How do I test my injectors on my 93 LT1? I unplugged the wires from the injector and checked the injector with an ohm meter; all the injectors read .011 ohms
I know the reading should be around 16.3
The problem with my car is it will start ok, run great for about 10 minutes then stumbles like it’s not getting fuel. If I shut the car off and let it cool it will start up ok then run good till it heats up then stumbles. Last year I had my water pump go bad (leaked) so my first thought was my opti was bad. I replaced the opti, plug wires, spark plugs, fuel filter, fuel sock.

Also what brand of injectors are best and why are OEM replacements so varied in price?
Autozone sells for 75.00 each NEW
Summit racing 260 for (8) NEW

 

Change your ohm settings on your meter. Looks like they ohm around 11 ohms which would be acceptable. All should ohm over 10 ohms and be very close to each other. I would also check to see if any are leaking with a fuel pressure gauge. Pull the spark plugs and look for raw fuel.

 

You need to check for error codes. Sounds like you may have a bad O2 sensor.

FWIW, my OEM injectors on my 93 all ohm out at about 13.2 ohms.

Here's a couple of links to get you started on how to read and interperate your error codes(Quick Paper Clip Test):
http://www.troublecodes.net/GM/
http://www.obd1.com/

 

Update: Yes my ohm meter was on the wrong setting; all the injectors read around 11.0 ohms not.011
I also purchase a fuel test gauge, the psi when the engine is first started (cold) is 40 psi and stays at 40 psi even after the engine starts to stumble and die. I guess that leaves out the fuel pump as being the culprit.
I did the paper clip test to check for codes. The only code was #12.
Is there other codes that would show on a dealers scan tool but not on the dash?
I pretty much ruled out a fuel problem and thinking either some kind of sensor.
Also what is the slim chance one or both of the cats are clogged?

 

clogged cats - usual symptoms would be a bogging of engine power during hard acceleration. This bogging is caused by the engine choking on it's own puke when the cats can't pass all the exhaust gases.

O2 sensors - When you first start your engine, the ECM is in "open loop", and AFR is determined by lookup tables. Therefore the O2 sensor voltage outputs are ignored by the ECM and have no effect on AFR calculation.

When the engine warms up, the ECM switches to "closed loop", and the O2 sensors are the main feedback for AFR calculations.

Anyway, that's the basic idea of open and closed loop operation, and since your car seems to run fine initially, and then starts runnning rough after warmup, this is a "clue" that it MIGHT be O2 sensor realted...

 

Thanks for the info. How do I test the 02 sensors (dealer scan tool?) and any tips on changing them?
Also if I do need to replace them what brand is best- AC Delco, Autozone brand?

 

There are two O2 sensors, one before each cat. Easiest to change them from underneath car. Due to very limited room, you need to get a 7/8" "Stubby" open end wrench(Sears)....

I would stick with AC-Delco....

If O2(s) bad , you should have stored History error codes indicating such though..

 

Check out your temperature sensor too. If the computer doesn't know the engine has warmed up, it will run crappy. Best guess is O2 sensor though.

 

pacat: The GM Multec injectors were used in years 89 thru 91 and these have a resistance spec of 16.5 +/- .3 ohms. I do not think you car came stock with Multec injectors. FYI only!

 

You can check your injectors with a noid lamp, you hook it up one injector at a time and it will detect the pulses. But that will only check the electrical wiring that goes to the inyector.

The inyector itself has to be checked at a lab for correct flow.
Good luck

 

Hello. I own a 89 corvette and recently it has been hard to start. Hot or cold. It takes about 3-4 tries and I have to give it gas. When it does start it blows smoke and idles horribly. When she runs, she purrs like a cat with no pblms what so ever. I have had the following done: new maf sensor, plugs, fuel pump and screen. I'm being told that the following could be wrong: leaking fuel injector, coolant temp. sensor, oxygen sensor or fuel pressure regulator. I am a young woman and don't know the first thing about this and of course I'm pouring money left and right because I am determined to get this fixed. Any fellow owner who has had the same problem that can help me out??? Thank you so much.

 

You should probably start your own thread, but blowing smoke is a sign of something getting into the combustion chambers that shouldn't be there -- either oil or coolant basically. My money is on work valve guide seals letting oil leak down into the cylinder when you turn the motor off. When you go to restart, it takes a little time for this to burn off. In the mean time it's there making it harder for the spark to ignite the fuel.

All of the things you mentioned as "could be" items are easily testable with some common tools. Throwing parts at the problem will just waste money. If you're not able to, or prepared to, make the investment in the necessary tools, your best option is to pay someone who does have them to do the diagnosis. Another extremely helpful resource is to acquire a Factory Service Manual (FSM). They're not cheap, but they will take you thru diagnosing a problem thoroughly, with parts replacements only coming at the end of the diagnosis.

Just remember though, you're driving a 20 year old car. It's going to have some "quirks". It's not going to a self-diagnosing appliance like new cars are. At the same time, they are relatively simple to work on once you have some basic idea of the various systems involved, some basic tools, and hopefully a diagnostic reference (FSM preferrably, some of the online info second, and perhaps one of the "Chilton" type manuals as a last resort.

Tool wise, at minimum besides the basic hand toold (wrenches, sockets, screwdrivers) you should have:

• A Digital Multi Meter (DMM) - to measure voltage, resistance, and continuity in circuits
• A 12 volt test light - you can use a DMM for some of this, but a test light is a quick way to verify that you have voltage present or even proper grounding
• Fuel Pressure Gauge - just a simple one, maybe $40? You might even be able to borrow this from an auto parts store.
• Wire to use a jumpers - a lot of diagnostics seem to make use of using a wire to temporarily bypass a relay or other device to verify function.
• Did I mention the Factory Service Manual? New, these were like $125 and up. Check e-bay and the for-sale forums here. Heck, even used book sellers sometimes have them.

 

wyoung03: I have to agree with travisd in that you are throwing $$$ at the problem in the hope you will get lucky and find the root cause. A suggestion to you....do a search on the internet for any Corvette Clubs in your area. Most clubs have contacts listed on their web sites. Contact a local club and find someone who will scan your engine electrical system and you will have a better idea of what parts to replace. If you live in the St. Louis area, I can do the scan on a L98 engine for only a cold Bud Lite!

 

Thank you guys so much. Sorry for not starting my own thread....You two have given me more info than the people I'm paying..lol. Lets see what happens.

 

wyoung03: I commend you for purchasing a 20 year old car and attempting to diagnose problems with it. Here are two comments that you may find helpful for your 89 Corvette:
1. The 1989 Corvette has an unusual anomaly programmed into the Electronic Control Module for starting the engine. Why did GM insert this software in the ECM??? The engine has to turn over two complete revolutions BEFORE the injectors will fire. In the starting mode, two engine revolutions will take a few seconds.
2. The fuel for the engine must be pressurized to at least the mid 20s PSI before the injectors will start to funtion. The normal fuel pressure for your fuel injection system is somewhere about 40 PSI. If you car sits for an hour or so, the fuel system pressure will go to about zero. If your fuel pump is showing signs of wear, it may take a second or so after you turn on the ignition switch for the pressure to reach operating range for the injectors.

The bottow line:
a. turn on the ignition and count to three. This gives the fuel pump time to pressurize the fuel system before the engine is started.
b. engage the starter and realize the engine must make two revoultions for the injectors to become active. I would guess this time to be about 3 seconds.

If your engine starts in a consistant manner, this may be "normal" for your car.

Try this procedure BEFORE you throw more money at the problem

PS to forum members: I apologize for hijacking this thread and please realize I am just trying to help a new member who may not familiar with forum rules

 

FYI; code 12 means normal, no stored codes. And if you do need injectors, go to FIC; he's a supporting vendor, and everyone has great things to say. You'll get a much better deal, and better injectors than if you go to an auto parts store.

 

I had similar problems with my 87 Vette. Two fixes cured my problems. I had an idle problem in cold weather especially after first startup - fixed by replacing the Coolant Temperature Sensor. The part is cheap, about $11 at Autozone. I also had a hard starting problem with alot of smoke at startup as a result of leaking injectors which flooded the combustion chambers with gas. Since I performed the work myself, I changed all 8 fuel injectors - basically the same amount of work as changing one. This immediately cured my startup problem. Starts up instantly everytime, even in very cold weather. A professional fee to replace injectors is rather pricy. I did the work myself for under $400.00 Good luck!

 

As a relative newbie, I had not heard about the 89 anomaly mentioned by Sam Lam and wondered if this also applies to an 88. My 88 always takes a little winding, but then cranks easily and runs good.

 

this is some pretty excellent advice, samlam's advice is common for most of these older cars, the advice to go with FIC injectors was great, just did mine and its perfect, price was excellent. Also if you find one bad injector, replace all of them. Its the same amount of work and if one is bad the others may be close to being that way. On the lady with the smoke on startup, I vote for the valve seals, if you have someone do them for you, ask them to put both intake and exhuast seals on 'all' valves. Its an 'old school' trick that works. Did those at the same time as the injectors and eliminated the startup smoke and smell. Some advise that may be relevent to all, find a mechanic that diagnoses and doesnt just replace parts hoping to fix something.

 

If there's an anomaly with the '89, mine doesn't have it. Twist the key and it fires. There's no "2" cranks or anything else. Given everything else I've dealt with over the last 21 years, I'd like to think that mine is an anomaly - but then the same problems keep getting posted around here time and time again.

Get yourself a scanner so that you can verify the Coolant Temp Sensor signal. That's it's choke. The colder it is, the greater the pulse width or fuel. If it's sensing cold when it's hot it's the same as a carb with a choke that doesn't open up and it will flood and die.

It's an '89 - check cylinder 7 for a leaking head gasket. It's better to run a compression or leakdown test but you can pull the #7 and #5 plug and compare the two. If #7 is cleaner or has rust on the threads there's a problem, though I doubt - if it is leaking - it has anything at all to do with it not running when it's warmed up. Trace amounts of coolant in the combustion chamber leans it out. It doesn't make it pig rich.