1994 Nissan Sentra High Idle Cold and Hard Start

CHRISELLINGTON

MEMBER
1994 NISSAN SENTRA
4 CYL
FWD
AUTOMATIC
89,000 MILES

I have a '94 Sentra with the 1.6 GA16DE fuel injected engine.
I've recently replaced the injectors as they were leaking, as well as the cap, rotor, plugs and plug wires, and the coolant temp sensor.
The car was running like new for a couple of weeks until suddenly it was hard to start especially after sitting for a while, along with a high idle when cold as well as lower than average fuel economy.
Once the engine reaches operating temp, or the ECM goes into closed loop, the idle seems to slow to normal.
There are no codes stored in the ECM.

5 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Check the IACV-AAC valve, throttle position sensor and fuel pressure

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Friday, June 5th, 2009 AT 12:05 AM

CHRISELLINGTON

MEMBER
3 POSTS

Thanks for the speedy reply.
I cheked everything as suggestedted and all seems well.
The problem persists.
I did clean the IACV-ACC valve and did help some with the duration of the high idle.
Sems to settle down a bit faster now, but still a bit hard to start.
Any chance the coil or cam position sensor is going bad?

Thanks again
Chris

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Saturday, June 6th, 2009 AT 1:20 PM

RASMATAZ

MECHANIC
75,992 POSTS

Test the throttle position sensor and the airflow meter.

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Sunday, June 7th, 2009 AT 10:16 AM

CHRISELLINGTON

MEMBER
3 POSTS

Thanks again
Air flow and TPS seem good with a small adjustment to the TPS.
Still no change, however, I did a second check on the fuel pressure.
While the fuel pressure is good while running, 43 PSI with the regulator disconnected, varying readings from 38-40 connected, should be 36 PSI.
The engine seems to get excited and smooth out some when the regulator is disconnected and the line plugged.
Must have a vaacum leak internally, and is bad.
Still runs a bit on the rough side though.
Also, as soon as the key is off, the pressure drops to zero in about 20-30 seconds.
Shouldn't the system hold some pressure for a while at least?

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Sunday, June 7th, 2009 AT 8:00 PM

RASMATAZ

MECHANIC
75,992 POSTS

Residual Fuel Pressure Test

When the pump is turned off or stops running, the system should hold residual pressure for several minutes (look up the specs to see how much pressure drop is allowed over a given period of time). If pressure drops quickly, the vehicle may have a leaky fuel line, a leaky fuel pump check valve, a leaky fuel pressure regulator or one or more leaky fuel injectors. Low residual fuel pressure can cause hard starting and vapor lock during hot weather