Technical Intermittent power loss, especially after starting the engine.

[Mr Oblong]

Good evening,

After several months of lovely, sweet-running fun in my '99 Sei, I'm experiencing a problem that causes the 'Injection System Failure' light to come on.

When this happens, the car really struggles for power, seemingly misfiring and revving sluggishly under the heavy throttle needed to maintain momentum to an apparent limit of 4k or so. It wouldn't exceed 25mph and a decent hill would defeat it.

It varies in severity, but the two worst instances were after a short run in the vehicle, a short break and then starting the engine again. These times the car wouldn't catch without some throttle and, once idling, gave a very uneven thobby note with the car noticeably vibrating (yes, even for a Seicento ) at the usual 1k on the tacho. The engine response wasn't its usual crisp and feisty self, feeling weak and leaden.

This happened once, followed by a milder (half as bad as earlier), momentary dip in power on the way to the garage that lasted perhaps 15 seconds. The garage thought an ignition lead being loose could be the culprit and handed it back to me without charge. A few days on I had another case of the more serious problens from start-up but, on the way home (after maybe two minutes of driving), I felt a firm kick in the back as full power returned underneath my heavy right foot. It made it to the garage the next day without incident, the mechanics tell me they can't see the fault and don't want to start guesswork, so I'm hoping the knowledgable benevolence of yourselves can give me an idea of what's to be done.

Thanks in advance for any help, it's truly appreciated.

 

[rallycinq]

When its dark tonight/tomorrow morning, fire it up with the bonnet up and look for any stray sparks.

Could be a coil pack on the way out, leading to unburnt fuel in the exhast which the 02 sensor sees,the ECU can't compensate for, so the ECU goes into limp home mode and puts the light on.


Cheers

SPD

 

[Mr Oblong]

Thanks for the quick reply, I'll be sure to look under the bonnet later and report back.

 

[Mr Oblong]

Okay, I've just had it out for a quick run. Started up fine, driving around fine, business as usual. After 10 minutes I returned home, intending to start the engine a couple of minutes after I'd stopped and thus recreate the circumstances where it'd been bad before.

As I was manoeuvring into a parking space in reverse, crawling speed, the engine started juddering again, Ignition System Failure light on etc. Handbrake on, popped up the bonnet and had a good scan around for flashes but saw none. Am I right in thinking these flashes would be easily visible with nothing needing to be removed or altered? I had a good look from all angles but didn't touch anything.

 

[fingers99]

Usually pretty easy to spot in the dark. Ignition "leaks" flash bright blue, low tension leaks orange.

So, that pretty much rules that out.

Next step, I'd suggest, is to take a long, hard look at the pipe to the MAP sensor, especially the rubber ends to the long plastic hose.

 

[Mr Oblong]

Okay, I went out to do as you said but realised I didn't actually know where the MAP was. Somewhere in the vicinity of the ECU I thought (isn't it?), but I couldn't pinpoint it. Are there any pictures of it, or could I have a detailed description of it? Sorry for being a bit crap.


Also, is the long, hard look at the pipe conducted with the engine running? The engine was off when I checked just now, but I wasn't sure if having it on would be of any use.

 

[rallycinq]

99 Sei should be SPi, so the map sensor should be up by the ECU. Its normally mounted downside up, so you see a round disc with nuts. Underneath is the MAP sensor.

However, it could still be a dodgy coil, so, with the engine running badly, take your thick rubber gloves and a pair of insulated pliers and remove number one plug lead.

If the coil/spark is good the engine will stop. If the engine continues to run badly, replace that plug lead and remove number 4. If the engine contines to run badly its that coil thats faulty.

If the engine stops after removing number one, refit, restart and remove number 2 plug lead. If the car stops, it ain't a coil problem, but if it continues to run badly, replace and remove number 3 plug lead. If it continues to run badly its that coil thats duff.

Cheers

SPD

 

[Pep0]

You are looking for cracks (or other damage) in the pipe or the rubber hose terminations, a small mirror will allow you to see under the pipe.

If the pipe leaks air it would cause problems.