MY 88 STARTS INSTANTLY THE FIRST START FOR THE DAY. FOR THE 2ND AND SEBSEQUENT STARTS AFTER REACHING OPERATING TEMP IT WILL TURN FOR ABOUT 6 SECEONDS BEFORE STARTING. IT WILL STUMBLE FOR A COUPLE OF SECONDS THEN SMOOTH OUT AND RUN FINE. OCCASIONALLY I'VE NOTICED BLACK SMOKE FROM THE EXHAUST. I'VE CHANGED THE SPARK PLUGS, THE OLD ONES LOOKED OK WITH NO VARIATION, 3 BURN OFF RELAYS AND THE ENGINE COOLANT SENSOR. A DEALER CORVETTE MECHANIC, AFTER A SYSTEM PRESSURE CHECK, DETERMINED I SHOULD CHANGE THE FUEL PUMP. HE FOUND NO EVIDENCE OF FUEL LEAKING BACK INTO THE CYLINDERS. A LOCAL VETTE SUPPLIER SAID I SHOULD CHANGE THE COLD START SENSOR. I'M LOOKING FOR HELP FROM SOMEONE WHO HAD THE SAME OR SIMILIAR PROBLEM OR SOMEONE KNOWS HOW TO REMEDY THIS PROBLEM WITHOUT CHANGING PARTS NEEDLESSLY ANY ADVICE WILL BE GREATLY APPRECIATED. :confused:

 

Might try posting in C4 Tech/Performance. I can't help you, but my '88 does the exact same thing. It fires up first thing in the morning in half a second. If I leave it for a few minutes, to run into a store or something, it fires up fine. If it sits for a while after being warmed up it takes a lot of cranking, and I depress the throttle about 1/3. It always runs fine though.

I would like to see some suggestions on this one.

:lurk:


[Modified by terrydennis, 7:31 AM 4/18/2004]

 

I'm no Vette expert, but I just had a similar problem with my 88. It started great when it was ice cold, started great when it was at operating temp, but started rough or not at all when slightly warm. Occasionally it would surge at idle no matter what the temperature. My problem turned out to be the IAC valve. It wasn't moving much, if at all, to regulate the airflow at idle. Hope I was of some help. Oh, the part was $26 at Advance Auto Parts.

Tom

 

:withstupid: same thing here on my 89. Interested to see the replies.

 

same thing on my 88!! I changed the plugs, and the 0/2 sensor. I also get an odor from the exhaust like it is running rich all the time. Thougt the sensor would take care of that, but I was mistaken :cry Someone told me that the problem lies with the injectors; that some may be leaking into the cylinders. I haven't checked this yet. Good luck!!

 

My LT-1 would start right up cold but after a drive it was a bear to start.
Corvette Fever did a story about leaking injectors and said the test was to floor the car on a hard start to see if the engine was in a flooded condition.

My LT-1 started faster with pedal floored. I suspect a leaking injector the car has 100k miles. The black smoke was fuel.

 

THANKS, I'M GOING TO POST IN C4TECH/PERFORMANCE. HAVE TRIED MANY DIFFERENT PETAL POSITIONS, FROM NO PETAL TO FLOORED, NO CHANGE. I'LL POST IF I FIND THE SOLUTION. :rolleyes:

 

I've been plagued with that problem too. I tried replacing the location of the MAT sensor, but that didn't help, I had pressure in my fuel rails after waitng a while after shutdown. It seems to start better when I depress the gas pedal halfway after cranking and release. I'm still looking for the little gremlin too. :banghead:

 

Same problem all last summer. Changed the fuel injectors and put in a new fuel pressure regulator. Now it starts right up, cold or hot.

Good Luck

 

Had the same problem with my '88 a while back. I bought a set of injectors from a fellow CF member and it cured the problem instantly.

You may want to try an injector leak down test. Hook a pressure guage to the fuel rail, start the engine, record fuel pressure, shut off engine, wait 2 minutes, check fuel pressure. If it drops more than a couple of PSI an 2 minutes your injectors may be leaking down. BTW, I think you need to also block the return line.

Mike.

 

I think someone might have told you right. Leaking injectors are more common than you may think.

 

Sounds like the right approach - I just had a similar problem with mine, turned out to be the pressure regulator. When I took it apart there was rust built up on the ring that captures the diaphram (adjustable regulator from aftermarket - be aware that the thing Will rust...). The rust was preventing the regulator from shutting. When it finally got bad enough I had to find it! Checking the pressure and watching it bleed off instantly when the pump stopped was a pretty good way to isolate it - then clamp off lines to the tank for return, then pump to see what was leaking down. The regulator was the culprit. It would start fine cold, and would hold the right pressure with the pump running, but took several seconds to build up pressure when restarting hot.

 

I used to have a 88 with the same problem it was the injectors. :thumbs:

 

Midnite 88, pretty much dead on the money. Pressure should stay for awhile. I didn't block anything off.

If holding the throttle down and it fires off, suspect injectors. Wanna have some real fun? Have some 36#s leaking, washes the plugs down pretty quick, my pressure was dropping to 0 quick.

Have those injectors cleaned or replace them, they're not terribly expensive. Another sign is sooty tail pipes, loss of some mileage.

 

This may not be what is happening to your car but when I bought my88 about 6 years ago sight unseen in San Jose (I live in Presacott) I test drove it for about 20 minutes and never restarted it until it cooled down. The next day on the drive home it started to stall about 2 hours out of San Jose when I got off the highway to get gas. It was hard to restart. I made it home and read there were service bullitins on this, something about the MAF burn off relay I think and the relay next to it.
Anyway I started to disconnect the battery after use and because it was going to sit for a couple of weeks. After disconnecting the battery about four or five times the problem went away for good. Never had a problem for the rest of the 5 or 6 years I have the car. What I think happened is that each time the battery is disconnected the IAC valve recalibrates itself by running to both extremes of its travel. I believe there was some carbon build-up in the bore and the IAC piston rubed it away during its full travel up and down the IAC bore.Can not hurt to try this. Let us know if it works.

 

Low mileage car? Bad gas?

 

In your case the plugs will not look rich with slightly leaking injectors because once the car warms up it goes into closed loop and the ECM adjusts the mixture to get it right based upon the O2 sensor readings. It will MAKE the mixture right as long as the leaky injectors are not leaking too much for it to compensate. After just a couple of minutes the plugs will look normal again due to ECM closed loop fuel compensation.

If it starts properly when cold and only has the problem when warm, my guess is
1) Cold start circuit
2) Injectors

The 88 and earlier C4s have a corld start valve (CSV) which is really a modified injector. It is connected to a cold start switch (CSS) which is a thermal time switch similar to a thermostat. When cold the CSS opens the CSV to allow additional fuel in during start. When warm this additional fuel is not needed and the CSS should not open the CSV. A defective CSS or leaking CSV will cause the problem you decribe in 88 and earlier. The CSS is located on the engine block just under the throttlebody and is easily checked or replaced at about $20 for the switch. The GM Factory manual details the relatively simple CSS test procedure.

If the CSS is good, but the CSV or one of the other 8 injectors is leaking you will also experience warm start problems since existing pressure in the fuel lines will cause fuel to leak into the cylinders causing a rich condition when started warm. The CSV is a special type fuel injector and cannot be replaced with a standard injector. GM and the aftermarket folks no longer make these injectors. You need to either send your CSV to be rebuilt or find a used one from a junkyard for rebuilding.

If you have an 88 automatic tranny it is possible to disconnect the CSS from the CSV, or remove the CSV and use a block-off plate, then replace the ECM memcal with one from an 89 auto or get your memcal reprogrammed with the bin from an 89 auto. the 89 memcals have additional "on time" programmed in for starting conditions and don't count on the existence of a CSV like the 88 memcals. This is not advised if you have a manual tranny since the 88 had a 4+3 whereas the 89 had a 6 speed and the memcals were quite different due to the transmission differences.

It is a full days job to replace the 9 injectors on an 88, but well worth it. If you suspect the CSV or one of the other 8 injectors, I would suggest that you have rich@cruzinperformance rebuild the CSV or a used CSV and
a) have rich also rebuild the other 8 original injectors or
b) buy 8 new Ford Motorsport 24# units.

Your vette will run SO much better and the warm start problem will disappear.
Been there, done that... :yesnod:

 

Hi Tom, thanks for the info my hard start happens when the car is at operating temp.