Canadianz Posted June 13, 2008 Share Posted June 13, 2008 Well the RB is running and can move the car now. We have a bit of a problem though as the engine seems to be constantly hunting for an idle, reving up and down with almost no power. If you try revving it it falls on its face and bogs. Does any one know what could be causing it ? I was thinking it could be a bum o2 sensor but im not sure. We have a big throttle body with a q45 TPS sensor which seems to be giving the correct voltage too. Any one have a similar issue ? Any input would be awesome ! This is on a stock block RB with an intake and exhaust manifold running on the stock ECU w/stock injectors. Thanks Chris Crombie Quote Link to comment Share on other sites More sharing options...
janaka Posted June 13, 2008 Share Posted June 13, 2008 hunting idle to me would say vaccuum leak somewhere...second would be th O2 sensors Quote Link to comment Share on other sites More sharing options...
fentin_fury Posted June 13, 2008 Share Posted June 13, 2008 i'm voting vacuum leak as well. But it could be so many things. Start with the simple stuff. Quote Link to comment Share on other sites More sharing options...
streeteg Posted June 13, 2008 Share Posted June 13, 2008 i had the same problem when i installed my Greddy intake manifold. Under the intake manifold there is some weird idle pressure guage thingy that you can adjust to zero in the idle. I towed my car all the way to a shop to figure out that 5 minute fix.... Quote Link to comment Share on other sites More sharing options...
Careless Posted June 13, 2008 Share Posted June 13, 2008 could be limp-home mode that the ECU is sensing from the AFM. bummed AFM? Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted June 13, 2008 Share Posted June 13, 2008 What is the condition of your fuel filter? I've seen clogged filters cause what you are describing. Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted June 13, 2008 Share Posted June 13, 2008 Bad or dirty Mass air flow sensor. My car always hunted for idle though with the stock ECU. Especially when it was cold. Evan Quote Link to comment Share on other sites More sharing options...
Canadianz Posted June 13, 2008 Author Share Posted June 13, 2008 Thanks for the fast responses, PanzerAce: Fuel filters are in great condition and I;m running big lines 3/8's janaka: Im going to check for leaks thats a really good idea streeteg: Im going to check that idle screw ... I took off my idle air crap though . . . . would that do it ? I blocked off the hole and the interesting thing is that it was running worse with the idle control hooked up. . . Evan/Careless: Im going to try a different Maf I have an extra lying around Thanks guys ! ! I have my night planned out now ! Quote Link to comment Share on other sites More sharing options...
janaka Posted June 13, 2008 Share Posted June 13, 2008 Bad or dirty Mass air flow sensor. My car always hunted for idle though with the stock ECU. Especially when it was cold. Evan This also could be a contender. I had issues with my grand prix over the MAf having crap on it... definately worth a look as its quick and easy to check. Quote Link to comment Share on other sites More sharing options...
Canadianz Posted June 14, 2008 Author Share Posted June 14, 2008 Its fixed !! Thanks guys, it turned out to be that the signal ground and the power ground of the maf were combined so the thing was reading all over the place. Thanks for the help.... now to get those fenders back on and take it out of the shop . . . Quote Link to comment Share on other sites More sharing options...
Careless Posted June 14, 2008 Share Posted June 14, 2008 There is a way to adjust the MAF sensor synch with the ecu. It's part of a Z31 mod listed on AZ-Bum's and Xenon's website. There's a small aluminum plug that was cast into the MAF housing right beside the connector. If you slowly drill it until you break through the plug, (5.5 mm or so). you can use a screw driver to adjust a potentiometer to adjust the output of the MAF voltage to the ECU. Makes sense, seeing as they do get dirty. Quote Link to comment Share on other sites More sharing options...
Careless Posted June 14, 2008 Share Posted June 14, 2008 ha! you typed the success story while I typed an alternative approach. LOL. congrats Quote Link to comment Share on other sites More sharing options...
Canadianz Posted June 14, 2008 Author Share Posted June 14, 2008 Well it seems I jumped the gun a little, the car no longer hunts for idle, however now if I hit the throttle or try to blip it any way other than very slowly the engine bogs right down. Falling on its face, the MAF was wired in incorrectly and that is now fixed, this bogging issue is weird though. Would a faulty TPS sensor cause the engine to be confused ? The engine seems to run pretty rich so Im not sure. Im going to get a new o2 sensor today hopefully rulling that out. Does anyone know the part # for a RB25Det series 2 o2 sensor? Or an cross reference ? Any how thanks for the ideas, the bugs are slowly getting worked out... Thanks Chris and Rob Quote Link to comment Share on other sites More sharing options...
jkube Posted June 14, 2008 Share Posted June 14, 2008 Check for intercooler tubing leaks and fuel pump pressure. Had the same issue with Adams sentra. Turned out to be both - Loose tube clamps and Chinese knockoff Walbro fuel pump couldnt deliver sufficient fuel. Quote Link to comment Share on other sites More sharing options...
Careless Posted June 14, 2008 Share Posted June 14, 2008 I think your MAF is pooched. Quote Link to comment Share on other sites More sharing options...
Careless Posted June 14, 2008 Share Posted June 14, 2008 All RB 02 sensors seem to be the same except for RB26. 22740-75T00 Quote Link to comment Share on other sites More sharing options...
Canadianz Posted June 14, 2008 Author Share Posted June 14, 2008 Thanks Jeff, Ill check the intercooler pipes ... we have a pretty badass external pump its a BBK one that the Mustang boys use on their Cobras ... Careless, Thanks man Im going to get a new o2 sensor today or monday Hopefully I can figure it out Cheers Chris Quote Link to comment Share on other sites More sharing options...
Canadianz Posted June 16, 2008 Author Share Posted June 16, 2008 Well got some more progress, we had the Z on the road this weekend, just a couple rips up and down the road. Heres a video of it . . . http://videos.streetfire.net/video/Test-drive_166437.htm I have a couple questions, once I get into it the engine starts to missfire and lugs a lot, what usually is the cause for this ? Second what rpm range are you fellas building boost at ? I have a t3/t4 hybrid and I was seeing 5psi at around 4k is that a little sleepy ? Would a crappy wastegate influence that, mine is definatly bypassing some exhaust at idle so it that normal ? Im going to get a new o2 sensor orderd up today so hopefully that might resolve part of the issue. Chris and Rob Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted June 16, 2008 Share Posted June 16, 2008 Well got some more progress, we had the Z on the road this weekend, just a couple rips up and down the road. Heres a video of it . . .http://videos.streetfire.net/video/Test-drive_166437.htm I have a couple questions, once I get into it the engine starts to missfire and lugs a lot, what usually is the cause for this ? Second what rpm range are you fellas building boost at ? I have a t3/t4 hybrid and I was seeing 5psi at around 4k is that a little sleepy ? Would a crappy wastegate influence that, mine is definatly bypassing some exhaust at idle so it that normal ? Im going to get a new o2 sensor orderd up today so hopefully that might resolve part of the issue. Chris and Rob Your car does not use o2 feedback under boost. Bypassing exhaust at idle is NOT normal, and from what your saying 4k is late for a t3/t4 I see 20psi before that. Is your base timing set properly? It would explain the running like crap. Do NOT rule out a damaged maf, or ecu. They are sensitive to being connected improperly. Quote Link to comment Share on other sites More sharing options...
Canadianz Posted June 16, 2008 Author Share Posted June 16, 2008 Thanks Evan, Whats the best way to run a diagnostic on the ECU ? I'll check the maf tonight its most likely that. Ill also check the timing. The wastegate is most likely messed up Ill try and get another . .. Thanks for the fast responses, were new to this and really appreciate it. Chris and Rob Crombie Quote Link to comment Share on other sites More sharing options...
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