Bravo hgt 155 Hesitation

[mike_bravohgt]

Hi guys. I've just bought my 3rd HGT but this time its the 155 version. I have a slight problem. Any suggestions would be a massive help.

When I drive it most of the time its great! But on the other hand, occasionally it holds back.

When it holds back it's usually after I've been booting it a little. And it holds back between 2500 and 3250 revs after that it fires and picks up almost as it should! There are no engine management lights on and I've recently Changed the spark plugs, cleaned all the injector plugs and coil plugs. I've thought of most things but can't put my finger on it! Its the VIS engine if that gives any of you any ideas.

Thanks in advance!

 

[DaveMcT]

The ECU will add more fuel when you accelerate so maybe its already running a bit rich. It might be worth checking the lambda sensor voltage trace. You will need http://www.fiatecuscan.net/ obd cable to suit the car and a laptop.

 

[mike_bravohgt]

Nice one. I'll give that a try. Anything else that you may know of?

 

[DaveMcT]

It could be the throttle or cam sensor but generally they work or they dont. Sometimes they are ok until the engine gets hot then the act up & the car just stops with no errors.

Dodgy earth connections from battery or even dodgy battery that shorts out at certain engine vibrations.
Clean the MAF sensor in the throttle body air intake.
Dirty contacts on the throttle body. I'm guessing it's drive by wire?.
Check for air leaks - split vacuum pipes etc.
Holes in exhaust ahead of the lambda sensors.

 

[mike_bravohgt]

Yeah Its wireless throttle. Looks like someone had changed that unit at some point. Its a really strange problem, this one has got me stumped.

The battery looks okay and I don't ever have starting issues. When the sensor which is causing my problem plays up, the Idle is very low, which leads me to believe its the MAF but I am still thinking its something else.

Its just had the mot and no leaks were advised. However its not to say it hasn't got one. And as for air leaks I found one and sorted that and then reset the ecu.

 

[DaveMcT]

Maybe you could get a used throttle body from a breakers with an agreement to take it back if not needed for a "restocking fee" perhaps.

On mine. the MAF sensor sits at the firewall side of the throttle body held in with two cross heads which will take a #1 Posi. I used a standard screwdriver bit and suitable ring spanner to get mine out. You can then carefully clean the filament wires with alcohol.

Air leaks in the inlet system usually make the engine rev high on tickover, but its always worth checking all pipes that could be under vacuum.