KetchupNinja Posted February 3, 2011 Share Posted February 3, 2011 (edited) Hello all, I'm having a few problems with my Z. It's a stock l28 with a K&N intake from MSA and a 2 1/4 Flowmaster 40 exhaust. I wanted to ask for some advice before I started blowing tons of money for replacement parts. Here's a little back story with this particular Z: Got the car a little over a year ago, it was running fine but I noticed that in lower rpm's it would kinda stutter. I decided to buy a fuel system cleaner but little did I know that this would cause a whole world of trouble for me. After driving it around the car died, didn't stall or anything, it just kinda shut off and rolled on. I had trouble starting it for the longest time and when I did, it would soon shut off after. I replaced the fuel filter thinking the fuel system cleaner was doing an awesome job of cleaning everything. The filter was dirty of course, and I thought I had found the source of my problems but it didn't really get any better. At this point, I took it to shop to get it repaired. The shop had the car a little over a month. They changed the spark plugs with NGK's the car still wouldn't start. They thought it was the ECU because the injectors would stay open, flooding the engine. Instead of fixing the actual problem though, they did find other things to fix such as replacing the rear output shaft seal, coolant temperature sensor, clutch slave cylinder, oil pan and valve cover gasket, and the oil filter. I took the car home and ended up dieing on the road twice, not being able to turn the car back on unless I waited about 15 mins or so. I then took the Z to a different shop and described the problem to them. After a few days they called to tell me that there wasn't anything they could find that was wrong with it. I was really scratching my head and drove over to meet them. It turns out, the car would start up all the time with no problems and they actually drove the car for 108 miles total without it dieing on them. I was happy as hell, I took the car home and started driving it daily. It didn't take long before a new problem showed up. I'm noticing that the acceleration was really bad unless I floor it. I seem to be getting stutters or something, the exhaust will make a small pop noise from time to time. At a light, I floored the gas pedal and maybe moved about 10 feet and then the car started to rev up really damn high. I checked out the fuel pressure recently and it seemed to be pretty normal: 38 psi at idle and 30-33 psi while pressing the gas pedal. The battery checked out okay too, getting a reading of 12+ volts. I'm kinda stumped now, the only thing I could think of now is a new ECU or a new AFM, anyone else agree? Edit: Sorry keep getting AFM and MAF mixed together lol. Edited February 3, 2011 by KetchupNinja Quote Link to comment Share on other sites More sharing options...
DCZ Posted February 3, 2011 Share Posted February 3, 2011 Many of your symptoms point toward debris in the fuel tank clogging the input to your fuel pump. However, this is a 33 year old car with who-knows-what done to it by previous owners so there can be many contributing factors. My best advise to you would be to get a Factory Service Manual (search this site for links to free download) and follow the troubleshooting sections in it. You don't need any fancy tools and you will become a lot more knowlegeable about your Z than any of your local parts swappers, er, mechanics. Have Fun! Quote Link to comment Share on other sites More sharing options...
NewZed Posted February 3, 2011 Share Posted February 3, 2011 I think that you lost a lot of people at "MAF" and "blowing tons of money for replacement parts." It's a sad, lonely road that no one wants to travel with you... DCZ is right, if you get the FSM and read the Engine Fuel (EF) section, you'll be able to describe your problem better. http://www.xenons30.com/reference.html It revs really high but barely moves? Automatic transmission? Read the AT section also. Even if you don't get a solution here, you should be able to save a lot of money with your future mechanics. Quote Link to comment Share on other sites More sharing options...
roger.svoboda Posted February 3, 2011 Share Posted February 3, 2011 first off you need to learn the difference between a MAF and an AFM. you have the latter. your fuel pressure is all wrong. it should be 30 at idle and higher when revving. What is your vacuum? vacuum leaks are the bane of FI engines. put a gage on it. below 18 BAD Above 20 good. quick and dirty pull the oil filler cap when idling. if it runs worse Good. stays the same you got a vacuum leak. have you checked your ignition timing?. The AFM might be your problem. They develop bad spots on the potentiometer that sends a signal to the ecu. download the fuel injection bible. Use google search you will find it. Quote Link to comment Share on other sites More sharing options...
cgsheen Posted February 3, 2011 Share Posted February 3, 2011 (edited) Poor electrical connections are also the bane of Z cars in general and EFI & ECCS Z cars in particular. Before you screw with the AFM or ECU, go through the wiring and check and clean ALL the connectors. Special attention on the AFM connector, ECU connector, CHT (cylinder head temperature) sensor connector, injector connectors, O2 sensor connector. Be sure to check / clean both sides of the connection. Run through the EFI component tests in the Factory Service Manual - they're not difficult and you can check every component associated with the EFI system AND it's wiring back to the ECU. Edited February 3, 2011 by cgsheen Quote Link to comment Share on other sites More sharing options...
KetchupNinja Posted February 3, 2011 Author Share Posted February 3, 2011 (edited) Thanks for the replies everyone. I got a bit of electrical cleaner and unplugged all the connectors to the injectors, TPS, CSV, AFM, and just about any connections I can find and cleaned them out. I did pull off the oil cap and it ran worse, which in this case is good as roger had said. I drove it around maybe a mile or so and I haven't ran across the symptoms mentioned before. I'll have to drive it a bit and keep checking. I did download the FSM and Injection bible, so I'll give those a read and check back. Edited February 3, 2011 by KetchupNinja Quote Link to comment Share on other sites More sharing options...
datsun723 Posted February 3, 2011 Share Posted February 3, 2011 I had something very similar happen with my Z but it turned out to just be the temp sensor. Call up Mike's Z shop in Whittier 562-693-9914 and ask for Marc. I'm sure he can point you in the right direction. http://www.mikeszshop.com/ Good luck Quote Link to comment Share on other sites More sharing options...
JSM Posted February 4, 2011 Share Posted February 4, 2011 Your fuel pressure does sound a little high. If you pull the plugs now, are they black? Also does it run good cold and then crappy once warmed up? If so I would lean towards the temp sensor connection first, then the sensor itself. Take the connector completely off and clean the heck out of it. I would highly recommend and inline fuel pressure guage on the motor so you can read the pressure when a problem occurs. I used this one: http://www.harborfreight.com/fuel-injection-pump-tester-92699.html All you need is the silver peice and the guage and put it inline. Quote Link to comment Share on other sites More sharing options...
KetchupNinja Posted February 15, 2011 Author Share Posted February 15, 2011 Just replaced the AFM and it works like a champ! Thanks everyone Quote Link to comment Share on other sites More sharing options...
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