The most freaky engine fault evah!

Kitch · Post by **Kitch** » Thu May 21, 2009 12:05 am

A while back, some nay hardly anyone might recall I mentioned I had a funny 'misfire' although it isn't a misfire technically, more of a lumpy hesitation!
I'd be driving along at and holding the throttle very lightly, and the rev counter would start bouncing up and down and the car would start to splutter without dropping any particular cylinder. At high speeds a bouncy rev needle was about the biggest effect, but at low speeds in 1st or 2nd gear the spluttering makes for jerky progress!

It's been like this for some time, and I've removed and rebuilt the head since to repair my bent valve. This involved removing all the gubbins fitted like Idle valve, AFM, injectors etc etc. I was hoping this would inadvertantly cure the fault, but it didn't.
I also changed the coil for a new one, as the old one died.

Now the freaky bit.....during my Wales trip on sunday I noticed something that really opened the can! It only does it when you're turning right!

It can be a sharp turn, or a very very gradule turn of the wheel along a motorway, literally a degree or two will set it off. When turning left its fine, no issues and in a dead straight line much the same (although how many roads are dead straight lines!?)

I started to think of something that might be moving with the lateral g-force, like a hose or wire but couldn't think of anything and nothing seems loose.
I used to have fuel starvation issues in an old AX GT I had, but this is MPFI!

Totally stumped and hoping that someone might have had something similar (though not holding out much hope!!)

Way2go · Post by **Way2go** » Thu May 21, 2009 1:04 am

I presume that your throttle body is similar to mine in that you have one of the two butterflies directly operating off the pedal but that the second butterfly is only on a self actuating spring shaft ?
I had a problem with this second butterfly due to it sticking. I lubricated the spindle ends and linkage first with WD40 and followed up with 3in1 and that was sufficient to regain smooth throttle operation at all speeds.

prm · Post by **prm** » Thu May 21, 2009 1:24 am

Kitch

I would go for the ignition module first.
If the engine cuts completely, terminal 4. Random misfires, terminal 1.

Could be an intermittent connection on the ignition side, that kicks off engine movement with the misfire which magnifies the problem.
Any new electrical equipment installed or operating when if misfres??

Remove the module multi-pin plug, check all the wires under the rubber boot. Some can be very brittle where they connect onto the rear of the spades.

With a very small blade, close up the female spades on the plug and a good clean on the module contacts.. Same operation with the coil multi-pin connections.

Cable tie the connecting leads to stop them possibly flapping around.

If fault remains, try to avoid roundabouts!!!!!!!!!!! And I’ll go back to cake making!!
Let us know how you get on.

Regards

DavidRutherford · Post by **DavidRutherford** » Thu May 21, 2009 8:26 am

If it's occuring on even the slightest bit of steering, then I suspect it's probably not anything moving under lateral load, and more likely a mechanical interference.
My immediate thought goes to a cable that is catching/chafing on the steering rack/shaft or similar. I've had cables catch in various bits before now meaning that if you applied full left lock, the engine cut out.

Aerodynamica · Post by **Aerodynamica** » Thu May 21, 2009 12:21 pm

DavidRutherford wrote:If it's occuring on even the slightest bit of steering, then I suspect it's probably not anything moving under lateral load, and more likely a mechanical interference.
My immediate thought goes to a cable that is catching/chafing on the steering rack/shaft or similar. I've had cables catch in various bits before now meaning that if you applied full left lock, the engine cut out.

you might be able to confirm this further by trying to get it to occur while stationary in neutral - rev, hold, turn steering a bit and observe

DLM · Post by **DLM** » Fri May 22, 2009 10:50 am

Kitch - is this the car you were getting ABS problems with? I suspect not but thought I'd ask anyway along the lines of prm's comment

Could be an intermittent connection on the ignition side.

Kitch · Post by **Kitch** » Fri May 22, 2009 10:25 pm

Way2go: I do have the twin butterfly setup, although it was all greased on the rebuild sadly.

Prm: I did think about switching the module with my other valver, but I'm sure sure it's gravity related, I think it's something electrical.

David/Aerodynamica: I was thinking along the same lines as you....something steering column related. However it doesn't do it when stationary, but I suspect it's because the engine isn't under load.

DLM: It is the same car yes (although both valvers have ABS lights jammed on!) I see what you're thinking!

Thanks all for your time so far

Mike E (uk) · Post by **Mike E (uk)** » Fri May 22, 2009 10:41 pm

Could it be something inside the cabin, mounted on the steering column, such as the ignition switch?

I would bypass that and head for the nearest roundabout to test.

Mike

Kitch · Post by **Kitch** » Thu Jun 18, 2009 2:58 pm

Fixed it!

PRM was half right.....loose connections, but not on the amp. They were on the plug for the AFM. I only noticed as while it was running, I nipped up some of the jubilee clips on various hoses, including the intake bellows, to see if this would cure the problem. When doing this I moved the AFM/air filter assy and the car started missing! I applied some leverage to various parts of the engine while running and the missing would come and go. So I tightened all the connections on the AFM plug, re-seated the intake bellows and hey presto! Problem solved!

One result in a week full of shite sadly.