Hi all,

I've got a problem I can't seem to solve.

Last weekend I replaced my n/s hard brake line. Ever since then the car is running very rough. At idle it lugs, and through the rev range it lugs and loses power intermittently. Almost sounds like a misfire.

I thought it was a vacuum leak caused by the old line scraping a hose when temovin it, but after clamping all the vac hoses from the throttle body but that didn't give me any indication as to whether it was a leak or not.

I've also removed, cleaned and refitted the throttle body.

I'm not just removing the intake, battery and tray to look around the area and try to get a better ear on whether there is a leak, but I don't think I'm going to find one.

Does anyone have any suggestions on what I could do to trace and fix the issue?

Thanks all

Did the car run OK before you did work? I can only guess you have moved/damaged something, or it could just be a coincidence. You're not very clear on when you cleaned the throttle body. Guess work at this stage. Is it worth getting codes read?

Howdy,

Yeah the car was running very well before I did the work - best it had ran since I owned it!

So I cleaned the throttle body first a year ago, but again about 30 minutes ago, so recently. I also just finishing removing the maf sensor and refitting, just to make sure that wasnt an issue either.

I did some more diagnosis and found that with the air intake off, if I cover half the throttle body mesh with my hand the car idles absolutely fine, and there's no lugging when revving either. I'm not sure what that indicates though...

Yeah I thought about codes too, I have an ultragauge and 3 pin to OBD2 converter but the ultragauge didn't connect using the 3 pin under the bonnet next to the brake fluid reservoir. I read there's another plug under the passengers console so I'll try to find that to see whether I can get codes from that port.

Air flow metre clean time/inspect/replace perhaps.

Vacuum hose to the break servo leaking ?

Update, ish.

So I removed the battery tray and had a good poke around. I tried clamping the 2 blue hoses going from the TB to the intake, with no change in revs. I also reclamped the vacuum hose to the brake servo again, with no change in revs.

Then I started the engine and removed and plugged the valve cover vacuum hose, to no change in revs....again.

Removed and checked all the spark plugs, they all looked similar apart from 1 and 2, which had oil around the top, which I guess was from some oil being spilt when filling as it was oily around the valve cover. The plugs themselves weren't overly oily once removed and there was no oil between the pack and the plug.


So yeah, I'm completely and utterly confused. Went for a fairly long drive to trace issues and there is lugging throughout the entire rev range, with noticable misfire at lower revs. I've got carb cleaner arriving in a couple of days but am not holding out hope as it cleaned fairly recently...

what may I ask is an n/s hard brake line?

It's the hard steel line that runs from the abs module to the divers side wheel well, which then connects to a flexible hose to the brake caliper.

I'm just wondering, what would the feel able symptoms be if there was a vacuum leak on the brake servo hose? Would I feel it when i was braking?

absolutely, a leaking brake booster will cause a lean condition and poor engine running. just behind your ABS controller and below it you will find your brake booster cannister. a black plastic line runs from the cannister to your intake manifold, maybe 16 or so inches long. its held in place by a small rubber clip. That line cannot be allowed to leak. I would try to block the line at the manifold and start the car. Remember if you drive away like that you will be without power brakes.

Alrighty. Today I removed and cleaned the IAC and MAF. No change to running conditions, still very rough.

I also removed the brake booster and plugged it up at the manifold side, with no change in conditions either. I also plugged the blue hose next to it, which made no change either.

Completely at a loss at what to do now!

It now sounds like the air idle valve stuck open.
What did you mean by covered half the mesh on the throttle body?
Mine has no mesh on it.
Or is the MAF sensor next to the throttle body , that has mesh on it?
Any pics.

When I take my intake off, there is a fine metal mesh at the top of the throttle body.

I've got a video that shows the throttle body with the car running. The high pitch intermittent whirring noise is the engine lugging, this is present at idle and all through the revs. When it does this, all ancillaries the car run also have the same 'pulse'. When I cover half the mesh with my hand, the revs rise and stabilize.

https://photos.app.goo.gl/mQaZaSwavZBdDcZQ9

Its a shared google drive location.

Actually thinking about it, if the car is lugging and all ancillaries are doing the same, that will explain the frequent but short lived drops in power I feel, rather than a misfire.

If it runs the same in the video as it does on the road then the maf sensor is disconnected?

It does yeah, the pulsing is a reduction in revs and that impacts the fuel pump too I guess. If I disconnect the MAF the car dies instantly.

What is lugging ? ..I have always thought lugging was a condition describing using a high gear with the throttle wide open rather than dropping down a cog .......am I wrong

Did you find the plug under the passenger glove compartment/ air bag to get codes?

Finally managed to connect to the ECU! I installed multiecuscan instead of fiatecuscan, played with the driver settings and managed to connect using the 3 pin on the firewall.

No error codes were stored.

I actually unplugged my icv to see what impact it would have and it sorted the idle issue, I'm going to take it for a quick drive to see whether it also sorted the running issued all around.

Will post results shortly!

Forgot about the idle control valve, can be problem on the coupe as well. Cars of this age need constant attention & maintaining.....

With the icv disconnected the idle is obviously much higher but the issue still remains when driving. The only difference is that now when idling the car isn't dipping and nearly stalling, so the noise on the video isn't present but around the back you can hear the engine note dipping, and in the engine bay the ancillaries dip as well.

When actually driving there is constant dips in power and occasional bucking when at lower speeds in firs gear. That's a symptom that's present when the icv is both disconnected and connected.

So back to square one!

Also just changed the spark plugs out for new ones just in case, with no change.

Jimboy what do you mean by a problem with the coupe?

minimayhem said:

With the icv disconnected the idle is obviously much higher but the issue still remains when driving. The only difference is that now when idling the car isn't dipping and nearly stalling, so the noise on the video isn't present but around the back you can hear the engine note dipping, and in the engine bay the ancillaries dip as well.

When actually driving there is constant dips in power and occasional bucking when at lower speeds in firs gear. That's a symptom that's present when the icv is both disconnected and connected.

So back to square one!

Also just changed the spark plugs out for new ones just in case, with no change.

Jimboy what do you mean by a problem with the coupe?

Click to expand...

ICV on the Coupe needs cleaning or replaced from time to time.