$750 L98

i have a 1988 formula 350, the other day it ran fine, then wouldnt start the other day, it just cranks, and will fire, and you can rev the engine while the starter is engaging, but once you let the key flip back into on position it will not stay running and either dies, or stumbles,dies,stumbles,dies and then give up completley. I know it must be ignition related, as it will rev, meaning it gets plenty of fuel and air, meaning the relays must be intact. However i think it could be the ignition module, as i think it takes over for firing after the starter dissengages, i found this trouble code, but im not sure if mine puts it out since i do not own a scanner, but it sounds similar to my situation.

any help would be greatly appreciated, thansk guys

Trouble Code 42 indicates that there may be a malfunction in the Electronic Spark Timing (EST) system.

During cranking, the timing is controlled by the ignition module while the ECM monitors the engine speed. When the engine speed exceeds 400 RPM, the ECM sends a BYPASS signal to the ignition module which switches the timing to ECM control. The ECM calculates what the timing should be then "tells" the ignition module via the EST circuit.

An open or ground in the EST circuit will stall the engine and set a Code 42. The engine can be re-started but it will run on ignition module timing.

The conditions for setting this code are:

* System in BYPASS mode but the ignition module is still controlling timing

- or -

* Engine speed > 600 RPM with no EST pulses (ECM controlled timing) going to the ignition module for 200 msec.


Typical causes for this code include:

1) BYPASS line is open or grounded
2) EST line is open or grounded
3) PROM or CALPACK not seated properly in the ECM
4) Poor connections between ignition module and ECM
5) Poor routing of EST harness and/or poor quality ignition wires (EMI induced electrical noise)
6) Faulty or incorrect ignition module
7) Faulty ECM

1987formula

first thing to check is the fuel pressure and spark so you can rule those out.Is it tpi if it is it could be your ecm or it could be the module. Tpi cars are know for the ecm's going bad.

$750 L98

fuel pressure is fine, and spark is awsome, it will run just fine, and i can rev the engine while cranking but when i let the key flip back to on position it just dies, i know its not fuel/spark/air, thats why im confuesed, must be module or ecm.

1987formula

that sounds more like its a ecm than a module.

$750 L98

well ill take my module to autozone tomorow, if that doesnt work new ecm goes in.

1987formula

Or you could try napa I know that they used to be able to test modules but thats been a while well good luck .

jonah88

my 88 T/A GTA is doing like the exact same thing, cranks over, and immeadiatly dies, almost sound like the alternator, but mine isnt, just changed it, and i replaced the fuel filter/TPS/ECM and the PROM chip, i have a stock prom and a hypertech prom, and it still wont do crap. and just before it died it was reading a sensor 36, Burnoff to the MAss Airflow sensor, could it be the burnoff relay? and if so where exactly is that located again? Any help would be greatly appriaciated, and i didnt check spark or fuel pressure yet, and last summer i just replaced plugs/wires/coil/cap/and rotor. SOOO PLEASE HELP! thanks

$750 L98

well if it starts but dies like it cant idle, i would suggest checking the idle air control valve, to be safe im goin to do the same thing, The ECM commands are mostly bypassed if im correct while cranking. But as soon as you let that key flip back to ON position and let the ECM take control the IAC valve may be stuck, and if so it will try to idle, but since no air can be ELECtRONICLY calculated with a stuck valve it may just simply strangle the car until it dies because of a ECM miss calculation of air actually entering the intake and it trying to correct that problem. Atleast that is my logic, Ill try it tomorow after work and keep you updated bro, im pretty sure that should do it for both of us, either that or our EGR equipment possibly. From what you are saying your electronics seem to be fine and new so i wouldnt suspect those, instead look to those tiny parts like EGR and IAC that will control small but vital parts of the ignition and idle process.

$750 L98

as for your relays goin bad i doubt it, if it were a bad relay you may have a bad wire, and not a relay, the relays seem pretty simple on mine and durable. Now if it will fire while cranking you have air/fuel/spark so those are out of the question, hell i can even rev my engine as long as i hold the key so that the starter is still engaging. That is a daring test but it proved to me that i have no actual air/fuel/spark problems, as the car WILL run without the MAF, and should run without the burnoff relay. Dissconecct the relays and try your luck, if it runs you have a bad relay, if it will still not run, then i would say you have a bad idle air valve or something a bit more complicated such as my issue, get back to me on the specifics.

jonah88

ok ill check the IAC and EGR, would be nice :P. where is the IAC on our cars? i know some just not a smuch as i would like to, i know where the burnoff relay/power relay are, so no worries there, ill check them tomarrow. thanks for your help, i hope we can help each other neough to het em working. and yea if i rev while starting, it kicks over, and if i hold it so its at like 700 rpm's, it will stay running, and idles, but as soon as i let off the pedal, it dies, and it seems ilke its squirting a LOT of fuel and flooding itself, not sure though, sure smells that way.

$750 L98

i have that exact problem, so i think i can definatly help your trouble shoot it lol, the iac valve is right below the TPS or about there, you can see the little connector on it, if you have AIM send a message to elementaltoad and ill get a pic of my engine and what i do when i work on it so i can give you visual help. I can usually hold the pedal down and let it go and it will idle at that position but i think the IAC is too clogged to be able to sense the amount of air that is actually there, that or i perhaps shorted mine out, ill get back to you on that. good luck.

3.8TransAM

Ohm the injectors too.

Should be near 17 ohm anything unde 12 ohm is no longer serviceable. Anything with like 1 or .3 ohm could be shorting out the ecm drivers and taking out your injection with it..

Pickup coil, it should read OL tfrom each wire to the case. should ohm out from 450-900ohm for the actual coil(wires to each other) and should generate .35 to.65 volt AC when cranked.

Off the top of my head, your not giving us a lot of hard evdience to go on

later
Jeremy

$750 L98

found my problem, i checked for new parts, and found some all new but the IAC, and with 140k on the motor and as much crap and sludge in that engine as there is, i decided to tap on the IAC motor and hook it back up then crank it. Well guess what, it runs, i cant give it too much gas or it will backfire. It seems that my ECM leans out the mixture as it overheated very quickly, and the radiator works. So my uneducated guess it that my IAC is stuck, nearly shut, and the ECM leans it out to compensate, but superheats when i give it pedal, and bacfires heating everything up? anyway somone get back to me on it. It will randomly run, but always cranks, ignition is ruled out as well as fuel pressure, oil pressure, and spark, new distributer, TPS, wires, and plugs, MAF is also good. I'm replacing the IAC tomrow just for ****s and giggles, and buying a book then rerouting wiring. I'll keep you guys posted, thanks a ton for all the help, i couldnt narrow this down without the suggestions you guys give me.

peace

TexasSilhouette

iTrader: (4)

Curious $750 L98, you said that fuel pressure was ok, what was it when you quit cranking?

$750 L98

i figured out the problem, either a short or defective EST module, it would almost 180 the timing it felt like and wouldnt fire right, so i pulled the wire to it and it runs like a charm. Gives me the code 42 but that will be fixed soon enough.

Bens3rdGen

Sorry if this is a dumb question, is the EST and Ignition module the same, I thought so...

Trickster

No, they're not the same.

Bens3rdGen

Where is the EST module located?

Trickster

It would be called the Electronic Spark Control module and it is located on the driver side firewall behind the relays located there.

$750 L98

so i either have a grounded wire in the ESC or its defective?

firebird310

YOU BOTH NEED TO CHECK YOUR EGR AND SOLENOID