Enginer Hesitation

[Kasler San]

Hi all

Just a quick one

Just bought my first ’95 manual GR and I’m finding it’s got some subtle engine problems as I’m becoming more familiar with the car.

The acceleration of the car pulling away from low speeds and low loads from idle up to about 4,000 rpm is very hesitant. The car noticeably slows then spends then slows until you get the revs high, then there seams like no problem with power after that. It’s more noticeable when it’s cold. . It feels like I need to pull the choke out to smooth the hesitation out. Also you can’t slug it around in high gears and low speeds. There seems to be no real torque below 4 grand. I’m not sure if this is typical of all non MIVEC’s but I’ll have to drop it down to 4th to even slowly accelerate from 60mph. When I do give it some beans there seams to be all the 180 horses on tap and I’ll soon have it on the speed limiter no probs.

SO FAR:

There are no codes in the ECU’s self diagnostics
The VIC wasn’t working, but it is now and did help no end, but its still not quite right
Engine temperature sensor is working within the manuals spec
If the inlet air temp is tied in with the mass air flow sensor then I think it’s in spec?
The lambda sensor is producing the correct voltages and the heater is conducting
Air filter looks pretty new
Fuel is always 97+ ron
There’s no black smoke which would suggest a rich mixture
Throttle position sensor is changing it’s resistance nice and smoothly
And the idle position switch is switching on when the butterfly is at idle.

What its has got that’s not standard is a mongoose exhaust although the cat is still on it…. Now maybe there’s a reduction in exhaust gas back pressure causing this problem. But I should imagine that many FTO’s have changed their exhaust and searching through all the forums I can’t find any one else with is problem. My exhaust is not loud at all so its not that free flowing.

Oh…. And the previous owner had the cam belt changed………. Could this be wrong?

Any help would be fantastic, before I have to give in, spend money, and have a MUT-ii plugged into it.

Thanks very much

Rich

[Muad_dib77]

The Very 1st thing I woul dcheck in this case would be the sparkplugs.

Do you know when they were last replaced?

[kevinod]

Hmmm you mention the last owner got the cambelt done...

The MIVEC changes injection timing after it gets to so many revs, not sure what that is but it would be somewhere around the 4k neighbourhood I reckon, someone here will know straight away.

So, if the timing was out after putting the cambelt on you may well have similar symptoms I reckon.

How does the engine run at lower revs, does it sound smooth and even or could it be missing? EDIT: I mean missing cylinders, not missing from under the bonnet!

Also, the old chestnut, have you cleaned the idler (proper name escapes me at the moment) that sits in the throttle body? Thats a pretty common problem.

[Kasler San]

Flicking through the old owners receipts they have been changed about 6months ago along with some magnecore leads. Although I will check that there the correct rating.

thanks

[Kasler San]

Idle is fine and smooth. It was hunting a lot but that was because the idle switch on the throttle pot wasn’t set-up correctly (i.e. didn’t switch on at idle).

I would imagine that idle will be rough if the cam timing is out, I think if it just one notch out on the pulley then that will = about 9° advance or retard. But then maybe the idle control solenoid is doing a good job of keeping it smooth….. that’s what its there for.

[CJ]

2 words - fuel filter. If it hasn't been changed in recent times, thats the first thing I would look at.

CJ

[Kasler San]

I found a brand new filter in the clove box. I’ve just changed it this afternoon. I cant quite tell if its cured the problem tho, but it is idling faster around 1000 instead of 750 before. And in my short test run the engine cut out once when I lifted off the accelerator. So it has done some thing. Perhaps an ECU reset will settle it back down. Time will tell tomorrow when I drive it from ice cold.

Thanks for your input.

[CJ]

I found a brand new filter in the clove box

Oil or fuel filter?

CJ

[Kasler San]

Fuel Filter.

Got it in one!

The car is so much more driveble now

Thanks