power dip

MX3KEV21 · Post by **MX3KEV21** » January 2nd, 2007, 9:41 pm

does anyone get a very slight power dip at 3900rpm jst before the vris kicks in coz my car has started to do that but is fine everywhere else. i also done the tps adjustment and the car is much better and i adjusted the idle air screw to 750rpm and needle doent jump up and down anymore. could this be caused by the screw being turned or something else? please help. does the screw just control the idle speed and not the air/fuel ratio for the rpm range.

jschrauwen · Post by **jschrauwen** » January 2nd, 2007, 9:59 pm

MX3KEV21 wrote:does anyone get a very slight power dip at 3900rpm jst before the vris kicks in coz my car has started to do that but is fine everywhere else. i also done the tps adjustment and the car is much better and i adjusted the idle air screw to 750rpm and needle doent jump up and down anymore. could this be caused by the screw being turned or something else? please help. does the screw just control the idle speed and not the air/fuel ratio for the rpm range.

I think I covered most of this in another thread. The tps adjust does take a couple of tries to get it spot on because it is a very sensitive measuring piece. That said, I might speculate that perhaps you may have a flat spot (dead pick-up area) in the VAF where the electrical pulse sent to the ECU is slightly tainted because over time the reostat type contacts in the VAF may get worn over time. It's not a normal situation but it can happen. Usually our JE50 VAF's are pretty rugged and reliable. If you have the opportunity to source a second VAF and try out on spec and perhaps see what happens. I believe there is a test that one can do to test the output signals from the VAF in the online shop manual. Get the multi-meter out.

BTW, I'm trying to stay away from the possibility that there may be a disty problem...... for now.

Note: You could have saved myself and perhaps others some time and effort by amalgamating your last 3 threads since it appears that they are all interconnected about the same issue. You'll have better success from other members trying to assist if you contain like problems within the same thread.

MX3KEV21 · Post by **MX3KEV21** » January 2nd, 2007, 10:06 pm

well i will try and remember that. thnx. so what can i do then put the car in diagnostic mode then start the engine ang adjust the screw. but what way would u suggest? and when i do turn the screw will the tps need adjusting again? dont know where the original setting was. thnx for the info

MX3KEV21 · Post by **MX3KEV21** » January 2nd, 2007, 11:06 pm

what way should i turn the screw to get more vacuum cw or ccw.

PATDIESEL · Post by **PATDIESEL** » January 3rd, 2007, 12:26 am

Huh, don't turn the "screw". That adjusts the idle RPM and has nothing to do with TPS or VRIS. First, what motor do you have a K8 or KL (if KL what version)? The K8 does have a recogizable pause just before the first VRIS opens at 4000 RPM. It only lasts a maybe a half second and then you get the kick in the butt. If that is all you feel then I'd bet you are fine. Maybe the intake it getting dirty and you are feeling the lag b/c the plates are not functioning smoothly. I'd try some intake cleaner first. TPS will effect the VRIS, but it is usually very definate and usually after you mess with the TPS or throttle body. Have you done with recently.

MX3KEV21 · Post by **MX3KEV21** » January 3rd, 2007, 8:19 am

soz ppl. noted for the future. ill just keep adding to the 1 topic and not start so many its just cause i didnt think i was getting a reply. yeah its only a half a second dip hardly noticable. im glad its not the idle air screw. cause everything is ok at idle and at everyother rpm. so just normal i guess. the other thing is ive only had the car 1month and the sparkplugs are sooted up and the air cleaner is dirty thats prob what the problem is.

hgallegos915 · Post by **hgallegos915** » January 3rd, 2007, 12:14 pm

The screw can be part of the problem however ONLY if your accel cable is badly adjusted.. you need to have it all adjusted properly.. make sure the cable is not pulling on the trottle at idle and make sure it opens it alot and make sure the screw is set using ten and gnd. On my dino I had a slight power dip before the vris kicked in and i had that set badly. I was running slow also for a ze then. I havent dynoed lately tho.

MX3KEV21 · Post by **MX3KEV21** » January 3rd, 2007, 1:28 pm

right i have just cleaned the sparkplugs and put a new filter in the airbox and the problem is still there. the idle sits perfectly at 750rpm with no movements up and down. but when i press the accelerator pedal lightly it makes the revs drop a little before they go up and the power below 4000rpm seems to be lower aswel. i did the tps adjust with the car in diag mode then adjusted the idle screw in fully then out three turns and then adjusted it till it sat at 750rpm. so surely the problem cant still be the screw. where do you have your screw set at fully in or out?

jschrauwen · Post by **jschrauwen** » January 3rd, 2007, 3:29 pm

Like Pat mentioned about the initial kick-in of the VRIS is normal. Also, if the plugs were sooted, the air filters were dirty and it's new car then I'd say there's probably few other little maintenance things to tend to since it appears that they were neglected by previous owner. Other things like PCV valve, remove disty cap and remove carbon deposits off of the disty cap contacts and lightly clean off the contact portions of the rotor (blade and spring loaded carbon core contact) with an emery cloth - but just lightly to get that copper colour back again. Hell, why not through a new fuel filter in there and pull the coolant thermosensors out and clean the oxidization off the copper sensor portions. Clean out all of the dust and dirt from the front intake snorkel leading to the airbox, remove the air filter and clean out all of the crap inside the airbox (it's mostly sitting on the bottom), clean out (carefully) as much of the VAF as possible, then the flex rubber tubing to the TB. Lastly, pull the rubber flex intake tube back from the TB and clean out the TB. The venturi and the butterfly are probably really gunked up. It's much easier if your willing to remove the TB to do a thorough job of it. In this way you'll be able to clean out any built up coolant crap from the bottom half and get at all areas of the venturi and butterfly. Probably the most significant part of the TB to clean is the actual air bypass passage that the idle air screw threads into. That passage gets extremely gunked up and can be very difficult to set an idle if it's never been cleaned before. I threaded the idle screw in all the way so as to remember my original setting and then removed the screw altogether. Be carefull because there is a rubber o-ring that's part of that screw. That rubber o-ring prevents intake air from escaping to the atmosphere. That passageway has the bypass air metered by the pointed end of that idle adjust screw. That screw tip/needle can get carboned up / gunked up and can be cleaned with a light cleaning of emery cloth. clean the threads of it alsp. The threaded portion of that passage way will also need to be cleaned. Along with TB cleaner I used a rifle barrel wire brush that I got from a hobby / sports store that would match the passageway diameter. For me, that was the biggest catalyst in achieving a good idle setting and excellent throttle response.
After all of this has been done, she should be running like a champ.

MX3KEV21 · Post by **MX3KEV21** » January 3rd, 2007, 8:40 pm

so can you tell me this then. if i do the tps adjust again and then adjust the idle air screw so that it sits at 750rpm the car should be setup ok. because it was said that the idle air screw has to be set correctly so mine should be at the optimum setting if the tps adjust is done correctly. but it still lacks power but that surely cant be the idle air screw if it was set at the tps adjust or can it.

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