Additional guages :S

[e34.535i.sport]

Hey guys! I know I've abandoned the e34 for the xjr but thought you guys might have some useful input on these!

I was looking into buying a vacuum and fuel pressure guage to check these were both in tolerance in order to investigate my long time sporadic misfire issue when I came across these... http://www.autodials.co.uk/ ... or more specifically http://cgi.ebay.co.uk/SWOOSH-VACUUM-...item2c53a390cf . I know they look a little tacky but I'm interested in the air/fuel ratio guage and the vacuum guage simply for monitoring purposes... I think it would be useful to have these working at all times (as opposed to checking then removing) to monitor various things that could be contibuting factors to my misfire and lumpy(ish) idle problems. (And not to mention to keep an eye out for vacuum leaks when they arise!)

My questions really are:
1. Does anybody here have experience in this type of thing - Do these look reliable and safe to use?
2. In terms of the Air/Fuel ratio guage - How will this work exactly? (The installation guide doesn't inspire my confidence tbh...)
3. Will installation be as easy as they make out? (I'm useless with electrics!) Would it cost much to be done by an auto electrician do we think?


I'm hoping you give me some positive responses to be honest as I think I'd have hours of fun with these things if they work!

[whiskychaser]

1. Does anybody here have experience in this type of thing - Do these look reliable and safe to use?
No experience of those you fit permanently. But a vacuum gauge is handy to have. Particularly if used in conjunction with a fuel pressure gauge. Think specs should include some sort of accuracy figures
2. In terms of the Air/Fuel ratio guage - How will this work exactly? (The installation guide doesn't inspire my confidence tbh...)
You would think they would measure the air flow and how many pulses the injectors make and compare the results. But AFIK they just monitor the output from the O2 sensor
3. Will installation be as easy as they make out? (I'm useless with electrics!) Would it cost much to be done by an auto electrician do we think?
The vacuum gauge will probably just T in to a vac hose. Probably need power and a ground so you can light it up
The air/fuel one might have some sort of inductance coil which picks up the voltage without you having to splice into the wires.
The hard bit would probably be finding a way through the bulkhead and finding a nice place to site them

[Tiger]

Since you have a relatively new car, why not use OBD2 device to tell you what you want to know at all time.

For example:
http://www.auterraweb.com/dashdynoseries.html

I am sure there are some UK companies that have similar product like this. There is one product that is very popular but I can't think of the name.

[Tiger]

Double check and make sure your O2 sensor is working properly... on OBD2 cars. there is always one set and mostly two sets of O2 sensors.

Of the pair:
One will always be fast changer... numbers jumping all over places.
One will always be super slow changer... only change when you revs the engine and hold for at least 4 seconds.

Both should never read zero.

[e34.535i.sport]

Haha hey Colin was hoping you'd spot this one! Really enjoyed testing the 535i at yours that time which give me the inspiration! Yes I can imagine routing the wire through the bulkhead will be a pain!

Yes the vacuum guage does T-in to one of the hoses but I wasn't sure which one to go for... I read somewhere that it must be forward of the throttle body?

And thanks Tiger that definitely got my attention - Looks awesome! I found a similar uk reader that I'm very interested in - http://www.vi-performance.com/homepage.aspx ... I really fancy getting one of these although I don't think I read anywhere on the site that it measures the vacuum... And as it works through the ODB port I'm not sure it could (as accurately as a normal gauge at least) (?) You can pick one of these up on ebay for £225 delivered which isn't bad at all...

[whiskychaser]

Hi John. Whats this a heard about disasters in the new house??

That vi-monitor looks the part and certainly has a good reputation. But remember we are behind the US on OBDII compliance. It only became mandatory in the UK from 2000 for petrol engines (even later for diesels).
You will get cars before then with the OBDII socket. My brother's Sep '99 Megane has one but the code reader I bought him doesnt work on it of course. (I blame the French) So maybe check with the seller or Jaguar (perish the thought) to see if it will work before parting with the cash?

[Tiger]

Yes, OBD2 does read vacuum...How else is the computer gonna know the condition of the engine?

What year is your Jag? You should check with UK Jag forum to see if others have done so.

[e34.535i.sport]

Disasters is right Colin! :P Had some issues with our water tank fooding and had to break into my own house LOL... This is within a few days of moving in! Got it mostly sorted now though and things are going a bit more smoothly now! (Although the car's been acting up - cracked exhaust manifold and oil leak causing problems but sortred now I hope!)

Hey tou and Alison will have to come down over easter and I'll do dinner (if you're feeling brave! LOL!)?! The spare room's all set up and there's a bottle of JD that needs some attention haha

Yeah I reckon that unit should work on my car it's got an OBDII port that I've used with my basic code reader (£25 ebay job!) - It will give it codes etc so I imagine it's all compatible. s you say though it may be worth checking... I think there's a supplier in blackpool so I could ask if I can try before I buy just to make sure!

Don't get me started on French cars lol - My Dad has been inspired by the XJ and is changing his beloved peugeot 406 for an X-type!


You make a good point there Tiger - Although it's how accurately the ecu measures the vacuum and by what means? (Please excuse my ignorance if that's a silly question!)

[Tiger]

They actually have a electronic vacuum gauge! They use it for diagnostic to see if you got some kind of major vacuum leak.

Borrow a full diagnostic scanner and hook up a simple vacuum gauge and test it... side by side... will be pretty darn accurate.

[ss2115]

Haha hey Colin was hoping you'd spot this one! Really enjoyed testing the 535i at yours that time which give me the inspiration! Yes I can imagine routing the wire through the bulkhead will be a pain!

Yes the vacuum guage does T-in to one of the hoses but I wasn't sure which one to go for... I read somewhere that it must be forward of the throttle body?

And thanks Tiger that definitely got my attention - Looks awesome! I found a similar uk reader that I'm very interested in - http://www.vi-performance.com/homepage.aspx ... I really fancy getting one of these although I don't think I read anywhere on the site that it measures the vacuum... And as it works through the ODB port I'm not sure it could (as accurately as a normal gauge at least) (?) You can pick one of these up on ebay for £225 delivered which isn't bad at all...

Hi.

Any one of those scan tools that use the OBD plug would certainly be the go.
No - they don't measure vacuum though. If you had forced induction then they would certainly read boost as there is always a boost sensor, but no normally aspirated engine has a sensor for vacuum that I'm aware of.

I don't think thats a concern though, because with your problems a vacuum guage is not going to show the cause, only the effect. Its not as if you have a constant problem like a burnt valve which would have the engine misbehaving at all times. And you can always plug a handheld vacuum guage in to take readings to eliminate that sort of thing anyway.

By the way - a vacuum guage does not go before the throttle body! It goes into any line that has a direct connection to the manifold proper. In the manifold between the throttle body and the inlet valves in the head is where the vacuum is formed and this is where you measure it.

If you've done all the usual things like plugs, igniters, fuel filters and looked for vacuum leaks, then replacing the O2 sensor(s) might be a good next step. The fast reacting one mentioned in the post is a wide band O2 and it can certainly cause the engine to misfire and do things if its faulty.

But if you haven't done the fuel filters yet - do them first. #1 on the list of a fuel injected car if its doing silly things is replace the fuel filter(s) - they also can do the weidest things to an engine that you would never imagine they could.