Help! My 1990 Dream car Will Not Stay Running

[2drtoy]

My 1990 Corvette Will Not Stay Running

I have a 1990 Corvette last week on the way home from a small vacation my car just stop running, as if someone shut off the power switch, the car would not restart,, had to have it towed home,, the check engine light did not go on at all, once home replaced fuel pump. fuel pressure regulator, before this trip almost all sensors and solenoids had been replaced. once the new fuel pump and fuel pressure reg had been replaced the car did start but once the temp came up on it it died. So replaced the distributor now it wants to run but it is runs very very ruff and dies, I just ordered a new computer today hoping this is the problem?? Before any of this happened my car ran great,, so as of now every sensor every solenoid (including the hard to find egr solenoid) has been replaced. The heads were done in sept. Any help would be appreciated. This is my baby and my husband is ready to go postal. He also checked the scanner for any codes and there none ad

 

[John Robinson]

What you don't mention doing is cleaning all the grounds. A sensor you have not mentioned is the water temp sensor in the water pump housing.
From your description I would bet you won't fix the problem with the ECM either. The ECM is not getting a good signal from a sensor that it does not read in open loop but uses when it goes into closed loop. What this means is that when the engine is cold the ECM takes control of the air fuel mixture to get the engine up to a temp that is will run without the added fuel.(for simplicity think of that as if you had a manual choke you would close as soon as the engine would run without stalling on a cold morning) At a predetemined temp the ECm then closes the imagninary choke and leans the engine out for normal running.

The following data sheets are from my 93 FSm but they will give you a better understanding of how the various sensors interact with the ECM. Again keep in mind The FSM is looking for a certain signal and if it does not get it will try to adjust all the other perimeters to trim out that circuit. As our cars get older the wiring becomes more and more fragle and the connectors get corrosion in them as well as the grounds go bad. All that translates to the FSM not being happy. So yes a scan of the system may show that the ECM or the Opti etc are bad but what it is really saying is the signal from that circuit is not what the ECM is programed for it to be.


Hope this helps you to find the problem.

 

[TedC]

Shorting fuel injectors? Measure injector resistance on each one with connector off and report back.

 

[boomdriver]

I'm not going to beat the long dead horse much more on this thread.....not a lot...

but I gotta ask,.

Are you changing these parts (aka big $$$ ) because of what the GM FSM is telling you? :ugh

Haynes manuals, Chitlens, and ANY $29.95 off the shelf manual is useless and WILL cost you everytime you pick it up. They are useless. The REAL FSM will cost $100 or more, but its the FACTORY guide and not a shadetree handbook thats better off under a table leg. The GM book set is far TOO precise, too direct and too detailed to be changing things from fuel pumps (btw what was the pressure of the old one?) then jump to ECMs? Impossible. Whats the steady pressure of the new pump? at idle? key off? How long does it hold?
Inj ohm test? Leakdown? Fuel regulator test?

As John mentions...GROUNDs. Not the battery ground cable...the doz or so harness grounds. The FSM tells you exactly where each and every one is located.

MAF or MAP system? <-great suspect when a very rough idle is mentioned. FSM describes the test process and all possible results. IIRC...1990 is MAP. The correct sensor is crutial for it to run. Vac leaks are also much more troublesome because of the MAP system.

EGR. FSM details test. Simple way is to use a small mirror and suck on the hose to the EGR (not the egr solenoid) and look for it to move. Engine off.

The investment of $100-$150 in a FSM 2 book set would have saved you...I'm guessing $750 already. Maybe twice that.
Find new books thru a link here, or search Flea-Bay for used sets ($75) or new ($125) or even CD versions. Search this website for the link for new copies. I prefer older copies because many new books do not have the electrical schematics in color like the older books do. Electrical is one book by itself. Drawings for everything..in detail. Diagnostics for everything...in great detail. You cannot fail to find a problem if you have the FSM. This is the factory test proceedure and flow chart for every possible problem with this car.

These cars are way to complex to try this or that. They have to have some accurate diagnosis or you can rebuild the entire car over a $6 relay. Pressures are exact, electrical values are precise. There is no "close 'nuff" for a C4 or newer Corvette.

Another point....the avg shop is not really qualified to do diagnostics on Corvettes either. I don;t care whose brother it is...Corvettes are made up of a control system and parts that are exclusive to Corvette, and most shop guys spend more time on accords and aerostar vans than they do hi-end American automotive technology. Most have never had an opportunity to sit in a C4 much less diagnose one. Find a qualified vette-tech thru local Vette clubs or asking around here. There may be a Corvette shop/dealer in your area. Why is a Corvette so special and more difficult to diagnose? Its a plastic car with a complex electrical system and control system. Unlike anything else made in this country.

Do yourself a HUGE favor and get a set of FSM books and start reading. There is not ANY issue that is not covered in these 2 books. You will kick yourself halfway to Bowling Green when you see how easy it is to trouble-shoot a C4....when armed with the right information.
Good luck in your search for answers

Buying a FSM is how you will find them.

 

[2drtoy]

Thanks for the information,, We had to heads done in Sept when we did that we decided to go ahead and change out most of the sensors at that time my husband also replaced all of the vacuum lines and went ahead and changed out the o rings on the injectors. The car had 120,000 miles on it so it was just easier to replace everything since the heads were being done and the car was already apart, Since Sept the car has only been driven once in awhile. I have owned this car for 5 years and on any car I get my husband always changes the belts and hoses, replaces fuel filter and fuel pump,, This was done with my vette also except for the fuel pump so it was not an added expense to do this. When my new computer comes in then we can test the injectors, he will also check the grounds, When we took the car out of town on the way there the car ran perfect the best it has ever run,, from my house to laughlin is approx 150 miles when we were in laughlin and we were on our way back to the hotel from another hotel he started the car up turned on the ac and then the lights since it was dark and the amp gauge shot down to 9 and stayed there Check engine light did not come on, as we were sitting at a light the car started to miss and run ruff still no engine light got to the parking lot shut off the lights and ac and amp gauge only came up to 10 my car has never done that,, the next day when we started the car the amp gauge was normal car was not missing nor running rough when we left laughlin we were headed up the hill with the ac on running approx 80mph the car seemed to run fine when we reached the top of the hill temp gauge was not even half and it was like someone just turned the key off.. No check engine light car would not start at all, had to have it towed home. (Not fun) We did change out the alt and when we did get the car running even though it was not very long before she died the amp gauge was back to normal One thing that has not been changed is the oil sending unit. I will let yu all know what happens once we get the computer back. My car has never been to a shop only the heads,, We do have the corvette shop Manuel book and we know that it is not the holly grail. It is just very frustrating when in the 5 years I have had the car the only real problem I have ever had before this was 2 injectors not working right, and that was over 2 years ago.:W

 

[noswalyeroc]

Thanks for the information,, We had to heads done in Sept when we did that we decided to go ahead and change out most of the sensors at that time my husband also replaced all of the vacuum lines and went ahead and changed out the o rings on the injectors. The car had 120,000 miles on it so it was just easier to replace everything since the heads were being done and the car was already apart, Since Sept the car has only been driven once in awhile. I have owned this car for 5 years and on any car I get my husband always changes the belts and hoses, replaces fuel filter and fuel pump,, This was done with my vette also except for the fuel pump so it was not an added expense to do this. When my new computer comes in then we can test the injectors, he will also check the grounds, When we took the car out of town on the way there the car ran perfect the best it has ever run,, from my house to laughlin is approx 150 miles when we were in laughlin and we were on our way back to the hotel from another hotel he started the car up turned on the ac and then the lights since it was dark and the amp gauge shot down to 9 and stayed there Check engine light did not come on, as we were sitting at a light the car started to miss and run ruff still no engine light got to the parking lot shut off the lights and ac and amp gauge only came up to 10 my car has never done that,, the next day when we started the car the amp gauge was normal car was not missing nor running rough when we left laughlin we were headed up the hill with the ac on running approx 80mph the car seemed to run fine when we reached the top of the hill temp gauge was not even half and it was like someone just turned the key off.. No check engine light car would not start at all, had to have it towed home. (Not fun) We did change out the alt and when we did get the car running even though it was not very long before she died the amp gauge was back to normal One thing that has not been changed is the oil sending unit. I will let yu all know what happens once we get the computer back. My car has never been to a shop only the heads,, We do have the corvette shop Manuel book and we know that it is not the holly grail. It is just very frustrating when in the 5 years I have had the car the only real problem I have ever had before this was 2 injectors not working right, and that was over 2 years ago.:W

STOP!!!!!!! I just had the same problem on my 89. The injectors were reading low ohms two of them was reading 6ohms and one 8. Get a ohm meter and pull the wires and read the ohms cold and then let the car run and check them again. if any read low leave them unpluged and the car should run. READ MY THREAD noswalyeroc Help 1989 want stay running.

 

[John Robinson]

I am going to throw this out for what its worth. I had a similiar experience with my car suddenly not wanting to idle or run smoothly and then it died at a stop light and I had it towed. After replacing the ECM it still would not start and that is when we discovered that the TPS had gone bad without showing any codes. Basically it was telling the ecm that the engine was flooded and so the ecm shut down the fuel pulse. New tps and it started right up. The next part of this story is that in removing the connectors to diagnose the sensors they were hooked too we broke the old brittle wire in the tps connector and had to repair that.

 

[2drtoy]

STOP!!!!!!! I just had the same problem on my 89. The injectors were reading low ohms two of them was reading 6ohms and one 8. Get a ohm meter and pull the wires and read the ohms cold and then let the car run and check them again. if any read low leave them unpluged and the car should run. READ MY THREAD noswalyeroc Help 1989 want stay running.

So sorry It has taken me awhile to get to yu all,, we just got the car home last week from my father in laws house (had it towed ) thank god we only live a few miles from him,, Okay the latest before we got it home, Checked all the connectors they were fine, checked every single wire under the hood all hot, checked the pressure that was in check, so my husband decided to pull off the top and check the injectors and the plugs ins all plugs in tested hot but he noticed the 2 new injectors the cylinders were wet and very clean the other 6 looked like there was no fuel in there at all he put it back together tried to start it it kind of started did not sound good so he went to step the gas and it died,,, so we are going to change all the injectors,, So I will let yu all know what happens next. I have to say this forum is great it has really helped us in the past with minor problems,,

 

[boomdriver]

So sorry It has taken me awhile to get to yu all,, we just got the car home last week from my father in laws house (had it towed ) thank god we only live a few miles from him,, Okay the latest before we got it home, Checked all the connectors they were fine, checked every single wire under the hood all hot, checked the pressure that was in check, so my husband decided to pull off the top and check the injectors and the plugs ins all plugs in tested hot but he noticed the 2 new injectors the cylinders were wet and very clean the other 6 looked like there was no fuel in there at all he put it back together tried to start it it kind of started did not sound good so he went to step the gas and it died,,, so we are going to change all the injectors,, So I will let yu all know what happens next. I have to say this forum is great it has really helped us in the past with minor problems,,

2 new injectors?

so you had some, not all replaced? thats not good...
A full set of modern fuel injectors can be had from FIC for <$250 and that comes with all the gaskets
and o-rings.

BUT, lets back up....

To work on this fuel system you have to understand how it operates..otherwise you WILL throw money at the problem and never find it.
This system is a "bank fire" injection system. That means that 1 injector on each side is split into 4 connectors and they ALL fire together. As C4 vettes evolved they went to independent systems after they got bigger faster computers that could handle 8 circuits instead of one firing @6000 times per minute.
So, each bank all fire together, and that also means that IF 1 shorts..that whole side shorts out. Depending on where the short is, the whole system can short out and stick OPEN and flood the engine with so much raw gas that it cannot possible run. This shorting can be an injector OR the wire harness anywhere from the plugs to the firewall trunk line where the wires all splice in to the main harness.
The simple test is to use a noid lite then take 1 inj plug off at a time and see if the problem goes away...try one then go to the next until all 8 have been tried. IF there is ONE thats shorted you d/c that 1 and the rest will come back to life.
The fuel regulator can also blow and flood the engine. Pull the vac line off to see if its wet with fuel inside.
Pull the dipstick to see if its got gas in the oil from flooding.
Ohms test only shows if the injs coil are strong enough to operate. That test does not tell anything about being stuck open or being plugged.

Buying the FSM is still your only way to get it fixed at home.
Good luck

 

[2drtoy]

I ordered 8 new injectors last week 4 came in already the other 4 will be in tonight,, I ordered new injectors and I got all 8 for 412.00, the 2 newer ones that were changed out 3 years I am going to replace also those 2 were changed out because my car was overheating at an idle and in traffic but when I got going on an open road she cooled down, I came here and was advised to check the injectors and we did and it was number 5 and 7 we changed and my car stopped overheating and I never had another problem with overheating, (and I live in Arizona) So this board has been very helpful and I trust the advice that I get. So I should have an update hopefully tommorrow or Wednesday :Twist

 

[boomdriver]

I ordered 8 new injectors last week 4 came in already the other 4 will be in tonight,, I ordered new injectors and I got all 8 for 412.00, the 2 newer ones that were changed out 3 years I am going to replace also those 2 were changed out because my car was overheating at an idle and in traffic but when I got going on an open road she cooled down, I came here and was advised to check the injectors and we did and it was number 5 and 7 we changed and my car stopped overheating and I never had another problem with overheating, (and I live in Arizona) So this board has been very helpful and I trust the advice that I get. So I should have an update hopefully tommorrow or Wednesday :Twist

Sure wish you had ask where to get new fuel injectors....$412 is almost double what you could have had them for...next time, contact Jon @ FIC. A matched set of 8 cost less than $250 and comes with ALL the o-rings, gaskets and instructions along with the best customer support on the planet.

Just out of curiosity, you said earlier that the shop manual that you have is NOT the Holy Grail...I am inclined to disagree with that.

What do you base that comment on and why??

if it was one of the cheap $19 books from an auto parts store, its trash and is useless. If it is a 2 book set that clearly states on the cover GM Factory Service Manual....then I find your statement odd...since the entire world swears by the contents of that book that details every possible issue that could possibly go wrong with a C4 Corvette. The real FSM cost $100 or more and is 2 books...

 

[2drtoy]

Thank You

I just wanted to say thank yu to everyone for all the advice on my corvette,,,,, It is fixed installed the new injectors and it runs like new, took it for a test drive it is like driving a new car.