bley49

I never had the original chip I never would put when in

bley49

Alright I'm officially stumped, now it's just inconsistent, one start it's rich and making popping and vibrating noises another start it lean as hell and jerking violently as it tries to accelerate and sometimes it's perfect now even a hiccup... got it to start while it was flooded out by feathering the throttle until the fuel mixture was corrected, that's a step in the right direction I used to get stranded for 20+ minutes waiting for the fuel to settle down.

xrav22

I think it is time to remove the distributor and rotor clean all the connections and reassemble just to be sure no carbon or anything.
Check the thing under the rotor also it can cause problems.

86C4Z51

Routine troubleshooting process for engines (if the problem isn't obvious): Ignition first, then fuel, then mechanical.

viii

Is it throwing any codes? Does it misbehave consistently once it hits a certain op temp?

bley49

VIII youre getting there it threw a code only once though and ran like ****, loves to act up when its running temp like 185-190

ex-x-fire

Check the grounds at the back of the heads.

bley49

Distributer and rotor were clean when I went in to do it myself so that wasn't and issue plug wires are brand new buddies and my dad are leaning towards a timing issue

xrav22

Double check tps adjustment because I could set mine to .54 but as
I tightened it up it would fluctuate because the inside was trashed. So put the meter on and tighten the screws and make sure it stays at .54.
My car acted weird till I found out and bought a new tps sensor.
Good Luck

bley49

thanks again for the advice but the tps is all good

Capt Mike

Progress ??

bley49

Nope the dealership is getting it for a diagnosis my master mechanics are at a loss

Capt Mike

Well, I'll be happy to assist. I've got a full day ,,but I'll try to get back to you tonight. Hope I can help to solve this !

I've worked with many of these issues for friends and a few performance shops, and they can be very frustrating. Even my C4 occasionally throws a mystery code. Some day I'll swap out the GM OEM EFI,

In the mean time, what was your original problem with the engine ??

And did this happen after a mod or event ??

Are you having any battery problems ??

Are there any odd or electrical problems, A/C, windows etc ??

Michael...

bley49

The problem was minor or almost nonexistent for the first couple months i had it, it slowly got worse poorer acceleration and horrible or lack of a start when it's running temp, started replacing everything fuel related down to the injectors and maybe the fuel pump took a crap again.

Capt Mike

Okay,

I want you to know that this series of ECU's, wiring etc, are not easy to deal with . I'm an Electronic Engineer with years of experience in Computer and systems designs. Never the less, this particular ECU is or can be very difficult to trouble shoot.

So, I'll take you though my typical process. Since I'm not there, I'm going to ask a bunch of questions, many you will think "What" and some you probably have already completed. But, I do need to know the answers to follow a path.

First, You will need to disable all non OEM accessories, Amps etc, and all components with electric motors and devices not required to operate your motor.

Remove all fuses from, Audio amps, radio, heater motor, seats, keyless entry, Bose amps, headlight control, A/C, cruise, GPS, and any and all non OEM electronic devices !!

Remove the connector on your air conditioning pump. You need to check the clamping diode integrated into this connector, as We need to know that the Diode is still working.

With your Ohm meter, measure the Resistance at the A/C compressor wiring harness connector. This diode only conducts Electricity in one direction.

How to test this Diode,,

place your Ohm meter test prongs, one on each pin of this wiring harness connector, write down the reading in Ohms. Now reverse the test prongs and measure the resistance, write this down as well.

You should have very close to Zero Ohms in one test and near Infinity in the other test,

If this Diode conducts in both directions, ie, low Ohm measurement in both tests, A faulty A/C surge diode can damage your ECU !! Rare event.Leave this connector disconnected, and let me know your test results. Leave this connector disconnected

Next.

Connect your Volt Meter to your battery terminals, the voltage should be close to 12.8 Volts DC with Engine off.

Start the Engine, now measure this Voltage. The voltage should have risen above 13 Volts and charge the Battery. Keep the engine running for 15 minutes if possible. The Battery Voltage MUST be under 14.4 Volts at all times .And typically will only be above 14 Volts for a few minutes if the battery has enough charge to start the engine.

Over or Under Voltages will very likely cause erratic operation and / or damage the ECU!! If the Volt rises over 14.4 Volts, turn off engine. you might need to replace Alternator internal regulator '

charge your battery. BTW, this diode clamps the Voltage spikes that occur of the +12 Volt wire when the A/C electric clutch is turned off

Lets assume the A/C diode is working and your Alt does not overcharge your battery, which can damage electronic devices.

If you engine still runs smooth when it's Cold, Open Loop,, and then the problems occur after it's warmed to operation temperature, Closed Loop. Then the first item to test and check is the Oxygen Sensor.

But, I'm skeptical because you wrote that with ECU replacement the Engine ran great, then went back t o previous probs..

Connect your volt Meter to the Oxygen sensor and set it to measure 1 VDC or less. The wire connections vary with what type of Oxygen sensor you have currently installed if it is the OEM 2-wire,, a 3 -wire or a 4-wire. That will be the next secession review

Measure the Oxygen sensors output, the Voltage when your engine is at operating temp should be very close to 0.45 Volts. the Voltage will vary a few milivolts.

Please let me know the Voltage results and which type of Oxy sensor you have currently installed.

If your in the 0,45 Volts and reasonably have a steady reading you can introduce a small about of propane, the Voltage should rise if all is working properly..

NOTE, RTV sealants contain Silica and damage all Oxygen sensors. Check your, Oxy sensor, valve covers, intake manifold, throttle body and etc for ANY RTV sealant. If there is any, you will need to remove that component and re-gasket and then replace your oxygen sensor (after the engine has run for 15 to 30 minutes) and change the oil as well. Besides AGE, this is a leading reason for defective Oxy sensors

Not counting any possible ESD damage to your new ECU, the most common intermittent condition or sensor difficulties is Electrical wiring.

I looked for the G.M. Tech report but haven't found it yet.

So here goes. If your like me or many other s,, We wash our Cars, We
wash our Wheel Wells and Engine compartment.

When I installed the ZZ4 engine in my C4 and the LS1 in my 56 Coupe, all of the wire junctions were soldered, all of the Grounding ring connectors were not !!, They were only Crimped..,,, not good

This means that cleaning agent and the water corrodes the exposed connectors !!

My C4 had several of the Ground ring connectors with some corrosion, one nearly all strands were broken off... I replaced all of the ground connectors with Marine ring connectors (thicker), Crimp & Soldered then and used the thick Marine shrink tubing for a strain relief.

You can get top quality at West Marines website.

As mentioned these ground connections are on the drivers side, mine are bolted on at the bell housing. Also make sure there is a braided ground wire routed to the frame. If you need photos do let me know..

Let me know how all goes. Further testing depends on the above

Good Luck,

Michael

bley49

Ill take all that time if the dealer cant figure it out I dont have time all I have is money to deal with my little bastard car

Capt Mike

Dealer trouble shooting a EFI Problems on a C4 Vettes, NOT Likely -

I would not waste your money at this point in time. Several other items to check. Most of the time it is some simple thing, grounds , RTV, or frayed wire..

You can complete all these tests I sent you in an evening. If you need to call me via phone, let me know,, happy to help..

Michael...

Capt Mike

bley,

re your C4 Oxy sensor,,,

IS it the Original 2 wire Oxty Sensor ??

Or has it been replaced with a 3 or 4 wire ??

Michael,,, Been nagging at me to know...

bley49

O2 sensor was exactly the same as the original i appreciate the advice but im so sick of dealing with it at this points its been 10 months worth of bs 8000k later in repairs or replacements on a car with only 102k on the clock and ive only driven it 1.2k of it It's my daily driver and some bitch on her phone rear ended my tahoe and wrecked it so now i need it. Again, I appreciate the help but I need to let the pros handle it.

Capt Mike

Okay, BUT.

I've yet to find a True PRO with EFI esp the older units at any GM Dealer.

Be sure to hand them the list of components already replaced. Plus, make them give you an estimates for repairs. \

Good Luck

Michael..