Mi16 1.9 Misfire And Backfire

[davemar 16]

My 205 1.9 Mi16 has started to occasionally misfire, or least 'miss' in some way where it just suddenly flat-spots for a split second. It also occasionally back-fires, particularly on coasting. The power seems fine when accelerating, it's when I using light throttle is when it feels not quite right.

 

I've got a new rotor arm and distributor cap, so they should be OK. The last time I looked at the plugs they looked OK, but ought to check again.

 

Any thoughts?

 

 

[dcc 855]

Air leak

Exhaust leak

Injector wear

Ecu temp sensor failing

Afm failing

Plugs dead

Leads arcing

Lifter issue

Oil pressure issue

 

Dont rule out cap, might be moisture or oil on the rotor arm and cap

[dcc 855]

Oh i forgot about timing too

[Tom Fenton 1,541]

Ignition amp I would check. I've had one before that would idle and run flat out and virtually nothing in between.

[Terry1600 14]

my mate had this and it was an earth on the injector wiring around the rail area either was loose or just resting on the head i cant remember, took a long time to find, went through alsorts of messing around to figure out.

[davemar 16]

The plugs all look fine, so I think the sparking is generally fine. It feels more like an occasional thing rather than all the time. Generally it runs well. I'm beginning to feel like it might be an exhaust problem, even thought the mid and rear sections are new. Surely an exhuast problem to cause these systems would be up an the manifold end of things?

 

I'll try and pick my way through dcc's list. As for timing, do you mean cam timing, or ignition timing? If it is the latter, then the Motronic ECU doesn't allow any adjustment of that as far as I know, but I suppose the sensors could be giving wrong info for it.

[Anthony 1,003]

Potentially the loom breaking down as well, as Mi16 looms are starting to get to that age where they're really suffering and causing all sorts of hard to diagnose issues. The loom gets moved with the engine on throttle changes, which might explain why it seems OK under power and particularly bad on over-run.

 

Worth leaving the engine idling and giving the various bits of loom and connectors a wiggle and seeing if you can make it miss or cut out.

 

Otherwise I'd guess it's ignition related somewhere - I remember having similar issues on an Mi where the engine hated running at low revs/load but was fine giving it some stick, and that was caused by a failing dizzy cap.

 

Can't see it can be exhaust related personally, that would logically be bad more consistently rather than intermittently and possibly worse under power (i.e. more exhaust flow)

[Alan_M 66 1 Cars]

Check for play on the throttle body. The spindles/bearings wear causing air leak.

[davemar 16]

I'll inspect the throttle body, as that's quite an easy job.

Regarding the loom, I replaced the original one with a freshly made one a few years ago, and so far everything had been fine. But it is always possible contacts onto sensors and other things can corrode.

[camgti 56]

Worn camshaft did this to me once.

[davemar 16]

Did the worn camshaft give any other symptoms?

[camgti 56]

Would idle fine and rev freely. As soon as loaded it it died or backfired. No power on throttle past 1/4-1/2 application. Check ur plugs again?

 

Also look for vacuum leaks and check the fuel pressure is correct.

 

How old are the injectors? I e had bad ones cause similar problems. Usually mobile guys can come to you.

 

Does the throttle 'click' lightly as soon as you move it by hand?

 

Timing spot on?

Edited November 14, 2017 by camgti

[davemar 16]

The thottle body seemed OK. I'm hoping the camshafts are fine, as it generally feels like the power is there and feels responsive.

 

The injectors are pretty old, so I could give those a check.

 

Just wish I can get a clear day of tolerable weather to do this!