Cultus 2007 VXRI EFI engine jerks on low rpm

aminjafer5441 (Amin Jafer) 2020-03-04 23:34:59 +0500 #1

The engine starts jerking violently when decelerating in any gear below 2000 rpm. Also when accelerating in any gear under 2000rpm it violently jerks like as if it is turning off and on. No work has been done on the engine recently, this issue started after a trip to Highland near Pir Sohawa. Could I have strained the engine or something?
Can any experienced member kindly help me out with this issue or short listing the possible causes.

shockxwave (Emad Arshad) 2020-03-05 08:48:59 +0500 #2

Get it tuned..

aminjafer5441 (Amin Jafer) 2020-03-05 09:29:33 +0500 #3

There are so many factors that could be the reason. Even Suzuki dealership said there is no issue on scan tool. Other maintenance has already been done like IAC valve and TB service etc.
Could you please elaborate what you mean by tuning?

Also I forgot to mention that the jerking starts once the engine warms up, on cold engine there are no jerks.

shockxwave (Emad Arshad) 2020-03-05 09:41:21 +0500 #4

Did you check the coils and spark plugs??

TypeA (TypeA) 2020-03-05 09:59:16 +0500 #5

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aminjafer5441 (Amin Jafer) 2020-03-05 10:31:05 +0500 #6

Yes, plug wires and plugs are new. Coil seems good even got it checked by electrician

margallar (margallar) 2020-03-05 10:34:16 +0500 #7

your car will have an timing advancer under the glove box, it is probably acting up.

Try to bypass it, on my 2011 model, there was a extra connector ziptied to the advancer wiring. It only has one wire.

Remove the male connector from the advancer and plug it into the other (above mentioned) and then start the car to check.

Our cultus is recently having a slight idle issue but not having the right scan tool is a problem...

engnr.mubashir (engnr.mubashir) 2020-03-05 10:45:44 +0500 #8

My cultus is also havong same issue and there is not factory fitted CNG it was after market one and have already got it bypassed but problem is still there. Even my mechanic said that it's not even running lean or rich. There is something ghost problem which is not being solved. One thing want to mention this problem was there for 2 year but now days this is problem is more annoying.

aminjafer5441 (Amin Jafer) 2020-03-05 10:53:13 +0500 #9

I'll try to bypass the advacer and check if the issue persists, I really hope it helps

aminjafer5441 (Amin Jafer) 2020-03-05 10:55:07 +0500 #10

Mine is FF CNG though. Same issue here, the car is actually even giving good economy on both petrol and CNG also which is why I don't want to fiddle too much. But the jerking is sometimes so violent it feels like the engine mounts will break.

chantalgardener (chantalgardener) 2020-03-05 11:06:19 +0500 #11

Awesome! Same here, I should be considering a different one.

aminjafer5441 (Amin Jafer) 2020-03-07 22:00:36 +0500 #12

Issue still persists after changing the advancer port. This is really a ghost issue as there is no error code or anything faulty as such. Could there be an issue with the Ignition coil?

engnr.mubashir (engnr.mubashir) 2020-03-08 01:24:45 +0500 #13

I think this issue has nothing to do with CNG even I have bypassed the Advancer even have removed harness whoch bypassed injectors and cng ro petrol load relay also removed still not success. It has something to do with fuel pump someone told me to get your fuel pump checked.

aminjafer5441 (Amin Jafer) 2020-03-09 18:46:13 +0500 #14

I tried bypassing the advancer by plugging into the white socket instead of red but the car ran like s*** after that. It was like it was running on only 2 cylinders, it was missing so much. Then even tried leaving the advancer unplugged and still too much missing.

I think I'll have to get the fuel pump checked also but the ustaads in Islamabad are highly incompetent at their work and total theifs. I'll try to check it out myself in spare time only issue is that the whole tank needs to be removed.

aminjafer5441 (Amin Jafer) 2020-03-09 18:48:40 +0500 #15

Kindly Do post on this thread once you get the pump checked. This issue is really annoying in slow traffic. Also the issue is there on CNG also but it only acts up going uphill or decelerating at lower rpms. This makes me think that it may not be related to the fuel pump as it has no function when running on CNG.

engnr.mubashir (engnr.mubashir) 2020-03-09 20:07:31 +0500 #16

Actually I'm driving car on petrol. I haven't find any good mechanic who can check fuel pump or diagnose this issue.

aminjafer5441 (Amin Jafer) 2020-03-11 11:19:55 +0500 #17

Did you get a chance to check the O2 sensor? Another mechanic told me it could be bad or dirty O2 sensor. I will try to clean it this weekend to see if it makes any difference.

engnr.mubashir (engnr.mubashir) 2020-03-11 11:22:45 +0500 #18

Bro dirty or clogged O2 sensor also ruins fuel average I'm getting good average so for me it's not the sensor.

aminjafer5441 (Amin Jafer) 2020-03-11 12:07:10 +0500 #19

Same here, I'm also getting good average on petrol also when cruising in one gear. But having to slip the clutch constantly at lower rpms to prevent the jerking is making the car undriveable on petrol for short trips in city.

aminjafer5441 (Amin Jafer) 2020-03-11 15:36:45 +0500 #20

Does the EFI cultus have external fuel filter or is it in tank? According to my knowledge it should be in tank.