Posted by Martin Bebb. on February 25, 2011, 8:23 pm
Year of Manufacture *: 2008 Engine Size and Code *: 1.8 Z18XER
Hi guys. I had a look at a 2008 Vauxhall Vectra 1.8 petrol Z18XEP, yesterday. The car is suffering with flat spots. there are no fault codes stored. I test drove the car with my scan tool connected and recorded a drive cycle. This was my first step in diagnosing the problem. I haven't checked the basics, compression or timing, firstly because I never had the car long enough and second of all I don't think the symptoms merit starting that far back. I did ask to see the service records and records and receipts of work carried out, and parts. The car has covered 70,000 miles, Going over the live data recorded during the drive cycle the only thing that jumped out was the throttle position shown as either Idle, partial load or full load was dropping down to invalid, which shows the car going flat. However other parameter's seem health, such as throttle position in volts, acceleration in volts and relative data, I may be missing something. I don't know how to post my data on ukat. The cars service records are up to date but there was no signs of the spark plugs ever being changed, which is what i was looking for. I removed the plugs and they plugs were deteriated bad, they was how can I describe it, slight melting, and had different gap sizes from the wear. I changed these straight away and was expecting the problem to be gone but still the goes flat. I am going back to the car on Monday but am thinking what route to take.
What scanner were you using and what protocol were you using ie: EOBD or GM? On vehicles with flat spots, I normally turn my attention to the MAF after conducting basic checks. Do you have access to Pico-scope or similar which easily shows up MAF faults? What are exhaust emissions like at normal and fast idle? If the MAF is ok (assuming it does not have a MAP sensor) then you will need to check out the TPS. One test for a faulty MAF is to disconnect the multi-pin plug and see how it goes. Best of luck.
<<< the only thing that jumped out was the throttle position shown as either Idle, partial load or full load was dropping down to invalid, which shows the car going flat. However other parameter's seem health, such as throttle position in volts, acceleration in volts and relative data >>>
Aside form being the fault, this could be a scan tool glitch or a software error in the ECU. Can you link the invalid pid to the symptom occurring as regards timing?
I am not familiar with the system and didn’t look it up but the idle, part and full load could refer to a load signal which is calculated rather than measured. In other words a fault elsewhere, eg maf or map, could cause this. Were there no fault codes? I think if you post the data, captured when the symptom occurred, it might help.
I have been trying to work out how to get the data from shopstream connect, onto ukat, or from shopstream connect to a file in my computer, so that I can email to someone, I'll ring the advise line, if i can't work it out the scan tool I am using is a snap-on solus pro.
Hi Martin, When you save data on your Solus Pro it saves it in a format, such as .LSS or .SCM, that as far as I'm aware can only be viewed using the tool or Shopstream Connect. I usually save them to a USB memory stick and then transfer them to the PC. I am not at my PC that has SC installed but it doesn't matter where you save the file, put it on your desktop if you wish. When you have started SC you just use that to open the files from whatever location you have chosen. This file can also be emailed to anyone else but they will also need SC to view the data. As far as posting the data on here you can only do that by saving a screen shot which will be saved as a .jpg file and then using the upload image button when you are posting. The problem with this is that you will have to do loads of screen shots to get all of the data. I also don't have access to pin data at the moment but I believe that as well as an accelorator pedal position sensor it will probably have some kind of feedback from the throttle body in the form of a throttle position sensor. If you suspect that there may be a problem in this area than see if you can get a screen shot of the serial data from these pid's, along with MAF maybe, in graph form and post that. As you know there are many things that can cause this without flagging any codes so you really do need to work through the basics. I know that a mityvac has been mentioned to you before but if you had one it would eliminate so much in just a couple of minutes. Do you have access to a fuel pressure gauge? I think these have a schrader valve on the fuel rail so the fuel pressure is another fairly quick test to carry out. HTH's, Bryan.
Fixed #
Posted by Martin Bebb on March 25, 2011, 1:23 am, in reply to "Re: Vauxhall Vectra C Z18XER. Flat spots." Message modified by board administrator March 26, 2011, 1:15 pm
Car now fixed. It had dirty fuel filters and contaminated fuel. new filters and fuel drained, now the car is fine.
Well done Martin. Bear in mind that when doing any diagnostic work, the cost of replacing service items can always be justified whether it's the cause or not. There used to be a company called "Home Tune" and they would always do plugs, points, condenser, air filter etc before any other work (they may even still be in business but I've not seen them for a long time). Even an oil change can have a marked affect on a modern engine. Regards, Bryan.
Hometune, like Computa Tune, Mobiletuning, and Tune Up all disbanded their francises a few years ago. Some of their operators (like me) still operate as one man bands.
Almost the first thing I do with running faults on diesels, especially hesitation, cutting out or low pressure DTC's, is check when the fuel filter was last changed and if there is any doubt fit a new one, it's surprising how often this sorts the problem.
I think this is a problem with the modern extended service intervals which were only brought in to satisfy the fleet market.
I'm as guilty as the next man for jumping in too deep sometimes without first checking the basics.
I must admit though the fuel filter wouldn't have been my first port of call on this one, maybe a pressure test but that probably wouldn,t have shown much unless under load, so fair play for cracking it.
on February 26, 2011, 7:40 pm, in reply to "