Long starts I believe is usually due to a stuck fuel pump relay. I would put a scanner on it and confirm that your CTS is accurate as well as put a fuel pressure gauge on it and turn the ignition to on, engine not running. See if it primes.

 

Was this with the new EGR?

 

I agree with Daniel as well. You should also look closely at the relay connector. They are famous for shrunk insulation and frayed, corroded or broken pins, wires and connections. This will cause problems with the relay and long start situations. The CTS provides input to the relay until you build oil pressure from cranking over the engine so if its bad or has a bad connection at the relay, thats when you have issues.

Good luck, we will help you figure it out.

 

Modern digital voltmeters use a very small current source to measure resistance. The current will probably be too small to forward bias the diode into conduction. There should be a position on the DVM function switch that looks like a diode symbol:

That's the switch position you should use for testing diodes.

The power supply input to the ECM is pretty robust and very difficult to damage. The ECM measures the ignition voltage and will shut off the engine if the voltage is higher than 17.1 volts.

You will not be able to measure 0.45 volts from the oxygen sensor. The ECM continuously switches the fuel mixture from rich to lean and back. The O2 sensor follows those AFR changes and the output will look like this:



Another reason that you will not be able to measure 0.45 volts on an O2 sensor is caused by the shape of its response curve. It's basically impossible for the O2 sensor to stay at 0.45 volts for more than a few milliseconds:



It's the SILICONE in RTV that damages O2 sensors. There are "sensor safe" RTVs available.

 

Never mind anything I said EGR didn't fix the problem completely 3/4 trips were fine last one it still had minor stutters at around 25 mph 42mph and 67mph if trying to accelerate slowly, but under load it hauls ***. Ready to push it off a cliff

 

did you ever check the injectors? 30+ years old you know.

 

How do you know it's rich or lean?
Did you have an O2 sensor bung welded in and you're logging it with a wideband?
My guess is no...

 

Replace the TPS?
Brake booster holding vacuum?
Compression check?

Sounds like a fuel injector is sticking.
http://www.mrinjector.us/

 

I believe he mentioned that he already replaced the injectors.

Were they used injectors? What was the flow rating?

 

In HIS OTHER THREAD it says the injectors were FLUSHED. (whatever that means.)

Somewhere it also says $8,000 in repairs.

I have a feeling this thread is going to stop updating, the OP is going to disappear from the forum and this is all going to be another internet mystery to add to the thousand others out there, seen it a million times.

I'd look at the engine computer/ECM/PCM/ECU/or whatever you want to call it. He says it's good/has an aftermarket chip/ordered a used one with chip/ never had factory chip. My guess is the chip (vehicle specific tune) is incorrect. Or all of the above is incorrect. Or replacing old with old just never works.

Also look into grounds, fuel injectors (sticking pintles), mechanical problems that cause vacuum issues (valves, valve springs, old timing chain), etc,

Seems like good advice is given on here, then next post is "TRIED A BUNCH OF STUFF, BUT NOTHING YOU GUYS SUGGESTED, WHAT CAN IT BE??? NEED MORE SUGGESTIONS SO I CAN TRY OTHER STUFF THATS NOT RELATED"

We will never know.

 

Looking at crate engines to put the non working TPI onto.....

 

Never replaced the ecm or fuel injectors. I've had the same syptoms as described in this thread solved by either replacing the injectors or ecm.

Sometimes a good kick in the pants will get someone moving in the right direction, being nice doesn't always work.

 

I bet the injectors are the problem. And it was mentioned like 5 times on the first page of this thread, so by now I figured he would have changed them.

 

Bley,

GM service bulletin below

Why I mentioned #6 & # 9, you'll have to decide the others. Another Tech Bulletin mentions low fuel pressure, which involves not only the fuel relay, but fuel pressure regulation - which is Vacuum controlled.

When I installed the ZZ4 engine (2000), I had horrible low throttle response but great hard acceleration as well. but, I jut don't remember the issue,, I had so many.\\

But, vac lines, grounds, and fuel regulator were the main problems.
try this site


http://www.alldatadiy.com/

low cost and they have all the info. And you can email for do's that you can not find and they will assist,,

Good Luck,

Michael...
\
Lack of Power/Sluggish/Spongy/Stumble

1 Check for plugged air filter and replace as needed.

2 Check for air leaks between MAF and throttle body.

3 Check Ignition timing and ensure ignition system components are satisfactory.

4 On turbocharged models, check wastegate and boost control system.

5 Check fuel filter and replace as needed. Perform fuel system pressure check as outlined.

6 Inspect ECM power grounds and repair as needed.

7 Check EGR system for condition causing valve to remain open or partly open at all times.

8 Inspect exhaust system for restrictions.

9 Ensure charging system output is within specifications.

10 Inspect engine for loss of compression, improper valve timing and/or worn camshaft.

 

Parts List is updated and full status update is there

It's about 99.5% there mike, the previous acceleration issue is very intermittent, has to be something little at this point drove it for a good 45 minutes earlier under load and smoothly, only had a couple hiccups but the idle is perfect and smooth 700-800 Rpms in gear Ill check #10 I've been told it needs a valve job, The car is leak free now as far as vaccuum, sort of off topic but what's your guys Oil temp averaging around town when it's warm outside and it's under load at times


as far as the starts though where can I find the fuel pump relay at

 

/////////////

Bley, GREAT NEWS !!!

Intermittent are tough. Still, recommend you re-check those Grounds drivers side @ Bell housing on my C4

I installed a 58 mm T-body after the ZZ4 crate motor install. I had a pesky intermittent problem similar to yours. After I worked out all the other issues, weeks and weeks, I had one left. The Car would run great for hours or days and then unbearable acceleration -- drove me nuts.

Since the T-body was the last part installed before this new Bug, I removed it. I removed the top aluminum Cover Plate,,, NO GASKET"..
Brand New T-body. I wasn't happy, but a new gasket solved the problem. Might check it out.

I know that you said the Vac was good. But, You might try spraying a flammable spray on all on the intake manifold connections, T-body and MAF. Might want to do it when She Hiccups...

It's been a long while since I've watched the Oil temp on my C4. But, I do think it was usually,,, +/- 10 degrees of the Coolant. I do have an Oil Cooler installed in my C4.

I also moved the Air Intake Sensor closest to the Air Filter end on the black Rubber Hose,,,that connects the Throttle Body and the Air Cleaner.

Mine was very close to the Throttle Body. Placing it farther away from the T-Body will result is closer to Actual Air Intake Temps, The mass from the T-Body heated the brass sensor base, in my case. I purchased the sensor wiring harness extension from Eckler's.

Well, if you have low compression, do check the Compression and get a Performance Shop to complete a "Leak Down Test"".

Being your problem is now intermittent, Compression is unlikely.

Keep at this, you will solve the problem,

Michael....

 

Bad news even though the ecm is new with a factory chip the car is back to its old bs not starting when at running temp stalling and smelling like gas

 

fuel injectors
Spend a few thousand more, or sell it.
Eventually it will get to the point where everything else was randomly replaced except for the fuel injectors.

 

Hard starting can be caused by bad injectors, stalling can be caused by bad injectors, smelling like gas can be caused by bad injectors, just about any driveability problem can be caused by bad injectors.

MOST of the stock injectors left over in any of these cars are BAD! The majority of C4s, or a very large percent, has had the injectors changed because that's how prone to failing they are.

I'll bet if you floor the gas while starting, it'll start right up.

 

Bley,

I agree, leaky Fuel Injectors. Typical after driving an EFI Car. You park Her and the fuel injectors leak down into the intake manifold, there is residual fuel pressure after turning off the engine.

I used Bosch Injectors. But that been a few years. See what other members prefer.

Michael