carl0s Posted September 29, 2009 Share Posted September 29, 2009 Ticking over, I hit the throttle and it hesitates and nearly stalls, then sets off. Sometimes I start the car and the revs rise very gradually to ~2k. Other times it refuses to start. Other times it's fine. I have replaced TPS. ICV looks fine and isn't gummed up. I have removed Thor FCD. Any ideas? It really does seem like it could be an ICV issue, but I just can't see what would be wrong with the ICV. Where does the ECU get its information that it uses to decide what to do with the ICV? Off the engine, the ICV plunges in and out like it should, and the revs go up and down like they do when the ICV is off. There are no error codes stored. It seems fine from a cold start, but once the car has warmed up it starts playing up, or especially once it's warmed up and been switched off, it plays up second time around when it's started up. The valve stem seals and cambelt were done not long before this problem appeared. Is there anything that they might not have tightened up properly? Please help I need to sell this car so I can have a home, but I need to fix it before I can sell it. Quote Link to comment Share on other sites More sharing options...
tooquicktostop Posted September 29, 2009 Share Posted September 29, 2009 Have you replaced the O2 sensor Quote Link to comment Share on other sites More sharing options...
carl0s Posted September 29, 2009 Author Share Posted September 29, 2009 Have you replaced the O2 sensor No. Is that likely a cause? Would that not throw an error code? Quote Link to comment Share on other sites More sharing options...
carl0s Posted September 29, 2009 Author Share Posted September 29, 2009 It's only idling BTW. WOT and general throttle usage are fine. It's just idling and setting off from idle. Quote Link to comment Share on other sites More sharing options...
Branners Posted September 29, 2009 Share Posted September 29, 2009 Has the fuel filter been changed any time during its life? Quote Link to comment Share on other sites More sharing options...
carl0s Posted September 29, 2009 Author Share Posted September 29, 2009 Has the fuel filter been changed any time during its life? Yeah I changed it about a year ago. Quote Link to comment Share on other sites More sharing options...
carl0s Posted September 29, 2009 Author Share Posted September 29, 2009 It did cross my mind that it might be some duffness with the Walbro pump, but WOT etc are fine, it's just idle control and raising throttle from idle. Once it's done its "dip" from idle (hesitating, nearly stalling), it goes full power just fine. Quote Link to comment Share on other sites More sharing options...
jevansio Posted September 29, 2009 Share Posted September 29, 2009 As Dean says could be the O2 sensor. The ECU will be using it on idle in closed loop mode to control fueling. The "only when warm" thing again points to a sensor breaking down when hot. Quote Link to comment Share on other sites More sharing options...
Guigsy Posted September 29, 2009 Share Posted September 29, 2009 i used to get a similar thing. start car up, fine. idle, fine. move car down to the end of the road. stop for trafic. and when i pulled out the car would just not rev at all and almost die. i could plant the throttle and nothing would happen for a second or 2. Then it would carry on. Would leave me stranded in the middle of the junction. However it seems to have stopped now. I havent had it happen since i had a new rad put in. but i doubt that was the cause. lol Quote Link to comment Share on other sites More sharing options...
carl0s Posted September 29, 2009 Author Share Posted September 29, 2009 i used to get a similar thing. start car up, fine. idle, fine. move car down to the end of the road. stop for trafic. and when i pulled out the car would just not rev at all and almost die. i could plant the throttle and nothing would happen for a second or 2. Then it would carry on. Would leave me stranded in the middle of the junction. However it seems to have stopped now. I havent had it happen since i had a new rad put in. but i doubt that was the cause. lol meh. There was me hoping for a solution! Just looking for o2 sensor part numbers .. Quote Link to comment Share on other sites More sharing options...
gaz1 Posted September 29, 2009 Share Posted September 29, 2009 meh. There was me hoping for a solution! Just looking for o2 sensor part numbers .. clean it with lemon juice;) Quote Link to comment Share on other sites More sharing options...
Terminator Posted September 29, 2009 Share Posted September 29, 2009 (edited) Could be the idle air control valve sticking, I had a problem with mine when we first started the car, after my engine swap, trying to get it to idle was a nightmare. I fitted a spare and end of problem. The IAC looked fine no deposits or gum, the problem was related to the park position at idle, it was only very slightly open, so we had to use a wide throttle stop to get the car to run. The problems you have starting again could also point to the valve not parking correctly at ignition off. Edited September 29, 2009 by Terminator (see edit history) Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted September 29, 2009 Share Posted September 29, 2009 I thought the O2 sensor was out of play on idle and WOT? I suppose if youre coming off closed loop and onto the O2 sensor it might affect it. Anyway mine has similar symptoms, bogs down a bit when you move the throttle to pull away, but only when cold Quote Link to comment Share on other sites More sharing options...
carl0s Posted September 29, 2009 Author Share Posted September 29, 2009 Could be the idle air control valve sticking, I had a problem with mine when we first started the car, after my engine swap, trying to get it to idle was a nightmare. I fitted a spare and end of problem. The IAC looked fine no deposits or gum, the problem was related to the park position at idle, it was only very slightly open, so we had to use a wide throttle stop to get the car to run. The problems you have starting again could also point to the valve not parking correctly at ignition off. It does basically seem as though the ECU doesn't know the position of, or can't control the position of the ICV/IACV whatever it's called. That would fit my symptoms (poor idle, sometimes high, sometimes low, sometime's won't start). Does anybody have a spare one I can buy? The o2 sensor is soaking in carb cleaner as we speak. I'll leave it overnight. Didn't look too bad though, obviously sooty but that's about it. Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted September 29, 2009 Share Posted September 29, 2009 Ive got an IACV spare if you need one Quote Link to comment Share on other sites More sharing options...
carl0s Posted September 29, 2009 Author Share Posted September 29, 2009 Ive got an IACV spare if you need one Yes please, desperately! Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted September 30, 2009 Share Posted September 30, 2009 An O2 sensor is most definitely very active at idle, or at least it SHOULD be. Quote Link to comment Share on other sites More sharing options...
pistonbroke Posted September 30, 2009 Share Posted September 30, 2009 An O2 sensor is most definitely very active at idle, or at least it SHOULD be. Am I right in thinking they are only reduntant at WOT? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted September 30, 2009 Share Posted September 30, 2009 Well, they aren't strictly speaking redundant, but the ecu will be running off the map, not the O2 sensor under certain load / speed sites. They can certainly *ugger up idle and cruise fuelling and ignition, the wifes Skyline has a knackered sensor and it's doing sub 17 to the gallon on a 40 mile drive to work an back at the moment, with a hesitation off idle when warmed up. As she's not speaking to me this week she'll have to live with it Quote Link to comment Share on other sites More sharing options...
pistonbroke Posted September 30, 2009 Share Posted September 30, 2009 Could be worse, she could be driving a porsche 968 with you not speaking to her. She'd be right up poo creek then Quote Link to comment Share on other sites More sharing options...
michel lane Posted September 30, 2009 Share Posted September 30, 2009 try and borrow a ignitor pack from someone, try that. We had a problem once with a car , on cold starts the idle was fine but as it got warm it started to miss. Quote Link to comment Share on other sites More sharing options...
carl0s Posted September 30, 2009 Author Share Posted September 30, 2009 try and borrow a ignitor pack from someone, try that. We had a problem once with a car , on cold starts the idle was fine but as it got warm it started to miss. It doesn't seem like a spark problem though. The car ticks over just fine, but when you touch the throttle the revs drop close to stalling and then pick back up. Other times it over revs, building up to 2,500rpm, as though your foot is very lightly on the throttle. I'm still thinking idle control valve so far, plus the o2 sensor is cleaned up now. Quote Link to comment Share on other sites More sharing options...
michel lane Posted September 30, 2009 Share Posted September 30, 2009 have you checked your TPS ?? Quote Link to comment Share on other sites More sharing options...
carl0s Posted September 30, 2009 Author Share Posted September 30, 2009 have you checked your TPS ?? Yes. Fitted a brand new one a few weeks ago. £90 down the pan! Quote Link to comment Share on other sites More sharing options...
carl0s Posted September 30, 2009 Author Share Posted September 30, 2009 I have an idle control valve coming hopefully tomorrow and have my fingers crossed.. plus the o2 sensor is cleaned up now. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.