mrrossi

I was soooo close!! It was the throttle position sensor after all; I'd corrected the idle speed voltage and checked the top end and seemed okay. Took it down to Zedworld today and Jeff was able to see straight away on the diagnostics that the issue was with the TPS and checked out the voltages again; it seems there was an intermittent issue (damn, I should have checked more than once!!) and on a few occasions the voltage would shoot through the roof as the revs increased! New TPS - issue fixed. Thanks Jeff, you're a star!!! :bow:

LOL some mixed opinions there! Well it seems chopping it in is going to be hit or miss depending on the dealer, but if I spot a decent car at a dealers I may as well ask and see what they offer... else I'm going to crack on sorting the paint and get it over to Zedworld to address the hesitation issue as soon as I can, and see if they can take a look at that crunchy gear change (it's only 4th, the gearbox and clutch are smooth/solid otherwise).

Thanks guys... well I'm off to the car wash in a mo, will hope for some dry weather to have another crack at restoring the paint tomorrow and then will either put up for sale privately or look at garages and a trade in, might be easier... Shame to sell but I've had my fun and I do a lot of miles so really need something more fuel economical.

Smithy, not that easy, I actually swapped it for a car that was also difficult to value. I guess it was circa 2.5-2.7k then and I thought that was good value, considering he'd knocked a grand off what he thought it was worth then as he thought the paintwork was screwed, but he hadn't even tried t-cutting. 2k would therefore be a little disappointing.

Ok no probs, thanks!

Just wondered if anyone had a rough idea on what my car was worth in it's present condition... It's a 1992 UK 300ZX Twin Turbo in Red with 146K on the clock, modified with a +70BHP EEPROM/boost increase/air filter, nice alloys, aftermarket rear lights. MOT is 13th April next year. It's had some rust issues in the past but seems they've all been addressed (extensive service history, lots at Zed World) although there's the odd rust bubble here and there. The paint is faded, quite badly in places, but I know it can easily be touched up/restored with t-cut and elbow grease - already started doing one or two patches; time and the weather is my enemy. The car has the common 'stumble/hesitation' issue although only seems to do this when cold for a few minutes then it's fine; runs sweet as a nut. Slightly crunchy going in and out of 4th but fine if you double de-clutch; otherwise, mechanically sound. Air con needs a new compressor but have it covered under warranty at Zed World - they're a bit far from me so haven't got round to replacing. How much do you think she's worth? And if I sorted the stumble issue, air compresser (and re-gas) and spruce up the paintwork, how much then?

Thanks Jeff - think it was your name the previous owner (Glenn) mentioned too - think you've got an air compressor waiting for me too - will give a call tomorrow!

phutumsch - sorry post overlapped there - that would still be £20 for the Consult-Serial then £10 for the Serial-USB cable though right?

Ah I see that makes more sense - a Consult to USB or Consult to Serial cable is what I need. CRIKEY - the USB ones are around £60!! Just found a serial one for £20 on ebay... it's still £20 though when all I want to do is rule this out being the ECU, I'd never use it again! Oh and I quick scout of my laptop suggests it's not got a serial port either :( I think getting a second hand ECU cheap and trying a straight swap might be an easier and cheaper (in terms of I should be able to sell it on again afterwards) option.

Ok well I was about to order a RS-232 to USB cable but a couple of things... erm... silly question, but is there even a RS-232 port on the ECU??? Looking at pics in Google I can't see one!! Also, do you need a specific type of cable - see the reviews for this one, sounds like some cables work with some things and others work with other brands etc... http://www.amazon.co.uk/product-reviews/B00077DJIQ/ref=cm_cr_dp_hist_one?ie=UTF8&filterBy=addOneStar&showViewpoints=0

Thanks guys... yeah I've checked, no fault codes. I'll look into the software and cables then :)

Are there any simple guides on how to do this/free software available?

Thanks guys... I put a note in here as well as the wanted section as the wanted sections always seem to be less well browsed/searched than the problems, plus knew a few people were already watching/following this post :D

Any idea where to find a cheap standard Z32 ECU?

I'll have a look to see if I can find a cheap standard ECU then to test out the map theory - I guess if it IS a map issue, then with a standard map/ECU the car should run fine at lower speeds/off boost for those first 10-15 mins? I imagine it wouldn't be great at higher speeds/full boost (and would I have to be careful to prevent damage?) as the standard map wouldn't know how to 'handle' that extra boost - but I can at least rule out whether it's the map or not? I'd forgot to say that I have accessed the ECU before - I did the O2 wideband diagnostic test (all ok).

Thanks... yeah I didn't understand half of what you said then :) Thank god for Google and these forums else I'd really be in the sh1te :) I'll do some more research/fiddling and see what I can suss out... spec of the mods? Erm, I don't know to be honest, the only details I have on the mods are: Upgraded eprom +70 BHP Nov 2004 Apexi induction kit Nov 2004 Turbo Boost increased from 9 to 13psi Nov 2004 In-tank “Broquet” fuel catalyst Nov 2004 Mongoose cat back stainless steel exhaust with twin 6” oval tips Mar 2005 PCV Valves Feb 2011 All done by Zedworld.

Thanks for the response Medallion man... to be honest I'm not very mechanical. I have just about managed to scrape by doing that long list of checks/fixes above by the piercing together lots of different docs/guides and pictures. In one case there was a very bad u-tube video that was too dark but by following that, matching with static pictures and reading several forums I managed to work it out! So no I'm afraid I'm not done any of the above, they may be beyond my capabilities. I have previous fiddled with maps on another car - an MX-5 with an Adaptronic ECU, but I had two local friends who had the same and showed me what to do - but again its a bit extreme for me. I've seen people mention a boost/vac test but couldn't find any info on how to actually do this? All I did was "Checked PCV hose/values (clamped as best I could, not fully closed, but there was no fluctuation at all)" as per the section in http://www.zhome.com/ZCMnL/PICS/hesitation/hesitation.html although I'm not convinced I did this very well, I probably don't have the right tools but I struggled to get access to the pipes to clamp them very well, plus they are quite hard/not very flexible... Thinking I may have to take it to the specialists.... unless someone has experienced this EXACTLY SAME issue and had ruled out the above already and says 'its this!'. Unlikely I know but crossing my fingers :)

Thanks for everyone's input here, there's been some very interesting (if not baffling!) reading :) I think if I was having issues at boost then yes replacing my 6's for 7's might be an idea. But I'm not; she drives beautifully once warmed up and under boost. My prob is at lower speeds for the first 10/15 mins when she's cold, get hesitation stumble - I've posted a separate thread here: http://www.300zx.co.uk/forums/showthread.php?165853-The-old-hesitation-stumble-issue-again-cold-starts&p=1690182#post1690182 Cheers Ross

Hi I know there's loads of threads about the stumble/hesitation issue that seems to be a common problem in the 300ZX, and I think I've read them all, and tried most of the suggestions within them, but I'd like some advice please. I have a 1992 UK 300ZX twin turbo, with a +70BHP EEPROM upgrade and Apexi air filter. The previous owner had the car for 9 years and had the EEPROM upgrade done when he first bought it. He thinks the stumble first started about 4 years ago but as he 'drove her like a granddad when she was cold' never really bothered about it. My particular stumble/hesitation ONLY occurs in that first 10-15 minutes. Once the car is fully warmed up, it doesn't happen at all. It seems to happen mainly when I'm doing 30mph or so in 2nd, or 40-50mph in 3rd, and the revs are between 2500 and 3500. It feels as if someone has taken the accelerator away for second, then it comes back. It may do it once or twice in a few seconds then it'll be normal. Seems to do it mainly when I'm at that constant speed (30mph zone) but occasionally will do it when accelerating. Even in those first 10 mins or so when it's still cold, it doesn't seem to happen at higher speeds/high revs. Every so often it's more severe, and the 'drop off' will last longer than a second and feel likes it's going to stall. It did this really badly tonight. The car hadn't been used since this morning (2hr run, little bit of stumble in first 10 mins then absolutely perfect). I took it to the shops 9 hours later, 10 min journey. Stumbled maybe four or five times, not too deep, but annoying nonetheless. Shopped for 10 mins, came back, drove for another 5mins to another shop, couple of minor hesitations. Shopped for 20, maybe 30 mins. Got back into the car and headed for home, about 2 mins in had major, deep, drop offs, felt like it was kangarooing - would get 2 second without power, 2 seconds normal, repeated, probably about 10 times. All the time my foot was on the pedal consistently. Came to a roundabout and stopped for a sec; pulled away and was fine again. Outdoor temp today has been 12 degrees, so not that cold really. I've been following this document for the last couple of months and trying different things out: http://www.zhome.com/ZCMnL/PICS/hesitation/hesitation.html So far I've done: Unplugged everything - injectors, all connections, cleaned all contacts up Checked PCV hose/values (clamped as best I could, not fully closed, but there was no fluctuation at all) Air flow meter - voltage fine Air filter looks clean enough Cleaned throttle intake valve Voltage checked TPS - adjusted to 0.47V Cold start temp sensor voltage check (readings here http://www.300zx.co.uk/forums/showthread.php?165253-Coolant-Temperature-Sensor&highlight= which I think are fine) Checked spark plugs - have the correct PFR6B-11C, they look relative new/clean Replaced Series 1 PTU with a Series 2 PTU There are a few more bits and bobs that I could chec: OHM check injectors Replace fuel filter Fuel pressure tests BUT, reading through that doc above, and other posts, they don't sound relevant to my particular problem - i.e. the fact that the stumble is only when cold (in those first 10-15 minutes). Any more ideas anyone? Reluctant to spend any more time/effort/money on her!!! I AM off to Zedworld in Birmingham at some point in the next month or two to replace an air compressor, I could ask them to take a look, but fear it may take them a long time (and cost me a lot!) to diagnose. I thought the EEPROM upgrade could be to blame but it was installed 9 years ago and it's only been happening for the last 4 years... Thanks Ross

Yes Lisa... Daddy's a teacher now.

Thanks... will see how we go when the PTU turns up and then at least that's one more thing ruled out :)

i.e. it's not at boost I'm having the stumble probs else perhaps a grade 7 plug would be better for my slightly higher boost

I was only going to change the spark plugs as a possible cause of the 'hesitation' issue I get, but reading through some details on this it sounds like spark plugs would only be the cause at higher revs, my 'stumble' is at lower revs and only for the first 10 mins or so when the car is cold. I've been working my way through the list of possible causes and have already ruled out: PCV hose/values Air flow meter - voltage fine Throttle intake valve clean Voltage check TPS - adjusted to 0.47V Cold start temp sensor voltage check The PTU is a common cause - I have a series 1 so have ordered a second hand Series 2 PTU from the states on eBay, had hoped would have arrived by now but have had to pay a £13 import tax plus another £13 'handling fee' from Parcelforce, what a rip off!! But will hopefully have that soon and will fit and see if that helps... if not I'll post a more detailed new forum question up to see if anyone has any other ideas.

LOL, even worse, some 10mm/16mm wrenches are advertised as just 10mm, and some are advertised just as 16mm. So I bought a '16mm' wrench when I already had a '10mm' wrench at home - and they're the same bl00dy thing :)

I finally got round to checking my existing spark plugs the other week and found they were PFR6B-11C, and looked pretty new and in good condition so not going to bother changing them (I'm actually working step by step at trying to sort the dreaded hesitation and this was one of the possible causes). Just a note on the spark plugs: my "10mm" wrench was fine; it's 10mm for the spark plug screw thread; and 16mm for the hex part at the top of the spark plug which the wrench turns :)