Guest Anonymous Posted October 7, 2002 Share Posted October 7, 2002 Guys, I've got a mysterious power and throttle response problem. I've tried about everything I can think of and need some advice on what else I should check. Recently, my stock '83 280zx Turbo developed a strange power and throttle response problem. I'm not aware of any "event" that would have caused it. The engine was running fine right before the symtoms started. The power and throttle response is normal at low speeds, and low throttle. It cranks and idles perfectly. The boost is smooth and goes straight to "7". But, the power curve drops off significantly after boost gets into the positive range. Also, when I let off the throttle, the power drops off instantaneously, which is unusual. It's almost as if the exhaust suddenly got clogged, but I know that's not it because I disconnected it at the Cat., and it does the same thing. I've got a fuel pressure guage installed, and it says about 40 psi, but I can't see it while driving. Another strange thing...after driven hard for only about a minute or two, the turbo's exhaust housing gets hot enough to glow, and I don't remember that ever happening before. I'm thinking "Holy Crap", I've leaned it out somehow, and maybe done damage. But it hasn't pinged once. Does retarded timing cause these symtoms? The timing is set normal, and I didn't tamper with it before the problem occured. Could the ECU somehow not be advancing the timing under high boost/high RPM? But what would cause the ECU to do that? One observation: normally, when idling, if you had removed the oil filler cap, the engine would die. Now, it just slows down some, and idles just a bit rough. Since the problem cropped up, I've: Replaced the Turbo (it needed replacing anyway) Tested the AFM, and even tried another one. Tried another set of plugs (not related...I know) Tried another distributor Tried another ECU (from an automatic 280ZXT) None of these made a difference. This makes me think it's something mechanical, but I can't think what it could be. The only part I haven't replaced, that I think could be suspect, is the fuel filter and the fuel pump. But the fuel pressure seems the same as it was before. Help....I'm STUMPED. Thanks, Shawn Boozer Louisville KY '72 240z '83 280zx Turbo Quote Link to comment Share on other sites More sharing options...
David K Posted October 7, 2002 Share Posted October 7, 2002 post this over in the turbo forum also. this sounds like a turbo related problem. Quote Link to comment Share on other sites More sharing options...
v8dats Posted October 7, 2002 Share Posted October 7, 2002 i had a very similar problem with my turbo z.turned out it was the throtle body position sensor. give it a try.its just a guess from past experiences Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 7, 2002 Share Posted October 7, 2002 Well, I checked the TPS at the sensor itself, but didn't check it at the ECU. I'll try that tommorrow. Can you elaborate on the symtoms you had? What was wrong with the sensor? Thanks Quote Link to comment Share on other sites More sharing options...
Tony240ZT Posted October 7, 2002 Share Posted October 7, 2002 You're right, sounds like you're going lean. Definately try replacing the fuel filter. Does it have any problem starting when it's cold, or rough idle? If a fuel injector wasn't pulsing the car would still start, but would run pretty rough. Would be nice if you had the that fuel presure gauge in a place you could see it. When I'm having issues I'll run a long peice of hose up so that I can strap the gauge on the cowl, leaving the hood only latched to run the fuel line through. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted October 7, 2002 Share Posted October 7, 2002 You may have mystery turbo death. The first thing I did on my ZX with the stock fuel injection when it misbehaved was clean the connections at the ecu and AFM with brake clean. Disconnect the harness at each one, and spray the pins and the connectors and then reconnect. Usually that solved the problem. 40 psi of fuel pressure? Is that at idle? That is to high if it is, it should be around 27 to 28 with the vacuum line connected. Also, you should be running some fuel injector cleaner thru the fuel system. STP in the black bottle has always worked well for me. Once a quarter should be sufficient. Make sure you pull the little filter out of the back of the fuel pump and see if it has trash in it. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 7, 2002 Share Posted October 7, 2002 Update: 1) Replaced fuel filter. 2) I got a visual on fuel pressure: 42 psi on full throttle...~24 at idle. Also, I experimented with the ignition timing. I advanced it considerably (sorry, don't have timing light). It ran stronger, but it pinged at WOT. (I let off imediately) It also still had the strange throttle response. I'm going to check cam timing next. Thanks SB Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted October 7, 2002 Share Posted October 7, 2002 DO the ecu and AFM cleaning first. It is easier and likely your problem. Man why do the hard stuff first. Quote Link to comment Share on other sites More sharing options...
Tony240ZT Posted October 8, 2002 Share Posted October 8, 2002 Yep, cam timing could do it. It's done it to me before when the chain slipped. Damn broken cam timing tooth, replaced cam wheel found tooth, put chain on, all is better. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.