One Quick ????, How does one adjust the PW in the car??? Thanks for the info, I'll iron out the start-up, but first I have to fix my blown tranny. Died this am on the way to work. :mad :mad

 

The PW is adjusted via the chip with reprogramming. That is the crappy thing. Its not an easy thing to do unless your setup for doing chips. :banghead:

But I assure you that is the problems with many of the cars here that won't start. As I said the ECM is only as smart as you teach it to be. :cheers:

 

So ski-dwn-it, let me see if I understand: what you are saying is that any of us that have any modification to our cars that are intended to increase the incoming airflow will potentially suffer from a hard-start condition because of too short a pulse-width during start-up. Is this correct - am I reading your posts right?

I am no doubting you in anyway. My '89 suffers from this, and has for a while now. The car is virtually stock with the exception of a cut-lid, K&N filter, and MAF screens removed. I replaced my original injectors about 2 years ago with a set of 'blue-streak' injectors - these are a stock replacement injector, not a performance type or anything. I don't think my injectors are leaking because the fuel system hold 40psi of pressure quite well prior to startup. But other than what I've mentioned, the car is stock. Do you think that just with these small mods to my car's intake that the pulse-width is not enough? I mean Corvette guys put cut lids and de-screened MAFs on these cars all the time and you never hear of any hard-starting problems. Why on the '88-'89 cars?

But thanks for all the great info.


[Modified by TheCorvetteKid, 4:49 PM 6/27/2003]

 

CorvetteKid,

The key word you used is potentially. I can't say for sure that every engine is going to react in the same manner to every mod. But I can tell you, that alterning the incoming air path on these cars most definately screws with the initial tune. Then add on to that all the other items I meantioned and you now have the "hard start" problem. I have been thinking about the MAF in this scenerio all last night after posting this and I'm sure that it has an effect, as does the IAC on it as well.

But I can tell you both my engines did exactly what you all describe after mods and this is how I fixed it. I had the injectors changed to larger ones too. So in my case I needed to reduce the PW in the coolant table, since the stock ones were previously setup for stock (smaller) injectors.

As I said if you crack the TB open with the gas peddle ~1/4-1/2 way, and the car starts bette, chances are its getting tooo much fuel with no gas peddle. So you , like me, will have to decrease the PW at that particular cell unit you get the desired results.

The whole sorting out of the problem is really a trial and error type scenerio. With the use of Romulator, it can be easily done in a matter of a <10 minutes.

But I would be willing to bet that 90% of the problems mentioned here could be solved with this method.

Its key to remember that all these setting are setup with a particular pressure, injectors, spark plugs, spark advance (mainly base), etc. If you change one of them the entire balance is messed up. Change a few of them, as many of us do, and you have a nightmare.

 

Im glad Im not the only one with this problem, I too replaced Everything in my 89, including the 2 MAF relays, I also swapped my ECM, still wont start when cold, it takes an embarrasingly long time cranking to get it started, I do all the work myself, I finally brought it to my friends shop, he cant find the problem, everything checks out OK, no codes, fuel system great etc,etc!!. The only thing I havent changed is the oil pressure switch, its really hard to think that will fix it, I am spending too much time and money on all this troubleshooting, Im ready to burn the car!! lol, I hope we can all put our heads together and figure this out! :auto:

 

What is there to figure out? I just told you what the problem is :banghead:

 

ski_dwn_it,

Thanks for the info, you have been very usefull, but a couple quick questions:
1- My hard start-up is directly related to temperature: cold-PIA, warm-not bad and hot-easy. Will adjusting the PW help?
2- Why did the car start correctly for 2 weeks regardless of temp after I replaced the ecm?
3- How long is the fuel pressure supposed to remain at what I set it at? I attached the fuel pressure gauge and by morning the fp wa down to 0, but with the turning of the key was right back to 42, where I set it.

Again, thanks for all the info, look forward to your reply.
P.S. What is the romulator??? :confused:

 

I'm with JFB.

Buy/borrow a fuel pressure gauge. The Sears Actron model even has the bypass button for a fuel volume flow check.

Fuel pressure/flow, values needed for proper diagnostics.

After getting the fuel numbers analyzed, I would head for the ignition module. Those darn things have some timing built in till the 400 RPM level when the ECM takes over timing. Could be a problem there. The modules are generally very reliable but perform several important functions. I would have that tested(ignition module), at two different places with reliable test equipment.

Tough problem for sure.

dlmeyers 90 coupe zf6 3 speed shocks

 

OK, I get the picture, but now we have to find someone who can re program our proms. Who, where and how much? I am willing to try anything at this point! Im sure everyone else is also! Please Help! :auto:

 

Redvette.

No not necessarily. Either post or explain thus far what you have done to the car, by means to correct/check the fuel supply. I can make some suggestions and see if you get any decent results. I will probably help some others also.

List any mods you have done....etc :cheers:

 

Okay, I have been timing my starts and have come up with the following. The average of my starts is 1.7-2.0 seconds from key turn to key turn. It is pretty consistant around this time frame.

Now, I have a question.... there have been a few posts here about coolant temp. According to my factory service manual, the temp sensor used by the ECM is the one in front of the throttle body... and that one I recently replaced. But what is the one on the passenger side of the block in between the back two spark plugs for?? Also, which one indicates on on the dash?

Skip

 

Check out this thread:

http://forums.corvetteforum.com/zerothread?id=575989

There is lots of valuable information about the coolant sensors in there.

For the record, when my 88 is hot it starts as soon as I touch the key. When it's cold it takes about 3 seconds to start. What's weird is I have very leaky injectors, so I'd expect the opposite. In any case I'm going to replace them in the next week.

 

In regards to the temp sensors, on my 89: the front of the manifold under the TB controls fuel/talks to ecm at start-up, passenger side displays on the dash the coolant temp and the drivers side controls the fan. Good luck with yours, I will be taking my down to LevelTen Transmission shop Friday to fix the tranny again, then I'll get back to the startup problem.

FRED

 

It seams like a great deal of us have problems with our 89 vettes starting hot. This must be a design flaw. I think we should go after Chevrolet and make them fix this problem as a recall. Any one else have any thoughts on the matter?

 

Well a lot of info here. Hope I can find the right answer. Car was running great. Parked it and when I tried to start next day it coughed and then no start. Smelled raw fuel. Engine acted as if it was flooded. Have not done any trouble shooting yet other than try several re-starts. With throttle wide open before truning crank it makes a slightly better attempt to start but still no start.I will replace the in-line fuel filter just as a maintenance issue since I'm sure it is original (64,000 mi.). Since I can smell raw fuel I am leaning towards stuck injector. This my first Corvette and have always wanted one but just couldn't justify a new one, bought SS Blazer with the 395hp aluminum motor instead. This car is faster than the 89 but not quite as "cool". Hopeful for succesful fix on the Corvette. If anyone has new info I would love to see it.
Thanks in advance

 

I've an 87 with the same prob more or less like yours. Bought & brought home a 87 Convert...oil level was over full & smelled of gas, but car ran Ok, but a little rough...knew the injectors were at fault (or some were leaking) replaced all 8 with new Bosch. After everything back together, oil changed etc., it won't start. Fuel pressure is about 45lbs, stays for a few minutes & slowly falls to almost 10lbs or so. After reading all these posts, I'm more lost than ever! Will try disconnecting the MAF in the am & see if it will start. Seems like the fan starts as soon as the key is on, think that is not right, fan shouldn't come on 'til it's warmed up. Could be some of the sensors have crapped out sitting for a month in my garage with batt disconnected? I have my doubts. I'll post my results.

 

Thanks for your note Peco. I have now learned that engine will start if I spray some starter fluid in the throttle body opening, removed the MAF hose to do this, but as soon as the strater fluid burns off engine quits. I would think this means I have a fuel delivery problem. Also removed the cap on the test port(scharder valve) on the fuel rail and nothing came out when I depressed the the valve stem. I had cranked the engine for about 30 seconds before doing this. I would have thought there would have been fuel pressure here. I am changing the fuel filter Thursday but I think the in tank pump may be bad.

 

You are correct, should have been fuel at the valve. I did the same thing, same no start results, but I'd bought a fuel injection pressure gauge set from Harbor Freight, on sale for 19.99 & my system shows 42 lbs when key is on...drops into the lo 30's - hi 20's when cranking. Drops to lo 20's within a few minutes when key is off. Injectors leaking or ?? I've touched the injectors while cranking to "feel" them working, seems like I could feel them work, but haven't verified via circuit test light (next test). All 8 injectors are new, so doubt any are bad, but ?? Pulled a few plugs, they were new @ same time injectors replaced (3 days ago!) & they are blackened as bad at the ones they replaced.
I'm really tired of this!

 

Buy one .Have you replaced the module? How many miles are on this car?

 

The ECM is $85 for a re-manuf unit at Advance A/P so until I check with a test lite at the inj, I'm not spending the $85. The pressure tester was $20. not $50. & I intend to keep this vette for a while + my '96 Chev PU also as injection & might be needed for it one day.
My 87 vette only has 65K mi., my '96 PU, however has 132K & starts every time.