ej20 non turbo - idle surges slightly

[DonTPushIt]

My '85 T25 has a TSR ej20 115bhp conversion done by the PO in 2009 - 6000 miles ago. The issue I have is that when the engine is warm the idle lightly surges between 700-900 RPM. It also very very occasionally misses under load in top gear and low RPM. I realise TSR don't have a great reputation but apart from the surging idle and the occasional miss, I cannot fault the engine, it runs great.

I have changed the spark plugs to the 4 prong 'power' variant but no change.

I have attached a picture of vacuum line(?) that has been siliconed sealed - is this the culprit.



If not what else can I check? I don't have a way of checking error codes - how do I do this and is it necessary?

[Kai]

Here we go lol

Do you know what year? Guess it's wasted spark so post 1996/7 to 2000 ish.

Regardless. A fuel injected engine has an idle control valve, this is basically an air bypass to the main throttle butterfly. It's electronically controlled to regulate and prevent the engine from stalling when the main butterfly is fully closed. Your symptom is called "hunting"....

Being a TSR conversion..... I'd start to resolve your problems by locating the ecu and showing us close up and detailed pictures of the stray and lose wires coming outta the ecu plugs. Id guess yours is a three plug ecu.

You need to locate the cel/engine management light. By locating this you and the neccassary read memory plug and test mode plug you can see if the ecu is detecting any problems.

You could already be in limp mode. Who knows.
_________________
Think......

Don't sleep and drive!!!

[DonTPushIt]

Thank you for the reply. I tracked the 'hunting' issue down to leaking air at the brake booster pipes and 2 small inlet ports. All closed off securely and engine runs great.