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348 Loss of power when hot and engine cutting out

Discussion in 'Technical Q&A' started by 348uk, Mar 7, 2004.

  1. 348uk

    348uk Karting

    Feb 1, 2004
    60
    UK
    Full Name:
    Andrew
    I took my 348 for it's normal Sunday blast today. It perfromed as normal when cold, but when it warmed up it wouldn't rev past 4,000 RPM. This then became 3,000 RPM and when I stopped in traffic it cut out altogether and was a B*****d to restart. I got it going eventually but had very little response from the accelerator, luckily I was 1/4 mile from home.

    At no time at all did the slow down lights illuminate. It was as though a bank of cylinders had shut down, the loss of power was that severe. I'm guessing this is related to the CAT thermosensors or ECU, but surely a warning light should have come on. On the ignition stage, both lights do illuminate so there's not a blown bulb.

    Has anybody any ideas as to the problem?

    More importantly, does anybody know of a way to diagnose and cure it?

    I'm having a tubi and test pipes fitted in a couple of weeks, will this naturally cure the problem? (Although I'd prefer to fix it before this anyway)

    My Sundays won't be the same until it's running smooth again........... :-(
     
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  3. 360CS

    360CS F1 Rookie

    Nov 1, 2003
    2,641
    Kent
    Full Name:
    Joe J

    Is the car running fine NOW!! Sometimes little things like this occur and never come back...but sounds heat related from an overheated cat which shut that bank down via the thermosensor>>

    Joe
     
  4. 348uk

    348uk Karting

    Feb 1, 2004
    60
    UK
    Full Name:
    Andrew

    Yeah just let it cool down, runs fine.

    Took it for another drive and as soon as it's warmed up, it suffers terrible power loss!
     
  5. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    22,028
    The Brickyard
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    The Bad Guy
    Are you sure it wasn't the clutch slipping?
     
  6. JSL

    JSL Formula 3

    Jan 5, 2002
    2,212
    California
    Full Name:
    J.S. Leonard
    I would be willing to bet it is the ECU. Should have had a light 1-8 or 5-8, but the symptom is most likely ECU's. I wouldn't disconnect them if you think there may be a Cat overheat problem. Try resetting them by disconnecting the battery for about 20 minutes then start the car without touching the gas and let it idle for about 15 minutes. Since you are having Tubi put on your problem should be fixed. Good luck.
     
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  8. fatbillybob

    fatbillybob F1 World Champ
    Consultant Owner

    Aug 10, 2002
    19,166
    socal
    try disconnecting the exhaust ecus both sides during the warm up phase to see if this stops problem. Exhaust ecus work just a bit less reliably than your dash lights. Your problem sounds electrical.
     
  9. 348uk

    348uk Karting

    Feb 1, 2004
    60
    UK
    Full Name:
    Andrew
    Definately not the clutch, I lost power, not drive.
     
  10. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    22,028
    The Brickyard
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    The Bad Guy
    Well since it isn't the clutch, I'm gonna have to go with what the fellas said. Check your exhaust ecu's. The other thing it could be is that your cats are history. The insides could be destroyed causing the loss in power. Ask billybob, he knows all to well what happens with that. His car didn't like chocolate chip cookies, so it spit them out. LOL!!!
     
  11. 92_348ts

    92_348ts Formula Junior

    Jun 6, 2002
    282
    Boise, Idaho
    Full Name:
    Chris
    I think Fatbillybob is right on the money. Try switching around your exhaust wiring to determine if it is simply a bad component. I just went throught the exact same thing on my car and it turned out to be a bad thermocouple (no warning lights on mine either). Check the "old" archives for litterally hundreds of threads on the subject.

    Also, I don't know what year your 348 is, but if it has the motronic 2.7 ignition you will be able to place the car in self diagnostic mode to determine the actual error that shut the bank down.
     
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  13. 348uk

    348uk Karting

    Feb 1, 2004
    60
    UK
    Full Name:
    Andrew

    Thanks for this suggestion, I'll try it later today and let you know how I get on.
     
  14. 348uk

    348uk Karting

    Feb 1, 2004
    60
    UK
    Full Name:
    Andrew
    Thanks for the advise guys.

    I'll try these suggestions and let you know the outcome.
     
  15. 348uk

    348uk Karting

    Feb 1, 2004
    60
    UK
    Full Name:
    Andrew
    An update on my loss of power problem.

    After disconnecting the battery over night (to clear the ecu memory), I've just unplugged both the CAT ecu's and then reconnected the battery. Having just taken the car for a drive to warm it up, the problem still exists.

    As soon as it warms up it starts loosing power at around 4,000 RPM, the effect is as though it is running out of fuel or running on kangaroo juice ! The whole car starts jerking and the rev counter needle jumps up and down. Below 4,000 RPM it seems fine. Very soon after this, the loss of power comes in at 3,000 RPM and then the engine will hardly run at all, as though it is on 4 cylinders. If I then have to stop in traffic, it'll cut out and be very difficult to restart. When it does restart, it hardly responds to the throttle, again I guess running on 4 cylinders.

    With the CAT ecu's disconnected, I guess this can't be related to the thermsensors. OR COULD IT?

    Should I have also disconnected the thermosensor plugs going in to the ecu's? I thought not, as I had connected the output from the ecu, the thermosensors would have no effect to the running of the car. AGAIN, AM I CORRECT HERE?

    Can anybody suggest any likely causes for this and the best way to test for them?

    It seems that it is definately engine temperature related as it is sweet as a nut when cold.

    Any help would be very much appreciated before I have to take it to the experts and part with some serious cash !
     
  16. 348uk

    348uk Karting

    Feb 1, 2004
    60
    UK
    Full Name:
    Andrew
    I have been checking a few more things out when the car has warmed up.

    With the engine ticking over at idle and the missfire present when the engine speed is picked up to 3,000 RPM + I pulled the electrical plug to each coil bank. This made a difference to the engine running for both sides. Thus eliminating the shut down of a cylinder bank.

    I think that this is fuel related as I opened the fuse cover in the footwell and can hear the relay for the RH Fuel pump occassionally click. I removed the fuse for the RH fuel pump and it made no difference to the running of the car, I removed the fuse for the LH fuel pump and the car cutout. I also did this for the relays and the RH made no difference but the LH cut the engine. I then swapped the relays over, put the RH in the LH slot and visa versa, but the result was the same, the RH fuel pump not working.

    Does anybody know how these fuel pumps work? Should they both be running at the same time or does the RH one cut in at a certain RPM or fuel pressure point?

    How do I check these and what controls the fuel pump circuit? Is it linked to an ecu etc etc ??

    I'd be grateful for any pointers here as I'm now totally stumped and think that I've been barking up the wrong tree with the thermsensors and CAT ecu's !!
     
  17. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,354
    Texas
    Full Name:
    Steve Magnusson
    The US 348 OM indicates that the fuel pumps "are controlled by the electronic ignition-injection control units", but there's also a separate pressure regulator gizmo for each bank too. (I've not downloaded any non-US 348 OMs -- but I'd be very surprised if your version was any different in this area -- have you read the ignition/injection/fuel section?).

    My take is that they are independent banks fuel-wise so your disabling of the RH fuel pump with no change in (the bad) behavior is a clue to keep looking in that area (i.e., RH fuel supply) -- although, whenever there's an ecu involved, some upstream control foo (or the ecu itself) might be the real problem.

    Good hunting...
     
  18. fatbillybob

    fatbillybob F1 World Champ
    Consultant Owner

    Aug 10, 2002
    19,166
    socal
    If you run without the exhaust ecus running and you still have a problem then your problem has nothing to do with the exhaust ecu's and thermocouples. I told you to disconnect them as a diagnositc aid. Your problem is the electronics in the fuel circuit. Or possibly in the secondary wiring. Or fuel to the fuel circuit. Look for burnt wiring and arching of sparkplug wires. Sometimes you can see a tell tale trace where the wire grounds out and you get no spark. You can hard wire the fuel pumps to make sure pressure is in the system. I spliced in permenant fuel pressure guages so that I can always see what is happening left and right. This allows quick diagnosis when problems occur. If you got pressure then you have fuel and your fuel pumps are working and the fuel pressure regulators work (see WSM specs) Sometimes you can go it a quicky tune place and just put the car on the scope for 30 bucks and see which banks are no firing over 4000rpm. Then switch a wire to see if that changes. That will tell you if the wires are good or bad. If the scope shows good firing with ****ty running you may have a high rpm fuel problem like a pliugged fuel filter. If that is not it then as your engine heats up connections are connected but increasing in resistence due to poor contact somewhere. The problem is where? It could be a simple connector. It is tough to find these problems. I had a problem that palgued me for 1 year. Ernie knows of my problem when he was forced to spray starter fluid in my airbox to help me get my car started at the alignment shop. Here is where you start. Look at the numbers for the passenger footwell relays for the two fuel pumps circuits. Find another relay with same numbers and swap them in for the fuel pump relays. See if your problem goes away. If not then start by reestablishing all grounds. First start with your battery ground. Next go to the grounds on your valve covers. Then if that does not work go to the grounds behind the passenger footwell fuse box. Then check your fuel pump connections under your gas tank. The fuel circuits are dual and independant. The pumps run simultaneously all the time the motor is cranked or running. They do not run when the engine is off even when key is in the #2 position. Also, go behind your seats and take out your ecu's. Spray contact cleaner and let dry overnight before reconnecting. Do the same with the TPS and MAF sensors and ignitors and coils

    With the engine ticking over at idle and the missfire present when the engine speed is picked up to 3,000 RPM + I pulled the electrical plug to each coil bank. This made a difference to the engine running for both sides. Thus eliminating the shut down of a cylinder bank.

    maybe you can have a bad wire on both sides

    I think that this is fuel related as I opened the fuse cover in the footwell and can hear the relay for the RH Fuel pump occassionally click. I removed the fuse for the RH fuel pump

    When the car was misfiring right?

    and it made no difference to the running of the car, I removed the fuse for the LH fuel pump and the car cutout. I also did this for the relays and the RH made no difference but the LH cut the engine. I then swapped the relays over, put the RH in the LH slot and visa versa, but the result was the same, the RH fuel pump not working.

    This all when car is missfiring when hot?
    No the right fuel circuit is not working. You can hard wire the RH fuel pump under the gas tank to ensure that it is o.k. Also if you have a plugged RH filter the result is the same.
     

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