Tooslow4u

Ok heres the deal.
94 z28 stock internals
Tuned by a shop in Tomball
Has bee hive springs and ported heads procharged at 5# with 42# injectors. Car made 465 hp. I just recently acquired the car with a blown head gasket. I fixed the gasket and car ran great pulled extremely hard. I drove it for about 3 weeks. I was dropping my girl off at the airport and it was pouring rain. The car began to act weird surging and shifting very weird. limped the car home and the alternator died. Replaced it and ran codes they are as follows 27 83 26 34 53 51 Also the tps was hung at 48% throttle replaced it and the map was stuck at 4.88 volts. Replaced it also. Still has all codes. I have checked all wiring the only problem I see is the map pigtail it is on order now. Checked compression and it is 170 with no more than 5# up or down across the bored. Car starts fine and runs excellent until warms up. Also fuel pressure is at 47# The trans will not shift past 3 gear and no torque convertor lock up. Any ideas would be appreciated.

Guest47904

DTC 26,27 and 83 all have the #6 10amp fuse in the U/H fuse panel in common. More than likely it's blown. While you're checking it, look for any others.

Once you have the fuse replaced and the codes cleared, check to see if you have any further problems.

If the 51 were a consistent problem I would say the PCM is fried. However, your problem when it warms up leads me to believe you have closed loop problem. You need to monitor the O2 signals and the fuel trims and confirm the problem starts with closed loop operation. But let's see what a new fuse does first.

Tooslow4u

All fuses good. The egr has been done away with the same goes for evap. It does have a problem soon as it reaches closed loop. I had planned on turning off the egr and evap with a new flash. As soon as codes are cleared and runs for about 30 secs all codes return. The o2 on the right has very erratic readings and fuel trim is insanely high. if I turn the car off and restart it while warm the fuel trim drops to an acceptable level. I am beginning to think the ecu or a bad ground. Also the ac will not engage the clutch anymore. Checked all relating circuits everything looks good. Also car has new opti with delteq coil pack ignition.

Guest47904

Before you go throwing money at the problem. Check the new alternator for leaky diodes. Set a meter to AC NOT DC, engine running of course, and measure from the negative battery post to the large post coming out of the alternator. Be sure the reading is below 0.03 VAC. If the alternator is leaking AC on to the DC output, it can create all sorts of problems with the PCM. If it reads higher than 0.03 VAC, have it checked by a reputable shop like NAPA. And stay away from Advance and AZ for electrical parts.

If that's ok and the 51 code returns, have the PCM reflashed at a place like Auto Value. During the reflash, they can determine for sure the PCM is defective.

Incidentally, your hot restart problem still sounds like a closed loop issue. If you shut down and restart, the PCM goes to open loop for a moment until jumping to closed loop and that is when you have the problem. I believe you have a problem with the signals from the O2(s). However, let's see what the PCM reflash tells you first. I wouldn't just go purchasing a PCM without having it professionally reflashed. Since I have never actually witnessed an OBDI PCM failure.

Tooslow4u

Car is fixed. Well almost trans is still acting funny. Changed 02 and bought computer and reflashed with my old maps. Car runs great. Trans is fried no 3rd or 4th. Sometimes it will shift into 3rd. Getting ready to swap 4l60e for a turbo 400.