Hello all. Firstly massive thanks to everyone for the years of questions and answers on here as it has helped me SO much with my recently-acquired 1997 1.3 MPI felly pickup. Figured it was about time I signed up.

 

Now on to the problem....when I'm accelerating, the car jerks back and forth. If I have my foot off or all the way down on pedal it's fine...only when my foot is 'hesitant' on the pedal. Also, when I start up the car, the revs 'hunt' (go up and down) for a few seconds before roughly settling. When the engine is warm it doesn't do this.

 

I've changed the timing chain, spark plugs + coil unit and checked the valve clearances to no avail. I plugged the OBD on and the following issues came up, which lead me to believe it's down to a sensor:

• Engine coolant temp. sensor: 00522: g62 open circuit/short with power

• intake manifold pressure sensor 00519: g71 open circuit/short with power

• O2 sensor: 00525: g39 input open

• engine speed sensor: 00513: G28 not a plausible signal

 

This morning, I ran the engine from cold. It climbed up to 95-100C before backing off slightly after 15 mins. The fan had not come on at this point but I'm sure it does kick in when I'm driving (need to double check). So as far as I can tell, the thermostat is ok?

 

As for help, I need to know how to test each of these sensors and how to test the wiring. Can I test the sensors and the wiring without removing anything? And are there common points where the wiring fails that might be worth checking? Also, is there one or two coolant temp and lambda/O2 sensors? I have a multimeter..just need to know how to test these sensors and wiring before I buy new ones.

 

Also, a bit of background on the car...when I got her, she drove absolutely fine (some rough idling). As far as I'm aware, it had hardly been used in a couple years. It only started jerking after I gave it new oil, new filters and sparks. I wonder if this is relevant at all...

 

Gutted I didn't test these before changing the timing chain haha! Any advice or info would be greatly appreciated. 

 

Thanks!! 

Also, here's a photo of the terminals on the MAP sensor plug. One of the pins looks pretty patina'd. Could it be this?

 

 

23 minutes ago, kinggwarn said:

Also, here's a photo of the terminals on the MAP sensor plug. One of the pins looks pretty patina'd. Could it be this?

I don't know if that will solve your problem but it definitely worth spraying the contacts with contact spray or WD-40.

What mileage has your car?

First advice: erase all codes and check after 2 engine starts if and what errors come back. If there are errors, paste their code in here. Add the freeze frames (engine parameters when the error was set) too.

6 minutes ago, RicardoM said:

I don't know if that will solve your problem but it definitely worth spraying the contacts with contact spray or WD-40.

What mileage has your car?

First advice: erase all codes and check after 2 engine starts if and what errors come back. If there are errors, paste their code in here. Add the freeze frames (engine parameters when the error was set) too.

Thanks Ricardo. Will give them a clean. Mileage says 54k but I also found out that the clock is faulty. After checking MOT history I think it broke a few years ago. Will try wiping the codes and reporting back!

 

Also just spotted this...not sure what the sensor/connector is..looks like a cable is cut short but can't see where it would connect to if it were to run with the other two wires...?

 

Just plugged OBD in and no codes came up  am using a Launch X431 this time and used a Snap-On Modis Edge last time. Might have to wait til my mechanic has his Snap On back...

 

I think I'm going to change the sensors too and see if that helps. The wiring all looks ok (minus photos above).

 

Found a Ridex coolant temp sensor...https://www.autodoc.co.uk/ridex/8140283

 

But struggling to find an inlet manifold pressure sensor...too many brands! https://www.autodoc.co.uk/car-parts/sensor-intake-manifold-pressure-15024/skoda/felicia/felicia-i-fun-797/11187-1-3?categories[0]=3947#

 

Any recommendations?

 

Thanks again.

My recommendation for now is stop looking for parts before having evidence of fault.

Clean the throttle body. Reset the throttle body. Not sure if Launch X431 can do it. I plan buying one.

7 hours ago, kinggwarn said:

Also just spotted this...not sure what the sensor/connector is..looks like a cable is cut short but can't see where it would connect to if it were to run with the other two wires...?

I can't see where it is located.

Most probably it is the knock sensor. The third wire is the shield that goes to the ground only at the other end of the cable.

14 hours ago, RicardoM said:

My recommendation for now is stop looking for parts before having evidence of fault.

Clean the throttle body. Reset the throttle body. Not sure if Launch X431 can do it. I plan buying one.

Cleaned throttle body and reset CPU (by disconnecting battery for a while). I swear it drove fine for about a minute or two before the juddering came back...just as I thought "I've fixed it!"...

4 hours ago, kinggwarn said:

by disconnecting battery for a while

That is not a throttle reset.

One other thing. Does the juddering appear only when the throttle pedal is pressed approximately the same amount? Let's say around 10-15% of wide open throttle? Or is it the car judders also if you keep the pedal pressed constant at let's say 50% then slowly press further?

 juddering was fixed in my case by replacing the cps

21 hours ago, RicardoM said:

One other thing. Does the juddering appear only when the throttle pedal is pressed approximately the same amount? Let's say around 10-15% of wide open throttle? Or is it the car judders also if you keep the pedal pressed constant at let's say 50% then slowly press further?

Will look into the throttle reset now. And the juddering seems to vary with different percentages. For example when in 3rd, there is a sweet spot at about 23mph where it doesn't judder..certain spots it judders a lot and sometimes not so much. But I would say variable juddering anywhere from 10-80% on the pedal.

 

After a drive I noticed my fan isn't coming on either, but the engine stays at about 100C. Going to investigate this too.

 

Thanks for the help.

Hmm don't think I can get Motordiag on mac and sadly don't have access to a windows laptop!

Cool got a mate popping over tomorrow with a Windows laptop so I can try the throttle reset. Will update then.

Update: mechanic's only USB-OBD cable is at his house so couldn't reset today. have ordered a cable for myself so will try this when it arrives.

 

However I found massive oxidisation on the spade connectors to the rad switch. wonder if this is why my fan doesn't come on. have given them a clean and running the car at idle now. need to find my multimeter and test the wires too...

 

I also noticed today..not sure why I hadn't tested the pedal in neutral before....but when the car is in neutral and I hold my foot on the pedal at various points (but steady at each testing point) the revs fluctuate. 

Cool, after 15 minutes or so of idling the fan came on at about 105C.  that's that problem solved.

 

Apologies for all the posts...shame I can't edit posts! 

Since you have found several connectors having corrosion, I would have a look at all of them in the engine bay. Also it might worth taking a look at electrical pump connector too.

54 minutes ago, kinggwarn said:

I also noticed today..not sure why I hadn't tested the pedal in neutral before....but when the car is in neutral and I hold my foot on the pedal at various points (but steady at each testing point) the revs fluctuate. 

That is why I asked about the throttle pedal. If the throttle position sensor (fancy name for the potentiometers that sense the throttle flap position) has developed a groove or some worn spots around idle position and cruising positions, then you have the culprit right there.

Do you have the factory service manual for Felicia?

Edited 6 December, 20205 yr by RicardoM

3 hours ago, RicardoM said:

Since you have found several connectors having corrosion, I would have a look at all of them in the engine bay. Also it might worth taking a look at electrical pump connector too.

That is why I asked about the throttle pedal. If the throttle position sensor (fancy name for the potentiometers that sense the throttle flap position) has developed a groove or some worn spots around idle position and cruising positions, then you have the culprit right there.

Do you have the factory service manual for Felicia?

 

Hi Ricardo. Thanks for the help.

 

Will check all the connectors and pump connector tomorrow. Interesting re throttle position sensor...I'll have to have a look at that too. 

Do you know where in the manual it discusses the electrical pump and the throttle position sensor?

 

Here's a nice pic of my felly the other morning...

 

All the best.

5 hours ago, kinggwarn said:

Hi Ricardo. Thanks for the help.

Read my signature.

5 hours ago, kinggwarn said:

Do you know where in the manual it discusses the electrical pump and the throttle position sensor?

Fuel System & Ignition / Simos 2P / Simos 2P Fuel Injection & Ignition System / Page 24-22

Engine / Engine 1.3 (135, 136) / 1.3 Itr. Engine, Mechanical Components / Page 20-18

On 06/12/2020 at 15:28, kinggwarn said:

I also noticed today..not sure why I hadn't tested the pedal in neutral before....but when the car is in neutral and I hold my foot on the pedal at various points (but steady at each testing point) the revs fluctuate. 

that a tell tale sign of a bad tps

On 08/12/2020 at 19:01, Thefeliciahacker said:

that a tell tale sign of a bad tps

 

 

Which i don't know if you can buy it separately or goes with he throttle together which means huge cost.

I just checked mine today.

 

 

The guys on YT are showing with 4 pins.

 

https://www.youtube.com/watch?v=xIB3H-HqhkE

 

https://www.youtube.com/watch?v=jXEOqvtuvII

 

So what's next?