HellaciousA

Car has been stumbling/hesitating very badly from idle all the way up to 3500 or so. 93 6 speed w/ 62k miles. Had a optispark replaced with the MSD unit, new plugs/wires, and also just put on a new tps sensor. Original cats. Original fuel pump, etc. Fuel filter is changed every year or so due to our bad gas out here. Car is completely stock. Runs smooth when its cold, but once up to operating temperature, it struggles badly. No CEL comes on either.

Second issue, Master cylinder started leaking at fluid sensor switch, replaced it, bench bled per the service manual and bled it at the ABS test port like it states to. Then bled all 4 corners. Brake pedal feels great, car stops no problem. After driving for maybe 20 mins or so, the Service ABS and ASR lights come on, and the parking brake light stays on (even when its off). I checked all the electrical connections and they all are snug. I used a mityvac to bleed everything, but Im not sure if the light is coming on due to air in the lines or some other reason. I havent had time to try and pull codes yet by doing the jumper trick, just trying to avoid a trip to the mechanic.

Any advice would be appreciated. Just trying to save her some money as she dropped quite a bit on the optispark (had a new water pump done as well) at a Corvette shop in Burbank.

aminnich

"Runs smooth when its cold, but once up to operating temperature, it struggles badly."

That can be because it is not going into closed loop. That in turn is usually caused by a broken or bad coolant sensor on the water pump. Two sensors on your car, analog gauge has a separate sensor in the right head. the sensor on the waterpump is for the ECM and the digital temp gauge. Does the digital gauge work? Bet it bounces around.

HellaciousA

The analog gauge is fine, I haven't monitored the digital one though---I'll have to check it and see if its fluctuating like you are saying. Is the coolant sensor on the water pump internal or it can be it changed from outside the pump without pulling the pump off?

aminnich

From the outside, easy to get to.

sailorsteve

I agree that a faulty sensor could be the culprit, although that would set a code. I would pull codes even if the service light is not on.

Re the brake issue, check fluid level in the master cyl, this system is particularly sensitive to low fluid. If it is low, top it off to the full mark and keep an eye on it to see if it goes down, there may be a leak. Also, you could look for a leak, anywhere in the system including the abs unit.

0ChandlerMotorsports

It could be the O2s, as was mentioned its a closed loop issue. Also an ICM test at Autozone can rule it out, test it 6-9 times.

larry93lt1

This comment from a provider of GOOD Optisparks.

That's where I'm getting my next one when I need it.

surfer93

Any Codes?
Are you throwing parts at and hoping one fixes or have you been diagnosing?

Do a leakdown check on the fuel injectors and OHM the injectors and any under 12 ohms, should be replaced.

Check O2's.

Download Datamaster and buy an USB ALDL cable and then run diagnostics.

Have you checked voltage at the throttle position sensor, I had to return 2 before I found one that worked right.

Have a garage check the cats for blockage, they hook up a meter to measure exhaust pressure.

GET A FSM(factory service manual) from Helms, inc.
It will pay for itself very quickly and 92-93 are quite unique.

dizwiz24

Msd optispark? I haven't heard much good about them

HellaciousA

I bought the ALDL cable and did some logging with datamaster. It kept losing connection every 5-6 seconds for some reason, but it did get some good data. The left long term fuel trims vs MAP was showing the car is running extremely rich. The left short term vs MAP was rich but not as bad as the long term. The right long term fuel trims vs MAP showed some richness but overall it was ideal and the right short term vs map fuel trim was fine.

The car has brand new 02 sensors installed as well which had been done when she had the new msd optispark put in. There was a new TPS sensor installed at that time also. Knock count also is listed at 30856. During the logging run the car was stumbling a lot and bucking hard.

I'll ohm test the injectors this afternoon. I did buy a fuel pressure gauge and tested that a few weekends ago and it was around 38 psi at idle. There's a lot of data to interpret, so if anyone can help me out, I can post screenshots of Datamaster. Thanks for the help.

**edit, car does go into closed loop, digital coolant temp on the dash was steady the whole time as well.
*****EDIT, TPS voltage was .65 at idle, 4.12 at WOT. All 8 injectors showed 13.2 Ohms as well.