Announcement

Collapse
No announcement yet.

Fiat engine rough running..

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Fiat engine rough running..

    Having just returned from a fabulous trip over to Applecross and Torridon in my Roadster with wall to wall sunshine and plenty of heat (like having a hairdryer blowing at us the whole time!) I encountered a problem which I need some advice about…

    I have the Fiat twin-cam 2.0 with the single original Weber 34 ADF250

    Driving up the Bealach na Ba which I think is the highest public road in the UK at 2,100’+ in 23*C the car performed flawlessly but I was watching the water temperature going up and up. It almost reached 100*C. We parked up at the top and opened the bonnet side to let the cool breeze help cool it down – all the while the fan was whirring away too. After stretching our legs we came back, closed the bonnet and then drove down the hill. The water temperature was now down to a respectable 75/80 however the engine was clearly unhappy and almost felt as though it was starving for a richer fuel mixture as it would cut out when idling – which meant passing places were awkward as I’d constantly stall and have to restart again. It wouldn’t idle happily and would struggle to keep alive but usually it’d just cut out.

    I figured the Carb might need a mixture screw tweak – but it is in such an awkward position right near the engine bay louvre side that I couldn’t possibly get a screwdriver into the channel to reach the screw deeper within. So the only option was to adjust the throttle lever stop screw until it would remain running, higher tick over (1000) but running at least. Nonetheless, even when running along at 10-30mph it just doesn’t feel happy and is pretty rough. Above 30 it was fine.

    We got back home and she’s parked in the garage awaiting surgery… I’d be surprised if it really needs a mixture tweak because prior to the hot hill ascent, it has been perfect – starts every time, runs smooth and no rough idling at all.
    So, knowing virtually nothing about Carb dismantling & repair I’m hesitant to start an overhaul – but the spondulicks are in short supply and this hot sunny summer weather won’t last forever.. So I turn my request for your advice… What would you suspect is the trouble and do you have a link to a web page showing step by step details / pictures of its repair.. – I’m better when I can watch / see another doing it than just attempting blindly on my own…!

  • #2
    Re: Fiat engine rough running..

    I would check the condition your oil and spark plugs. Oil is easily done by inspecting the dipstick and checking nothing serious has been done to the engine to cause coolant to leak into the oil. The spark plugs can indicate a problem with ignition or fuelling and any discrepancy between the cylinders.

    As you say the settings should not require changing but something has probably altered and you need to try and isolate that. Do the simple stuff first.
    Paul

    Comment


    • #3
      Re: Fiat engine rough running..

      I noticed on Sunday which was a hot day my 1800TC engine was running hot even at 40+mph. When I turned the fan on it cooled better. I wondered if the idling fan was restricting the airflow on a hot day?

      Comment


      • #4
        Re: Fiat engine rough running..

        I have a spare day today, so I'll check the spark plugs and oil (only changed it 3 weeks ago).. someone has suggested the carb jets might need cleaning and maybe a bit of dirt has got in and blocked one, particularly the idle jet.. that would be a major task for me...

        Comment


        • #5
          Re: Fiat engine rough running..

          I think that doing a compression check would be a wise route as I fear that the turning the engine off as soon as you reached the top may have done the damage.

          If the engine wasn't actually boiling over after working hard up hill then it would have benefited from being allowed to fast idle with the water pump and fan running for a few minutes to dissipate any hot spots.
          Ben Caswell probably not the last word on anything here!!

          Comment


          • #6
            Re: Fiat engine rough running..

            Look for air leaks. I have the fiat twin cam and they are very robust engines. There are 2 outlets from the carb that can be used for vacuum. Check they are sealed tightly. Check the pipe work from the inlet manifold to the brake servo for leaks also. Air leaks will make the engine run lean. Running an engine lean makes it run a lot hotter than normal. The Weber carbs only use the mixture for idle running and early progression. Check that the run on solenoid is functioning correctly as this will starve the carb of fuel if not fully retracted.
            Do not be tempted to increase the idle speed by opening the throttle butterfly past 2 1/2 turns as you will start to expose the second progression hole and this will effect the overall running. Check the bleed screw o ring is sealing well.
            Do you have a fuel filter fitted? Is it between tank and pump or pump and carb. If between pump and carb then remove it or move to between tank and pump.
            Mk2 SWB Marina Roadster with a 1800 Fiat Twin Cam engine and 5 speed Abarth gearbox built in 1987
            - I have no idea what I am talking about........ but my advice is always free! -

            Comment


            • #7
              Re: Fiat engine rough running..

              Ok here's the update...

              I checked the oil - to find it was very low; the dipstick is small but it only showed 1/4" on the bottom of the stick. No white residue so no water contamination and the oil was still its lovely brown colour. Considering I only changed the oil 3 weeks ago, I looked underneath to find I definitely have an oil leak from somewhere. Odd given that it didn't apparently leak prior to the oil change & as far as I can see, the (new) oil filter seal seems good. However thinking methodically now, I looked all over and the highest point I can see oil appears to be around the oil pump area; but without really getting underneath and using a mirror & torch, I can't say for sure. So I went out & got some more oil and intend to thoroughly clean everything then top it up again and warm her up and look for the first signs of a leak. Low oil would likely make it run hotter...

              Next up the plugs, took off no4 lead and found it rusty inside so I thoroughly cleaned up the contact terminal, all other leads were fine. All plugs seem to indicate it has been either running too lean or running very hot (low oil?). All plugs were virtually correct in their gaps.

              I don't have a compression tester.
              Attached Files

              Comment


              • #8
                Re: Fiat engine rough running..

                Originally posted by element View Post
                Ok here's the update...

                I checked the oil - to find it was very low; the dipstick is small but it only showed 1/4" on the bottom of the stick. No white residue so no water contamination and the oil was still its lovely brown colour. Considering I only changed the oil 3 weeks ago, I looked underneath to find I definitely have an oil leak from somewhere. Odd given that it didn't apparently leak prior to the oil change & as far as I can see, the (new) oil filter seal seems good. However thinking methodically now, I looked all over and the highest point I can see oil appears to be around the oil pump area; but without really getting underneath and using a mirror & torch, I can't say for sure. So I went out & got some more oil and intend to thoroughly clean everything then top it up again and warm her up and look for the first signs of a leak. Low oil would likely make it run hotter...

                Next up the plugs, took off no4 lead and found it rusty inside so I thoroughly cleaned up the contact terminal, all other leads were fine. All plugs seem to indicate it has been either running too lean or running very hot (low oil?). All plugs were virtually correct in their gaps.

                I don't have a compression tester.
                That rusty plug connector is shot. Look at burton power, they do Magnecor ht leads for the Fiat twin cam 7mm. I used them for my classic and the difference is amazing. Peter.

                Comment


                • #9
                  Re: Fiat engine rough running..

                  Did cleaning lead 4 make a difference?

                  Running lean is a common cause overheating particularly under load. It might be time to take the engine louvre cover off and adjust the mixture. If it only takes a small adjustment it could be down to normal wear and tear. A large adjustment might indicate some more dramatic course of action.

                  When driving in traffic with the top down I am only too aware that many cars do not have their mixture right – even modern computer controlled ones.

                  I know rough running can be an indicator of gasket problems, warping or some kind of other serious damage but usually it is not.
                  Paul

                  Comment


                  • #10
                    Re: Fiat engine rough running..

                    I haven't started it since the other night returning from the trip away. I want to top up the oil and try to resolve the oil leak issue before starting her up again. That rusty clip is now clean and as shiny as I could get it with the fine Si C paper I used, I don't think it will be a problem anymore. I also put a bit of grease around the inside of the rubber plug cover to try to prevent that happening again. I suspect it only happened there to that lead because in the rain it probably drips onto that area; I try not to drive in the rain but did a while ago.
                    Hadn't thought of removing the louvre side.. I'll look at that.

                    Comment


                    • #11
                      Re: Fiat engine rough running..

                      A number of sources agree that changing the leads every 5 years or less is advisable. It's a very easy job.
                      Paul

                      Comment


                      • #12
                        Re: Fiat engine rough running..

                        Hi Element,
                        I too have the Fiat 2.0L Twin Cam in my Roadster with the stock Weber 34ADF 54/250. Do you have the Haynes manual for the Mirafiori? There is a very good section in the supplement explaining the carb and its adjustments. Also, Haynes do a very good book called Automotive Carburettor Manual. In it there is a whole section dedicated to the Weber carburettor and explains in detail how it works and more importantly, how to adjust it.
                        chris

                        Comment


                        • #13
                          Re: Fiat engine rough running..

                          Did you change the oil filter with the oil change? If so just check that the oil filter is tight, if you have a leak where you never had one before it might be seeping past the filter seal.
                          Originally posted by element View Post
                          I have a spare day today, so I'll check the spark plugs and oil (only changed it 3 weeks ago).. someone has suggested the carb jets might need cleaning and maybe a bit of dirt has got in and blocked one, particularly the idle jet.. that would be a major task for me...

                          Comment


                          • #14
                            Re: Fiat engine rough running..

                            Originally posted by stevepritch View Post
                            Did you change the oil filter with the oil change? If so just check that the oil filter is tight, if you have a leak where you never had one before it might be seeping past the filter seal.
                            Hi Guys
                            Always change the filter!
                            Oil lasts a surprisingly long time before it degrades - the Chrysler study I read detected the first degradation at 70,000 miles
                            But filters do block up and that lets unfiltered oil into the gallery
                            So it's more important to change the filter than to change the oil!

                            Comment


                            • #15
                              Re: Fiat engine rough running..

                              If it's heat affected it has got to be either sparks or fuel. I had another heat affected fault on my Classic which was a blocked idle jet and it kept happening during a very hot European tour which was very annoying. It was eventually found to be due to minute scale deposit in the cross drilled feed passages in the carb body. The heat caused this to flake off in very small pieces but enough to block the idle jet. Remove the idle jet(s) and give it and the feed passages a good blow through with compressed air as a starting point. Peter.

                              Comment

                              Working...
                              X