'89 runs rough when at operating temperature

[marathon26]

The '89 has a problem when it reaches operating temperature. It starts to run rough and sometimes dies. If it has not reached operating temperature by the time I reach my destination, when I come out it won't start until the engine has cooled down. I have replaced the control module inside the distributor and the coil. Since I was there and it was so much fun to work in that area, I replaced the distributor and the rotor. Prior to doing this I had the fuel pressure checked and it was on target.

Does anyone have any ideas?

 

[redvett]

The '89 has a problem when it reaches operating temperature. It starts to run rough and sometimes dies. If it has not reached operating temperature by the time I reach my destination, when I come out it won't start until the engine has cooled down. I have replaced the control module inside the distributor and the coil. Since I was there and it was so much fun to work in that area, I replaced the distributor and the rotor. Prior to doing this I had the fuel pressure checked and it was on target.

Does anyone have any ideas?

Have you replaced the CTS sensor on the front of the intake manifold? It has black & yellow wires and tells the ECM how warm the engine is. Bad sensor will make engine run rich when hot.

 

[Schrade]

See post 3 http://www.corvetteactioncenter.com/forums/c4-technical-performance/116844-89-runs-rough-when-operating-temperature.html] here:
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[k2bob]

My 89 did the same thing. After all the small stuff, it all boiled down to the injectors. Check the ohm readings cold then hot. They all should be very close. My hot readings were all over the place but cold was fine. I replaced all eight with the NAPA's and have not had any trouble since. Do a search for "won't start when it is warm" in the forums and you will see a lot of similarities to your problems.

 

[Curious George]

My 89 did the same thing. After all the small stuff, it all boiled down to the injectors. Check the ohm readings cold then hot. They all should be very close. My hot readings were all over the place but cold was fine. I replaced all eight with the NAPA's and have not had any trouble since. Do a search for "won't start when it is warm" in the forums and you will see a lot of similarities to your problems.

If you need injectors, visit FIC (Fuel Injector Connection). You cannot go wrong.

CG

 

[marathon26]

Problem solved

New injectors and the problem was solved.

 

[T.M.808]

what brand did you go with if you don't mind me asking?

 

[RonnieH]

Injectors Changed

what brand did you go with if you don't mind me asking?

I had a similiar problem. Car ran great when started up. As soon as it got up to temp, idled very rough. Readings were all over on 5 of my injectors. I replaced them with the Bosch III's and all was well. Runs like brand new. One funny thing - all my miles were highway miles. With the bad injectors, I was getting 28.5 mpg on the road. After replacing injectors, getting 22.5 mpg on the road.

 

[Schrade]

I had a similiar problem. Car ran great when started up. As soon as it got up to temp, idled very rough. Readings were all over on 5 of my injectors. I replaced them with the Bosch III's and all was well. Runs like brand new. One funny thing - all my miles were highway miles. With the bad injectors, I was getting 28.5 mpg on the road. After replacing injectors, getting 22.5 mpg on the road.

Maybe you didn't get one injector connector plugged in right? Maybe fuel leaking past an O-ring?

Get a multimeter on the new ones, cold and hot, and get some impedance reads...

You can't decrease your mileage by over 20% with new parts over broken parts...

 

[T.M.808]

Humm,ya never know,maybe his bad injectors had restricted flow,so the PCM reads the car as lean and retards the timing and adjusting pulse width,giving him better milage,sorta like economy mode,then he puts in new ones,and the a/f ratio and flow is good,timing stays advanced,performance went up a hair,and milage went down,or back to normal.... just saying.lol. anythings possible..
Oh,28.5? Seems a bit higher than normal though.

 

[G Winter]

Oh,28.5? Seems a bit higher than normal though.

I have gotten 28.6 on the highway. No reason it shouldn't.

Glenn

 

[T.M.808]

I have gotten 28.6 on the highway. No reason it shouldn't.

Glenn

Damn,is that a 2:59 gear? Just realized you have 6 speeds. I do 60 miles a day on the freeway,about 2 miles in the city. I have never seen more than 25mpg. Although i do have the 3:07 gears,cold air intake,true dual exhaust with no cats..some other minor mods..In feb,i'll probably be around 15 miles to the gallon.. lol...new cammed stroker motor..:cool

 

[G Winter]

Think it is 3.33 gears The six speed has a double overdrive, both 5th and 6th. 5th I think is .75 and 6th I think .50

The lowest my mileage has ever been is 15 on poor gas in all city driving , under 45 mph stoplight to stop light.
I live in the country and drive a lot of 12 to 20 mile jumps on 2 lane roads and get 22 to 24. If I get it on a 50 mile run which is through a couple small towns I get 26 or 27 real easily.

Glenn