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classictech, Auto Service Technician
Category: Car
Satisfied Customers: 220
Experience:  20 years On-Job experience in troubleshooting drivetrain driveability issues
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Rechecked..tensioner..Distributor tested OK on a working car

Resolved Question:

I ahve rechecked the cam timing and put the old tensioner back and still face the same problem.
I have verified the following on a working car and definately the following units can be ruled out:

1. Distributor tested OK on a working car.
2. Fuel pressure regulator tested ok on a working car.

the car does not produce any diagnostic trouble code.

What could be the problem>also note we could not find the knock to test the knock sensor on a mazda ge with a FP engine.
Submitted: 5 years ago.
Category: Car
Expert:  classictech replied 5 years ago.

Hi from JustAnswer!

According to Mitchell documentation, the 4 cylinder Mazda 2.0 is not equipped with a knock sensor.

(If the engine is a 2.5L DOHC V6, the knock sensor is threaded into the center of the block on top, between the heads and under the intake manifold assembly. A pigtail connecter is usually visible with a wire leading down the center of the intake valley to the sensor.

To be certain that knock is causing the retard condition, simply unplug the knock sensor. If normal acceleration comes back, and you hear no pinging with regular fuel, the sensor may be oversensitive due to age or water intrusion. )

Note that the distributor CAN be inserted improperly in the engine - be certain that the rotor is pointing DIRECTLY at #1 or #4 cap contact (and not halfway between two contacts) when the timing marks are lined up. Having it any other way introduces a huge gap in the distributor for spark to jump. While watching electronic timing control, timing is ADVANCED by the computer to a setpoint at all speeds above cranking (500+), then more at hot idle and steady cruise to stabilize idle rpm and efficiency, and RETARDED upon acceleration (older distributors have a mechanical advance that reindexes timing proportional to engine speed - to a predetermined rpm and no higher). This is a normal condition. I had to read back on your previous posts to check on what the original condition was. Set "base" (unadvanced) timing with idle speed at specs or else overadvance will happen at cruise speed. For 4-Cylinder engines, more spark lead doesn't necessarily mean more power, in fact it means a choppy idle in gear and no gains in performance or economy.

If all else is fine, a significant stumble can be caused by dirt contamination inside the Mass Airflow sensor. If the sensor on your working vehicle is of the same design and part number, substituting the sensor and road testing might turn up any big differences anywhere in the normal range of driving. Also, a restricted exhaust will cause poor airflow readings as if the engine throttle weren't opening completely on acceleration.

Customer: replied 5 years ago.

I am delighted to tell you that the problem has been isolated to fuel pressure. What we did was that we fitted an in-line external fuel pump and picked the mains for the new in-line pump from the feed of the original submersible pump. The car runs perfect.

Now we have to drop the tank and find out what the problem is with the original pump or line.

How we isolated this was as follows:
we ran the car and as soon as it started to bog down we shut the negine off and removed the fuel filter.There was no fuel pressure in the line and hence we went and replaced the fuel pump with and in-line one to prove that the fuel was really the problem.

Earlier on we had also tried pinching the return line but this had no effect and hence we had thought that the fuel pressure was ok all thoroughout.

What i need to buy now is a multi pressure gauge.

Once again thanks for the advise.

Arvind Autar.
Expert:  classictech replied 5 years ago.
Go you! Glad to hear you're up and running.
classictech, Auto Service Technician
Category: Car
Satisfied Customers: 220
Experience: 20 years On-Job experience in troubleshooting drivetrain driveability issues
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