Dougs 90

Now I am having issues, spat a code 42, now car wont start and no codes, I did pull off the distributor wires, 2 had corrosion, so I cleaned them and I am waiting for new set to get here. My question is where to go from here, and do I need a new prom or ECM? How do I check these?

Thanks
Doug

Wadoka

Doug, think about ordering the factory GM service manual from Helminc.com.

Other than that, hope someone that already has an '89 - 90 -91 service manual reads your thread...

~Matt

TTT

BIG K

Me too! I'm interested in what the others have to say. I'm having code 42 problems too. Know you have me afraid to do anything else :eek:
Dougs 90, let us know what you find out

SunCr

Well, that's the diagnostic aid in the Shop Manual: Memcal not fully seated in the ECM, but if you've never removed the memcal, they rarely work loose. The first thing to check is the timing connector wire - tan/blk - the one you disconnect to check base timing. When it's disconnected, a code 42 is set and the check engine light comes on until its reconnected, but the code should stay in history. Make sure this wire hasn't opened or shorted too - it's fairly close to the driver's side header and if it accidently got moved so that it was close or making contact with the header, well you know what happened. Also, if you recently had a smog check and the tech checked the timing, make sure he/she didn't forget to reconnect it. (Or you could be like me and simply forgot you disconnected it the last time you checked the timing). If it isn't the black/tan wire & the memcal is seated, then it's either the ignition module, the connection at the module (4 pin at the distributor - do make sure it's fully seated), any of the other wires in the module harness, or the ECM.

Dougs 90

The tan and black wire is connected, I will probe it today. All of my wiring has been loomed to keep it together and hopefully avoid thing like hitting the headers etc. The code 42 was for the loose prom I believe (I have no codes now). Problem is, now my car cranks, but doesn't start. I was curious if there is a way to ensure that my prom didn't fry while it was jiggling around in the ecm. I can get a refurb ecm at autozone, but what do I do if I need a new prom? I am going to check the distributor and the ignition module today. Hopefully it is something simple.

Thanks
Doug

ps: The Helms Manual is on the way!!!

:banghead: :banghead: :banghead:


[Modified by Dougs 90, 8:03 AM 4/25/2003]

SunCr

How do you know it was loose? Did you remove it & reconnect it? Logically, if you had a 42 and it won't start now, suspect the module. The ECM works because it gave you the code. The black/tan timing connector wire, even if open, would not keep it from starting.

BIG K

Dougs 90. Did you get a code 51? I would be curious about it being the mem-cal, because it's specific to that.
You may want to concider the GM shop manual. I'm not sure about the sourse listed above, but I got mine used for not much more than what I paid for my Haynes. Wish I could remember where I found mine. When I do I will Pass I on.


[Modified by BIG K, 11:27 AM 4/25/2003]

65Z01

I agreee, code 42 is the dist code: the MemCal related codes are:
51=PROM failure, wrong PROM or installation problem
52=CALPAK missing

So if the blk/tan wire is ok and code 42 recurs, look for a short in the ignition wiring.

Dougs 90

I started with a rough idle, hard start, loss of speedo(it just displayed 0), and then I got a bunch of codes.
The main code was a Code 41 Loss of ECM serial Data. So I went to the source first and checked the ECM wires and connectores visually (including the tan/black one), they appeared okay. I then removed and opened the ECM, there I found the prom wasn't snapped in the retainers(kinda like ram on a motherboard). I pushed the prom back into the socket until it clicked. When I reconnected the ECM (12277727) I also ground the head off of a bolt to replace one of the bolts that was missing to secure it better to the bracket.
Car ran great for about 30 minutes, then idle became extremely rough, surged with acceleration, idle was bouncing around from almost 0 to 1000.
I also got a code 42 for the EST Circuit. When I finally got home (I was wondering), I first checked the plug wires at the distributor, I found the front 2 were gunky, the others looked fine. I cleaned the distributor posts with a brass brush, and took a bore brush to the wire caps(gently). When I hooked everything back up, I reset the codes. Now the engine cranks, but wont start. I double checked the wires at the distributor ( mixed 2 up ), switched them back right and stopped there as it was getting dark. Today was nasty/rainy and long, so I haven't had a chance to get back under the hood yet.
Question 1:
Is it possible that my either my ECM and/or Prom got fried when the prom was bouncing in and out of its socket?
Question 2:
Is there a way to verify this before I replace the ECM? The local Autozone has one in stock for $89, but it almost looks as if it was just shot over with a can of spray paint and called remanufactured.
Question 3:
How do I check the prom? Where do I get a new one? AutoZone had no listing for it.
I have a new set of plug wires to go in, plan on checking the plugs/spark, fuel pressure, and the ignition circuit tomorrow. I also suspect the fuel filter as it was in the shop and they ran it almost out of gas. Maybe some junk got into the fuel filter from the tank. New fuel filter is $8.99 at AutoZone. Any more ideas or pointers as to where to go with this or what to check? I am a newbie mechanic and could use all of the help I can get here. My Helms came in today, thank goodness!!! Just in the nick of time!

Anyway, Thanks alot to everyone and will keep you posted when I get her running again.

:banghead: Doug :banghead:
dreaming of :auto:


[Modified by Dougs 90, 12:25 AM 4/26/2003]

65Z01

The best way to check the ECM and PROM is with a scan tool; it might also show up the source of the problem.

That wild idle could be due to IAC or MAF problems though.

bill mcdonald

I have a 90 too.
I also had my prom fall out before, no damage suffered. When it came out my car shut it self off.

Have you looked in the ECM again to see if the prom fell out again?

Second, I had a hood slamming into ECM mishap thats to a buddy, and now I have an autozone ECM, it works great.

SunCr

Depending on what wires you hooked up backwards you could have fried the module or the coil. To check the module, disconnect the ECM and then measure ohms on the white wire back to the module. Should be less than 1000 ohms which verifies the ground path. To check the coil, remove a plug and ground it against the block. Then have someone crank the engine while you check for spark.

Dougs 90

1. I have spark and fuel to all 8 cylinders. My ignition control module(the 7 pin module in the distributor tests okay, AutoZone checked it several times)

2. I have Code C12 in Module One CCM OK, and nothing but --- in module 4.7.

3. I regapped the plugs and put on a new distributor cap and rotor while I was in there, and the coil seemed okay, I had 8k-9k ohms across it. and continuity on the tapped side.

4. I can get the car to start now, but still wont idle for crap. I have .52 volts at TPS while closed and it goes up to 4.69 or so if I open it wide open.

5. I believe I have leaky injectors, Fuel pressure test spiked to 50 psi, and dropped to 42 psi immediately. Then I could watch it as it bled off fairly quickly. There are no external leaks at the fuel rails, ..... never really worked with fuel areas before. Could this be the culprit?

6. I bought the car a couple of months ago and the previous owner had reflashed the PROM. Car had all emmisions removed, (which I had to replace to pass inspection, 160 degree thermostat gutted cats etc.). Apparently it wasn't pushed all of the way in, the cnx on the side weren't engaged.

So I don't know where to go now other than to limp over to the dealer and get hosed. ....... any suggestions?

Thanks to all of you for your assistance,
Doug


[Modified by Dougs 90, 10:50 PM 4/26/2003]

SunCr

Fuel pressure should be about 42, key on, engine off & hold steady. At idle, about 3 psi less, and holding. If it's dropping to zero, suspect an open injector. Pull plugs until you find the one that is soaked in fuel. Do not continue to run it if an injector is stuck open and be sure to siphon the fuel out of the cylinder or turn the motor over by hand until the piston for the problem cylinder is at TDC which will get most of the fuel out through the open plug hole. Watch for coolant too just in case the head gasket is shot.

HighHopes85

Doug-You mentioned the EST module tested good. If you had your module benchtested, then listen up ;)

I bought a Wells brand pickup coil. Installed it, car ran like crap. Took me a while to figure out what happened because I did a few things at once.

Discouraged, I broke the connector on the pickup coil and reversed the leads (IOW, I hooked it up to what would be considered incorrect). Car ran like a champ.

I would normally pass this off as dumb luck, but I helped a buddy who installed GM TBI on his Jeep. Had the exact same problem with the Wells brand pickup coil.

If you had the EST module out, it could be this simple.

It is really easy to tell with a dial back timing light, because you will be able to see the timing retard when it is supposed to advance.

Dougs 90

The problem was before I removed the module. The cnx looked cruddy so I did clean it with alcohol and a soft wire brush. The module is a GM one so I don't see switching the connector on it helping anything. I am taking it in tomorrow. I do think I have fuel in my oil, I dont think that is a good thing. Anyway, I will let them hook it up and maybe they find something out, or verify that the injectors are the problem. Not real confident in my beginning mechanical abilities and dont wanna screw it up worse!

Thanks
Doug

Dougs 90

Monday AM
No Start again
Towed To Shop

Parts Replaced/Bad
Fuel Pump
Fuel Filter (Just so happens I was gonna put one in, just didn't get a chance)

Still hard to start, but starting
Mechanic says new plugs, they were questionable, I cleaned and regapped em
Thats all for now, at least the computer and prom seem to be okay so far

Doug