 10 in/hg in gear even. Fought the intermitent code 33 myself for a while. Rbob showed me some parameters to change with in my chip, haven't had a problem with it again.

FWIW, my old 355/305 Head/Mellings MTC1 cam would pull about 13 in/hg of vacuum at idle in gear. It would not code in normal driving. Turn the A/C on and the vacuum would go to between 9-10, when the A/C clutch was engaged the light would come on, when the clutch would disengage it would go out (At Idle in Gear)

 

Sorry guys I didn't have time to do my logging today. I did check the map vac. line and replaced it along with a new map sensor. I probed it with a DVM and found no problems. After clearing codes and cold start up it takes about 3-5 seconds for ses light to light up. Still giving me 33 and 42 on codes. Is there any other settings that could be interfering with this like egr or *** kn ows what. I am pretty lost on this one.

Fast355 thanks for your reply and I will keep that in mind but my vacuum is not quit that low. Thanks though much appreciated....

I will try to get the logging done tomarrow, that should tell something I hope and thanks again all.

 

All of the sensor grounds along with the ECM ground is tied to the engine. There are no other grounds except the ones tied to the engine block/heads/intake. It may be worth while to use a scan tool to see what the ECM thinks the MAP value is. If it stays high it will run rich, and trip code 33.

You can increase the MAP threshold at $539. This is the MAP high error trip point. Need to keep it from tripping so you can tune it with the real MAP value, not a made up one.

Code 42: this is an distributor to ECM interface issue. Once this trips the ECM locks out it's timing and forces the distributor into backup timing mode.

A code 42 can sometimes be difficult to troubleshoot. It has to do with the BYPASS and EST signals. Can be caused by a bad ECM, bad pickup coil, a bad ignition module, or bad wiring between the ECM and ignition module.

RBob.

 

That is the best info I have herd today! I was just going to print out the ECM pinout for my 7747 and triple check my wiring to the ecm. Reason being, I removed the harness plug and wired it direct due to random connection problems at the ecm plug. Crap connection from the factory. Smart or not it solved alot of maybe's and I can always change it back later.

Thanks for the info on the map $539 that will help out alot I am very sure of it.

The code 42 showed up after the last time I unhooked the bypass to keep it running otherwise it would keep stalling. I will check all the wiring with my DVM and check for possible corrosion at the bypass or broke wire. Thanks For your Help! I appreciate it very much. REALLY!

Thanks Guys I'll be back by this evening with good news I hope.!

P.S.-I have a new Module I will throw in it to.

 

42 also sets if the timing set connector has been or is unplugged.

with what you have you will need to find a good base timing to start with.
with the timing connector unplugged, fire it up & set the timing to best idle & see where it is & what you have for engine vacuum. then set the base timing in the bin & do a burn & check the vacuum again.

 

And the war is not over yet. Thanks for the info DENN_SHAH. I have asked a number of people what my base timing should be because my ride is a 88' and the engine is out of a 74 camero that run at -8 degrees and my 88' timed at 0 degrees. I have it set to -6 currently following info found on searches done here at Thirdgen.org and tunning articles I have read. A lot of information available here and Thanks to All for the Help!

If by chance I unplugged the Bypass while the engine was running did I possibly burn something up?

I didn't get a chance today to put the new module in but will tomarrow for sure. I tried the logging and RBob was right about it tripping back to befault if the code 42 set. My map said 4.4 Volts at 96 Kpa. I don't understand that at all. I did probe grounds and such with DVM and all looks correct. Also checked my pinout and found no errors. Also installed new map and vacumm hose.

I will go with your idea first and set the base timing and climb the ladder from there. I would like to know more about where to set the timing in the chip if you have time DENN_SHAH! I will check back in tomarrow with some improvements I hope. Thank you ALL very much!!!!!!

 

I would use 6° for the base timing. Set this with the bypass connector open. Then turn off engine and re-connect the bypass. Don't forget to set the initial timing term in the BIN to 6°.

No problem opening and closing the bypass with engine running or not. Reason I state to turn off the engine before re-connecting it is to give the ECM time to power down and clear the EST lock out. Then the engine may be restarted.

RBob.

{edit: the recommended 6° of base timing is BTDC, not after}

 

I had to use more that 6* ON MY CAMMED 305 though. The bigger the cam the more timing you will need at startup.

Second, remove the negative battery cable after you set the timing. That will eliminate the possible false code 42 after setting the timing. It will stay for 50 starts or until the power is removed from the memory.

 

Do what RBob said to set the timing and rule out the code 42

1) disconnect the timing bypass weatherpack plug
2) Start engine and set timing at 6* BTDC
3) connect the timing bypass plug
4) disconnect the battery for 1 minute or so


The MAP error. Either you do not have it wired correctly at the ECM or the MAP ground is not tied to ground. Did you re-wire anything in the ECM harness?

1) disconnect the MAP connector at the MAP sensor
2) insert a DVM probe in MAP connector pin A
3) connect a DVM probe to the battery negative terminal
4) set the DMV to "continuity/buzzer" and verify a direct connection

If that is OK, then
1) insert a DMV probe in MAP connector pin B
2) insert a DMV probe ECM connector
3) verify a direct connection
If not a direct connection, then test all other pins to figure out where it was mis-wired.

 

Thanks for all the great info you guys. I can't believe all the good help I have found here at the forum. I do appreciate it.! I took the day off today to stay on this while you guys are so willing to help. I am going out to do the DVM checks now (junkcltr) Thanks!
I have already set the engine timing to -6 (RBob)Thanks and I still need to look up where to set that in the bin. While I am there I can also set the $539 map threshhold setting, Thanks again RBob. I did find corrosion in my bypass connector so that has been corrected. I will be back shortly with updates! THANKS!!!!!!

 

Map code 33 gone! Yess!!! junkcltr you were right with the DVM check. It paid off and my Bad on the wiring. Thank you! Right before closed loop still popped me a 42 but I am off to search for where in the bin I need to set the base timing. Thanks All! more updates to come.

Please just because I mention peoples monikers in my post don't feel your help or advice is not equally appreciated. Thanks Thirdgen.org!!!

 

Thank you guys here at TGO so much. Sometimes you just need that little extra help to give you the confidence to trudge onwards. I fixed the code 42 on my 7747 now only shows me a 45 (rich 02) and if I am correct, that will slowly go away in the tuning and battery clears. (Right?) Today will be my first day of logging and tunning in the posetive direction. Thank You!

I realize this is a Firebird site and I am working on a 88' subburban but somehow I feel Its ok to be here because I have a girl with a 91' Bird that I wrench on cause we're cool together and I have been into that car deeper than I care to tell. We completely removed the VATS and replaced it with a home built PCB that supplies the 5V square wave signal the ECM requires to start. You can only pay so many tow bills before change is in order no matter what it takes. Thanks TGO=Respect!

 

Last night all was great only code I had was 45 o2 rich. I go out this morning hook up all my toys(Datalogging stuff) and code 51 prom error, the pig will hardly run. ALDL info skipping on screen what a mess. I went in and took a shower, came out and ran the codes for the hell of it and all 12 12 12 no 45 even on there. I have wondered about a short all along but am I right in assuming the ECM lost power at some point in time. Baffeled!

 

If anybody is interested in an 88 suburban with a fresh engine give ma a yell please because it is going to be out of my driveway by monday if I have to call pick a part to come get it I'am done with this thing. Thanks for the help though really.

 

try reseating the PROM. sometimes i have the same problem & i have to pull the chip out & put it back a few times & flip the ZIF lever to get a good connection.

it sounds like your close to getting it going but now your getting rid of it? i take it you don't have much patience. seeing a problem through gives a huge amount of satisfaction.

 

I am going to dvm all my ecm pins to source first to make sure all wiring is correct. Reseat the prom as you suggested cause its a great idea, and as far as patients is concerned. I have not found a car I couldn't fix yet accept my own to date for some damned reason. Thanks for the suggestion and the prodding I obviously needed to keep working on it. I very well may owe you one before it's over DENN_SHAH. I agree, I think it is close too, other than the fact I have been working with these same issues of and on for over six months. But I belive you are right, It has to be close no if's ands' or buts'. Thanks I'll be back...........................

If it only ran like my 06' HEMI Magnun "Just a wish LOL!" I am still partial to the tuning vehicle bevuase I built it. Thanks all.

 

Fixing and figuring something out yourself is worth more than plunking down XXX amount of dollars on a new rig. You seem to have the skills to figure it out. Get crackin' and get that thing running. It is like you were told.......either a bad chip connection or wiring probably at the ECM. Sometimes when you re-pin ECMs the pins need a little tweek on the lock to make them hold in the connector properly.

 

Thanks for the push you guys. I did find a cold solder joint on the EST line , ECM side. Only after reseating the chip to make sure I had a good connection at the socket. :-) Now still popin' a 42 right at closed loop. Can the fact the timing on the engine is at -6 and the ECM wants it at zero have anything to do with the code 42? I'm not sure where in the code to change that if indeed that is the problem. I will pull the module out and run it to autozone to have it tested, maybe the short could have burned it. better safe than wondering. Thank you you guys you are the best.!!!!!!!!!!! I will check back shortly in hopes of some info and thank you in advance.

 

no problem. sometimes i need a little prodding too.

i understand about having problems with your own car.
i have a very intermittent stalling problem with mine, it runs fine 99.9% of the time, but every once in a while just as i touch the gas petal taking off from a dead stop it dies. i have been trying to find the cause for the last 4 years, it has only done it twice when i had my pc hooked up & recording data, first time the pc had gone into hibernation & the second time windows crashed when i went to save the log, it can be very irritating to drive around for 2 weeks data logging & never have a problem only for it to show up the first time i drive it without my pc hooked up.

the timing being off shouldn't cause a code 42, it has to be something with the wiring, ECM or the module. if it was a wiring problem it should set the code at startup. if you have a spare ECM i would give that a try. its not uncommon for the module to work fine cold but fail when warm, so it may test good but still have a problem. i have never had much luck with aftermarket modules, it seem they are not made to the same standards as a Delco module is.

when you say -6 on the timing, do you mean 6 after TDC?

 

4 years wow you are the patient one. Kind of it will kill me or I will fix it one day love hate relationship, but I can respect that. Sounds like Murphy visits you too. LOL! I am not alone. The code doesn't set until right before closed loop. You hear the engine rpm go up and down a couple of times then it drops into default when the code 42 happens. Or at least it seems. Started and ran much more solid after finding and fixing the cold solder joint, that is why I was suprised I got a 42 instead of the usual 45 o2 too rich. I wonder why the 45 didn't show up also? It had enough time too. On the -6 it is before TDC , the engine is a 74 camero motor I happen to have removed from my 65 chevy truck that I built with only 15,000 miles on it. It runs at -6 where as the original 350 ran at TDC. Good point on the module and when it warms up. But the fact remains that 3 days ago I showed no codes but the 45. I will have to get the module tested tomarrow and have them do it several times to warm it up perhaps it will fault then. Thanks for your time all and any suggestions more than welcome.

 

Thank you very much all. It works with no codes. I am finally pleased. The fact remains I sold it. But I am still going to tune it for the guy or it will be the death of me. But Thank you ALL so very much for all the support to get to this point. Off to tune I go hi ho hi ho. Thank You TGO>