Terrible Hesitation

[zamazz10]

Sorry for posting a post similar to this and proceeding to forget about it. I have a 1990 300zx N/A that has recently become undrivable.I have checked many things with little avail. The car jumps and hesitates whenever the throttle is pressed and the idle has also become erratic lately. When cold or after idling for a few minutes, the car will nearly die, osculating from 1200 to 200 rpm. If I let off and reapply the throttle it will momentarily accelerate before once again losing all power. The car will not even accelerate in 5th gear and is extremely jumpy in 1-3. Here is what I have checked: Using a program called ECUTalk and a cable to the OBD port i have found that most sensor work as they should. Temp sensor all check out. The two O2 sensors seem to be low (but I can't hold even remotely close to 2000 rpm to get a good reading). The Speed sensor does not register on the computer but runs the speedometer fine (really wanna figure out why since it ruins cruise control). I do not know anything about injector duty. Plugs are new bosch double platinums, all sparks checked, Air flow is fine, CAS is not worn and all 6 injectors click when the CAS is rotated. fuel pressure appears to be around 40 (i will get a better reading tomorrow, i was in a hurry tonight). Thats about all I know.

If anyone can help I would greatly appreciate it. Thanks!

[es.biggs]

First and foremost - this is essential to getting your 300zx running right - Get the correct spark plugs - NGK PFR6B-11
Check your ignition timing with a timing light
Make sure you have no vacuum leaks.
Set the throttle position sensor.

[GerryO]

http://home.swipnet.se/e-solutions/IdleTech.html

http://home.swipnet.se/e-solutions/IdleTech2.html

[zamazz10]

Okay, I'll pick those plugs up tomorrow. How do i go about setting the TPS? or testing it for that matter? Also, the problem is far from an idle problem. I have to pump the gas to even get the car to accelerate. In 1st gear i practically get whiplash! Thanks for the replys!

[zamazz10]

Nevermind on the TPS questions... I just read those links. Let me test these and see what I get

[zamazz10]

Okay, so here is what i have found. The TPS reads .44 at idle according to my computers ECU program. At full throttle it says 3.8 to 3.9. There is no hesitation or hiccups in the areas between. I pulled all six plugs, and the drivers side ones appear slightly darker (as if burned) the other side remain gold (I cleaned the plugs a week ago, so they have had little time to change color). I have not checked timing and when I restrict the PCV hoses the engine does not change speeds at all. Is there a procedure somewhere on this sight as to how to check timing? Thanks.

[es.biggs]

Timing check is in here:
http://www.twinturbo.net/net/viewmsg.as ... _id=922678

[zamazz10]

Any new ideas on the problem? what are the chances that it is injectors? If it was, how could I check them out?

[es.biggs]

Did you check your timing?

You can ohm your injectors to check the resistance of them with a mulitmeter

[Rich@RDZ]

sounds like MAF sensor. Try swapping with know good one.

or OHm test injectors, 12-15 Ohms is within spec