ECM not processing info properly?

[tscruggs]

Craig Moates at Moates.net helped me diagnosis some serious flooding issues today. My 87 GN, mostly stock, 32# injectors, chip, etc... Sensors are sending info to ecm but it is giving weird numbers. Intake air temp shows 75, correct, however, upon starting the car, temp jumps to 140+ and continues to rise. Idles way high and WAY RICH. No codes tripped. IAC stays open. wiring tested good. ECM is a new oem from CarQuest - have also tested one from OReilly - oem. Where could I get a good one? Does anyone have one that I can test with that we know works properly? Car floods out at anything less than WOT - can't be driven. PLEASE HELP!!!!!:frown:

 

[bobc455]

Travis,

It is very unusual for the software to not process properly. Chances are that it is getting bad info to process.

One of the things I would try, for example, get a resistance table for the temp sensor, and see if the sensor has the proper resistance. Then, see if the ECM is interpreting it correctly (with a scan tool).

If the temperature sensor is correct when standing alone, but the ECM sees the "wrong" temperature, I would start to check out grounding. The "wiring checking out okay" is a very, very difficult statement to make- there can be a lot of potential issues. Is the body grounded to the frame? Is a fusible link acting funny?

You can also spot-check other things in the wiring harness. Is the ECM sending out 12V over lines which should be 5V? etc.

It is very rarely (never?) the software just messing up, unless perhaps the ECM you got was for a different car. But since you've switched ECMs (presumably to fight this problem???) and the car is acting the same, I would be all over the wiring with a multimeter.

One more thing to check. Has a previous owner (or someone else that has worked on the car) changed the injector size or fuel pressure? Is the ECM controlling the devices that it expects to?

-Bob C.

 

[tscruggs]

Bob;
THANK YOU!!!!

The software tested properly on a seperate computer. We tested all of the wiring, with a multimeter, one at a time - hours. The wiring seems to be running proper grounds, voltage, etc. The concensus came about that there is some kind of hardware issue with the ecm, but... It does have 32# injectors now, however, the chip is porgrammed for those injectors. The ecm is an oem 1227148 from CarQuest. I have tried one from OReilly's also. Should I buy one from a more reputable specialist or.......?

This is my fist foray into the innermost parts of the electrical/computer aspects of these cars, so I am enlisting professional help.

Travis

 

[TurboDave]

Many times, radical fuel related issues such as you describe can be traced to a couple of the more common issues.
One being a bad ground somewhere ( a real bear to track down)
Or your MAF sensor has probably gone bad.

 

[ijames]

You mentioned the IAT sensor - how about the engine coolant sensor? If it is bad and showing -40 degrees the ecm will think it is in the arctic and will dump in lots of extra fuel. Also, is this a new-to-you car? If so, any chance it has the turbolink boost sensing harness that sends a MAP signal in through the IAT wire? That would explain the big jump in IAT when you cranked it up. If those are ok, and you have a scan tool hooked up, turn the key on but don't crank it up. Make sure all the sensor readings look normal - the IAT and coolant temp should agree and should be wahtever the ambient temperature is if the engine hasn't been run in several hours. Rpm and mph should be zero, battery voltage about 11-12 V, and the MAF should be 2-3 g/sec, not zero. If the maf is zero or some other unlikely number, turn the key off, unplug the maf sensor, and then start the engine. It will set an error code but should run in limp-home mode okay if that was the problem.

 

[tscruggs]

Have been unable to find a bad ground and MAF is good. Have tested other mafs in car, etc. Expalin turbolink boost sensing harness diagnosis deal - this particular car is relatively new to me and that is exactly what is happening - all of the others items you suggested to check have been checked and appear to be operating properly - sensors read correct until start up and then they skew dramatically - engine coolant sensor, iat, etc, etc have all been replaced - unplugging any sensor does not affect the way it runs although it does trip the code for whatever sensor is unplugged

 

[ijames]

Let's back up a little - do all the sensor values (mat, coolant, whatever) have a dramatic shift right after the engine starts up, or just the mat? The ecm does not measure map, so TurboLink came out with a wiring harness to let it so you could log boost with a scan tool (see http://www.turbo-link.com/tlink/details/catbst001.html). This harness plugs into the tps sensor for power, has a 3 bar map sensor that is tee'd into a vacuum line like the one going to the stock map sensor, and has a plug that connects to the mat harness instead of the mat sensor. If you have this, you may still have the mat sensor to plug the hole but there should not be any wiring connected to it, and only the mat readings should change with startup.

 

[tscruggs]

The MAT and MAF and IAC skew dramatically at start up. The MAT skyrockets at start up and continues to climb. Coolant seems to read correct. MAF readings skew. IAC stays wide open. Have not looked to see this kind of setup. I will look as soon as the flooding stops. It is pouring rain here and supposed to continue for two days. THANKS for the help!!!!!

 

[ijames]

Don't mean to abandon you, but I'm going to be out of town until next year. Good luck (if you are desparate, email me a phone number and I'll try to call you next week).

 

[bobc455]

Just a hunch here. If you test the voltage to the TPS, do you get the full 5V (when measured to ground)? or do you get more (or less) than that?

Do you still get 5V after the engine starts also?

-Bob C.

 

[SloGN]

is it possible that the chip he has for the car is actually using the iat sensor to control the fuel? On the stock chip the IAT temp scalers were set @ 0 so there was no fueling change depending on air temp since it's a MAF car not a speed density.


Some of the aftermarket chip now use the IAT tables to control the fuel. If that the case if he has a boost sensing harness it would affect the fueling cause it is changing the temp value.



have i confused everyone

 

[tscruggs]

Thank you BobC. TPS reads 5 and rises as accelerator increased, etc.
slogn, you make good sense to me. I do not know anyone who has done this boost sensor harness thing... where would I look for it to be located and how do I check it. This condition began suddenly on a standard drive on my way home from work, last March. It is killing me - has been an awesome car and suddenly... no less than 12 mechanics from all over the midsouth/south have been baffled by this problem. Please continue assisting me!!!!

 

[SloGN]

Thank you BobC. TPS reads 5 and rises as accelerator increased, etc.
slogn, you make good sense to me. I do not know anyone who has done this boost sensor harness thing... where would I look for it to be located and how do I check it. This condition began suddenly on a standard drive on my way home from work, last March. It is killing me - has been an awesome car and suddenly... no less than 12 mechanics from all over the midsouth/south have been baffled by this problem. Please continue assisting me!!!!

well it would be located in the pipe that is on the inlet side of the turbo somewhere around the MAF sensor it has 2 wires on it. unplug that iat sensor and see ow the car reacts.

also have you tried another known good MAF sensor to see if it's could be causing some problems

 

[tscruggs]

Thank You!!

I have tried a known good MAF and chip. I have unplugged each sensor one at a time and all at once and none changed the way the car runs. All tripped the proper codes, etc, but did not affect the richness. This all started suddenly. I was driving through my neighborhood at 20mph when it suddently began sputtering. Will not stay running except at WOT due to extreme richness. nly code tripping is rich o2 sensor. When monitoring with winaldl, the only odd numbers are the iat which read correct when key on engine off - when running iat doubles and contiues to climb indefinitely and car runs WAY rich. What part went out that could suddenly cause such a problem? THANK YOU for assisting me!!!!!!

 

[SloGN]

have you changed the o2 sensor lately. If it's a yr or 2 old i would suggest getting a new one. Also what is the fuel pressure @ idle?


The stock injectors are 29lbs the ones that you have are the 32lbs. You can run those injectors on your stock (BBKJ, or ACXA) chip . just lower the Fuel pressure about 5 psi and it should be within a range that the ecm can compensate. give that a try.


Also what brand are those 32lb injectors. I have not personally ever heard of a 32 lbs injectors. are you sure that there not a (009) 42.5 lb injector?

with a 32 lb chip with 42.5 (009) that would cause a problem.

Also how long has this injector/chip combo been on the car?

also please give a break down on the mods that is done to the car.

The known good maf that you tried, It was a turbo maf sensor from another running buick. The aftermarket stock replacements are junk. Also most parts stores don't usally list the rite part # for a turbo regal. They some times list the part # for a 2.8 liter MAF witch i a different animal all together.

hope this helps

one more thing is when it's running try unhooking each injector one at a time (electricly) to see if the engine starts skipping on that cylinder. if it don't change with it unhooked you may have a stuck injector flowing fuel all the time.

 

[tscruggs]

Injectors are Accel, O2 has been replaced several times during these testing periods. MAF is from Jerryl here at TB and is known good. The chip.injector combo has been on for a while. This problem began suddenly while driving - did not change a part and it began - it just began one day while driving through my neighborhood. Any other suggestions? I am at my end and need help. I do not have the funding to ship it to one of our "GN Speciailists."

 

[SloGN]

Injectors are Accel, O2 has been replaced several times during these testing periods. MAF is from Jerryl here at TB and is known good. The chip.injector combo has been on for a while. This problem began suddenly while driving - did not change a part and it began - it just began one day while driving through my neighborhood. Any other suggestions? I am at my end and need help. I do not have the funding to ship it to one of our "GN Speciailists."

sounds to me like a fuel pressure problem. or a bad injector. what are the Block learn #'s @ idle?

 

[tscruggs]

Fuel pressure steady at 40psi - does not fall off when engine shut down - I will post the BLMs in am - I am not at home and do not have ready access - sorry - THANKS for helping - we will get it figured out yet

 

[SloGN]

ok try this put in your stock chip and turn the fuel pressure down to 35 psi with the vac line off.


then see what the ecm does. Also one other thing to check is to see if the EGR has gotten stuck open by pushing up on the diapharm on the underside.

 

[tscruggs]

EGR has been replaced twice during this process and tested several times. I will test the ecm in the am. I have unplugged the vac line and dropped teh fuel pressure and there is no change in the way the car runs. I will report ecm issues tomorrow. THANK YOU!!!!!