North West Corvette Guru

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Dave Burns

CCCUK Member
Hi, new member but long time owner here looking for a recommendation. My 89 C4 has been off the road since pre Covid, it was pushed in to the garage with a failed fuel pump and for one reason or another sat there until this year.
I fitted a new fuel pump and it fired straight up no problem, but its not at all happy at tick over and gets worse as it gets hotter. I have replaced plugs leads distributor cap rotor arm coil TPS and ICV none of which have really made a difference.
I have used the paper clip on the diagnostic port and am not getting any fault codes, so I'm running out of things to swap.
So my question is, can anyone recommend anywhere in the North West who really knows these cars.

Vet.jpg
 
teamzr1

teamzr1

Supporting vendor
With the gas sitting that long, did you also change the fuel filter and
using a fuel gauge pressure tool to connect to the fuel rail, I think back then it should be 43 PSI
Maybe the fuel injectors are clogged up, and you need to use a good gas/injector cleaner

Best is to connect an OBD-I scanner and see what is not working well
 
D

Dave Burns

CCCUK Member
teamzr1 said:
With the gas sitting that long, did you also change the fuel filter and
using a fuel gauge pressure tool to connect to the fuel rail, I think back then it should be 43 PSI
Maybe the fuel injectors are clogged up, and you need to use a good gas/injector cleaner

Best is to connect an OBD-I scanner and see what is not working well
Click to expand...
Done the filter and run fuel injection cleaner through the tank
 
teamzr1

teamzr1

Supporting vendor
Yes, the 1989 C4 has EST and ESC

Attached below the OP should save this PDF as it has all the GM engineering design specs, option codes, and more

Interesting, this has a GM screwup in that all the specs for the ZR-1 show as a 1989 model
when it did not go into production until another year of 1990
 

Attachments

  • 1989Corvette.pdf
    5.2 MB · Views: 8
Mr. Cricket

Mr. Cricket

Committee Member
Parts USA are the go to guys for 'newer' Corvettes and I think that may include C4's. Supporting vendor that gives a tidy discount for club members. Rates reduced from £90 to £60 and 10% on parts



Parts U S A

​

www.partsusa.co.uk
13 The Gate Centre, Bredbury Park Way, Stockport SK6 2SN · ~19.8 mi
0161 872 7744

Edit, just spoke with Chris at Parts USA and yes they work on C4's. All NW members use them and have nothing but good to say about them
 
Last edited:
D

Dave Burns

CCCUK Member
Mr. Cricket said:
Parts USA are the go to guys for 'newer' Corvettes and I think that may include C4's. Supporting vendor that gives a tidy discount for club members. Rates reduced from £90 to £60 and 10% on parts



Parts U S A

​

www.partsusa.co.uk
13 The Gate Centre, Bredbury Park Way, Stockport SK6 2SN · ~19.8 mi
0161 872 7744

Edit, just spoke with Chris at Parts USA and yes they work on C4's. All NW members use them and have nothing but good to say about them
Click to expand...
Tried them they were not keen on looking at a C4 bit to old for their software
 
FelixP

FelixP

CCCUK Member
Check the coolant temp sensor on the front of the intake. If it's failed or the wiring is dodgy it'll think it's freezing cold and run too rich. Unplug the MAF, does it change the running condition? Could be worth swapping the MAF relays.

Are they the original fuel injectors? If so they're probably due replacement. You can get new Bosch III from Fuel Injector connection. Try unplugging the injectors and checking the resistance on them. They should all be similar.

It'll be something simple, be methodical and work through one thing at a time once you've proven it.
 
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