Brief period of vibration poor mpg

[barnaclebill15]

Yesterday I did a different run to the usual, same distance about 14 miles with a long stretch at 50mph. Notced my mpg was showing about 35 instead of usual 43 ish, thought i'll check today as back on the normal run, all ok at first got on the a road with the 50 average speed camera's so doing exact 50 on cruise, end of restriction start to speed up and getting vibration at the steering wheel to the point I thought I was getting a flat, slowed down found a layby got out and all tyres ok, pushed them but all firm no rocking, started engine ticking over ok checked exhaust all clear reved up sound smooth. Drove off again keeping at 40 still slight vibration, couple of possible gearchanges at unusual times.
Back in the 30 limit ok but not fully smooth, noted the mpg was 35 as yesterday. On the return all seemed better, I remained at 50 in cruise before the cameras, going up a slight incline felt a little vibration at the wheel but on the flat it disapeared then I noticed the mpg was creeping up ending at 37 ish.
The rev counter is smooth but some gearchanges not as smooth as usual, anything autobox related would give the vibration and poor mpg, would expect injector problem to show on the rev counter
Just checked the auto box level, normal and clean, no smell.

 

[Kev555]

Injector problem might show up in DPF filling quicker than expected if your car has one. Vibration could be an injector on its way out. check for injector blow by too.

 

[barnaclebill15]

No DPF on this model, had the top cover off when checking the auto box oil level, no sound or smells of exhaust at tickover.
Would an injector on it's way out show up with a code reader? maybe time to get an MB II.

 

[barnaclebill15]

It just did the same today in the same place, this time on the down slope I pushed it up to 70 and am sure it's an injector. I slowed back down when i got to about 35 it stopped vibrating and I slowly speeded back to 50 no problem. On the way home no problem and the mpg about 42.
Have booked it in with my indy on Thursday.
How much are injectors these days, can you get good recon ones?

 

[Kev555]

My Delphi injector was intermittent and missing at certain speed ranges like that as well. There was a vibration with it was hard to pinpoint. If you have an icarsoft i980 you can check the running smoothness of the cylinders to see if one is behaving oddly. Also check for sored codes on ECU along the lines of parameters of injector. Delphi injectors are about 150 to refurb or buy new

 

[barnaclebill15]

My indie has had it on star, manual inspection and road test up to 70, he said it was driving well, I asked would an injector or gearbox give the problems I noticed and he said no. Good thing he did not charge for the investigation, good to be a regular customer.
I drove away hoping it would be ok, got on the main A road past the 50 limit and speeded up to 65, no vibration or noise and very smooth so what it was is a mystery just hope it does not return.

 

[Wighty]

My indie has had it on star, manual inspection and road test up to 70, he said it was driving well, I asked would an injector or gearbox give the problems I noticed and he said no. Good thing he did not charge for the investigation, good to be a regular customer.
I drove away hoping it would be ok, got on the main A road past the 50 limit and speeded up to 65, no vibration or noise and very smooth so what it was is a mystery just hope it does not return.

Did he do an Italian tune up ?

 

[Kev555]

Did he do an Italian tune up ?

LOL

 

[barnaclebill15]

Has been good since the original problem but on Thursday I had an A service and MOT, passed ok. Short drive home so max 40 mph. On Friday on the same road I got the problem the last time it returned, same symptoms exactly, only realy notice it if you go over 50, at 70 its like you have a flat tyre then you have to slow to under 40 for it to slowly decrease then you can get back to 50 slowly and it will cruise ok at that but fuel cons showing 35 ish. Was due a fill up so added a bottle of Redex to see if that does anything. Funny it was just after the service it started doing it, only thing would be the fuel filter was changed.
Last time it did not show on star, any ideas?

 

[ssheikh93]

If you get vibration at the steering wheel. Get your wheels road force balanced.

 

[barnaclebill15]

Sorry but to have the problem for a few days then it disapears for a few months only to reappear after an A service is not indicative of wheel balance, also not accounting for the change in fuel consumption.

 

[ssheikh93]

Sorry but to have the problem for a few days then it disapears for a few months only to reappear after an A service is not indicative of wheel balance, also not accounting for the change in fuel consumption.

Only mentioned it as I had a steering wheel vibration that not 1 tyre shop could fix. And it was noticeable on some type of roads not all. Issue was only fixed when I got a road force balance done.

 

[barnaclebill15]

have ordered an icarsoft mb 1.0 to see what shows up

 

[mattkh]

What a mystery.
What is the mileage..?
Vibrations felt at the steering can also be driveshaft and engine mountings related.

 

[Kev555]

Possible caliper sticking causing vibration and bad fuel economy? Did you notice a brake smell or check the wheels for heat after its happened? We can rule out injectors from earlier in the thread. Possibly could be related to the filter having air. any of these two wont be picked up on a carsoft barnacle bill but always good to have one handy when you own a Merc

 

[barnaclebill15]

Right first time Kev, I was driving today, same problem thinking what did they do on an A service and MOT and it hit me, hard brake test, got out and felt the wheels, off side front was hot, booked in for caliper work.

 

[Kev555]

lucky guess

 

[mattkh]

lucky guess

A well educated guess.

 

[Kev555]

A well educated guess.

I would never claim to be well educated Mattkh
Just glad I was able to help even though Barnaclebill had it figured out by that stage himself