Misfire... Rough idle

[nash.98]

Hey guys. In need of a little help. Coming to completion on thw build of my clio but cant sort a rough idle and slight misfire. When revving from idle the revs drop before raising. Idle is quite lumpy too. Compression test shows all 4 cylinders between 195-200 after cylinder head rebuild and new valves. Cleaned injectors and tested resistance on injectors. All at 15 ohms. Had new spark plugs and leads. No codes coming in atm. Running lightweight billet flywheel, ac and pas delete and lightweight pulleys. Decat with o2 spacer. Anybody got any ideas?? Sorry for the long post

 

[jp_lcr]

Both times I've had loss of power at low revs and rough idle it's been injectors failed no2 then no1.

 

[nash.98]

Just out of interest did you test the reisitance of the old injectors. Only mine all tested ok at 15 ohms

 

[jp_lcr]

I ended up taking it to local specialist understand to trace it, think it was case of taking them out getting cardboard and carefully checking spray pattern, probably a thread on here somewhere with steps to do it.

 

[robzracing]

If it’s a new build are you certain the timing is correct?


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[White16valver]

No air leaks?

 

[nash.98]

So i took the end caps out and pinned the crank. Cam tools slides straight in so happy the timing wad correct. Replaced 4x injectors and still no better. It improves a little when warm but idle is still around 1200 rpm and a little lumpy. If i rev hard from idle it misses but will pick up, its fine higher up the rev range.

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[robzracing]

So i took the end caps out and pinned the crank. Cam tools slides straight in so happy the timing wad correct. Replaced 4x injectors and still no better. It improves a little when warm but idle is still around 1200 rpm and a little lumpy. If i rev hard from idle it misses but will pick up, its fine higher up the rev range.

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The high idle I think possibly points to an air leak. However, I'd also look at the coil pack and leads. Genuine leads are prone to breaking when they are taken on and off multiple times.

 

[nash.98]

The high idle I think possibly points to an air leak. However, I'd also look at the coil pack and leads. Genuine leads are prone to breaking when they are taken on and off multiple times.

Thanks for your reply robzracing. Continued investigation into this today. Thinking along the lines of air leak, thought i'd triple check the timing. With the crank pinned, the cam horseshoe slides straight in. Although i thought this was a good time when i last checked, i today found out the tool was worn and bent, hence setting the inlet cam too far advanced. I need to get hold of another tool and hopefully have a shot of timing it up correctly next week. Ill update with my findings. Thank you all for your help so far.

 

[robzracing]

Thanks for your reply robzracing. Continued investigation into this today. Thinking along the lines of air leak, thought i'd triple check the timing. With the crank pinned, the cam horseshoe slides straight in. Although i thought this was a good time when i last checked, i today found out the tool was worn and bent, hence setting the inlet cam too far advanced. I need to get hold of another tool and hopefully have a shot of timing it up correctly next week. Ill update with my findings. Thank you all for your help so far.

Advancing the inlet slightly isn't that bad. Very unlikely to cause the symptoms you are experiencing so I'd persevere with the air leak theory. Good luck!

 

[nash.98]

I think its enough to be causing my symptons. Its visibly out compared to exhaust cam and every now and then it pops back through the inlet, meaning inlet valves must be open during a combustion stroke. Ive smoked the intake system and its free of any leaks...

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[incy-spider]

You say you are pinning the crank, are you certain you have the pin in the correct groove which should lock it both ways with the pin right in.. I’ve seen the pin being located in a drilling on the crank just above the locking groove it feels like it’s locking but The pin sits slightly out and doesn’t lock both ways as well, still movement...

Just a thought. The incorrect hole/drilling is slightly clockwise of the correct groove


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[nash.98]

You say you are pinning the crank, are you certain you have the pin in the correct groove which should lock it both ways with the pin right in.. I’ve seen the pin being located in a drilling on the crank just above the locking groove it feels like it’s locking but The pin sits slightly out and doesn’t lock both ways as well, still movement...

Just a thought. The incorrect hole/drilling is slightly clockwise of the correct groove


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Thanks incy spider, yh its definately pinned in the right place. The cranks doesnt move at back or forth

 

[KebabWarrior81]

Thanks incy spider, yh its definately pinned in the right place. The cranks doesnt move at back or forth

Did you find the solution/cause to this issue mate?