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Discussion Starter · #1 ·
hey guys my lt1 is still not acting right. i replaced the coil icm plugs wires opti fuel filter and mass air flow. im at a loss. i took it to the dealership and it threw mass air flow circuit problem and lean condition (most likely because of mass airflow?) the tech said replace the mass air flow and opti and it should be good. but thats not the case. the car will start when cold but it does not the climb the rpms like it should and will mis and backfire but i can steady cruise it, then when i turn the car off and wait like twenty or thirty min till when the car doesn't "fully" cool down and go to start it acts up horribly and is surging and missing badly and wil sometimes die if i cant get it back to optimal running temp. im going to get the fuel pressure checked thurs but i still have my doubts about it being the fuel pump. maybe jumped timing? I need help!
thanks-chaz
 

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I'd put the car on an obd1 scanner that does real time sensor data. Then see what the sensors are telling you.

Dealers love to change expensive parts and hope it fixes the problem. Remember when you have a code, say for the maf, it could be the wiring, connectors, grounds, power supply, causing trouble.

For the opti, check out it's wiring harness that runs from opti to passenger side of intake manifold. It causes many problems. Open the diagnosing the optispark thread, in the sticky threads of this section. Watch the video, run the tests. shbox.com also has opti and coil testing. Run the tests and see if proper voltages, and signals are coming through.

If you don't have an obd1 scanner, get a cable that hooks car's dlc to usb port of laptop or notebook. Get it at ALDL OBD1 OBD cable OBDI OBD2 engine codes you will need the 16 pin version for your 95.

Then go to 4th gen section and download the free 94 & 95 f-body obd1 scan program. It was written by our member GaryDoug and should fit your needs. It scans for codes, does running sensor scans, and also reads abs & sir codes which no other available obd1 scan program does.

Might want to download the trail version of the scan program DataMaster also. It's advantage is it logs scan data to a file that can be played back in real time. That way you could upload the file to a data sharing site, link it back here, so members can help you with the data.
 

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Forgot to ask, did you put heat sink compound on the back of the new icm and on heat sink when you changed it? If no, icm will burn up in short order. And dielectric grease is a no no. Only use heat sink compound, available at radio shack and computer parts stores.
 

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Discussion Starter · #4 ·
coco. yes i put heat sink compound behind the icm not dielectric grease. and i checked the opti harnes and the wires and connections look fine. i also checked the mass air flow harness which had a wire broke. (thats what the tech at the dealership and he fixed it ). i took it to a shop that a quality obd1 scanner and brought up the same codes except it had one more which was injector circuit problem. could an injector being out cause this problem? and if so how can i go about finding which one is bad. and where could i get an ALDL cable for a relatively cheap price?
thanks-chaz
 

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The 2nd link in post #2 is where to get a cable for $59 + shipping.

When you check wires and connectors, looks can be deceiving. You need to unhook both ends of the wire harness and chack for continuity with an ohm meter. Then check for high resistance in the wire, as that can cause problems also.

A dead fuel injector will cause a cylinder not to fire, but it would make running somewhat rough rather than surging & back firing. You can test for injectors not working by first using an ohm meter on the injector with the connector unplugged. Resistance, I believe should be 12 ohms. But a injector which has infinite ohms- it's open, or no ohms- it's shorted, is what your looking for.

If that test is inconclusive, it's time to test each injector connector with a noid or 2 lead test light. Keeping in mind that injectors get battery power anytime ignition switch is on. It's the ground which is provided by the pcm that makes injectors open. So test each injector with noid or test light. Have assistant crank engine while you watch for light to turn on and off. Every time the pcm supplies the ground for injector, light will blink on and off. Do all injectors.

If this test is inconclusive, then you will have to unbolt the fuel rail, lift the injectors out. Crank engine with jars under injectors to catch gas, and a fire extinguisher handy, for just in case. As assistant cranks engine check 1 injector at a time. Make sure it sprays and make sure spray pattern is good. Then make sure, after cranking is over, there is no leakage from injectors.
 

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Discussion Starter · #6 ·
ok thanks for the info so it is improbable that a faulty injector is the root cause? i dont even no how to use an ohm meter or where to get one for a relatively cheap price. any suggestions?
 

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Still don't think one bad injector would cause problem. Now, on the other hand, if all your injectors are clogged, your car would run very lean and have those problems.

Digital multimeter, with high input impedance can be bought at radio shack, walmart, etc. Cheap one should be in the $30-$40 price range.
 

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Discussion Starter · #10 ·
ok man thanks alot. i will try to get a digital meter and cable and download sotware. and like i said im getting my fuel pressure checked tommorrow so i will let you no how that goes as soon as i can. you said to post my results from the software on here so others can comment on it. where would i go about posting it and should i just post pictures of results or just type out numbers? again thanks alot i greatly appreciate it!
-Chaz
 

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If you choose DataMaster as your scan program, you can post the log file that DataMaster creates when you do a running sensor scan. Do a Google search for file sharing sites. Become a member of one of them. Then you can upload the DataMaster log file to the file sharing site.

Next you create a link of where the DataMaster file is. To create the link you need to know the complete web address of where your file is uploaded to, not just the address of the site, but the complete address. It will be in the address bar at the top of your page.

Even though the link doesn't show it, I started with www. then added lt1pcmtuning and at the end the .com Of course all of that is together with no spaces. When you type in the complete web address, a link is made.

To create a link, just post as usual just type in the complete address. Here's an example of a link. LT1 PCM Tuning - Welcome!
 

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Discussion Starter · #12 ·
i fixed it coco!! it was the fuel pump. im so glad i got my girl runnin good again! thanks for all the help man.

-Chaz
 
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