Hesitation after boost: 940 B200FT 1991.

StrongSpearWorks · Nov 27th, 2020, 18:38

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

360beast · Nov 27th, 2020, 19:13

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?

StrongSpearWorks · Nov 27th, 2020, 19:36

Quote:

Originally Posted by 360beast

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?

I’m not getting any codes other than a known wiring issue with the ECT signal to the EZK. (224)

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 - it’s 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.

Laird Scooby · Nov 27th, 2020, 23:39

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:

360beast · Nov 28th, 2020, 06:51

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.

Nov 27th, 2020, 18:38	#1
StrongSpearWorks Member Last Online: Nov 26th, 2022 15:34 Join Date: Sep 2019 Location: BRISTOL	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, 23:39	#4
Laird Scooby Premier Member Last Online: Yesterday 20:02 Join Date: May 2012 Location: Lakenheath	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: __________________ Cheers Dave Next Door to Top-Gun with a Honda CR-V & S Type Jag Volvo gone but not forgotten........

Nov 27th, 2020, 19:13	#2
360beast Go redblock or go home Last Online: Today 01:27 Join Date: Feb 2012 Location: UK	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?

Nov 28th, 2020, 06:51	#5
360beast Go redblock or go home Last Online: Today 01:27 Join Date: Feb 2012 Location: UK	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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