Cultus 2007 VXRI EFI engine jerks on low rpm

engnr.mubashir (engnr.mubashir) 2020-03-11 16:16:08 +0500 #21

Pump is in the tank. Fuel filter is placed outside nearby Rear Left tire. If you jack up your car you will see it there.

aminjafer5441 (Amin Jafer) 2020-03-13 14:24:03 +0500 #22

Just an update on the issue. I've managed to solve the jerking issue on CNG by increasing the flow, but on petrol it remains. I've changed the fuel filter and there was a lot of black dirt coming out of it. Is it possible that the filter had failed and allowed dirt into the injectors?
Do you think any fuel system treatment like Liqui moly would help ?

engnr.mubashir (engnr.mubashir) 2020-03-13 14:47:12 +0500 #23

I when I changed my fuel filter it was also clogged very badly and replacement didn't solved jerking issue. I have used alomest 3 bottles of STP fuel treatment till now didn't help. I think there is nothing wrong with injectors seems main cultprit is fuel pump because it's loosing pressure when rpm is low or car goes in highr gear with lower rpm. One thing I have notice that these jerks suddenly disappears and comes again put of now where. BTW this issue with my car was there since long ago like 2 to 3 years but it has gotten worse now. I contacted a workshop a guy there is asking 1000 to get the fuel pressure check with gauges.

RehanBhatti (RehanBhatti) 2020-03-13 16:11:32 +0500 #24

Check your injectors ground wiring from some skilled electrician.

aminjafer5441 (Amin Jafer) 2020-03-13 18:14:07 +0500 #25

Does your car have the jerks even when the engine is cold? Mine doesn't have these jerks when the engine is cold I guess because the ECU fuel delivery is in open loop mode. The issue only happens once the engine warms up to about a quarter on temp gauge and the ECU probably enters closed loop operation. Even on higher RPMs or wide open throttle the jerking stops but return immediately at lower RPM.
I'm really stuck at the cause of this issue but will be investigating further this weekend.

aminjafer5441 (Amin Jafer) 2020-03-13 18:15:07 +0500 #26

Ground wiring has been checked also by electrician and it is solid.

RehanBhatti (RehanBhatti) 2020-03-13 18:16:56 +0500 #27

Did you get that Vgate elm 327 scanner?

aminjafer5441 (Amin Jafer) 2020-03-13 18:23:34 +0500 #28

Not yet. It is quite expensive online and I don't know of any shop in ISB/RWP where we can buy it.

RehanBhatti (RehanBhatti) 2020-03-13 18:27:11 +0500 #29

How much is it online? I got mine in Rs1500.

engnr.mubashir (engnr.mubashir) 2020-03-13 18:51:22 +0500 #30

From where ?

RehanBhatti (RehanBhatti) 2020-03-13 19:03:20 +0500 #31

It was on Daraz in 2018.

engnr.mubashir (engnr.mubashir) 2020-03-13 19:06:53 +0500 #32

Now someone is selling it for 2500. While on AliExpress it's for 1000.

engnr.mubashir (engnr.mubashir) 2020-03-13 19:08:42 +0500 #33

Yes happening worst with hot engine. Any possible solution.

aminjafer5441 (Amin Jafer) 2020-03-13 19:12:52 +0500 #34

Online on Daraz it is around 3000.

aminjafer5441 (Amin Jafer) 2020-03-13 19:14:14 +0500 #35

I'll try to have it diagnosed tomorrow and post back the findings.

aminjafer5441 (Amin Jafer) 2020-03-14 17:30:09 +0500 #36

Just an update about the solution to this problem. It was a faulty TPS sensor. Today I had everything opened up, fuel tank, fuel pump injectors fuel filter and replaced pump and filter. Then had the injectors cleaned and tested on machine but still no resolution to the problem.
Finally after a lot of troubleshooting we decided to change TPS sensor and the issue vanished like nothing ever happened!
So I would suggest that anyone with this problem should first have the TPS changed and then check. Please note that Faulty TPS does not give any check engine light only a dead TPS will give check engine light.
The TPS costed me 1600 from an electrician in Islamabad.

RehanBhatti (RehanBhatti) 2020-03-14 17:45:08 +0500 #37

Good to know that you solved the issue. BTW, a faulty TPS can be checked with a digital multimeter. A good TPS voltage increases smoothly till wide open throttle.

aminjafer5441 (Amin Jafer) 2020-03-14 18:11:14 +0500 #38

The TPS was Cheched twice before replacing and was giving even voltage increase/decrease when enigine was not running.
During engine operation there is vibration and heat which then affects the voltage output of the TPS. We tried getting the voltage once the engine was warm and running and the voltage started fluctuating randomly especially on closed throttle.

engnr.mubashir (engnr.mubashir) 2020-03-14 19:28:35 +0500 #39

Sounds interesting let me visit the my mechanic on monday.

sid.siddiki (Sid) 2020-10-12 19:48:36 +0500 #40

Experiencing the same issue with my car. Will you kindly tell me whether TPS will be repaired in this case or new one can be installed. Previously sparkplugs have been changed due to this issue.