Raymic

Hi Gang
I'm baffled at this behavior. My 94 runs awesome until the temp gauge hits approximately 215. Once there, it falls off the cliff....stumbling, pinging etc. I can drive from here in New Jersey to Florida on the highway and the thing will stay at a nice 185 degrees and run perfectly all day, but as soon as I get in traffic and go above 215 I have this problem. I have put in a new OPTI, plugs, wires, ICM, cleaned the MAF & Throttle Body, had the ECM checked at a service center. I had a code only once, H44, but the O2 sensor checked out OK also at the shop. No codes recently. Any suggestions will be greatly appreciated!!.. I love my C4 until this starts, then I just want to park it!!
Thanks
RM

antfarmer2

Change the front two o2 sensors.

dizwiz24

possible optispark failure.

electronics fail when hot. work fine when cooler

antfarmer2

it could be any codes? O2s are cheaper and normal maintenance.

Raymic

I had an H44 code. Is it possible that the ecm is trying to compensate and going too rich?

antfarmer2

A scanner would be great. But just telling him what fixed mine.

Kevova

IMO car needs driven with scanner to see what is happening. Audible pinging is an unusual condition and will cause ESC (knock sensors) to retard timing trying to stop it . Coolant level and condition of the little "steam" hoses at rear of heads ? Possibly some localized overheating? Any repairs prior to this happening?

Raymic

Thanks everyone..Are there any good affordable obd1 scanners that i can buy out there? I would love to see what it says when this #€*+= starts acting up. In the meantime, I'll order a couple of o2's since they are cheap. Im reading a lot of posts that say to check for exhaust/ intake and or crankcase leaks. Is that relevent? Wouldnt that cause mixture issues at all temperatures in closed loop? My problem doesnt start until the digital temp reads 215...long after it goes into closed loop. Thanks again to all

antfarmer2

Could be do you have any leaks? The hotter the more it will open changing the o2 to the o2s. If you are hitting 215 on the freeway I would pull and clean your radiator and clean ac coils. Pull your knocks flush and fill.

Raymic

No...on the freeway i'm golden...it'll stay under 200 degrees on the freeway all day. This only happens in traffic. In fact when this starts, i jump on the highway for a few exits and it drops right back down to 200 and the stumbling almost goes away..driving me crazy!!

antfarmer2

I would change the front two o2s and hope it is not the opti. Testing the icm and coil would not hurt either.

illenema

Id try to Datalog it, could see what the sensors say when it starts to stumble

Klondike

Check EGR. The temperature might just be a coincidence because it's happening at lower speed when temps rise anyway.

antfarmer2

Might checl your temp sensor on your water pump too.

Raymic

Thanks gang....Update!

I had all o2's changed and things have improved considerably, but we didnt get into the end zone yet..

here's the latest:

The car ran great on the highway ( a/c is OFF ), but after about 2 miles at 70mph the check engine light came on....H63 code. The fan turned on ( the one that's only supposed to turn on if we hit 228, or if the a/c is on ) and it stayed on so it never went over 185 degrees.

I shut her down and start her back up, and the check engine light is gone. It stays off until i get on the highway again, and then it lights up again.

Also, I see a white wire disconnected from the front right heated O2, but is that normal?

still frustrated, but feeling like we are getting close. It still pings over 215, but much less now.

thanks
Ray

antfarmer2

Good job. now finish hooking up your o2 sensors.
Clean your radiator and test the temp sensor on your water pump but burp the air out first it has two bleeders there. Do not get your opti wet.

GaryDoug

I know the CP9185 one works on my 94 LT1 pcm bench-top setup when it is set to a 94 Corvette 5.7L: https://www.amazon.com/Actron-CP9185...ct_top?ie=UTF8

At $71, that is by far the best price I have seen, so I recently bought one. Most places sell it for about $250.

You won't need a cable adapter; the 16-pin one that comes with it will work for you. You can monitor most of the real time data that is available as well as the trouble codes.

But I cannot say absolutley for sure it will work in a Corvette car with the CCM and other modules. I assume so, since it can be set to that vehicle.

Raymic

THANKS GANG!! The O2's did the job. Running great all day long. Now its on to the next project, that squeaky roof and loose door panel.

antfarmer2

good job


Door panel drill a hole on a slight angle just under the inter door sweep rubber lip. Then put a inch and a half screw in it to hook over the door frame it will be totally hidden.

The roof rub dielectric grease on the rubber seals both sides and tighten the back first.

Raymic

I've read quite a few tips on the loose door panel, but not yours...can you explain where to drill the hole in more detail? Thanks