Running rich and misfire

Red088
Learner Driver
Posts: 2
Joined: Mon Dec 18, 2017 8:48 am

Running rich and misfire

Postby Red088 » Mon Dec 18, 2017 9:30 am

Hi,

New here and new to Subaru!

I have purchased a 91 Legacy GT with an EJ20 fitted from an 97 GC8 WRX.

I bought the car not running with the intention to fix and drive for some fun

After a couple hours work I discovered a completely blocked muffler and fouled plugs as the culprit for it not running.

Once fixed it ran and idled ok - had a misfire under load though.
After about 15 minutes of driving the misfire was so bad I could barely drive.
I have also lost idle.

When I start the engine now it will run at 1200 rpm for 5-8 seconds smoothly and then start to break down 1 cylinder at a time until it eventually stalls. If I rev the engine it will rev with a misfire and black smoke from the exhaust.

Since then I have replaced plugs, coils, MAF & MAP. Checked timing too.
There are no leaks in the intake.
I have good fuel pressure 45psi on the FPR
Won’t start without the TPS plugged in so I assume it’s not that..
It’s has a standard computer and I believe it cannot be flash tuned so I assume it’s not that.
Injectors are standard and I have lifted the rails to see that they are all working and possibly not stuck open, all look ok.
If I unplug the 02 sensor it makes no difference??
If I unplug the temp sender for ECU the fans cut in so I assume it’s working ok.
I plug in the flash code plugs and I get no faults. Unless I unplug something important.

I feel like something is telling the ECU to dump in fuel and I don’t know what!

I could really use some experienced advise as I am all out of ideas!

Cheers


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mv75
WRX STi Driver
Posts: 855
Joined: Sat Dec 27, 2014 9:26 pm
Location: Brisbane Northside.

Re: Running rich and misfire

Postby mv75 » Mon Dec 18, 2017 7:22 pm

Sounds like it's running rich as F. Get a wideband o2 sensor in there, or at least get some sort of monitoring. FreeSSM might work, I'm not sure. Is it running the 97 wrx ecu?

Difference when unplugging maf?

Are the injectors really standard?

Check the crank case ventilation valve that it's working.

Check the oil condition.

Compression test?

Is there any silly chip resistor thing on the ecu or the maf that's causing it to force run rich?

Red088
Learner Driver
Posts: 2
Joined: Mon Dec 18, 2017 8:48 am

Re: Running rich and misfire

Postby Red088 » Wed Dec 27, 2017 12:32 pm

Thanks for the reply - problem now solved.

The FPR is in Kg/Cm3 not KPA as I had suspected so turns out some peanut had wound the fuel pressure up to 120+ PSI, probably when the previous owner was trying to get it running.

Now the fuel pressure is set I have changed the plugs again and it’s running perfect!

Thanks


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mv75
WRX STi Driver
Posts: 855
Joined: Sat Dec 27, 2014 9:26 pm
Location: Brisbane Northside.

Re: Running rich and misfire

Postby mv75 » Wed Dec 27, 2017 3:33 pm

Dang. I thought you added a pressure gauge to the line to test it, not had an aftermarket one. Good to know you tracked it down.

Change the oil again too, probably contaminated pretty bad.

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