# Cold misfire and dodgy start



## LozGT (Dec 8, 2005)

I've a cold misfire problem with my R33 GTR. When cold it will idle ok but with the application of any throttle it misses and hesitates. Once fully warmed the problem completely disappears. I suspect the problem may be with either AFMs or coil packs.

The other day another problem appeared. When I tried to start it from hot (been running for over an hour) it would start and then stop, any throttle would stall the engine. It was behaving somewhat like a vacuum leak. I fiddled with the AAC valve (wound it in and then out again) and managed to get the car to start and run but with ABS, 4WD and Engine check lights on. Re-started the car and it ran perfectly with no warning lights. This has only happend once though.

Has anyone experienced similar problems and what were the results of any investigations? It's not causing me huge problems at the moment but the cold misfire is getting worse. I live in a fairly quiet village so spluttering up the road isn't too much of an inconvenience. I would like to get it sorted though. I'd appreciate any thoughts, comments or suggestions.

Cheers


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## LozGT (Dec 8, 2005)

Just thinking a bit more about the cold hesitation/spluttering problem. Coil packs would become a problem under load/heat; but will try them anyway. Can't imagine why an AFM would play up when cold; the thermistor could be caked in crud I suppose? Could it be a general engine earth problem? Or some issue with the temperature sender to the ECU? The car is more or less standard. The ECU is one out of a middlehurst supplied car. 

Any ideas anyone?


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## typerchris (May 8, 2007)

Sounds to me like an air leak at the plenum. If i were you spray some carb cleaner along where the plenum connects to the block while car is running and see if your idle changes. if it does then theres the culprit.


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## typerchris (May 8, 2007)

Loz i forgot you were in cumbria. Im in Penrith if you need to try any bits to eliminate problems. 

If you get it sorted in time how do you fancy a trip to teg sport rolling road on saturday?


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## LozGT (Dec 8, 2005)

Hi Chris

Plenum leak could be the problem. I was reading another post that cited the same culprit and then mentioned replacing the standard gaskets with metal ones. If it is the plenum leaking then I guess the gap closes up when the head and plenum get warm. I had a leaky exhaust manifold gasket on my R33 GTSt that used to make a ticking noise when the engine was warm but not when it was fully hot. That was due to the manifold warping somehwat after the studs popped off. I will tinker with it when I get the chance. I have been doing some other tinkering prior to this problem emerging - but that just consisted of cleaning the engine's earth connections and putting in a few more - but I don't think that will have had an impact. I've just checked my ECU harness and that was half out of it's seat with the ECU. I've plugged it back in and I'll see what happens when I start it next.

As for Saturday, well my wedding is coming up soon and I may not get the chance this side of the end of May. However, we must get together some time to chew the Skyline fat. Thanks for the offer of assistance, I may need your help if my tinkerings don't pay off. Hopefully we'll have some bridges back soon. They've nearly finished our temporary one - we may have it as long as the one near Langwathby. I hope not! Speak to you soon.

Cheers

Loz


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## typerchris (May 8, 2007)

I had the plenum leak and caused similar issues the guys down at rb motorsport sorted it in day i wouldnt reccommed trying to fix yourself as its a job and a half. 

I have the issue as it stands with leaky turbo elbow need to try and sort that but dont think i will be able to sort that myself either :-(

As i said i have plenty of parts lying around to try if need be or could even swap bits of mine if need be. 

Im over that way quite often with my job as i deal with all the Newspaper advertising in the area for motor dealers so cant wait for the bloody bridge to be sorted will make my travelling to dealers much easier.


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## LozGT (Dec 8, 2005)

Thanks for that Chris, much appreciated. Just out of interest how much did RB charge you to sort out the plenum? I don't mind undertaking tasks like that but if the price is right I'm more than happy to pay someone. However the idle is stable (the vacuum leak symptoms have only happned once) and I can adjust the idle speed up and down by fiddling with the AAC valve. The problem is when I try to drive the car it splutters (when cold) above 1800 rpm - almost like it's in limp-home mode. The engine manual gives some interesting diagnostic tips so I will work through them and see how it goes.


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## typerchris (May 8, 2007)

Hey well if you dont mind doing it then thats a bonus. if you ever fancy doing my turbo elbows i will be more than happy to pay you lol.

I will did the invoice out from rb and see what there charge was it was very reasonable for the quality of work done. The std gaskets on there are terrible and they replaced with hks metal ones. 

Its def work checking by spraying some carb cleaner / wd40 and will give you a instant answer.


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## adz1282 (Jan 6, 2010)

Loz, What was the outcome of this in the end? I have a similar issue at about 2.5 - 3k rpm. I am thinking temp sensor or inlet manifold gasket?


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## LozGT (Dec 8, 2005)

I'm afraid I don't have an answer to this one. I had some really bad luck with the GTR and ended upside down in a stream. Needless to say the car was written off. However, I did notice an improvement with this issue when I cleaned my afms. They were getting really coated with oil mist and I found it hard to clean them until I removed the grills and got in there with a long cotton bud and some cleaning fluid. The day before my accident I'd really gone to town and cleaned the afms. The problem seemed to have been cured. However, this was all back in July and the problem seemed to be more pronounced when the weather was on the chilly side. The thing is I don't know a great deal about how afms work and what affects them. I did test the temp sensor and it didn't do anything unusual. As for inlet manifold gaskets, I suppose it could be possible but surely you'd hear the air getting drawn it (that's just a guess - I know with the exhaust manifold on my GTSt, as it became more loose as studs broke off, the gasses getting out became quite loud. In the early stages of the problem a mechanic tried to tell me it was a sticky valve)? The whole remedy thing is a lot of trial and error with a large helping of conjecture. I hope you have some better luck then me. Let me know if you find a solution. Cheers


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## protoman (Jun 6, 2009)

My car did the same kinds of things when the solder in the AFMs went south. Resoldering the connections fixed it for me. It makes sense that if the car was only having issues in the cold or hot then that is the prime time for the connections to move just a little and screw up the idle and/or stall the engine.


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## LozGT (Dec 8, 2005)

You could be right there but I did a visual inspection of the solder in both AFMs - as far as I could anyway. I looked for dry joints and couldn't find any. That doesn't mean that there wasn't any issues with the solder, I just couldn't find any.


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## adz1282 (Jan 6, 2010)

Bad news about your car, you getting another?

I will check my afm's, when i bought the car one of them was not connected properly to the filter box.


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## LozGT (Dec 8, 2005)

It was bad news about the car. I was quite upset really. The most important thing was that noone was hurt. As for another, I gone down the Stagea route and now have a series 2 RSfourS manual. I'm just waiting for HM customs papers to come through... Happy days


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