[Ison bros]

Hello guys.. I have a 1995 4afe toyota corolla. First i change all of the sensors that has given to ecm diagnosis but still the car engine run poorly.. So i change the distributor and sparkplug and also the high tension wire but still it runs poorly... I found out that the egr valve is always close so i replace a new one and then it runs normal.. In the morning i tried to start the car but sadly the engine runs poorly again, its like he is limpmode.. I try to reset and pull the negative on the battery.. Still no improvement.. I tried to start but it cant start no more and the cel flash and flicker in a sec. And then the cel light never came on again even the key is in the on position.. Could it be my ecu is bad? Guys pls help.. Or should i replace another ecu?

 

[94RollaDad]

Throwing parts at the problem isn't working, eh?

Part of the issue with randomly replacing parts isn't just that it's expensive, it's also that in many cases we see the situation deteriorate when people replace an original part "assumed to not be working" with an aftermarket part that - as it turns out frequently - is of lower quality or defective right out of the box. So you can actually make the situation worse by replacing parts willy-nilly, especially if they are aftermarket. Prime example is distributor - aftermarket is flat out junk for the most part. See the sticky on top of this forum: List of confirmed distributor-at-fault issues

So, start with proper diagnostics. Work your way through and confirm what's working and move on to the next part.

As far as I can tell we have never seen a bad ECU on this forum. You may be the first one but I'd also not consider that very likely.

Based on what you describe (intermittent electrical issues on top of poorly running engine) it sounds like you might have some issues with poor wiring. Check all your ground wires, battery wires, etc.Confirm good connectivity by resistance testing them.with an ohm-meter.

Also, I'd personally replace back any original Toyota/Denso brand sensors/distributors if what you now have installed are aftermarket. Maybe with the exception of any aftermarket Denso/NSK/NGK brand parts.

 

[75aces]

Throwing parts at the problem isn't working, eh?

Part of the issue with randomly replacing parts isn't just that it's expensive, it's also that in many cases we see the situation deteriorate when people replace an original part "assumed to not be working" with an aftermarket part that - as it turns out frequently - is of lower quality or defective right out of the box. So you can actually make the situation worse by replacing parts willy-nilly, especially if they are aftermarket. Prime example is distributor - aftermarket is flat out junk for the most part. See the sticky on top of this forum: List of confirmed distributor-at-fault issues

So, start with proper diagnostics. Work your way through and confirm what's working and move on to the next part.

As far as I can tell we have never seen a bad ECU on this forum. You may be the first one but I'd also not consider that very likely.

Based on what you describe (intermittent electrical issues on top of poorly running engine) it sounds like you might have some issues with poor wiring. Check all your ground wires, battery wires, etc.Confirm good connectivity by resistance testing them.with an ohm-meter.

Also, I'd personally replace back any original Toyota/Denso brand sensors/distributors if what you now have installed are aftermarket. Maybe with the exception of any aftermarket Denso/NSK/NGK brand parts.

I agree with putting back the original parts and start your diagnosis over. There are a few threads on here where the capacitors within the ECU have leaked and caused the ECU to go bad.

Have a look inside the ECU to see if one or more of the capacitors have started or are leaking onto the PCB or other solder joints.

 

[94RollaDad]

Agree that some models have capacitor issues... But: I haven't seen any ECU capacitor issues in the 7th gen Corolla forum. Not saying they don't exist, I just don't recall seeing any here. What I have seen is threads upon threads of concerns that the ECU is bad, only to find out that... the ECU isn't bad. So as it pertains to the 7th gen models I think the ECU is a very unlikely cause of concern. Not impossible... but unlikely.

 

[DrZ]

If the CEL doesn't come on with key in ON position then check fuses. EFI fuse maybe? Then check for power to the ECU.

 

[JacRyann]

Could be as simple as vacuum-line to MAP-sensor disconnected or cracked.
Vacuum-line to FPR cracked or disconnected.
Loose hose-clamps on intake-tubing.
Partially-stuck idle-control valve.

All of these can be found by measuring vacuum at intake-manifold after throttle-body.

Fuel-pressure can be off due to bad FPR or vacuum-source. Measuring fuel-pressure in rail will confirm or deny this is issue.

Bad TPS adjustment, or bad TPS pot. Again, measuring will confirm or deny.

You must measure parts to confirm they are good or bad before replacing. Otherwise, you're replacing good parts with new good parts and nothing changes. The real problem still has not been found and you can continue to replace parts randomly for LONG time before you accidentally replace the one part that's bad. A lot of times, it's not even bad parts, but improper assembly and/or adjustment that's issue.

Real common issue is mis-adjusted distributor sensors. Or bad aftermarket distributor components such as ignition-coil and/or ignitor. These can be bad right out of box.

What brand is your distributor?