I've seen sooo many threads with this issue. Basically when the engine is cold and you start it up, it idles fine (maybe a bit high ... well in my case) and as soon as you just lightly touch the throttle it seems to drop rev's and hesitates a bit until the rev's build up then it corrects it's self. But when it gets to operating temp, it runs fine. I've also had this problem for a LOOONG time (actually since i've owned my Zed) and have been scratching my head for just as long. I've tried cleaning EVERY connector many times and checking via Datascan any figures that may not look right - particularly TPS, CAS and O2's. All have been fine the whole time. So i've been baffled. Well, I had another look around on the weekend and found that the butterflies on my throttle bodies were not sitting completely closed when at idle (closed throttle position)! - They were actually sitting slightly open due to the 2 little adjuster screws that give you balancing adjustment on the balancing rod between the Throttle bodies. Now with these, they may in fact be open but as long as the TPS sensor is adjusted to suit, it won't give any false readings via Datascan. So, I unscrewed these butterfly adjustment screws till both were sitting completely closed at idle then balanced them again with the same screws and re-adjusted the TPS to give an accurate .45v readout (Tech article on TPS adjustment here: HERE) What has happened from years ago, a dodgy mechanic or previous owner has wound the butterflies up (only a tad) maybe to increase idle or to try to cure some rough idle issues. And in doing this has caused this secondary issue where the TPS info going to the ECU is not accurately representing the correct position of the butterflies - thus allowing too much air into the A/F mix for cold starts (when they need to run rich until the engine is at running temp) Once all that was done, that completely cured any hesitation while still cold. This may have only been the cure in my case, but seen as though i've seen this question asked that many times, I thought I'd post my findings in case anyone else has the same issue. Maybe even as a Tech article as this is quite common. Hope this may help some people :zlove: Benny_C
Easy... when you unscrew the little adjuster screws on the left-hand side of both throttle bodies, the butterflies still have "spring" tension until a certain point - that's when they're closed. The thread in the adjuster screws don't need to be up much before they start pushing the butterflies open, so only a couple of "exposed" thread from the adjuster screws is about all you need. (well in my case)
might be a good idea to add the solution to the idle tech - ill certainly be checking mine out. sounds similar to my idle prob.
I have a similar problem and posted in the other thread, but the details have changed since then. At the time, the car was very sluggish until it was warm. I discovered that was a secondary problem, as not only was the knock sensor faulty - it wasn't even connected! (and the loom is all broken connecting to it anyway from both sides of the plug) Anyway, I ran a bypass which fixed that issue - now the engine doesn't like revving past 2000rpm much when its cold. It will, but it intermittently resists. If you start driving while this is going on, you'll have almost no power around that rev range or above it...but its the best way to get the car to behave itself. Not really knowing too well, could this be a mass airflow sensor issue? I'll point out that since i've run the knock sensor bypass, i'm getting code 55 - so am I right in assuming everything is fine sensor wise?
Be careful when doing this fix as it can cause your butterflies to stick/catch slightly when going from the closed position. Some people do adjust there idle this way, and it can be the cause of hesitation when cold, but if your throttle starts sticking you'll know you adjusted them too far.
Good find mate. Might have been coinsidence but I have seen once before that although the voltage from the TPS is reading fine, the closed TPS signal in datascan is reading false meaning the ECU is operating the AAC from a driving mode of operation which causes the same symptoms you were experiencing and when you readjusted the TPS it came good. I found with the example I gave, it was a sheer PITA to get the correct voltage and TPS closed reading true in datascan, indicating a very dodgy TPS but once the locking screws where tightened it was taboo to even consider touching it But hey, everything worked as it should after that.
Thats why my same problem was solved when i adjusted the TPS voltage slightly higher to tune the idle by ear. IE adjust TPS to reference (closed) voltage and open throttle slowly by hand, hear revs drop slightly before starting to increase. Readjust TPS volts slightly higher, same audible test. Repeat until revs increase immediately throttle starts to open - old school approach here BUT IT WORKED!!!!! Taught to me by Bluey in Mackay, QLD who was brilliant tuning my ZED. After all the computer and dynotune and datascan rigmarole was done he listened to the engine run. The car was always brilliant after he had finished with it, so sorry to see him retire. Good find this one Benny but a little light on details, ie pics for tech article - PM sent Neddey
Good find. Those bloody TB screws being mistakely adjusted by dodgy mechs as a way of adjusting idle is all too common. :bash: I've found a couple similar idle issues caused by this. Adjusting these screws away from the factory settings is a recipe for problems (unless you are fixing someone else's fiddling...)
I'm having the same stmptoms as benny. But No one has youched my car between when it ran fine and now. So I can say it's not the tb butterfly. What else? no error codes aswell.
I've learnt a bit more about injectors since a recent dead injector situation. Have you checked the resistance of each injector with a multimeter set to resistance? Should be no more than 10 -14 Ohm. I worked on a zed that had one injector completely dead and two injectors showing @~20 Ohm each. Naturally the dead open-circuit injector caused a constant misfire, but the other two didn't really show up as a misfire, just running rough in general at idle yet no hesitation under load. We replaced them along with the dead injector and the idle has improved.
please explain I have a multi-meter and know how to use it, but just in case can you please tell me exacly what to do. Do I check while running or not running???? Also could this still be the case even if the problem is only while cold?
I just realised how dumb that question was... Just unplug injector and test resistance...deeerrrr.:bash:
Disconnect the injector connector wiring plug then set your multimeter to continuity / resistance then place each multimeter probe across the injector 'male' terminals
well I got to three of them all read 12.5ohms, I'll check the other three when I do the plennum pull and clean the injectors.
culprit TPS. Datascan was reading .44-.46 wich was fine but I thought I'd fiddle anyway. Got it to .44 and car was idling at 1600, closed position was off? Then fiddled some more and got it back to .44-46. Still idling high. Turned it off cleaned the self learn and came back about an hour later. Bang on 800rpm and no hesitation? Well all seemed fine bbut a fiddle with the tps and it's all good? A mystery.
Forgot to check the other three when the plenum was off. But now the injectors have been cleaned and have new o rings and all back together I still have the problem. When I get the car out I roll out of my drive then open the throttles to drive off and nothing... then after about 3 sec the car stumbles a bit and then off it goes rough as guts for about 1min. Also it used to start up sweet every time no cranking required, now sometimes you start it (still no cranking required) and it stumbles then almost stalls then runs fine. Further to all of this when pulling up to lights as I put the clutch in just before stopping you can feel the engine stumbling for a second or 2 then it idles ok???? Could it be a fuel/vacume problem? I did mean to do a blow up test when putting it all back together but I ran out of time and havn't worked on the zed since.
