OJ GTS

Hi Guys,

Had a search and couldn't find any mention of anyone having previous problems, but I've noticed that my GTS becomes noticeably 'looser' in its throttle response, with what seems like a slight but noticeable drop in power when the car has been driven at low speed for a period of time.

In particularly cold weather or if the car is driven on the motorway, it feels noticeably sharper and more responsive. The effect has been less significant since I replaced the MAF with a JDS unit a few weeks ago, but it's still there.

The foam inlet hoses have been replaced relatively recently, so it's not breathing from the engine bay or anything like that. Also worth pointing out that this isn't just an 'all cars run better in cold air' observation, this happens even in sub 10 degree C conditions.

Any suggestions?

Cheers

OJ

AO

Auto or 5 speed? Any trouble starting the car when it warm?

Mrmerlin

have you done a complete intake refresh including replacing the knock sensors the hall sensor and the TPS and the CPS. did you also replace the plastic connectors that plug into both sides of the MAF boot

OJ GTS

Auto and no other noticeable problems. Car is and (aside from its first 18 months) has always been maintained regularly by a mechanic that knows the flex-plate issue well.

Plus as the car 'comes back' if taken on a higher speed run, I'm reasonably confident it's not something getting too hot and binding up.

OJ GTS

To be honest I was trying to pin point the problem rather than use the scatter gun approach, particularly with an intake refresh as it might introduce another problem. I was hoping the milder climate here would be kinder to intake seals and such.

The car is a very late model and is mechanically in otherwise great condition. All of the connectors and such that I've encountered so far have been in good condition, even the MAF was right on the edge of not worth bothering with after 98,000 miles of town driving.

the flyin' scotsman

the car has essentially 100k miles on it and is at least 17 years old....it just might need some intake TLC.

have your mechanic hook up the car to a diagnostic tool.......JDS spanner or Theos system, you might be amazed what little things are not quite right.

the scatter gun approach is advised as the work involved in removing the intake normally doesnt warrant pulling it off again and again hence typically most folks replace all.

AO

A bad knock sensor - or one that's on it's way out - will pull 6° of ignition timing, and make the car much less responsive. I think hooking it up to a Hammer/Spanner/DT928 is a good start to eliminate that as a culprit. Or you can test yourself by disconnecting one of the knock sensors and see if the car feels the same or worse. One is under the right side fuel rail cover near the fire wall, and the other is to the right of the oil filler neck.

One other thought... the throttle cable can stretch. Check for proper adjustment. It can definitely affect throttle response and overall feel of the car.

OJ GTS

15 actually! It was originally registered as a 96 model, so presumably was one of the last to come out of the factory!

Mechanic plugs it into a full diagnostic system every time it goes in and anything that pops up gets sorted.

Excuse my hesitancy over a full intake refresh, but totting it up on the 928 specialist's site came to over a thousand dollars just in parts! There's also a possibility that Leigh (mechanic) has done it in the past for my Dad (car is a hand me down) as part of another job, or just as routine maintenance.

AO

Fine, then... don't listen to us. What do we know? Leigh is obviously the master here.

OJ GTS

Yeah, knock sensor was high up on my list of suspects but the last time the car went in it wasn't showing any errors. I'll get it checked again next time the car is in!

It's intermittent so I don't think it would be the throttle cable.

OJ GTS

Blimey a bit sensitive, no?! I'm not referring to my mechanic as the god of 928's, I'm just discussing what I've looked at on the car so far, and my reluctance to separate cash from wallet without exploring all the possibilities!

AO

Sorry... I sprained my ankle this morning and I'm not feeling 100% (chills, etc.).

Mrmerlin

the intake refresh is something that every 928 will benefit from,
just because it runs doesnt mean its able to run as it left the factory,
replacing the parts listed and then some will result in continued top performance.
Yes it is expensive but so was the car when it was made with top of the line parts.

Note you should check the ignition wires in the dark see if you find any fireflies if so a new set of Beru wires should be installed Roger has them for about 375.00 they are plug and play

OJ GTS

I know you're right, but after chucking 2k on renewing the suspension, 4.5k on a respray and still having a car with a fairly manky interior and extremely ropey stereo, the will to spend another grand on anything that might conceivably fail to yield an obvious improvement has waned somewhat

I would say the moral of the story is to buy a decent car in the first place, but I've always loved the thing and it was worth saving

Good suggestion on HT leads (as we call them), but already preventatively maintained

SteveG

These cars are cheap to buy (handmedown would be zero??) but expensive to maintain. Especially if you pay someone else. Sounds like a true hand-me-down as you are not sure what has been replaced. You might want to get a history and start a folder so you know. Or unload it now and get something newer, no shame in that. I spent 4 hours bent over the engine yesterday finishing up a fuel line replacement (are yours 15 years old?), water bridge reseal and TBelt tensioning. That was probably $500 labor; I won't tell you how long it took (me) totally. Sharks are not rational.