The new ecm fixed my problem but only for a couple weeks, back to ground zero, any other suggestions??? :confused:
Thanks for the replies.............

FRED

 

Ooops My Bad:bb! You’re correct about the Sensor I referred to earlier; it’s for the Digital Cluster, not the ECM. I read about this Sensor/switch many years ago, so the details and facts got a little fuzzy for me, sorry:(.

The item’s name is actually “Ambient Temperature Override Switch”, sounds like a bi-metallic switch to me. What I would like to find out is, it’s real purpose! Does it modify the LCD drive/contrast voltage for low temps, or does it enhance the Cluster’s Micro-Controller/Oscillator Clock stability at low temps? In any case, it’s probably a long shot that it would affect starting.

But perhaps my technical foul has led me down a different path! In my Service manual it states under the Digital Cluster section “If the Digital Cluster is intermittent and the engine misses, check for bad Capacitor ground or a bad Capacitor at the Generator.” & “ Check for a bad Tachometer Filter.” The “engine misses” has got me thinking about EMI/RFI on the digital signal circuits.

What if the ECM/Digital Cluster/ALDL Serial data path was intermittently corrupted by noise generated from any number of items (Digital Cluster, Alternator, AC Clutch, Starter Motor, Emissions Solenoids/Servos, Etc) on the vehicle?

I pose this concept only as a shot in the dark, as it sound like you guys have already R&R’ed the usual suspects.

This is just grasping at straws, because it’s a slim chance that someone has a Digital Bus Signal Analyzer at home. Trying to find corrupted bits/bytes/hand shakes, or quantitative analysis of clock jitter is a little out of scope for most of us. As a consolation prize, the cure may be as simple as replacing a few filter caps on the DC power/charging system, or on the signal lines, or perhaps getting a rebuilt ECM/Cluster. Who knows, maybe it’s an intermittent ground failure somewhere; after all, the Y-body is notorious for having ghost problems created by bad grounds:rolleyes:!

As a side note, the Service manual also said something about an “in Tank, Fuel Pump Check Valve” as causing hard starts. If this device fails, it causes the fuel to siphon back into the Tank when the car sits for a while. I wonder, a few of you said you thought you had good FP upon cranking, but what if the initial pressure was compressed air after the Pump re-primed? The Fuel lines would purge them selves through the Injectors/return line, within ten seconds of cranking right?

Anyway, sorry I sounded like I was talking out of my butth0le; I also hate disinformation:mad. I really hate being the source of it- Doh:banghead:!

PS, I told you I might be:crazy:!

:crazy:NanoBrain:crazy:


[Modified by NanoBrain, 1:07 PM 6/20/2003]

 

As best as I can tell, the ambient air override switch is in the cruise circuit; closing at 32 degrees, which I think is a signal to the display to disable cruise control below freezing temps. It's function isn't described in the Shop Manual or in Killebrew's Digital Dash repair manual, but it is shown in the cruise circuit and it indicates that it closes at the above temperature, so that's my best guess. It doesn't get cold enough here for an actual test - so other than disconnecting the blue wire and providing a ground, I have no way of testing it to see if it works this way. As to the cold start, this seems to be a fuel issue only - too little; especially since after cranking it and stopping and then cranking again produces an immediate start. Try priming the rail a few times with the key on and off with no crank and then see if it starts. If so, pressure isn't high enough to give it the squirt it needs to fire when cold which could be the filter, the pump (including it's electrical circuit), the regulator, or the injectors. Seriously doubt that all these hard starting '89's have too narrow of a cold start pulse width programmed into the chip, but maybe someone over in tuning could give us a heads up. I'd also make sure that the TPS signal is at specs along with minimum idle and that timing is deadon at 6 BTDC.

 

I think you have defective injectors whose internal solenoid valve is sensitive to temperature. You start ok at work because the car sits for 8 hours at daytime temperatures and when you start it, the engine is at a higher temperature than when it sits all night at a lower temperature. Starts in the morning are at a cooler engine temperature because it sat longer and in lower temperatures. A leakdown test after work and a leak down test in the morning might show faster leak down in the morning. You have a fuel pressure gauge now, give it a try.

 

Can I play too? My '89 is a black Z51 6Spd coupe. Long cranking before start and it defies detection! What I've done so far:

New plugs, coil, cap, rotor - stock type
New battery & alternator - probalby wore out cranking too long :)
New coil, cap & rotor - DUI (have a near new stock set on the shelf now)
New fuel pump & screen - old one is available & works fine
New fuel filter (improved fuel delivery, but still cranks a long time)
New injectors & AFPR (holds pressure fine - same long start all pressures)
New plug wires - Taylor 8mm
New IAC & TPS (properly adjusted per Helms manual)
New throttle body
New temp sensors

Once started - runs geat, never misses, stalls, etc.

Maybe it is a black thing :D


[Modified by NavyVet, 12:15 PM 6/20/2003]

 

How frustrating! You've replaced all most everything and still no solution! If it's a hard start both hot and cold, use the code 54 chart to check the ECM driver and relay. Also, make sure the pump continues to run while cranking and isn't shutting down (with a hose attached to the inlet line & in a gallon jug, crank it over . Did you flush the inlet when you replaced the filter? The fact the flow improved could mean that some junk was past the filter. Best to clamp a hose to the inlet at the rail and then cycle the pump a couple of times to be sure its clean. Otherwise, crap can find it's way into the new injectors. Make sure injector resistance is 10 ohms or better hot & cold and that all are the same. Make sure the EGR is closed. Otherwise, I guess our '89's suffer from some sort of design malady. Mine was a hard start new and a cheapo set of Accel injectors solved it. Along the way, I've replaced the heads, rebuilt the fuel rail, throttle body and changed out the filter and every sensor, all modules, and the ECM was replaced twice under the factory warranty. In fact, about the only mechanical things I haven't replaced in 56,000 miles are the short block, tranny, diff, shocks & fuel pump - but dammit at least it now starts right.

 

Like I mentioned earlier, I too replaced all that NavyVet replaced and then some. I also have new bosch injectors and have tested the fuel pressure, it drops over night but when you turn the key it jumps right up to 42 psi where I have it set. Same starting problem, really tough in the am, not so bad after work on a warm day. Thing was a new rebuilt ecm fixed the problem for about 2 weeks then same problem came back. The new ecm mentioned something about one needing to test all sensors, if any were bad they would corrupt the the ecm which I believe happened to mine. Try replacing the ecm to see if it helps, there under $100 at the local store, plus if you buy from the right place you get a LT warranty with, like me. Good Luck, will be reading to see if I can find out what caused my ecm to go bad. Later!
FRED
89' Black L98 Owner & Frustrated :confused:

 

Your ECM may not be bad, but something else, that possibly shares the same driver as the FP or injectors may be acting up causing the driver to shut down. It's kinda like a built in circuit breaker - so the ECM doesn't fry. Unfortunately, other than to tell you that the ECM has this protection, GM doesn't tell you what the shared components are for each driver, if any. The tune and scan guys may have the knowledge to point you in the right direction.

 

I checked the fuel pump circuitry and the common element is the power feed which is shared with the MAF, both MAF relays and the oil pressure sender, all off of the main power feed from the battery to the ECM. You might want to check this circuit or the MAF components. High circuit resistance or perhaps a faulty relay? Might be worth looking at or see what data you can capture with a scanner while cranking.

 

Just a shot in the dark here, but nobody's mentioned the MAT (manifold absolute temperature) sensor on the underside of the plenum. Anybody try changing this? For the $20 or so dollars that this sensor is worth, it may be worth it.

But I will admit it's just a guess...

 

What is different about these cars 88 & 89 than some of the others ?
It has to be something we are overlooking.
I supect injectors is my problem because they will not hold pressure,
But, they was tested & flowed when the new motor went in.
Maybe we could start a fund and take a car to Gordon.
:confused: :mad :banghead: :confused: :smash:

 

MAF sensor is about 4 years old, but I think I read where one can disconnect it and try to start vehicle to bypasss it, I'll try that seeing as the car has sat for 2 days now. As for the oil pressure sender it is about 2 years old, but I haven't touched either of the maf relays. Where are they and is there a test for them or just replace them??? Thnaks Again!
FRED

 

MAF Relays are behind the battery and are relatively inexpensive. The orange wire is the common power from the ECM to the fuel pump relay, oil pressure sender, MAF and MAF burnoff relays. You might try cleaning the MAF sensor wire with electrical cleaner, especially if you've removed the screens and/or have a K & N filter (I've seen a couple of posts with owners reporting that filter oil wrecked havoc on the wire) - though be careful, you don't want to break something that may be ok; so first, you might try observing the wire at shutdown. Should glow if it's reacting to the burnoff signal. Air temp sensor under the plenum is easiest to troubleshoot with a scanner. Like the coolant sensor, cold reading should be about the same as the outside air temp. Otherwise, 3400 ohms if it's 70 degrees.

 

The biggest difference is the lack of the 9th (cold start) injector, and that the '89 was the last year for the MAF sensor - '90 switched to a MAP sensor.


If you know that your injectors won't hold pressure, then you've found your problem. But from the sounds of things, the rest of us have tested our injectors/fuel system and are finding good steady pressure.

That's a great idea! :lol:

When you add up all the money that we've ALL spent on new sensors, relays, ECMs, switches, injectors, etc... just to find out that it didn't make a difference, it would be cheaper to have a hard-starting '88 or '89 flown in from OVERSEAS to have Gordon take a look at it. :lol:

 

Thanks Again for the info, btw, I hace removed my screens and I am using a K&N air filter, but just started the car and ran it, shut it down 3 times and no glowing of the wires :confused: Does this mean a problem with the relays?? Are they both refered to as maf relays, so when I'm at the parts store I don't sound like a complete idiot. Thank You!

FRED

 

In my case, you touch the key and it starts.....NOW. However, when I connect my FP gauge, it'll leak down to nothing in 15 minutes. I'm thinking that the fuel pump can let it leak down too.

 

I think 88 and 89 have different injectors - Multec brand, and this style of injector MUST NOT be cleaned with injector cleaner or anything else, because it rots the insulation on the injector solenoid (or something).

Just a thought.

 

One additional question, When I removed/replaced my motor I eliminated the egr and all the smog equipment and I just taped up all of the wire plug ends with electrical tape and placed where they would be out of the way under the hood. Could this cause any of the problems I'm having with the start ups??? Thanks!

 

check to see if the injectors are getting pulsed when in a slow start condition

 

i have a problem like this on my 91 changed everything except it only does this in closed loop it starts up when cold takes 5 sec but when it heats up the idle surges any thoughts on this