Tim240z

This time the problem isn't with my 94 Z28, but with my Datsun 240Z (which has a 94 LT1/T56).
It drives great when up to speed and cruising on the freeway, but when in traffic, or in surface street driving it bogs and splutteres pretty badly (almost like an overrich carbed engine that needs a couple of high rev bursts to 'clean out' the carb). Feels like it's lost 2 or more cylinders. If I put it in nuetral and free rev it, it's fine, but when in gear (under load) it's no good.
I replaced the O2 sensors, but no difference. The plugs and wires are new (MSD 8.8 wires). No EGR equipment, no air pump. PCM has been editted to forego the above.
Running the MSD inline pump and fuel pressure (at least at idle is good). Open freeway driving is fine, plenty of power, as I said above.

Any clues as to what I should check next. Could well be the Opti i suppose, but I would image that the problem would also surface when I really 'hammer' it on the freeway, but it doesn't.

Any suggestions would be appreciated...
Thanks
Tim
http://tim240z.iwarp.com/

eaglesadog1955

Sounds like my problem

I have a 95 Z28 and it does what you decribe, I have almost new Bosch platinium plugs, then I put new plug wires, Then I checked my exhaust manifold bolts and found 5 of them where slightly loose.

when it runs ok it is more powerful than ever with new plug wires and tightened down exhaust mnanifolds.

When it bogs down it is just off idle and when I am at low revs in town it feels like I am only firing on 6 or 7 cyls.

If I push the car into neutral and rev it it sounds fine.

It seems worse when the car warms up

If I try to do a burn out it bogs down and stays stuck there (Sort
of like a stumble).

If I stab the throttle there is a delay in the engine picking up and reving cleanly until it rises above1,500 revs or so.

If I shift down into 1st gear the revs rise a bit and it goes like hell
I am at at loss at what to check next.

I am going to get a cable and connect to my laptop to see if there are any fault codes.

Let me know if you get it sorted.

Thanks Andy
http://www.cardomain.com/memberpage/441297

shoebox

Perhaps your coil is not putting out good voltage. You could try swapping the coil and ICM assy from your other car for a test.

Tim240z

Shoebox,
Thanks for the reply and suggestion, and I will try that. I thought about the coil, but then I also thought that if the coil was getting weak, it would show symptoms while under high load on the freeway? While under high revs and high load, my thinking was that the symptoms (if coil or spark related) would tend to show themselves more at the higher RPM loads?

Is my thinking flawed?

Thanks again,
Tim

shoebox

My suggestion was more to rule it out as much as anything. When I had a dying coil, it was sluggish on hard take-off and lacked top end power. Other than that, the car ran fine, but began to be hard to start, until one day it would not start at all. Not saying you have the exact same symptoms, but they don't always manifest themselves in the same way.

Tim240z

I think that since the engine had 97k miles on it when I pulled it from the donor Z28, and that I have no idea of the mechanical history of the engine (apart from the obvious signs of silicone on the water pump and intake), I am going to replace the Opti, waterpump (have it ready to go), and the coil. I am also going to clean the injectors.

I have reading the reams and reams of posts via the search function on this very issue and it appears as though definitive conclusions as to the remedy are completely elusive. It appears as though haphazardly replacing parts is the only solution

Tim

Tim240z

I think that I may have found the problem...at least a contributing factor:

I have just pulled the intake, water pump and Opti.
I pulled the opti apart and found lots of arcing signs inside and lots of corrosion and signs of arcing in most of the plug wire 'ports', and actually the coil wire 'port' was so bad that the top of the 'tower' had actually begun to melt. All of the inside terminals were corroded and signs of moisture everywhere. I am going to put everything together now and see what happens.

BTW, I know most folks here 'rave' about Jason Cromer, but my first order of parts from him was less than ideal!
I ordered a coil, coil module, intake gasket set, and opti.
The package was packed so poorly that the coil wire terminal on the coil was broken when it arrived. There was no module in the box. Very disappointing!
Just an extra 30 seconds to ensure that all the parts were secure in the box and all would have been good! Oh well....he's overnighting the coil and module to me....I just hope that he doesn't charge me shipping again!

Tim

eaglesadog1955

My problem is still on going.
I have oredered an MSD coil and a harness so I can fit a MSD 6al ignition box that I had left over when I bought the Nova I have put new NGK splugs, because when I removed the other 4 plugs 2,4,6 & 8, 2and 4 looked like they had been missed last time the plugs were changed. I found 5 exhaust manifold bolts slightley loose and now when it goes man does it haul ***. stumble is still there but only when it warms up.
I have two new O2 sensors on order from the USA $72.50 shipped for the pair they would have cost £75 each over here. My car is running rich cause everytime I remove a plug there is always black soot on it.
I am still waiting for Andy Whitticker to get back from vacation so I can get a cable to plug my laptop in and see what is going on with this motor. I smoked a Nissan 200sx turbo the other day so when it goes it goes!
I will leave the opti till last and replace all the cheaper bits first hopefully I will have it cured before I have to replace it!

Thanks Andy
http://www.cardomain.com/memberpage/441297
http://www.cardomain.com/memberpage/537476