Hi, I'm new to this, so please be patient. I just bought a '90 C4 that had been sitting in a garage for about 4 years. Charged the battery & she fired right up & ran well even on the old gas (the tank was mostly full). Got home & put fuel cleaner in it & topped off tank (6 gals). Put about 100 miles on it & ran fine. Took it out Sat., ran good for 30 mins., then developed a miss, barely made it home. Pulled plugs (clean), changed rotor, cap seemed fine & put back together. Changed fuel filter (seemed to have plenty of pressure). Miss was still there. Had battery checked (needed new one), had alternator checked (was fine). There are no codes (used simple code reader). I've noticed that when certain power items come on (cooling fans, etc..) it sorta blinks (don't know how to explain it). I'm thinking bad ground ?? I just can't understand how it could go from decent running to sh** in 100 miles ! Also, don't really know how to check injectors (I've searced for threads, but they're kinda vague). I'm not really a wiz on electrical problems. Any help, would be greatly appreciated. Thanks.

 

It sounds to me as if you did a bunch of things wrong. Before driving it I would have done the following. However, I understand the driving - the cars ARE fun to drive.
Old gas drained, fuel lines blown out and a new fuel filter installed.

Brake fluid replaced through the entire system. Watch the brakes carefully as DOT 3 fluid absorbs moisture and can cause rust in the master cylinder and calipers. That can lead to instant brake failure.

Coolant drained, system flushed, and new coolant installed.

The six (on a 92, anyway) chassis points lubed.

Oil and filter changed

Tranny fluid changed.

That is a minimum. You have not mentioned the number of miles on the car or whether it is a manual or automatic.
The blinking you mention may be normal. I have never had a 90, but noticed similar on my 1991.
Without codes it is a little harder to diagnose. You ned to get a factory field service manual for the car (not a Chilton's or Haynes) and start diagnosing.
A search on this forum will tell you how to ohm out the injectors and check them with a noid light. They may be suspect if they are the originals. If they are the originals I would replace them as a normal maintenance item.
I would suspect your problem is fuel related. If the injectors are the problem Jon at FIC will set you straight with quality replacements.

 

Thanks KMcoldcars, did most of what you said, except trans change & brake fluid. It has 54K on the clock. Got a FSM, but it's like reading Greek ? Where can I get a noid light ? Thanks for the response.

 

Whar was the 'fuel cleaner'? How much of it?