: Car misfires then dies when hot.
My 1991 214si 16v has a problem. It starts fine every time and runs ok until it gets hot. As it gets warm it starts to hesitate and then misfire and stall. By the time it gets to normal running temperature it is undriveable.
I have cleaned out the vacuum hoses, replaced the crank sensor, checked the HT lead resistance, and checked lots of electrical connections.
Any suggestions to what I should try next? I think it must be something that gets hot, since it consistantly happens when the engine gets warm.
Thanks for your help.
Is your car really a rustbucket??
It happens EVERY time the car gets hot, yeah?
It could be many things; it could well be an ECU fault (sorry to be downbeat)
I would really like to know what happens to the exhaust gas HC and CO content when this problem occurs - that would be a great help. Trouble is, you're gonna need a garage exhaust gas analyser to do this ???
Well, 'rustbucket' might be a bit cruel, but it is starting to show it's age.
A few weeks ago, I noticed the odd bit of hesitation when driving it, but now it does happen every time the car gets hot.
Hmm. ECU was not what I wanted to hear. I'm guessing a dealer diagnostic is gonna set me back at least 40 quid? If is is the ECU, can I fit one from a scrapper?
Maybe I'll try new dizzy cap, rotor and plugs first, in the vain hope that will fix it. They look ok, but it's worth a shot right?
[Edited by rustbucket on 17-06-2002 at 05:52 PM GMT]
Well, yes you could try it - but I wouldn't want to see you waste your cash.
The dizzy cap and rotor together with the HT leads are the usual suspects, so go for it.
I guess you have to start somewhere :)
1796cc GTi Se
My car used to do this occasionally when it had been for a long run. It was annoyng when joining motorways from sliproads.
One trip to my local motor factors saw me im possesion of a new coil and all has been fandabedozie since
:D This might not be what is wrong with your car though.
Joel - I love your little 'get out clause' :D 8)
Actually I had another potentially stupid idea. If the ECU is dodgy, then it seems to be the high temp settings that are out. if I fool the ECU to run at cold settings all the time, the engine should still run at high temp. Ok it won't run perfectly, but it shouldn't cut out like it does now.
If it does exactly the same, then it probably isn't the little grey box at fault.
Did that make sense?
Anyway, if that doesn't help, or it points the finger at the ECU then I'll get a diagnostic done. Would I be right in thinking that a diagnostic will not show up any faults in the HT circuit though?
Back to square one. Do not pass GO, forfeit £200 :( Its lucky I don't really need my car that much at the moment.
A T4 diagnostic will not show up an HT fault - you'd need an engine analyser for that. Even then it is very difficult, sometimes, to identify faults.
If you fooled the ECU into thinking it was 'cold' you'd consume mega-loads of petrol :( as it would be on cold start all the time.....
[Edited by Dr Dave on 18-06-2002 at 08:29 AM GMT]
lol, yeah I guess fuel consumption might suffer a little. I don't suppose it'd pass an emissions test either.
I meant it more as a test, if that cures the problem, then the ECU is probably at fault and I'll get a diagnostic.
If the problem is still the same, then it might be worth buying a few ignition parts first, especially since a diagnostic wouldn't find ignition faults anyway.
Or perhaps I've lost the plot completely and everyone can have a good laugh behind my back :D
Go for the ignition bits first; they are 'serviceable items' and only have a certian lifespan anyway, so you'll do no harm in changing them
Coolant temperature sensor? If it is dodgey it may give the ECU wrong signals. ie, hot coolant but reading cold will make the mixture rich and will foul the plugs resulting in bad running or not at all. I'd check/replace this as electrical components like coil/leads etc aren't as sensitive to temperature, usually worse when cold/damp.
Yeah, good point, Dave
Coolant sensor isn't going to be much more than £12-£15
They can sometimes give trouble, although they're fairly reliable 8)
Thanks for the suggestions everyone. Hopefully it's fixed now. I need to put some miles on it before I'm sure, but it seems ok.
I hooked up a variable resistor to simulate the temp sensor. When the engine was cold, it ran fine at any temperature setting but when it was hot, it misfired at any setting. So, I figured it wasn't a bad mapping in the ecu.
The ignition system seemed a suspect, so I changed the dizzy cap and rotor arm, since they heat up with the engine. It hasn't happened since.
It's weird that it was so consistant and came on so suddenly. I suspect that some metal part in the rotor was expanding when hot and shorting to the engine. Rotor and dizzy cap both looked fine though.
Oh well, thats cars for you.
Dave, thanks, and congratulations on your upcoming wedding. I hope you manage to avoid the temptations of people-carriers and caravans.
[Edited by rustbucket on 19-06-2002 at 09:19 AM GMT]