rblakeney

The car is a stock 89 with 63,000 miles. Manual. I purchased it with 58,000.

Usually starts and runs very well with good idle quality. I'll drive it a mile or many miles and it will run fine, then it will randomly be hard to start, not idle, won't accelerate under throttle/load, cough, sputter, and not be happy at all. I'll let it sit for minute or more and then it usually is back to normal.

No codes stored in ECU. The service light comes on and off as the engine speed rises and falls as I feather the throttle trying to keep it running. The service light is off otherwise.

New MAF (not rebuilt). New O2 sensor. Appears to be original distributor cap. Plugs are unknown. Plug wires look to be in good shape and are seated.

Fuel pressure steady at about 44 PSI when on and will hold that pressure for quite a while after turning the engine off. Fuel filter is unknown.

Cats are empty.

OK, what am I missing? Temp sensor? Throttle position sensor?

PatternDayTrader

What is fuel pressue while it's malfunctioning ?

rblakeney

Ah, don't know. Will check and report.

Tom400CFI

X2. First test I would do, with the symptoms that you've described.

PatternDayTrader

The connector at the sending unit is probably all melted and deformed .... we have only seen that about a thousand times.

vader86

If the SES light is coming on with the engine running, there is a code there.

rblakeney

You guys may have nailed it -- tank level and fuel consumption numbers go nuts when this is happening.

rblakeney

I'd have thought so too, but my code reader reports no code and the jumper method at the port is the same.

PatternDayTrader

Well if that turns out to be the case then you are doing good. Its an easy fix and the parts are not particularly expensive.

vader86

Does it correctly flash Code 12?

rblakeney

Yup, I've seen instructions and such on this job. Any recommendations on the part and source? Typical sources? Any brands to avoid?

rblakeney

Yes, 12 over and over.

Right now, the car runs normally and the light is off. It doesn't seem to set it permanently when the problem happens.

rblakeney

Dang it -- I was just cleaning up and preparing the car for a road trip out to the Texas Hill Country, but I suppose I should take something else. AAA takes forever in the middle of nowhere.

PatternDayTrader

For myself I tend to go to Napa because its around the corner. My preference is always whoever has the parts in stock locally. I would go out of my way to buy an actual ac delco fuel pump though. Beyond that, whoever has what you need in stock is where I would go.

PatternDayTrader

12 means its in diagnostic mode and that the ecm is capable of flashing codes. So that's good.

3D-Aircrew

A bad distributor cap and rotor will cause bad running and intermittent stuff ... if it's original I'd replace that.

You can have a perforated fuel pressure regulator and still have good fuel pressure ... pull the vacuum line off and check for gas in there ... if there is it's bad. Good luck

rblakeney

I agree - new cap, rotor and plugs are in line on the bench. I think I`ll to wait on the regulator until I do the manifold gasket.

3D-Aircrew

You should do the quick check on the FPR to be sure.

rblakeney

OK will do. Its good to eliminate it as a problem and I also like the idea of a new one to establish a baseline for my ownership anyway. I am the third owner after the second bought the car off an initial lease. He had it since 1991. Nice guy but I wouldnt call him a car nut like most of us here. He didnt know there are switches on the doors to open the hatch for example. He thought the breadbox was an air bag, etc. I think he liked owning his vette but he didnt turn his own wrenches.

Have an AC Delco fuel pump and sender unit on its way. I'll R/R and check FPR and report back.

Good stuff!

rblakeney

OK, feller Vetters...new cap, rotor, and wires (MSD red...looks great), and new plugs. The number 2 plug was an absolute X8@#!#$%*& and was original to the car! The previous mechanic or owner just simply did not bother changing it. I see why.

New fuel pump and sending unit. Fresh Red Line in the transmission and rear end.

The car runs like new! I am impressed. The whole character of the engine has changed and so has my opinion of the L98. I have always felt it sounded rough and unpolished.

So now I am on to the suspension.