Lumpy when hot!

[Glenn]

When i run my GTi-R from cold it runs fine with good boost; nice and smooth. However, when i have been driving it for anything from maybe 5 minutes upwards, and the temperatures are at there prefered levels, the engine can suddenly run lumpy on acceleration, as if there is hardly any boost. The boost builds up slowly and hesitantly. I have changed all leads, plugs, filters, dizzy cap, rotor arm and given full service, but it still happens! This is really frustrating as it doesn't always happen. An ideas as i dont want to have to change everything trying to locate the fault?? Any easy repairs for this?? Cheers in advance!

 

[J-GTi-R]

This sounds very much like the car going into safe mode, caused by either the engine detonating, or a fault with the detonation sensor. Do a search on det sensors, as this is a common problem and has been covered many, many times.

 

[Toady]

sounds more like a coolant temp sensor to me, if its only doin it when engine is warm. is the engine using more fuel than normally, and is the zorst really sooty and perhaps blowing out black smoke? i had this prob once but i fink it turned out to be a bad connection on the afm. although your prob sounds more running temp related which is why i suggest testing the coolant temperature sensor!

 

[J-GTi-R]

Yeah, but if the car is up to temp, it moves out of the richer 'cold start' map and into it's normal fuel map, then you get the det. Possibly anyway...

 

[Anonymous]

just had the same problem,turned out to be an air leak in the boost
system :x

 

[Glenn]

Thanks for your help guys. I was starting to think of a det sensor problem myself having done a bit of digging on the net. I take it this wont be an ignition problem then? I'd assume this would be faulty no matter what the temp if it was this!. In relation to the coolant temp sensor, there isn't any black smoke coming out the zorst, and i haven't had the car long enough to know if the fuel econ has been affected, but it seems ok. Last returned between 250-300 miles to the tank......Obviously didn't cane it enough!!
Who knows where the DET sensor is located? Is there an easy fix for it? And if not, then how much to replace and where from? If the coolant sensor is cheap, maybe i should replace that first anyway....just in case.
Thanks in advance for replies... :lol:

 

[Glyn]

Hi Glenn, I've had similar probs with mine for as long as I can remember, I changed everything obvius I could think of. Now I can do a fault code check (my plug uses different pins) came up DET sensor every time. Took it off and the only thing evident was a split outer plastic coating. Nissan want £159+vat :shock: I've just been to scrapper and taken one from a Primera GT engine, it's identical, same part No. and everything. I fitted it and started engine, switched off and the fault code has gone. I'll go for a spin later as I am replacing a couple of water hoses. I wii let you know. The sensor was £15 after haggling

 

[Glenn]

Cheers Glyn, Took mine out today and again ran fine from cold, but after about 5-10 mins, it started hesitating on boost. Boost climbed slowly but hesitantly only up to 0.5 as well, instead of 0.6-0.7 as it would normally. So felt like it was really working hard to get up to speed. However, after i had left it for a couple of hours i drove back home (same journey time) and it ran fine the whole way, with good fast boost. Its def an intermittent problem. I'm assuming a leak in the system would have the same effect the whole time.
Drop me a line mate to let me know how it went, and also where the sensor is located so i can have a look at mine :? Cheers

 

[Willy]

I had a similar intermittent problem. It affected idle as well, though. It ended up being my timing over-advanced to 25 degrees. Knocked it back to 20 and it was fine since. Get the ERU to give you the fault code. It's easy to do. All you need is a piece of wire like a paper clip or something. Do a search and you'll find out how.

 

[J-GTi-R]

Boost climbed slowly but hesitantly only up to 0.5 as well, instead of 0.6-0.7 as it would normally. So felt like it was really working hard to get up to speed

That sounds almost certainly like the DET sensor, but do check the timing as that may be too advanced and is triggering the sensor (rather than the sensor itself being faulty).

 

[Glenn]

So how do i check the timing then??? And how is it adjusted and to what level??? :?
Cheers guys

 

[Willy]

Have a look in the 'how to' section. It's covered in there.