dmyruski

92 Z28 .305 Manual.......... Starts and stays running but not smooth as usual. Surges some and a little high about 900-100RPM. However it will not rev or drive. Touch the throttle, it spits sputter and sometimes backfires. It does not have any codes when I hook up my OTC Genisus. When I turn Key On Engine Off no dummy lights come on, only the SECIRITY light. Tach, oil, coolant guages all work. Will the Vatts allow it to run but not drive? Is this a sign of a bad ECM and or Prom? Also another thing I noticed was my oil temp reads -39 wich is what my CTS reads when it's unplugged. Does a 92 have a OTS? If so, will not reading it put the ECM in "limp" mode? Could limp mode made the dummy lights not do a self test? I know there is a lot to unpack but any help or opinions would be appreciated, Thanks.

Tuned Performance

iTrader: (92)

You might want to start with checking fuel pressure and ohm injectors.

dmyruski

Fuel pressure is perfect 45psi with regulator plugged. Also brand new Walboro 255 pump, regulator, MSD distributor, coil, & wires. TPS, CTS, MAP, all test good. Also used some carb cleaner to check for an intake leak. Did not OHM the injectors, do you happen to know the specs?

Tuned Performance

iTrader: (92)

The injectors should be in the 15.5-16.5 range. If they have a grey body they are problematic multecs.

sofakingdom

iTrader: (1)

Your problem is fuel DELIVERY.

Not, fuel "pressure"... fuel DELIVERY. The AMOUNT, otherwise known as the VOLUME, of fuel the system can flow (DELIVER), when the engine demands more fuel in order to create power based on the load placed on it (some sort of relatively greater fuel DELIVERY requirement); not, the pressure it's capable of delivering sitting in your driveway under NO load (near-zero to minimal DELIVERY requirement).

You can use pressure as a proxy (stand-in, indicator, substitute) for evaluating DELIVERY, however. Tape your FP gauge to your windshield with duct tape or some similarly high-tech substance and drive around. See if you can correlate what you see on the gauge, with what you feel on your butt dyno. I.e., when the car falls on its face, what is the fuel pressure THEN? (as opposed to sitting in your driveway under no-load conditions) The pressure should STAY at 45 psi or whatever, even if you're accelerating as hard as the car can go, at as high a RPM as the engine can turn, for as long as that set of conditions remains in effect. If it doesn't, … you do the math.

Your parts list is IRRELEVANT. If your fuel system isn't DELIVERING the fuel the motor needs, then, … it's INADEQUATE in some way. First thing you need to do is, identify the problem, in such a way that you can clearly see the difference when you get it fixed.

dmyruski

That's my problem, I can't drive it. Soon as I push the throttle it's stalls, And fuel pressure does not budge. I thought the same thing, I was hoping to see it drop when I hit the throttle but nope it stays at 45psi then the engine stalls. This is why I feel it might be by ECM. But short of buying a new one and a little luck I don't know how to test it. I was hoping someone would confirm that none of the dummy lights coming on was a common sign of a bad ECM or Prom chip.

dmyruski

I do believe they are grey. Thanks for the info! I'll let you know what I come up with tomorrow.

dmyruski

Cyl 1-4=16.0 / 5=5.7 / 6=16.0 / 7=16.0 / 8=9.7

So apparently I have 2 bad injectors? But would 1 injector on opposing banks cause it to not be able to rev up? I know that it will cause power loss but figured it would still be able to drive. Also checked and none we're shorted to ground. And yes they are the grey ones.

Tuned Performance

iTrader: (92)

I would be inclined to replace the injectors and see if the problem persists.
You might want to contact southbay fuel injectors and get 19#hr replacements.

Tuned Performance

iTrader: (92)

Wil it rev with the two bad injectors unplugged?

dmyruski

Just unplugged 5 & 8 and ......... I love you! LOL idol has not changed but it will rev. I have a responsive throttle again. Any ryme to reason why or just something you picked up from experience with these old beasts? Either way, Thank you.

Also I have a zex Nitrous system and I usually just keep the nozzels set to 75 but I can shoot 150 so I'd like to go with a good injector and might as well change them all. Any suggestions?

dmyruski

I will check them out, And NY based. 👍 Thank you again.

Tuned Performance

iTrader: (92)

just a guess on how it would run. Southbay has a few options for 305 19#hr injectors.
some have experienced lean running with the Bosch 3s without ecm/prom retuning.
There Delphi’s should be a direct replacement but costs more.
or there is this option which I think is a direct replacement as well.
https://www.southbayfuelinjectors.co...tors-1985-1992

Tuned Performance

iTrader: (92)

If you do order from them try tg11 code at checkout.

dmyruski

Any recommendations on someone good to get the prom tuned?

Tuned Performance

iTrader: (92)

I would do the necessary changes yourself.
You need to look at the diy prom section and stickies.
At the least get a moates.net extreme aldl and cable 1.
You would also need tuner pro rt so you can datalog to see where your fuel trims are at.

dmyruski

Went with the 305 Bosh 3 for now to get her running untill I can read up on programing. But southbayfuelinjectors.com was awesome and the people are very knowledgeable. Plus that code worked! Saved me $20. I'll let you know how everything goes after they get here and I put them in. Thanks again.

Tuned Performance

iTrader: (92)

The first step for tuning is to change the battery voltage offsets.
That should put the fuel trims back inline .
https://www.thirdgen.org/forums/diy-...0-voltage.html

dmyruski

Injectors are in and everything is back together. It drives good but idle is still high and it surges a little, 900-1100ish. That's reading from my Computer not the tach. Also the throttle percent is changing from 0-3% but voltage is right around .54v. While I had it apart I cleaned the throttle body with carb cleaner and a rag. Should I pull the IAC and reset it maybe?

Also I set my base timing since I installed the new distributor as well, and when pulling the car out the garage I realized I never hooked the brake booster back up so I definitely had a vacume leak. That shouldn't affect the base timing correct?

Tuned Performance

iTrader: (92)

The vacuum leak and higher idle while setting the base timing shouldn’t be effected. As long as you set the timing correctly with the est disconnected. As far as the high idle check for vacuum leaks first then set the minimum idle speed. After the minimum idle speed is set you can adjust the tps up to .67-.76 vdc.

dmyruski

Sprayed carb cleaner around the intake and vaccume lines with no sign of an leak. Then I followed the idle speed adjusment procedure and when I plugged the IAC back in and restarted she went right back up to 1200rpm. Also to set the IAC I have put it In diagnostic mode but when I jumped the top two right hand pins, and turned the key on my fan was running constantly is that normal. And no CEL but that could just be the bulb.