scotty Posted February 15, 2019 Share Posted February 15, 2019 Just wondering on people's opinions on where to look. Just made some changes to the car ,boss 260, and now the idle is around 1000rpm and when I rev it it just holds the revs instead of dropping back to idle. I think it's the under drive I installed which has changed things. Engine load would of changed but any pointers on where to look to sort it before the blower gets hooked up. Thanks scott Quote Link to comment Share on other sites More sharing options...
Roland@pcmtec Posted February 15, 2019 Share Posted February 15, 2019 Assuming you added a lower friction under drive pulley? No other changes? There is an engine friction model and torque at idle table which would be the proper way to fix this. You could also fudge it my adjusting the idle air flow or even just dropping the idle rpm. I'll have a look at what the tables are called for you when I'm on a PC Edit: could be an idle air leak as well. Eg if a vac hose has come off that will cause this as well. What is your idle spark sitting at? This will tell us if the spark is pegged at 0 degrees etc. Quote Link to comment Share on other sites More sharing options...
Puffwagon Posted February 15, 2019 Share Posted February 15, 2019 My guess would be a vacuum leak. Quote Link to comment Share on other sites More sharing options...
scotty Posted February 16, 2019 Author Share Posted February 16, 2019 I will do a another check for a vac leak monday morning when I am at the car again. Had the same issue when I put the monoblade throttle body on it and it was idle air I changed then to fix it. Just wondered if I was missing something else. Quote Link to comment Share on other sites More sharing options...
Roland@pcmtec Posted February 16, 2019 Share Posted February 16, 2019 Here is how I diagnose a vac leak. Log spark then pull the PCV line off the rear left of the rocker cover. You should see the idle spark drop to 0 degrees to try and get the idle speed down. If not much happens and your idle spark is already very low (eg below 10 degrees) it indicates a vac leak. Idle spark will usually clip at -2 I believe. Quote Link to comment Share on other sites More sharing options...
scotty Posted February 18, 2019 Author Share Posted February 18, 2019 Thanks for the help boys it was a vac leak. 3 Quote Link to comment Share on other sites More sharing options...
Roland@pcmtec Posted February 18, 2019 Share Posted February 18, 2019 Sometimes it is just the simple stuff! Definitely recommend a smoke machine if you work on boosted cars regularly. 1 Quote Link to comment Share on other sites More sharing options...
scotty Posted February 18, 2019 Author Share Posted February 18, 2019 Or just someone who doesn't forget to put the plenum lid seal in. Lol. 1 Quote Link to comment Share on other sites More sharing options...
Roland@pcmtec Posted February 19, 2019 Share Posted February 19, 2019 Better than my skyline, I managed to fit the wrong intake manifold gasket and not even notice that it was wrong. Took me a while to figure that one out. Quote Link to comment Share on other sites More sharing options...
scotty Posted February 19, 2019 Author Share Posted February 19, 2019 Now just found today that I have a faulty petrol injector grrrr. 1 Quote Link to comment Share on other sites More sharing options...
scotty Posted February 21, 2019 Author Share Posted February 21, 2019 Just as a side question can someone tell me base fuel pressure for a boss 260? Been hunting on the net and all I find is xr6t info. Thanks Scotty Quote Link to comment Share on other sites More sharing options...
Gabbo32 Posted February 22, 2019 Share Posted February 22, 2019 it's same mate Quote Link to comment Share on other sites More sharing options...
scotty Posted February 22, 2019 Author Share Posted February 22, 2019 Thanks for that Quote Link to comment Share on other sites More sharing options...
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