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Vauxhall Astra 1.4 X14XE 1998 - Slight hesitation through the rev range #

Posted by Sam Green on October 27, 2011, 4:34 pm

Year of Manufacture *: 1998
Engine Size and Code *: x14xe
( Optional ) Scanner Used: modis
( Optional) Fault Codes: none

Hi all....please help. I have this astra in with a slight hesitation throughout the rev range but most noticably at just over 3000 and just over 5000 rpm. i have scoped the crank and cam sensors/ ignition primary and injectors. I thought that id found the fault when i found the trace from the cam sensor to have a lot of spikes in it but when new one fitted it still does the same. Since then i have noticed that the 12v feed to the sensor spikes also i have noticed the crank(5v) and map(5v) feeds have got the same spikes in. Obviously this may not be my hesitation fault but feel that it could be and need to rule it out before continuing as this is a none coded fault. Just for everyones info, i have looked at live data and cant see any suspect areas.The 12v feed only spikes when the engine is running and not ignition only or cranking only, many thanks
Sam

Re: vauxhall astra

Posted by Pete Mutlow <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1569' width='330' height='300' border=0 style='border:none;'> on October 27, 2011, 5:52 pm, in reply to "vauxhall astra"
Peter Mutlow

Hi Sam,

Cannot comment on your "spikes" except to say I get spikey hash when using picoscope. Have you scoped the MAP sensor over the rev range? What are exhaust emissions like? Also how is the Lambda sensor switching? You could also try measuring the inlet vacuum at idle and up to a sensible high rpm to check for blocked exhaust/cat.

Regards

Pete M

Re: vauxhall astra

Posted by Sam green <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3007' width='330' height='300' border=0 style='border:none;'> on October 27, 2011, 10:01 pm, in reply to "Re: vauxhall astra"
Sam Green

Thanks Peter. I will do some further testing tomorrow. The only thing that I can see what happens of the event of the spikes is the peak of each coil firing??!! This car has had two coil packs on in the last two three years as well.
Sam

Re: vauxhall astra

Posted by Kevin Apps <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2589' width='330' height='300' border=0 style='border:none;'> on October 28, 2011, 11:25 am, in reply to "Re: vauxhall astra"
Kevin Apps

Sam

Genuine coil packs ?

Kev.

Re: vauxhall astra

Posted by sam green <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3007' width='330' height='300' border=0 style='border:none;'> on October 28, 2011, 5:26 pm, in reply to "Re: vauxhall astra"
Sam Green

Well the second one which we put on was, not sure about the first one. I have ruled out ignition now anyway!? I think i could just see a little bit of noise on the trace as it was on a small time scale. I am looking at the ho2s at the min and when on a road test and the engine is WOT the reading keeps dropping from rich to lean when hessitation happens, an i right in thinking that it should stay rich untill i let go of the throttle?

Re: vauxhall astra

Posted by Pete Mutlow <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1569' width='330' height='300' border=0 style='border:none;'> on October 28, 2011, 8:26 pm, in reply to "Re: vauxhall astra"
Peter Mutlow

Hi Sam,

The HO2S should react to the accelerator pedal. On acceleration, I would expect it to read rich (0.8v approx). On deceleration. I would expect it to go lean (0.2v). At cruise it should switch in the normal manner.. When hesitation happens, does it stay lean or just momentary.

How bad is the hesitation? I had an Astra a few years ago (single point) which on a motorway at cruising speed would "hold back". Best described as a big hand coming out from somewhere and physically hoding the car back. Turned out to be a Lambda sensor.

Regards

Pete M

Re: vauxhall astra

Sam.
"I am looking at the ho2s at the min and when on a road test and the engine is WOT the reading keeps dropping from rich to lean when hessitation happens, an i right in thinking that it should stay rich untill i let go of the throttle?"

Chicken or egg ?

Kev.

Re: vauxhall astra

Posted by Steve Kefford <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1094' width='330' height='300' border=0 style='border:none;'> on October 29, 2011, 4:08 pm, in reply to "Re: vauxhall astra"
Stephen Kefford

While under WOT the signal from the O2 is ignored and has no influence on fueling so I would say your fault lies elsewhere and the O2 is just reporting what it's seeing.

Scope pedal tracks next?

Re: vauxhall astra

Posted by Nigel Yardley <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2837' width='330' height='300' border=0 style='border:none;'> on November 16, 2011, 5:35 pm, in reply to "Re: vauxhall astra"
Nigel Yardley

did you cure this one?

We had a hesitation similar to what your describing on an astra, Turned out it was worn crank sprocket keyway, and crank pully bolt not 100% tight.

It would only happen on the road, never in the workshop, and i would have sworn it was ignition related.

Worth a look. if you run out of ideas

hth Nigel

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