Here's the saga. Nasty Girl had the plenum pull done last weekend. Afterward the Z was running sweetly, except for an oil leak in the cabin which turned out to be a split line to the mechanical oil pressure gauge. Chrispy to the rescue a day or two later - disconnected the oil pressure line. After this, the idle suddenly jumped to 1800rpm which is really odd since he was working at the bottom of the motor so there should have been nothing that could have happened from that. Chrispy took another look the next day and noticed that the TPS was a bit loose so that was the first thing we checked - normal at .46 volts. Base idle adjustment was next. As soon as the Conzult was set for base idle adjustment, it dropped to 850 rpm immediately. Checking the IACV indicated that it runs at about 63% even when hot and idle is normal when it's forced to 0%. When squeezing the 'S' hose into the AAV on the passenger side, the engine stalls, but we've got the base idle set pretty low to make the Z drivable. Squeezing the hose from to the air regulator or between air regulator and AAC makes no difference. We've also checked for boost leaks and fixed one. Nothing significant. Timing was checked and is correct. So, because the idle drops to normal as soon as the IACV is forced to 0%, does that mean that it is working? I'm assuming that the connector is OK for the same reason. Is that correct? What else could be causing the high idle?
Bit more info: When I went to fix the oil leak in the cabin, I plugged in my ECUTalk and notcied that the TPS was over 0.55V, so I adjusted back down to 0.45V. I know that Al had adjusted this after the plenum pull to 0.45V using a multimeter at the TPS. I thought it was a bit weird to be off that much after I saw him adjust just days before. As soon as I had adjusted it, the idle jumped up to the problem we have now. Only thing I can really think of is the closed throttle switch in the TPS not closing at the right time, but I can't check that with the hand held ECUTalk, and my lappy wasn't behaving. Maybe a faulty TPS?
Simple solution. Dont mess with stuff after I have fixed it Chris !!!!! Just kidding. I would be checking all the earths on the engine. There may be a voltage difference between the TPS and the negative battery terminal (where I measured from) and the earth at the ecu. I know there are a few earth points on the plenum. May be worth checking it out. Failing that just get a multimeter and put the TPS back to where it was.
Very interesting. I didn't know you had adjusted the TPS. Despite it reading .46, I moved it to max and back to .42, a little low but I didn't get too fussed over .02V, and then disconnected and reconnected as usual. Anyway, reset the base idle and now the IACV is back to 32% and idling at 850. I'm a bit sus on the TPS. Something to watch in the future. Thanks for the suggestions. We'll see how this goes over the next week or so. Garry
I don't think so Max, but might be worth adjusting after all these years. I might still have a spare TPS in the shed, will be a NA one though.
plug in ecutalk and get to the page that shows your throttle closed switch, then play with the trottle switch wires coming from the TPS, you might have a dodgy connection if your switch flashes,
The AAC value is determined by certain conditions, if it is being held at +60% by the ECU then it will likely be a connector that is undone, or dirty IMHO, especially if it has been working OK. In other words, the ECU is picking up an incorrect value, which is holding the solenoid value too high. If it was a vacuum leak, setting the AAC manually would make little or no difference.
Pex, I checked the manual for the inputs and the only one I couldn't tick off was the power steering pressure sensor. It was going to be the next thing to check. Pregz, that's a good point. There's bugger all vd between the throttle bodies and -ve terminal so it should be OK. I'll check it also. We'll see how it goes for the next day or so. Thanks.
re painting the plenum ..... ... I gave it a fairly heavy dosing of Primer .... all over ...... magic mike finished off the top coating after my early departure ... so, it would be likely to have significant Primer and top coat cover ..... worth following up on the point made by Pregz ......
Where's the love Baz? But at Gary said there is bugger all voltage difference between the plenum and the battery terminal so it isn't the issue.
Checked for vac leaks? I couldn't figure out why my car would idle at 2500rpm after checking and double checking everything. Turns out I had a huge vac leak coming from where the egr connects to the plenum.
The thot plickens. There's been an issue for quite some time - when taking the foot off the accelerator and clutch in, the revs would drop very low then come back to normal idle or sometimes stalling. The idle valve has been rejuvenated with little effect. After the plenum pull, it was fine so we thought we had that one sorted, but after adjusting the TPS the other night, it's back. I'm really starting to suspect that this TPS is a bit dodgy.
