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Amedee
Amedee, ASE Master Tech
Category: Car
Satisfied Customers: 21843
Experience:  ASE Master Tech advanced level specialist. Wisconsin certified emissions state inspector
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I have a 1995 Geo Tracker 4WD engine serial # XXXXX 6 for

Customer Question

I have a 1995 Geo Tracker 4WD engine serial # XXXXX 6 for engine type. It's fuel injected 16 valve with 150,00 miles. The problem is that has erratic idling and stalling, poor gas mileage, and a surge at driving speeds..It is a 16 valve motor and 5 speed. When the motor is cold the idle is the same as when it is hot around 700 rpm. When driving cold, as well hot it has a surge at low speed as well as cruising speed. This continues even at operating temp. When stopping it may idle at 700 rpm, then again the idle may drop to around 300 and gradually go back up to 700 rpm. A times it may stall, but, it starts quickly. It has no problem while hard accelerating
The coolant temp. is 185 degrees when hot.

Repairs that were made:
valve timing belt was replaced before this problem and ran good afterwords

replacement of fuel filter
O2 sensor
converter replaced
coolant temp. sensor
plugs @ .028
cap, rotor, wires

Timing set at 5 degrees w/jumper
compression 165# XXXXX in all cylinders
egr removed and cleaned
fuel pressure @ 40# XXXXX key on, 35# XXXXX
no codes showing, light on with key, goes off when started
checked TPS and reset to factory specs as well as the ISC, it was removed and tested and showed no problems.
It is a 16 valve motor and 5 speed. When the motor is cold the idle is the same as when it is hot around 700 rpm. When driving cold, as well hot it has a surge at low speed as well as cruising speed. This continues even at operating temp. When stopping it may idle at 700 rpm, then again the idle may drop to around 300 and gradually go back up to 700 rpm. A times it may stall, but, it starts quickly.
The coolant temp. is 185 degrees when hot.
Submitted: 1 year ago.
Category: Car
Expert:  Josie-Mod replied 1 year ago.
Hi, I'm a Moderator for this topic. I've been working hard to find a professional to assist you right away, but sometimes finding the right professional can take a little longer than expected.


I wonder whether you're ok with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, please let me know and I will cancel this question for you. Thank you!
Customer: replied 1 year ago.

Yes, I will wait for your answer

Expert:  Josie-Mod replied 1 year ago.
Thank you for your continued patience. We will continue the search for a professional for you.
Expert:  Amedee replied 1 year ago.
Hello and welcome to Just Answer!

My name is Amedee and I can assist you with your question.

If this is a VIN 6 engine, then you could have a bad fuel pressure regulator causing this condition. The diaphragm can rupture inside the fuel pressure regulator and cause fuel to leak into the vacuum hose/line and go into the engine and cause this rough idling condition. I would start by checking for fuel in the vacuum hose/line going to the regulator. All you need to do is remove the vacuum hose/line from the regulator. If there is any fuel present, the fuel pressure regulator is bad and will need to be replaced. Again, this is only if the 8th VIN number is a 6. Here is a picture of the fuel pressure regulator.

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If this checks out ok, then the next step is to check for air/vacuum leaks under the hood and check the MASS AIR FLOW sensor located near the air filter. Also, be sure that the air snorkel from the mass air flow sensor to the throttle body is not ripped or cracked in anyway. Be sure both sides are secured nice and tight. Here is a picture of the mass air flow sensor.

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Customer: replied 1 year ago.

I have previously done the two items of concern that you mentioned.

Expert:  Amedee replied 1 year ago.
Excellent!

Now we check for vacuum leaks and check the TPS sensor next.
Customer: replied 1 year ago.

Tps was tested and met all factory specs with feeler gauges at different thickness and ohm meter.
Can't find any vacuum leaks all hoses are in great shape with no deterioration. All hoses tight on lines and fittings.

Expert:  Amedee replied 1 year ago.
Excellent!

Please provide me with the TPS readings.

Thank you

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