poor running - brain ache
Discussion
OK - i have a problem which has persisted for 3-4 years now but only intermittently.
The fans cut in and out when they should and the engine runs rock steady at 88 on the motorway at 70-80mph, at higher sustained speeds it runs rock solid at 90-92. It does not overheat at all.
It only occurs on a hot day ie 20 degrees plus such as yesterday.
If I am driving around the car runs fine, its fast, sorted etc etc runs beautifully. Even in a traffic jam it has noi problem at all. If however I stop and switch the engine off for just 3-5 minutes to fill up for fuel (or yesterday to refix the rear exhaust box that fell off) it will not restart. It just churns and backfires. It can be bump started but it is not easy. BUT once it has started it idles at circa 1600rpm and has terrible pinking - so bad that I dare not use any throttle travel because it will just destroy the engine. If I leave the car for an hour to cool down and restart it the car will be back to normal.
This problem has presisted through 3 engine rebuilds and a full remap (which made the car much smoother and quicker), it has new plugs, leads, coils (now relocated in front of the engine), massive high start up load battery, independant directly wired starter switch and leads, all new and additional earths, new starter etc so its not that. It's not exhaust related choking because I have had 2 complete different systems and its decatted. The exhaust is lagged. The fuel rails are lagged. The fuel pipes have been renewed with lagged steel braided hoses which now run through the cabin to avoid heat soak off the exhausts. The fuel filter is new and is now in front of the engine to keep it away from exhaust heat.
My guess that it is a sensor breaking down when it gets hot. Can anyone tell me what and where all the engine sensors are so that I can change the lot.
TIA
Jes
The fans cut in and out when they should and the engine runs rock steady at 88 on the motorway at 70-80mph, at higher sustained speeds it runs rock solid at 90-92. It does not overheat at all.
It only occurs on a hot day ie 20 degrees plus such as yesterday.
If I am driving around the car runs fine, its fast, sorted etc etc runs beautifully. Even in a traffic jam it has noi problem at all. If however I stop and switch the engine off for just 3-5 minutes to fill up for fuel (or yesterday to refix the rear exhaust box that fell off) it will not restart. It just churns and backfires. It can be bump started but it is not easy. BUT once it has started it idles at circa 1600rpm and has terrible pinking - so bad that I dare not use any throttle travel because it will just destroy the engine. If I leave the car for an hour to cool down and restart it the car will be back to normal.
This problem has presisted through 3 engine rebuilds and a full remap (which made the car much smoother and quicker), it has new plugs, leads, coils (now relocated in front of the engine), massive high start up load battery, independant directly wired starter switch and leads, all new and additional earths, new starter etc so its not that. It's not exhaust related choking because I have had 2 complete different systems and its decatted. The exhaust is lagged. The fuel rails are lagged. The fuel pipes have been renewed with lagged steel braided hoses which now run through the cabin to avoid heat soak off the exhausts. The fuel filter is new and is now in front of the engine to keep it away from exhaust heat.
My guess that it is a sensor breaking down when it gets hot. Can anyone tell me what and where all the engine sensors are so that I can change the lot.
TIA
Jes
Hi Jes.
It sounds much like additional ignition timing and fuelling added such as with a cold start .. by ramping up the ignition by say 20 degrees you could easily see 1600rpm tickover, and the excess fuel would make it hard to start of course.
As said above it would be great to see the ignition values when it is playing up .. tickover should generally be around say 12-15 degrees but with cold start trimming that would be say 25-30degrees?
The most obvious culprit for a cold start scenario when the engine is hot would be the temperature sender for the ECU or it's associated wiring back to the ECU itself.
The good news is youve got another scorching day today to try that out
It sounds much like additional ignition timing and fuelling added such as with a cold start .. by ramping up the ignition by say 20 degrees you could easily see 1600rpm tickover, and the excess fuel would make it hard to start of course.
As said above it would be great to see the ignition values when it is playing up .. tickover should generally be around say 12-15 degrees but with cold start trimming that would be say 25-30degrees?
The most obvious culprit for a cold start scenario when the engine is hot would be the temperature sender for the ECU or it's associated wiring back to the ECU itself.
The good news is youve got another scorching day today to try that out
Thanks gents.
two small problems - 1. the starter motor just died so i cant even start it - will swop it for a new one tomorrow 2. dont have the laptop, lead or sfotware and wouldnt know waht to do with it if i did.
Joo - when you say temp sensor do you mean the air temp one on the air intake? I would like to replace all sensors anyway - what are they called and where are they?
thanks
Jes
two small problems - 1. the starter motor just died so i cant even start it - will swop it for a new one tomorrow 2. dont have the laptop, lead or sfotware and wouldnt know waht to do with it if i did.
Joo - when you say temp sensor do you mean the air temp one on the air intake? I would like to replace all sensors anyway - what are they called and where are they?
thanks
Jes
He is referring to the water temp sensor, it's under the front panel. Looking from the front of the car it'll be on your right fitted into the metal pipe, same plug that goes onto the throttle pots connected to it.. Peel the rubber boot back and check the wiring while you're in there easily damaged.
update - carbon can and breather to it removed and plugged. Roll over valve to be fitted to fuel tank tomorrow along with new air temp sensor and barometric pressure sensor. Water temp sensor already changed.
the crank sensor must work or the engine would not run
Can anyone think of any other engine input sensors to change just for the sake of completeness?
where are the lambda sensors and are they easy to get at/change?
the crank sensor must work or the engine would not run
Can anyone think of any other engine input sensors to change just for the sake of completeness?
where are the lambda sensors and are they easy to get at/change?
Jes, the lambda sensors are on the top of the manifolds (one each side)just before the manifold down pipe joins the cats (or decat link pipes), (under the gearbox). they are a bit of a pita to reach in my humble opinion. Your trying the scattergun approach then?!! See you at Abingdon!
Jes, get Alex on the case with the software!
I can send you my lead if you like and all you need is an old PC laptop with serial port, you can borrow that as well if you need it.
The software is available from Dave Hinns site or email me and I'll send it over to you.
Even if you don't understand the diag' software you can get some screen grabs and post them here so we can all have a look, it's all pretty intuative and common sense will see you right.
ATB
Tim
I can send you my lead if you like and all you need is an old PC laptop with serial port, you can borrow that as well if you need it.
The software is available from Dave Hinns site or email me and I'll send it over to you.
Even if you don't understand the diag' software you can get some screen grabs and post them here so we can all have a look, it's all pretty intuative and common sense will see you right.
ATB
Tim
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