94 PCM questions

[aj_94ssei]

I think I have a PCM problem on my 94 ssei. and was wondering if I install a new one or used do I need to have it "flashed"? Also what is a good brand to go with some brands mention needing flashed some do not. thanks

[MattStrike]

Pull one from a junkyard, it's cheaper especially when you're guessing, IIRC all you have to do is swap the PROM.

What is going on that makes you suspect PCM? I found that replacing parts on guesswork leads to replacing more parts...

[aj_94ssei]

Hard cold starts sometimes cant get it to start at all, turns over hard like timing is to far adv. starts good warm and runs fine after warmed up.No service engine light.I changed ICM, a coil, plugs and wires also the starter have tested fuel press. and most sensors. I am almost positive it is spark related. also cleaned ALL grounds. thanks

[myfirstbonnie]

Have you cleaned the MAF? Try starting it with the MAF unplugged. When was the TB and idle control port cleaned?

[aj_94ssei]

I did clean MAF sensor and tried to start it with it unplugged no change.Have not messed with the idle control port how do u clean that? Should it set a code if it is bad enough to cause starting issues? thanks for the help.

[pbrktrt]

Test the temp sensor for the PCM.

[aj_94ssei]

tried to start it with temp. sensor unplugged no change. also tried a junk yard PCM no change

[1oldman]

There are a whole host of things that can cause a hard start when cold. When did you do the last major tune-up on the car? - BC

[aj_94ssei]

last tune up was about 2 months ago along with a can of seafoam.

thanks

[1oldman]

I'm no expert, but the only other thing I can think of off hand is that the valves might need to be ground. Did you do a compression check? - BC

[aj_94ssei]

No compression check yet. but this seems to be spark related to me, when I can get it to run it will miss and run very poorly until it gets up to operating temp. gradually getting better as it warms up. I seems like it should crank easier rather than harder if it had low comp. A side note if I disable spark it cranks over like it should. Thanks

[01bonneSC]

What were your fuel pressures at *key on*, crank, and running?

[1oldman]

No compression check yet. but this seems to be spark related to me, when I can get it to run it will miss and run very poorly until it gets up to operating temp. gradually getting better as it warms up. I seems like it should crank easier rather than harder if it had low comp. A side note if I disable spark it cranks over like it should. Thanks

Sure sounds to me like you have two spark plug wires reversed - BC

[aj_94ssei]

fuel press. are 42psi key on, running 38psi. Spark plugs in wrong location is what it acts like but this problem started gradually just before I did the tune up recently. thanks for the help.

[1oldman]

Did you find the specs on the plug wire resistance and ohm out the plug wires? - BC

[MattStrike]

The next thing to check would be the crank and cam position sensors, but:

What all did you do in your last tune-up? A weak spark could cause your symptoms, I've found that the last thing you worked on is usually the culprit behind a new problem. I'd be checking all 3 of your coils for strong spark again.

My method can get you shocked, just a warning, so don't attempt this without rubber gloves and don't touch anything on the car at all. But it is easier than using an ohm-meter and checking the resistance of the primary and secondary coils. Use a plastic plier-like (make-shift or other) device to disconnect a wire from the ignition coil. The spark coming off it must be very violent (loud) and a bright blue with a steady, fast pace rhythm. If it's yellow, weak, or doesn't have an even rhythm (especially if any other single coil does) then you immediately know that the coil is bad.
I have had bad luck with the cheap Autozoo (and similar other stores) ignition coils, usually failing within a few weeks. Good quality coils are OEM (junkyard pull...), I've had good luck with Borg-Warner and Accel.

[1oldman]

I've found that the last thing you worked on is usually the culprit behind a new problem.

Matt is correct, at least in my case anyway. - BC

[aj_94ssei]

I double checked plug wire positions. positions are correct. I tested crank and cam sensors... both tested good. i have strong spark, it just seems to be at the wrong time. I'm not sure about plug wire resistance, but I had the problem before I changed the plug wires and it continued when I put the new wires on. So i don't think that is the culprit.. but it won't hurt to test.

thanks

[MattStrike]

I tested crank and cam sensors... both tested good.

How did you test them?


The next thing to check is compression. Should be 100-120 while cranking (unplug fuel injectors so engine doesn't start)

[aj_94ssei]

Tested with a volt meter at ICM when turning engine over by hand, since they are just Hal-effect switches.As hard as it turns over cold do you think it could be low comp.? Plug wires all test good. Thanks for the help.