So I just bought a 90 C4...took it to the shop had oil change and lube done they also did my rear rotors and brakes and hubs and put a new y pipe on. I drive it one day and I'm already breaking down...so I hop in rhe car start it up and sometimes this takes a few miles to start happening but when I press the gas I'll get a slight hesitation.i mean tap...just a little bit cause when I'm pulling out in 1st gear I'll rev the engine a bit before releasing the clutch..anyway this car immediately acts like it's flooding itself or chokes out. Now if I slowly work into the throttle I can get it to keep rpms that's when I pull off but if I feather it or tap it repeatedly she will die out. Once or twice when I noticed it was going to happen I just gave it more throttle thinking it would work past it but it would die off immediately and I smell alot of fuel. When I go to restart it it would not fire I would have to leave it for a few minutes before I could get it to FIRE OR I would jam the pedal to the floor and crank it and she would fire up. Now crushing down the road she would act as normal up to 6th gear..When in 6th and I jam on the pedal I would get the same choking out but when I drop to 5th I get it to come back. Today I put a new fuel pump thinking it's like my camaro which did the same but it didn't fix it. Any suggestions

 

check the fuel pressure regulator for fuel in it. I would also ohm the injectors, it's quick and easy. Put a flat head to the injectors 1 at a time. Listen for a constant pulse. If not a constant pulse, it's mis firing. Are there any codes? Do you know how to scan for codes?

 

If the coolant temp sensor is not working properly the car can 'think' it is cold, and over enrich the air fuel mixture, causing all sorts of problems including the one you are having. My CTS failed and no codes were shown. I figured out the problem by the behavior of the car, put in a new CTS (and flushed and filled the coolant at the same time) and the problem (several problems) were solved. My 1990 is back to being a rocket across all operating rangers.

Of course this might not be your problem, but it is easy to check with an ohm meter, although the CTS is hard to get to. Check the factory service manual for details.

Good luck with fixing your car...

 

If stock 3.33 rear gear ratio don't use 6th unless your running 60+ mph & the terrain is flat. Use 5th going up hill.

CTS is in the front of the intake below the T-stat.

Stock 90 injectors are problematic, cold engine remove the connectors & ohm each injector they should be 14 - 16 ohms. Check them again when the engine is hot if any are out of spec change them all. Many here myself included use Bosch 3 injectors from Jon @ FIC here on this forum.

 

Maybe he doesn't have to get to it directly. IIRC, it is in the front of the manifold so if the scanner says the ECM sees 45 degrees and the infra red gun says 75, we have a problem.

 

Check TPS, check MAP sensor.

Sounds more like AE is not kicking in on sudden throttle movements. While I'd always recommend getting rid of the stock rochester injectors, I don't think that is your problem. Easing into the throttle seems to be fine, and frankly injectors usually either work or don't. They don't have problems with sudden pulsewidth increases.

A faulty TPS might do it though, or a lazy MAP sensor.

You need a scanner. I recommend you buy an ALDL cable from moates, and download a copy of tunerpro R/T. Log the car while this is happening and post the log. One of us tuners would be happy to look at it and tell you what we think is going on.

-- Joe

 

One comment on the above...my original fuel injectors from the factor worked well from when the car was built until last year, so 25 years without trouble. A local Corvette shop told me that whenever they have tried aftermarket injectors they've ended up with some idle issues, not a big deal, but the car and the PROM were designed and set up for the OEM Delphis. When it was time to do my injectors, I got the OEM ones, at some expense, and the car runs great. Very smooth idle, rocket like acceleration, great fuel economy. While I'm sure aftermarket injectors can be made to work, personally I stuck with the OEMs and am very happy with that decision.

 

Ok thanks guys today I'll get a TPS and CTS and a MAP sensor before I start on the injectors. I'll keep everyone updated tonight when I'm done

 

Well I didn't say that, I said scan/log it and test.

The log will quickly indicate where the problem is.

I wouldn't just start swapping sensors.

-- Joe

 

Who is this "local corvette shop" you keep speaking of? What are their credentials? Lots of people also have gone aftermarket without the issues that you say they see.

 

I'd get a scanner before I change stuff