Bad Ecu?

[BpuVR4]

So my VR4 stalled yesterday and couldn't start again. It was running fine, then stalled. Cranked just fine, smelled fuel but had to leave her to go to a long night of work. Had to push her into a parking spot and today, I tried to run codes with a multimeter. The needle just oscillated back and forth the whole time at a constant rate. As far as I know this means bad ecu, correct?

Some observations:

-Monday I ran codes, and one of the two codes was 44 and thought it was odd because i thought my ignition system was operating ok. Opened her up and snapped some pics for you geniuses in hopes someone can shed some advice or observations as it looks ok to me:

-thought my interior smelled a little odd last week but thought it was due to cracking the windows during rain to keep windows from fogging.

-when it stalled there was no CEL at all. my autometer boost gauge needle sits at 0 with key on, and the factory boost light is at the middle too.

I know the only real way to see if the ecu is bad is to swap with a known good one or put my bad ecu into a good running car, but obviously this is not very convenient for me.














any tips before i go buy a used eprom ecu? hopefully i get one that is from a vr4 and will slide into the original spot unlike the one in there now

 

[StreetThisVR4]

Looks like one or more capacitors has been leaking, and thatll do it.

When ECUs go bad in these cars it smells like burnt rotten fish, its nasty.

 

[toybreaker]

^^^ those are replacement caps.

It is of paramount importance that the board is thoroughly cleaned to remove all traces of electrolyte before new caps are installed.

... otherwise the residual boric acid and ammonia salts will continue to eat the traces, causing troubles years down the road.



What are the mods on your car?

That's a non e-prom ecu, so replacing it with an e-prom will allow you to get a chip/link etc to get it dialed in


A test by substitution is probably your best bet to quickly troubleshoot your issue.

... looks like you just need a non e-prom for this task.

 

[toybreaker]

Does the tach needle "bounce" while you're cranking it over?

... may have a bad cas/ptu /ubbthreads/images/graemlins/dunno.gif

 

[BpuVR4]

Quoting toybreaker:
^^^ those are replacement caps.

It is of paramount importance that the board is thoroughly cleaned to remove all traces of electrolyte before new caps are installed.

... otherwise the residual boric acid and ammonia salts will continue to eat the traces, causing troubles years down the road.



What are the mods on your car?

That's a non e-prom ecu, so replacing it with an e-prom will allow you to get a chip/link etc to get it dialed in


A test by substitution is probably your best bet to quickly troubleshoot your issue.

... looks like you just need a non e-prom for this task.



so if my non eprom ecu is bad, a straight swap with an eprom ecu is not the right move?

my mods are 272 cams, evo 3 16g, smim, 560cc injectors etc.

i don't remember if the tach needle bouncing but it may have done it slightly.

 

[BpuVR4]

was able to the see the full table of ecu code checks, didn't see that short pulses alone meant normal state- thought the short pulses= constant pulses...back to the drawing board tomorrow.

 

[toybreaker]

Quoting MoMoVR4:


so if my non eprom ecu is bad, a straight swap with an eprom ecu is not the right move?


my mods are 272 cams, evo 3 16g, smim, 560cc injectors etc.

i don't remember if the tach needle bouncing but it may have done it slightly.



either ecu will work fine for test purposes

... but at some point you're going to have to compensate for your larger injectors if you want it to run correctly/take advantage of that turbo.

That will require either an e-prom ecu with a custom chip or some other means of tuning.

 

[BpuVR4]

sorry, i have an safc also, for some reason didn't mention that. gonna go check the car again in a few hours my troubleshooting abilities as well as reading comprehension are very rusty apparently.

 

[BpuVR4]

thinking again the ecu may be the reason for the no start.

-was getting no fuel and no spark.
-had my friend(great at electrical) test the cps and it checked out ok
-had him check out the mpi relay under the glove box. said that pin 7 was open, so jumped it and then heard the fuel pump sound and felt my fuel line stiffen up. got spark as well evidenced by spark witnessed on plug.

-car still wouldn't start, as even though i have spark, i don't see fuel being dumped in the cylinder while cranking.

so once again, is this something a bad ecu can do? had the multimeter hooked up for code checking, and it just oscillated back and forth so i take it now as no codes being thrown which is even more concerning cause it did this even with the cps unplugged.

 

[91bgvr4]

i had a similar issue and even though it appeard to be not burnt it was the Mpi fuse under the hood i still could hear the pump and mpi clicking but had no spark , also had NO check engine light (thus making me think ECU) But after i pulled the fuse and took the clear cap off the fuse i seen it was burnt. Replaced and it started up just fine .

 

[big_d]

I still don't understand why people can't replace capacitors and clean the ecu properly so it doesnt look like a hackjob. When you turn to the key to the "on" position, see if pin 8 of the MPI relay is pulled to ground. If you are seeing this happen, the ECU will next try to boot. Notice the CEL turn on for about 5 seconds then turn off (you'll also see the stock boost gauge read 0). To make triggering the fuel pump easy, I would pull the CAS out and give it a spin. The ECU thinks you are cranking the engine, and you should hear the pump kick on and injectors fire as you keep turning.

 

[G]

Very good 2nd post^^ He's right.

 

[BpuVR4]

by the way gentlemen...my no start problem ultimately came down to the fuel pump rewire fuse that was blown. I didn't realize the fuse was hidden behind trunk trim, so it took some time to figure it out. Frustration got the better of me on this one. Month later, i also replaced the fuel pump as well.

all in all: swapped ecu's, cas, mpi relay before i found the issue. car was down for 7 days without a proper diagnosis...longest ever and I was pretty bitter.