Resolved 2G Fluctuating Idle

[Fcrz23]

Need help
I have 2g 1997 Eclipse GST, which I'm experiencing bad/rough idle and sometimes the engine dies when revving the engine or even when driving to stop the RPM goes completely down and dies. The RPM needle fluctuates up and down.

Before the car experience bad idle it is running fine but since I cleaned the MAF sensor the idle changed. The MAF sensor does not indicate a CEL and it is working fine, then I suspect of the IACV since when from cold start the engine start easily and idles fine but when it is running engine temp the idles roughly especially when AC is on, I bought a new IACV and even cleaned the old one both works fine but it didn't solve the problem.

Then I notice that from cold start to engine running temp, we installed a pressure gauge on the fuel filter to check the fuel pump, at first it reads at 40psi and as time pass by at bad idle the pressure goes down even to 0psi but the pressure on my AFPR is still at proper pressure which reads to 35-40psi.

Before I start diagnosing the sensors, or other parts, is there any relation of the fuel pump why the pressure gauge reads 40psi to 0psi eventually but the AFPR remains the same pressure all through out. The fuel pressure gauge is place in the engine bay above of the fuel filter, I suspect that the engine heat may cause the gauge gives a faulty reading, or it may be the fuel pump rather than the IACV/Sensors. Is it possible that the hose connecting from the pump to the nozzle may have a leak or can't sustain the pressure?

Currently at lost where to start diagnosing the car. Any Advice or suggestions will be muchly appreciated!
Thank You

Installed parts
K&N Cone Filter
Aeromotive AFPR
Walbro 255LPH
All Stock Engine 4G63T

 

[dwb]

Here are some possible culprits causing erratic idle:
Boost leak
BISS mis-adjusted, missing, or leaking
Throttle cable too tight
TPS out of adjustment or malfunction
FIAV leaking
Vacuum lines incorrectly looped
ISC malfunction
ECU malfunction

Also check for any diagnostic codes (CEL).

 

[SixBolt_16G]

Before the car experience bad idle it is running fine but since I cleaned the MAF sensor the idle changed.

What did you use to clean the MAF? A local guy told me a long time ago to never use any type of liquid/spray on it because its a different type of MAF compared to other cars and could damage it.

 

[pauleyman]

What did you use to clean the MAF? A local guy told me a long time ago to never use any type of liquid/spray on it because its a different type of MAF compared to other cars and could damage it.

You are correct. MAF cleaner cans typically even say on them "not for karmann vortex style "

 

[Fcrz23]

Here are some possible culprits causing erratic idle:
Boost leak
BISS mis-adjusted, missing, or leaking
Throttle cable too tight
TPS out of adjustment or malfunction
FIAV leaking
Vacuum lines incorrectly looped
ISC malfunction
ECU malfunction

Also check for any diagnostic codes (CEL).

Would CEL fault codes appear even no check engine light?
What laptop software can I download for the OBD of the Eclipse? The common scanners in the Philippines cant read the ECU.

What did you use to clean the MAF? A local guy told me a long time ago to never use any type of liquid/spray on it because its a different type of MAF compared to other cars and could damage it.

I used a electric contact cleaner, Aeropack Electric Contact Cleaner

 

[pauleyman]

i used a electric contact cleaner, Aeropack Electric Contact Cleaner

Please dont do that again.

 

[chrysler kid]

If the gauge on the fuel filter shows zero psi then I would assume the car is losing fuel pressure

The idle hunting could be a symptom of something else though;

and the aftermarket fuel pressure regulator could have a bad diaphragm and be pushing fuel through it and not regulating it. If you have the stock fuel pressure regulator you could try switching back to stock to see if the fuel pressure gauge on filter still shows zero

 

[Fcrz23]

We found a pressure leak in the fuel injector seals and will also do a diaphragm replacement on the AFPR

Thank you

 

[chrysler kid]

We found a pressure leak in the fuel injector seals and will also do a diaphragm replacement on the AFPR

Thank you

Good to hear an update. Usually on a cold start I will spray brake cleaner all around the intake manifold and throttle body to see if when I spray it the car throttles up or down indicating a vacuum leak. Your post was around the time 3 other people posted all with similar issues so if you find the problem please report back to us

 

[Fcrz23]

Thanks a lot for the advices the car now runs fine, we installed a new surplus MAF sensor and checked for any leaks it now idles well and does not fluctuate,

What Brand and model of OBD2 scanner does support our 2g?