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700/900 Series General Forum for the Volvo 740, 760, 780, 940, 960 & S/V90 cars |
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Hesitation after boost: 940 B200FT 1991.Views : 299 Replies : 4Users Viewing This Thread : |
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Nov 27th, 2020, 18:38 | #1 |
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Hesitation after boost: 940 B200FT 1991.
Adding a new problem to the catalogue of errors with my smoking 940.
Last week and again tonight I took the motorway home. I gunned it up the sliproad to get up to speed. Once cruising, I felt it backing off, and hesitant to go again if I gave it a bit of throttle. If I give it plenty of throttle it picks up and off it goes again... but just crusing along at 60, it feels like it's bucking and backing off. Suggestions on a postcard please |
Nov 27th, 2020, 19:13 | #2 |
Go redblock or go home
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Vacuum leak
MAF needs cleaning Throttle body cleaning When were the spark plugs last changed or cleaned and gapped to 0.7mm? When was the fuel filter last changed? Have you checked both fuel pumps are working? Have you read the codes? |
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Nov 27th, 2020, 19:36 | #3 | |
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Quote:
The inline pump is working - can hear it wirring away. Have yet to change the filter.. Plugs are actually getting changed tomorrow as well as the O2 sensor - its original and very overdue a change at 170k. Not sure how to clean the MAF - I thought it was self regenerating? I reckon a soapy water test is in order. |
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Nov 27th, 2020, 23:39 | #4 |
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Until you sort that wiring to the CTS/ECU then you will have this problem as it's trying to run too much advance. As you are cruising it's trying to (usually) add more advance for economical running but it will add too much for a hot engine so the knock sensor will kick in and retard it again. Then it will advance again until it triggers the knock sensor and just keep doing this, hence the kangaroo petrol effect.
Don't forget to erase the codes/fuel trims in the ECU when the new Lambda is fitted! :thumbs-up:
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Cheers Dave Next Door to Top-Gun with a Honda CR-V & S Type Jag Volvo gone but not forgotten........ |
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Nov 28th, 2020, 06:51 | #5 |
Go redblock or go home
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You've answered your own fault there then. As Dave says if the signal for the ECU coolant temp sensor isn't getting to the ecu properly then it will never run right.
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