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Rough running engine

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Old May 22, 2018 | 03:47 PM
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Default Rough running engine

Thought I had fuel filter problems but after replacing the filter the engine still runs rough like almost about 6 1/2 cylinders....was told injectors might possibly be the problem.....am checking the distributor and wiring but it seems to look OK. Do injectors go bad one at a time or are they connected so one bad one affects the others....?? also....was wondering what the best coolant suggestion might be.

Last edited by Mark Liberty; May 22, 2018 at 04:26 PM. Reason: additional question
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Old May 22, 2018 | 05:23 PM
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Originally Posted by Mark Liberty
Thought I had fuel filter problems but after replacing the filter the engine still runs rough like almost about 6 1/2 cylinders....was told injectors might possibly be the problem.....am checking the distributor andwiring but it seems to look OK. Do injectors go bad one at a time or are they connected so one bad one affects the others....?? also....was wondering what the best coolant suggestion might be.
Information that will help here:

- Year and Engine
- Recent Maintenance
- Check engine Light
- Any Codes present
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Old May 22, 2018 | 06:39 PM
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Originally Posted by Mark Liberty
Thought I had fuel filter problems but after replacing the filter the engine still runs rough like almost about 6 1/2 cylinders....was told injectors might possibly be the problem.....am checking the distributor and wiring but it seems to look OK. Do injectors go bad one at a time or are they connected so one bad one affects the others....?? also....was wondering what the best coolant suggestion might be.
Which do you have?


Multecs are fine with 100% gasoline. The fuel is set to run past the coils to cool them. That is where the problem is. Some stations might have ethanol contaminated gas or many don't even sell it. If you have Multecs, just replace them and know that you don't have to find a specific place to gas up.
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Old May 22, 2018 | 07:25 PM
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Mark-

As Aklim and AgentEran have eluded... you have a lot that could be going on and we have little information.

Sometimes a simple tune could be all that is necessary up to including a full on injector swap.

Whatever you do, don't throw parts at your car until a proper diagnosis is complete.
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Old May 24, 2018 | 04:18 PM
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Originally Posted by AgentEran
Information that will help here:

- Year and Engine
- Recent Maintenance
- Check engine Light
- Any Codes present
Working with 1990 but am not familiar with various engine variations. Just replaced cap and rotor on distributor and also replaced fuel filter on the passenger side just behind the right front tire. Other than "Change Oil" (which I did with filter) light...don't see any other check engine lights or codes.
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Old May 24, 2018 | 05:18 PM
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Originally Posted by Mark Liberty
Working with 1990 but am not familiar with various engine variations. Just replaced cap and rotor on distributor and also replaced fuel filter on the passenger side just behind the right front tire. Other than "Change Oil" (which I did with filter) light...don't see any other check engine lights or codes.
So you have a L98 TPI motor. Im sure some of the resident L98 pros will chime in with some advice.
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Old May 24, 2018 | 06:13 PM
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Originally Posted by Mark Liberty
Working with 1990 but am not familiar with various engine variations. Just replaced cap and rotor on distributor and also replaced fuel filter on the passenger side just behind the right front tire. Other than "Change Oil" (which I did with filter) light...don't see any other check engine lights or codes.
Turn that light off. It's in the manual how to if you want. Gets annoying otherwise.

Don't trust the check engine light or codes implicitly. The system is pretty rudimentary and it doesn't always tell when something is wrong until it is FUBAR. Get a Factory Shop Manual for your year and a true scanner that can read data. If it is cheap, it is an overpaid for paper clip.
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Old May 24, 2018 | 06:15 PM
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Go to Autozone or someplace with an injector testing light and check all 8 injector connectors for signal. Easiest way is to get the motor running and take one out at a time. If the idle doesn't change, that is where the issue is. The light will tell you whether it is getting a signal. So if it gets a signal but doesn't change the idle, you have an issue with the injector.
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Old May 25, 2018 | 08:13 PM
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Originally Posted by billschroeder5842
Mark-

As Aklim and AgentEran have eluded... you have a lot that could be going on and we have little information.

Sometimes a simple tune could be all that is necessary up to including a full on injector swap.

Whatever you do, don't throw parts at your car until a proper diagnosis is complete.
Thanks for the helpful replies everyone....so far I feel like I'm digressing. After the work I've done so far I test drove a short run yesterday and came back home and shut her down in the driveway.....wanted to relocate a bit but now the engine will not even turn over. As I turn the key in the ignition....all I get is "INFL REST" on the screen and no action whatsoever under the hood....what did I do....? Also the proper diagnosis you speak of....is that strictly from a Chevy dealer or what....?
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Old May 25, 2018 | 08:25 PM
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Originally Posted by Mark Liberty
Thanks for the helpful replies everyone....so far I feel like I'm digressing. After the work I've done so far I test drove a short run yesterday and came back home and shut her down in the driveway.....wanted to relocate a bit but now the engine will not even turn over. As I turn the key in the ignition....all I get is "INFL REST" on the screen and no action whatsoever under the hood....what did I do....? Also the proper diagnosis you speak of....is that strictly from a Chevy dealer or what....?
I believe that is the air bag light.. seems like you may have some sort of short somewhere.
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Old May 26, 2018 | 09:55 AM
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Originally Posted by AgentEran
I believe that is the air bag light.. seems like you may have some sort of short somewhere.
Thanks AgentEran ....still working on this project (and having a little fun) but would sure like to discover why she will not even turn over now....going to keep digging. Would like to hear from some others with their opinion about some of my problems too... Do you do your own diagnostics or take it somewhere for help....?

Last edited by Mark Liberty; May 26, 2018 at 02:55 PM.
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Old May 26, 2018 | 10:41 AM
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Originally Posted by Mark Liberty
Thanks AgentEran ....still working on this project (and having a little fun) but would sure like to discover why she will not even turn over now....going to keep digging. Would like to hear from some others with their opinion about some of my problems too... Do you do your own diagnostics for take it somewhere for help....?
1 idiot light. 1 wire to the battery ground the other to the solenoid where it gets a signal. It will be the thinner of the 2 on the starter. Crank and observe .
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Old May 26, 2018 | 11:39 AM
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Originally Posted by billschroeder5842
Whatever you do, don't throw parts at your car until a proper diagnosis is complete.
A-MEN!!!
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Old May 26, 2018 | 04:35 PM
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Default Rough running engine

Originally Posted by aklim
1 idiot light. 1 wire to the battery ground the other to the solenoid where it gets a signal. It will be the thinner of the 2 on the starter. Crank and observe .
....but first I have to get her to crank again.... now when I turn the key to start....I get nothing....
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Old May 27, 2018 | 02:44 AM
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Battery maybe?
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Old May 30, 2018 | 11:44 AM
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Default Rough running engine

Originally Posted by mfowler
Battery maybe?
Battery is new and I do get lights on the dash when turning the key...just nothing more....no starter....engine cranking etc. ...going to check all connections to starter and see if something is missing or came unconnected. thanks for the help...!

Last edited by Mark Liberty; May 31, 2018 at 06:53 PM. Reason: additional information
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Old May 31, 2018 | 06:56 PM
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Well we're back up running.....found small wire to starter broke and lost connection. After replacing the bad connection we back to the point that I can start the car now and try to analyze some of my other problems.....if it would stop raining continuously I would like to take another short run.....waiting.....waiting.....waiting. ....the weather here in Middle TN has been horrible the last few days.....
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