Gtir Missfire

Hi All,

So I took a Gtir out for a spin today

The gearbox and clutch was spot on, and it has a quick shifter fitted which made changes lovely.

No nasty knocks or rattles and the engine started up on the button and sounded spot on.

Two issues I noticed, the engine check light was on and the oil temp gauge wasn't working, would the oil temp gauge not working cause the check light?

Also it had a misfire if you planted the throttle above about 3k rpm, If you built the revs and boost up slowly with 1/2 throttle then it revved clean all the way.

So initially Im thinking it could be a boost leak from somewhere causing the missing...
Then I thought the plugs and plug gaps might need checking,
Then HT leads and ignition timing,
After that MAF sensor could be on the way out

Has anyone had any experience like this / have i missed anything that might also need checking / changing?

Cheers

Do a fault code check first.
Then check all vacuum hoses and ic hoses.
Then check afm plug and maybe take it apart and clean with electrical spray.
Check the dizzy cap and rotor arm.
Leads could be the issue and so could the plugs as you say.
Check all obvious before buying and replacing...

Oil temp gauge is probably the spade connector on the sender either loose or wire broken, easy fix but not great access, its next to the oil pressure sender.

As above do fault code check as may determine cause of misfire.

Usual suspects as mentioned, leads, plugs, dizzy cap, rotor arm, coil, ignition amplifier (coil transistor)

Could also be a faulty fuel pump or if the boost is high and it's still on a standard fuel pump.

I would say plugs gaps to big blowing spark or something causing weak spark

Had the same problem with mine, all it needed was some bcr8es plugs and the missfire had gone.

I would also look at a HT circuit misfire, leads and plugs would be good starting point then cap/rotor, is it missing on one or two cylinders ?
Anything over say half throttle with one or maybe two cylinders misfiring is usually HT circuit.

I'd check ht leads while your there get the owner to put new plugs in for what it's worth and check condition of the old plugs and as your there there do a compression test to, but I'm sure the owner is aware of the missfire and started to look into it??

Thanks for all your help, Would you suggest attacking the oil temp sender wire from underneath? does that make it a bit easier to get to?

Did a fault code check and it came back all clear,

Going to have a look at the plugs next and HT leads fingers crossed its that!


Cheers

Would say there is more than one issue with this car
Oil temp is an easy one to remedy

As for engine check light staying on that could possibly be a wiring issue or ecu fault.
Other thing I would suspect would be a dodgy afm if mis firing over 3000rpm it as others have suggested could also be one of many other faults so normal process of elimination

Had a similar issue with one of my other cars produced misfire above 3k turned out to my cam position sensor not on an r but just something that you may be able to check aswell.
Good luck.

So the issues continues.... slightly....

The pulsar was one I was looking to buy and now have as the compression check came back all good!

I've now changed the plugs, dizzy cap, rotor arm, ht leads, cleaned and re-earthed the afm, and checked the tps voltage.

The engine light still stays on on start up, but not all the time!
When it does stay on the car seems to run rich, but when it goes out it runs like a dream.

Apart from some dodgy wiring/connector somewhere is there anything I might be missing now that could cause this?

The red LED on the ECU stays on when the engine light on the dash stays on, What does the screw on the ECU do? Am I right in thinking this adjustes the idle mixture / speed? When I turn it, it doesnt seem to change anything!

When it's turned all the way clockwise and clicks should this put the ecu into diagnostic mode?

Any Help much appreciated.

Cheers

I wouldnt fuss with that screw use the paper clip method to do a diagnostic check to see what is going on. Could be in some sort of limp mode or issue with det sensor, I had a very mild issue with mine and caused funny things.

For info on the screw I have copied this as its the most logical explanation.

On most other Nissan ECU's of similar age its used to set the diagnostic mode, the same as using a paperclip on the connector trick.

I think I'd probably go with 'diagnostic mode' to be honest as its more believable.

This is copied from another site, not Pulsar specific though, might be of some interest -

"Switch on the ignition, turn the selector screw clockwise all the way, and watch the LEDs. They'll flash once, then pause, twice then pause, and on up to five times to indicate the five diagnostic modes. When you see the number of the mode you want, turn the screw counter-clockwise. 
*Modes & codes

Mode 1 is called the "Exhaust Gas Sensor Monitor" because it informs you about oxygen sensor activity. With the engine running and fully warmed up, the green LED should blink, going on when the sensor sends a lean signal and off when it sends a rich signal. You should see 5-10 flashes every 10 seconds. If the LED is on more than it's off, there's a lean condition, and vice versa. Sluggish blinking should make you suspect a fouled sensor.

Mode 2, the Mixture Ratio Feedback Control Monitor, lets you know whether or not the air/fuel mixture is being controlled within the proper range. If the red and green LED's flash pretty much simultaneously with the engine running, mix control is okay. If the red LED is off more often than the green one, richness is indicated. If the red is on more than its mate, think lean.

Mode 3 has the name "Self-Diagnostic," and it's more what you're used to on other vehicles because it yields fault codes, both hard and intermittent, which are communicated to you by means of the flashing of both LED's. The red one gives the first digit, and the green one the second digit. For instance, if the red flashes twice, then the green flashes once, you've got a Code 21.

Get the engine up to normal temp, preferably by driving the car for 10 minutes, then pull the codes. In the case of a no-start, crank the engine for at least two seconds. If you see 55, all is well (in older models, 44 meant the same thing). Be sure to write down any other codes because they'll be erased when you go on to Mode 4, which means you will have lost any help on intermittents. Normally, codes are retained in memory for fifty starts.

Mode 4, called the "Switches On/Off Diagnostic Mode," checks the function of the switches that serve as inputs to the ECU, specifically those for ignition key start position, idle, and vehicle speed. For the first two, the red LED will go on or off when switch status is changed. In other words, with the ignition on, the red light should illuminate both when you step on the gas pedal and when you turn the key to start. If not, check the appropriate circuit. The vehicle speed sensor lights the green LED when you exceed 12 mph (get the drive wheels off the floor to do this in the shop, or have a helper drive while you keep your eyes on the ECU).

Mode 5 ("Real-Time") gives instantaneous trouble codes to let you know what's going on right now in four monitored circuits. Codes are flashed out just once when a malfunction is detected, then they're immediately forgotten. And the way you read them is different -- you observe the flashing of one LED or the other, the red one reporting on the crank angle sensor and the fuel pump circuits, and the green on the air flow meter and ignition signal circuits.

If the red LED pulses out a series of long flashes separated by equally long pauses, a malfunction in the crank angle sensor or its circuit's indicated. Groups of three short flashes of the red LED point to the fuel pump or its circuit. With the green LED, two medium flashes followed by a pause, then two again, and so on, should cause you to suspect the air flow meter and its related wiring. Groups of four flashes mean there's a problem with the ignition signal."

Could this not be a dodgy cold start valve? Running too rich until engines warmed up? Not a genius by any measure but worth a shot?

The engine check light doesnt discriminate to when the light stays on and it runs rich, it can do it when its both hot and cold!

Ahh that rules that one out then

Thanks though

It's okay like I said I'm just a thicko who occasionally has half an idea what's going on lol