Gtr Runs Like A Three-legged Billy Goat

[cash0]

For a while now my 32 gtr has been carrying on a bit first thing in the morning. On light throttle it sort of misfires and I can hear the air going chew-chew-chew (while I've still got the power down). On more throttle I can hear this loud sucking noise, but it is way down on power.

But then as the temperature gauge gets to half way, it’s like a switch has been flicked and the car becomes totally normal, full power and full boost available. All good.

This is something that’s been getting gradually worse, but today (coldish day) the switch didn’t flick when it warmed up and it carried on like this for ages. Got out looked for loose hoses or anything like that, but all appeared normal. I turned it off, waited a minute, turned it on again and everything was sweet. WTF?

I’m thinking it might be a dodgy air flow meter screwing with the computer as it fixes itself so quickly. Does that sound right?

Things I can rule out:

- Turbos – because they are the best part of a week old and it was doing this before

- Oxygen sensors – brand new

- The plugs were recently checked out and gapped

Ps. Running stock computer

[RB30-POWER]

you really want to check the coolant temp sensor. this sensor is used for fuel enrichment when the engine is cold.

chances are its stuck at a hot value (resistance) and the car is running real lean when its cold.

can measure the resistance of the sensor with an ohm meter with it disconnected or use a volt meter with it connected to see if its in spec, but either way from your description this sounds the culprit.

[Jazza12]

Hey, I'll be interested in what you find is wrong. I have a 33 GTR with the exact problem. However i have not replaced the oxygen sensors. But i did check the coolant temp sensor last night, i got a reading of 2.4k ohms which is a little below the spec of 2.6k at 20 degrees.

Jazza.

[mikel]

Jazza,

not sure if I can add value to this issue, but I wouldn't expect the diference in resistance between 2.6k ohms standard vs 2.4K ohms measured will be an issue - that difference is within 10% - so I suspect you have another gremlin somewhere.

Typical electronics specs for resistors (non automotive) is +/- 10%. Automotive won't be very different.

Mike

[Adriano]

I would try checking trouble codes, and clean the airflow meters

[sinistaGTR]

id check your fourth leg hasnt been donated to that goat the had cancer in two legs, remember they cut both legs off but a goat cant run on two he needs three.......

[blind_elk]

It WILL NOT be the O2 sensors - only used at cruise when engine at operating temperature.

Skyline ECUs are extremely sensitive to voltage - how old is the battery?

[Jazza12]

The battey has been in the car since i have owned it (about 8 months) it sometimes sounds like it's lacking cranking power if havn't driven the car for a few days.

Whats interesting is if i rev the engine (below 3k) it has the missfire and chutter, then if i unplug the O2 sensors it revs freely. Makes me think there giving the ecu wrong readings.

I've checked alot of other things i thought it may have been like trying another good set of coils, changing igniter, changing plugs & gaps, cleaned air flow meters & check voltages, throttle voltage, fuel pressure, coolant temp sensor, timing, there are no ECU error codes are coming up. So it's got me pretty buggered at the moment.

Thanks for your help.

[blind_elk]

The fact that it ran OK after you stopped and re-started suggests the battery is on its way out. You don't know how old the battery was before you got the car, so it could well be the source of the problem.

If you are not prepared to replace the battery immediately, get hold of a mate's that you know is relatively new and see if that cures the problem.

[Jazza12]

Sorry, i wasn't that clear. The car only runs like crap when it's cold. When i unplug the O2 sensors while it's running like crap and rev it, it clears up and revs smoothly. That gives an indication of a faulty sensor or incorrect reading maybe.

It runs fine when it warms up, and like the post above, it's almost like a switch gets flicked because the car goes from running very poorly, e.g. hesitating and chattering out the air filters to absolutely fine and normal in half a second.

Thanks for you help, i will replace the battery soon to something with more grunt.

[cash0]

Yeah well as I said in my original post my o2 sensors are brand new as they were changed with the turbo/dumps a week ago - so rules them out in my case.

I'm going to see how much a new coolant temperature sensor is tomorrow, and also see about my air flow meters. I have heaps of oil and crap in my intake pipes (bigger issue) so that's why I suspect afms.

I'll keep you posted.

[7yphon]

I have a sim Issue but it happens sometimes even when the car is warm going to take it to hyperdrive tomorrow let you know what they think and maybe it might give you a direction

[SLIPPERY]

any updates on price of coolant sensor? or with hyperdrives verdict?

[cash0]

any updates on price of coolant sensor?

Yeah rang up today about the coolant sensor. The guy sounded a little confused... he concluded there is a sensor right near where the top radiator hose goes into the block that sends messages to the computer. It's $93.40 retail price and the part number is 2263001U00 (if I can read my shite hand writing correctly).

I'm going to hold off on it until I can rule out my afms. I cleaned them today with electrical spray, but obviously can't see if it's made any difference until the morning when it's fully cold. I'll let you know.

[RB30-POWER]

if you have a multimeter or can get one from dick smith for $10, i can tell you how to test the coolant temp sensor if you want?

[RB30-POWER]

alternatively buy a consult cable and download the free software if you have a laptop and check all values in realtime.

let me know either way.

[SLIPPERY]

The AFMs wont be the culprit because the cold issues disappear instantly every time once the temperature reaches a certain level. (like flicking the light switch on) Ive got the same thing when i run my standard computer. When i run a non-tuned PFC, then the problem isnt there.

I reckon rb30-POWER is onto the problem...it has to be temperature related

[cash0]

Well this morning, after cleaning the afms and resetting the computer - it didn't do it!

But I'm not going to claim victory yet - I bet the twisted bastard of a car is just playing games.

So yeah anyway RB30, that would be tops if you could give us a run down on testing the coolant temp sensor. Firstly, where is it? I'm told it's near the top radiator hose - but there seems to be a few different sensor looking things around there.

[cash0]

Well this morning, after cleaning the afms and resetting the computer - it didn't do it!

Scrap that... the mongrel bastard was playing games. It's as bad as ever. So not the AFMs after all.

[JETZLR]

When cold and engine running try unpluging the coolant temp sensor and see if the engine rpm changes.