Technical P0300 seicento

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Technical P0300 seicento

seanhyde12

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Help ! Again.
Daughter drove car this evening. Ran fine no problems on outward journey. On journey home seemed to lose power and just not run properly . Called recovery who got P0300 code and said sounds and looks like one of the coil packs is problem . Before I start changing things does this sound about right ? Engine starts but clearly running rough with no power and engine management light on with above code. Thanks
 
P0300 = random misfire.
Could be one of many things so first you need to check the coil packs are working -there is a guide to testing them somewhere on the forum.... but it's late & I can't remember where. Think it's in the manual you can download.
IF only one of the coil packs has gone belly up it might have been taken out by the ECU, the micro-ECU fitted to a 2001 are well known for that, but lets hope it's something less serious. With luck it might be something as simple as a dodgy connection.
 
Maybe. See if you can identify which cylinders are misfiring. Wet plugs, cold(er) exhast mani stubs, etc.

If you can identify the misfiring cylinder(s), swap the ignition lead pair over from coil to coil. If the misfire jumps cylinders, it'll be the coil pack.

It's worthwhile replacing the ignition leads anyway, but that would be my first port of call if I was getting a misfire I couldn't track down to a particular cylinder.

P0300 is a bummer in that it can mean multiple or random misfire. Multiple misfire is genenerally either plug leads or coil pack, random misfire can be a faulty ECU.

In the Punto Mk2 guides/FAQs are a series of tests to determine whether the evil nasty micro ECU is at fault. If you have a big metal ECU on the passenger wing it's unlikely to be the ECU. But even the evil ones can be repaired.
 
Thanks
So I've got some HT leads coming later this morning. So I'll change them first. What I've tried so far: So , engine starts but runs rough . I looked at punto guide and did as described . "(1)First thing to establish is which coil is not firing,
Easily done,simply disconnect the 2-pin connector on either one of the coils & try to start the car...if it still runs(a.k.a. like a bag of s*it)then the coil you have disconnected is the one not firing.
If it does not start then the one you did not disconnect is the one not firing....simple."
I removed plug from each coil pack one at a time . Engine would not start with either disconected. next I tried removing HT lead from coil pack one at a time. Engine would not start with any of these removed. Engine will start with all conected ? I'll post again when I've tried the new HT leads.
 
1. Replaced HT leads. Engine starts but still runs very rough.
so is next step to replace coil packs?
 
I'd -- with the engine running, and with insulated pliers -- try pulling and re-attaching each plug lead at a time. Do pull on the rubber bit that holds the plug rather than on the lead.

A "good" running cylinder is indicated by the engine slowing or stalling, a non-firing cylinder will make no difference at all. Note down the cylinders which don't affect the engine speed.

So far, it's not looking good for the ECU.
 
As i look into the engine I refer from left to right as 1234. If I removed either number 1 or 2 engine stopped. If I removed 3 or 4 or even both at same time engine continues to run the same. I note that 3 and 4 are connected to same coil pack ( one closest to front of car). Does this suggest that coil pack is broken or does it still point to ecu.
 
Sorry I'm an idiot just checked and leads are connected as you describe together 1 and 4 and 2 and 3 together on front coil pack. The other info still stands when 3 and 4 are removed from top of spark plug engine runs as before. when I remove 1 or 2 engine cuts out immediately
 
ok. I tried various co binations of swapping leads that all resulted in non starting. This is complicated so I'll try and explain. on coil packs looking down from front I labelled connections Aa Ab on first coil pack (furthurest away from front of car) followed by Ba Bb ( on coil pack nearest front of car.I did this as not sure if position on same coil pack would make a difference. Original connections were 1 -Aa, 2-Ba, 3-Bb,4-Ab. First I swapped connections from one coil pack to the other so 1-Ba, 2 -Aa, 3 -Ab, 4- Ba . Car would not start . Also It would start with original connections and not change if I removed 3 and 4 from spark plug end. .But it would not start without these connected in the first place ?
 
The cylinder numbers for the leads are cast into the alloy mounting bracket for the coils. Connect the leads as per those numbers and report back.
 
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Thanks . OK This is now driving me mad. I've started with a clear head. I found the order stamped on the coil pack mounting bracket. 2 3 1 4. Looking down at the engine from front of car I am assuming 1234 goes left to right . I have checked re checked and checked again and everything is in the right place. I have used a spare spark plug to check the spark from each HT lead. All appear good. I have repeated the original test of removing the Ht lead from the top of each cylinder in turn. Again remove 1 engine stops. remove 2 engine stops . Remove 3 or 4 no change in engine tone,makes no difference and engine continues to run. So no power from cylinders 3 and 4 . I note that 3 and four are connected to the same position on each of the seperate coil packs ? I ordered new coil packs which should arrive today if I'm lucky.
I also removed spark plugs from cylinder 1 and 4 . ! looked very slightly sooty. 4 looked normal . I expected this to look wet following repeated turning over of engine in previous tests. It did not appear particularly wet ?
 
Sounds like the head gasket may has blown between cylinders 3-4. It's very unlikely for both coils to suddenly run on half windings. The coil drivers in the Ecu could have a high resistant joint on a common 0v rail to earth from corrosion? Check the Ecu connections and associated earths.
 
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Thanks. I've just fitted new coil packs. NO difference. Exactly the same. I've done the cylinder head about a year back. In fact I did it twice as having skimmed head and replaced it had problem with noisy tappets. Re shimmed and still had strange problem so I bought a good cylinder head from fingers and fitted that. It has not done a huge amount of miles since ? If it is the cylinder head would water not have filled the cylinders and the water bottle be missing lots of water ?
 
Justbought a compression tester. Either it's not working properly or I have little or no compression any where . It reads about 16 psi on 1 barely moves on 2 and nothing on 3 and 4. So either I have little or no compression or I can't get the new tester to work properly. I've run engine for a bit ,removed all plugs as stated in instructions for tester and those are the readings I get. I 've tried a couple of times and with the compression test connector fitted without the dial I can definately feel each cylinder pumping but little or nothing from the dial except on 1 and a bit on 2 and yes definately psi
 
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