Help engine has random fault..

mjpuds · 05-05-2006, 05:56 AM

Seems this problem has been with me for some time now...car is a (86 3.2 ) starts fine ides fine ...battery charge not great but turns over well..i have replaced dme relay..fuel filter..timing and tappets done and mixture ...the problems seems to get worse when driven hardish....over 5000rpm...at this point the car almost cuts out...and then you have to leave it for ten mins or even longer .last night it needed at least two hours rest ....but even then drives very rough missing .firing at wrong times amount of judgering....could this be fuel pump..as in presure. have looked at ht leads for sparking at night all seem fine .and also done a quick leak test with eay start around inlet manifolds and other areas.....seems to flood very easy...could lack of power to ecu buy a weak battery do this ..last time i check battery with car running it was only picking up just over 12.volts

2.7RACER · 05-05-2006, 06:14 AM

The sensor on your flywheel is failing. There are two sensors. Replace them both.
Just happened to friend of mine this last weekend.
Get your charging system checked out. These cars like good voltage. Low voltage causes all kinds of problems.

mjpuds · 05-05-2006, 06:18 AM

thanks for that is it a complete engine drop..or just a half drop...

mjpuds · 05-05-2006, 11:19 AM

dose any one know if this is a engine out job or not

cmcfaul · cmcfaul's Garage

Clogged gas tank screen.

Remove the fuel gauge sender unit to gain access to the fuel tank. Right at the bottom is a quarter sized screen where the gas exits the tank and heads to the engine. Poke a hole in it and you are done.

Had the same problem and it confounded me for about a year.

Chris
73 911 E

nhromyak · nhromyak's Garage

If your replacing the flywheel sensors (2) you don't need to drop the engine. But it is a bit of PITA with the driver's rear tire removed.

If I were you, I would get a set of some known good replacement parts, before you buy them. As sensors (last I checked) were $150 each.
It could also be a bad or overheating coil.
Or worse, a bad DME ignition circuit. The ignition circuit are known to do just what you describe when they overheat.

If you have to let it "rest"after a higher RPM run, because it quits??? or does it simply run poorly?
If it quits...I think this will rule out a high-rpm fuel starvation.

Good luck!

mjpuds · 05-05-2006, 01:40 PM

thanks nick ...but do you mean the ecu when you say the dme ignition circuit......and sorry what do you mean by pita ...no it will cut out(sort of pitter out) and then run badly) when still moving about 30 seconds after the blast when i over take ..this is mostly when the car is running fine under a normal load. the milage on the car is 54000 and it is mostly still orginal...i got it at 41000 been in a private collection for 8 years just sitting there..(sin)the odd thing is if you just coast around with no harsh(5000 to5500rpm) out burst it wont happen.

nhromyak · nhromyak's Garage

Oops, yep. I mean the ignition circuitry inside the DME ECU. Sorry.

PITA = Pain In The Arse

That sounds like a fuel problem...

Try to differentiate if it is running rich or not when this happens.

IF IT's LEAN
Fuel Filter been replaced, or as above mentioned, the fuel pickup under the tank. It could also be a fuel pump going bad. Good luck.

IF IT's RICH
Could check the fuel pressure regulators, or the IA "barn-door" I forgot what this is called. It is just after the air-cleaner.

You will need to see if this is getting appropriately consist resistance readings as the barn door is moved across it's rang of motion. There is a check for this somewhere.... DVOM is required, I believe.

mjpuds · 05-07-2006, 11:24 AM

hi again would the ecu allow the car to run ok .(just thought dose the ecu need to be ground to the body work under the seat well or dose it have a ground in the wiring loom?).until the car was driven harder...or would this be best to think it was pump problem...what is the best way to fuel pick up is it to remove pump...and also where are the fuel pressure regulators on a uk car..sorry i no longer have any o fmy book to help me out ..

stlrj · 05-07-2006, 05:43 PM

Sounds like enough time for the ignition wires to have gone bad. Why not replace them and go from there?

Joe

nhromyak · nhromyak's Garage

It could be anything really.

It could be a faulty fuel accumulator, or filter.

If it takes 10 mins and then it runs fine after a hard run, it sounds like something is overheating or is rattled loose.

It could be a loose ground...

You can do all the regular stuff...

Is your Head Temp Sensor the newer two-wire style???
You can bypass this with some kind of resistor, not sure what Ohm sizing though. I suspect it is in the archives somewhere.

Check the grounds on the intake number one cylinder.
Check engine ground (is the only one on the transmission anyone?)

Check battery grounds, it could also be a voltage problem as you mentioned in the original post.

Does it run up to 5500 rpms and stay there for a while with no load? Does it still run OK?

If not, check your voltages at idle and at this rpm.

Good luck.

ChrisBennet · ChrisBennet's Garage

If the speed and reference sensors are original, they are at the end of their reliable life. Replace them anyway.
-Chris

mjpuds · 05-11-2006, 11:25 AM

ok thanks for all the help...took off all air box and air flow meter and noticed one of the breather hoses to top of engine was missing the clamp...this was where the leak must of been..so runs fine up to line with no cutting out ...BUT...did stall when i went to pull off and took 40 seconds to restart..could this be the coil ..all voltages seem ok at idle and high revs..at battery and coil over 14.volts...this wouldnt be a fuel problem because would happen more often i would think ...after it stalled it ran fine ..if it was the head sensor i looked and i could seem to see it ..i could see two sensor on the topo of the engine near beather pipe from oil tank..is it one of them