No codes 1993

[Frank K.]

Car runs rough at 180 degrees and above ! Is the begining of the closed loop ?Idles drops and car does the shake! Tried three different code set ups including the Killebrews diagnostic grounding plugs.

[Keith B.]

Re: No codes 1993

reading a scanner is all the sensors giving a good read out? are there any reading on the low or high scale of there perimeters? Have you driven the car at least 15-20 miles to get the ECM to learn since the last clear out of the codes?

[Frank K.]

Re: No codes 1993

Car is not driveable after it hits 180 and up degrees! So a mile and less it will only go!

[Keith B.]

Re: No codes 1993

what is the reading of the mass air flow sensor? how about the coolant sensor in the water pump. that coolant sensor can do a lot of strange things to your ECM. so check the plug very well and add a ground to it to see if it helps

[Edward J.]

Re: No codes 1993

Frank there are a lot of fuel injector problems with the older C-4 , cause a rough idle and misfires at hwy. speeds. this does not away set a code but if plugs and wires are new, what else can it be. maybe a prolonged trip may set a lean code po171( lean code). I seem to remember you have done a lot of work on this car as of recent, Opti spark?

[Joe L.]

Re: No codes 1993

Car runs rough at 180 degrees and above ! Is the begining of the closed loop ?Idles drops and car does the shake! Tried three different code set ups including the Killebrews diagnostic grounding plugs.

Frank------


1993 Corvettes use the OBD I diagnostic system. I've found this system to be somewhat problematic when trying to pull codes. In addition, the codes are often quite non-specific and don't really allow you to "pinpoint" a problem.

OBD II is much better. However, and unfortunately, the only C4 Corvette that used this system was 1996.

[Keith B.]

Re: No codes 1993

Joe I never had any trouble pulling codes on my 94 with the Snap On brick scanner my only problem was buying good parts to replace the failed ones.

[Joe L.]

Re: No codes 1993

Joe I never had any trouble pulling codes on my 94 with the Snap On brick scanner my only problem was buying good parts to replace the failed ones.

Keith-----


1994 Corvettes went to a different type ECM. Maybe they are more "user friendly" than earlier.

[David H.]

Re: No codes 1993

Car runs rough at 180 degrees and above ! Is the begining of the closed loop ?Idles drops and car does the shake! Tried three different code set ups including the Killebrews diagnostic grounding plugs.

Frank,

I believe your assessment of open to closed loop transition is correct. Fact that open loop is ok, would indicate to me that injectors, fuel pressure, etc are ok. Problems occuring at transition to closed loop indicates something is wonky (technical term) with heated O2 sensors. Could it be as simple as a grounded HO2S wire with an exhaust pipe?

Dave

[Keith B.]

Re: No codes 1993

My experance with this would be to make sure the water pump coolant sensor is not giving a false reading either due to a faulty sensor or bad ground

[Jim T.]

Re: No codes 1993

Mr. Killebrew might be able to help solve the problem.