The car cranks fine, runs good while cold. A little "bumpy" idle, but this has always been the case. But now the idle is just a bit slower than before. Once warmed up, the idle gets more "bumpy" and surging takes place even while driving. Not serious surging, but enough to be felt. Then, the SES light comes on. Checking this out, I find code 44 -- "lean running condition."

 

Code 44 remedy: "44 Check wiring.connectors at Oxygen sensor. Check fuel pressure. Replace Oxygen sensor."

From this link: http://www.corvettephotographs.com/c4vettes/ecm.htm#44

 

o2's get lazy new ones will give new life.

 

Thanks for the reply. I am aware of these directions. I have checked out the wiring but have not checked fuel pressure. I will do that later today. The oxygen sensor is not very old, but I will replace it once I verify that the fuel pressure is ok. Thanks.

 

Will a lazy o2 sensor create the eratic idle and surging issues?

 

If they are new might just be a bad connection or burnt wire.

 

I would get in there and clean up your intake with some cleaner

 

The o2 sensor is not new, but not more than 2 years old. I checked the wiring out and all seems well. I will investigate further later this afternoon -- especially the fuel pressure. Thanks a lot. I have a replacement MAF sensor that has the circuit board type element instead of the thin wire. That thing has never been good to me. I am wondering if something coming from that area might be triggering something in the o2 sensor area. Just a thought. I am planning to replace the o2 sensor real soon anyway.

 

Have you done the fuel filter?

 

Fuel filter was replaced November 2014

 

Ok go up to harbor frieght they have a fuel pressure gauge for $20 that has a hose long enough to tape it to the windshield. Might just be a plugged sock or the rubber hose in the tank from the fuel pump.

 

At dentist office now (OUCH). Will look further into this later this afternoon. I have a gauge already.

 

Fuel pressure is normal. A little lower than the specs, but what it has always been since I have had the car since 1997.

 

you could check/clean/replace the IAC and clean out tb if carboned up.
also pull the vac line on your fuel pressure regulator for evidence of fuel..spray some tb cleaner up/down the vac lines to eliminate possiblity of a vac leak...D

 

Hi

How old are the spark plugs? perhaps replace them.
Have you checked your ignition leads with a multimeter and made sure they are good.

Is the ignition timing correct? 6 deg BTDC. Do not trust the harminic ballancer marks, the outer ring can slip.

I would confirm no.1 piston is at max stroke with ballancer on TDC mark.

Vacuum leaks are the most common cause of rough idle, check the EGR Exhaust Gas Recirculation valve is fully closed.

(You can put a vacuum hose to the EGR and apply vacuum and see it raises ok and lowers fully) you will need a flashlight and perhaps a mirror.

Try running it with the egr vacuum disconnected and plugged for a test if it runs better when warm.

The fuel pressure on the 85 is lower 32-36 psi due to the larger 24lb injectors, have you checked the fuel pressure when ignition is off does it hold or drop to 0 psi?

Get a torx set and check the inlet runners are tight.

Has the base idle been adjusted? is the block of tab still over the trottle screw, if it has been removed you may need to do a base idle setup. the ecm controls idle speed however if the screw has been messed with you can end up with all sorts of problems.

The ecm doesnt know the base idle screw has been adjusted, it can get itself into knots trying to compensate.

good luck

 

Thanks a million for all the replies. Here is a little history on the car.

1. The engine was replaced Nov. 2014. Not a new engine, but one from a lower mileage car.
2. New spark plugs installed.
3. New timing chain, harmonic balancer, air temp sensor, coolant temp sensor, oil pump, main bearings, vacuum hoses and just about all other items like this.
4. MAF sensor replaced Oct. 2013
5. o2 sensor replaced around Oct. 2013. But that was with the old engine. I did not replace the o2 sensor when I installed the newer engine.
6. Thoroughly cleaned out the intake plenum and throttle body.
7. Fuel pressure is held with ignition off.
8. Intake manifold bolts all torqued properly (as was the case with all other bolts).

When I looked into the exhaust pipe while the engine was out, I saw that the o2 sensor was extremely white. This was likely from the old engine developing a taste for antifreeze
The car has been running great from Nov. 2014 until a few days ago. Timing has been set to 6 degrees BTDC and double checked. I have put about 3500 miles on the car since the engine installation.

From all that I have researched, I am thinking for sure that the issue I am having now is with the o2 sensor. The car is good until it reaches near operating temp. Then the rough idling and surging begins and the SES light comes on. o2 sensors are cheap and worth taking a chance at replacing. I will post the results. I will have this issue resolved by Saturday afternoon (I think). Will not have much time to work on it tomorrow.

 

Problem resolved !!!!!!!!!!!!!!! I replaced the o2 sensor and the connector on the wiring harness. Now, the car runs good. Took it out for about a 20-mile run and all was well.

 

good job