Chris.Porter Posted April 30, 2022 Report Share Posted April 30, 2022 My PI TR6 has developed an annoying misfire but only between about 1500 -2000 rpm. Idles smoothly, as does initial acceleration, then the lumpy phase and back to smooth running. Thinking about checking injectors but if one was blocked, presumably it would misfire constantly? Have just taken it out for a good blast (Italian style -as suggested elsewhere) but just the same. Any ideas gratefully appreciated. Chris Porter Quote Link to post Share on other sites
Iruka Posted April 30, 2022 Report Share Posted April 30, 2022 Hi Chris, had a similar problem with my CR car last year. Would idle and accelerate smoothly until about 1600 rpm then become “lumpy”, clearing at 2000 rpm. Checked the points, condenser, rotor arm, distributor cap, ht leads, coil and all ok. Checked the fuel pressure (106 psi), throttle body butterflies, checked all the injectors were spraying correctly. All ok. Eventually bit the bullet and sent the metering unit off to Neil Ferguson for recalibration and set up. (Great service by the way) Refitted the overhauled metering unit, problem solved!! Steve Quote Link to post Share on other sites
Waldi Posted April 30, 2022 Report Share Posted April 30, 2022 (edited) Hi Chris, Steve (above) sums it up nicely. If the lumpyness disappears with more throttle, it could very well be the balancing of the throttle bodies, but other parameters are affected as well (change in vacuum which affects the fuel amount). Waldi Edited: I meant the opposite of what I wrote. Edited April 30, 2022 by Waldi I wrote the opposite of what I meant. Quote Link to post Share on other sites
Andy Moltu Posted April 30, 2022 Report Share Posted April 30, 2022 If the lumpiness dissappear on full throttle that may well indicate throttle imbalance. At light throttle the imbalance is more significant. A dribbling injector or partially blocked one is often most noticeable in the mid rev range. Pull them one by one to check they are all spraying nicely. Any iffy ones: remove and blow through with an airline before spending money on replacement. The golden rule of all things Lucas PI: check the ignition system first. Quote Link to post Share on other sites
Mike C Posted April 30, 2022 Report Share Posted April 30, 2022 If you have a timing light check that you are getting a smooth ignition advance and that the weights aren't sticking. Quote Link to post Share on other sites
Brent C Posted May 6, 2022 Report Share Posted May 6, 2022 Hi Chris Have you been able to trace the cause of your misfire? Quote Link to post Share on other sites
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