My P0300 Fix...

[JLangevin]

Ok, so I have been searching here for weeks and doing various things to my 95GST forever trying to fix the various CELs I have been getting.... the most common one was the P0300 (Random Multiple Cyclinder Misfire) and apon searching here, found that many people here have been having the same problem... the CEL would come on, the engine would sputter, and you would have to either turn the car off and on to clear it, or let the engine drop to idle... The idle drop only worked a couple times... and I found myself having to put the car in neutral and restart it on the freeway to stop the misfire...

Since the P0300 codes, I got 2 more that all happened at roughly the same time including P0400 (EGR flow malfunction) and P1400 (Manifold Pressure Sensor Malfunction)- again, unable to be fixed including new EGR, solenoids and hoses... These codes would come on silmultaniously after about 15min of driving guarenteed... BUT... the other day, I had an alternator failure and since replacing the alternator, had no more rough idle, no misfires, and NO CELs in days...

Ive put roughly 100miles on the car with no CELs when before, I could get them when driving to the store... I saved myself money from replacing the Coil packs (which was my next step, even though they tested fine)....

So, I would reccomend checking your Alternator, since even small drips from the powersteering pump can kill yours. Thats what killed mine! I hope this info helps, and I am now installing a Volt Gauge to keep an eye on things a little better.

I hope this has helped someone!

 

[akdsmer]

When an alternator starts sending too much A/C ripple voltage into the system, things like that can happen. Your voltometer isn't going to show you that though...It's always a good idea to measure the amount of A/C voltage being produced by the alternator with a meter. Reading of near or over 500mV of A/C (NOT D/C) voltage can cause PCM problems. If you suspect that it may be a problem, you can always remove the belt or feed wire and see if the symptoms disappear.

Good catch

 

[PieEyedPiper]

Just wondering if, after a little while now, you were still certain that your P0300 problem was solved by replacing the alternator.
Thanks!

 

[Artago]

Just wondering if, after a little while now, you were still certain that your P0300 problem was solved by replacing the alternator.
Thanks!

Yeah I'm in the same boat. I have p0300 and p1400 codes and same symptoms. I would also like to know if the issue was resolved with a new alternator. Thanks OP.

Also, what is the testing procedure for the alternator? Should I just follow the test procedure in the Haynes repair manual?

Thanks,

Tom

 

[jake247]

Yeah I'm in the same boat. I have p0300 and p1400 codes and same symptoms. I would also like to know if the issue was resolved with a new alternator. Thanks OP.

Also, what is the testing procedure for the alternator? Should I just follow the test procedure in the Haynes repair manual?

Thanks,

Tom

turbo timer tells raw alternator ouput.

as for testing... just go over to advanced auto parts, they'll test it for free for you. same with starters and batteries.

 

[Artago]

turbo timer tells raw alternator ouput.

as for testing... just go over to advanced auto parts, they'll test it for free for you. same with starters and batteries.

Turbo timer? Can you elaborate?

Unfortunately we don't have advanced auto parts stores here.

 

[jake247]

Turbo timer? Can you elaborate?

Unfortunately we don't have advanced auto parts stores here.

my HKS turbo timer reads how many unregulated volts the alternator is putting out.


try calling your local shops and asking them if the test alternators, otherwise try a rebuild shop somewhere and see what they say.

 

[Artago]

^^ Sounds good. Thanks for the help.