i have an 85 berlineta h.o 305 q-jet that the service engine light flashes on.now no codes at all read thru the aldl port,but when i run sea foam in the gas tank light stays off and car runs great until the sea foam run thru system.any thought on whats up here cause im stumped.also the water pumps going out and has 1/4 to 1/2 inch of play back and forth could this be part of proplem.

 

After the check engine light flashes when driving around, you go shut 'er down and there's absolutely no codes??

I don't think the seafoam has much to do with anything... Boy, I hope not.

I don't think the water pump has anything to do with it, unless you're overheating the car. How's the temp gauge look when the check engine light goes off?

How does the car run? Totally stock car? Berlinetta and HO don't match up I think, what's the deal there?
Any modifications, different carb, distributor, etc?

 

it a rebuilt motor out of a z-28 h.o. and the temp never goes over 100-120.the car runs great when the check engine lights off but when it flashes car kind of sputers a little till light stays on or goes out.water pump just did start to go out cause all accessories are used except altnator its new.also car runs slugish when light on not as much pick up at all.

 

I wonder if your computer is the problem ??? You couldn't have used the wrong ECM because all the "HO" motors used an ESC module and a knock sensor. Your Berlinetta (and all other LG4 engines from 85 & up). also used the ESC and the Knock Sensor.

The Check Engine light should not be "Flashing" when you drive the car, even if there is a problem. The light should come on and stay on until the car is turned off.

The fact that your engine never reaches operating temperature could cause problems - but my guess is that the ECM temp sensor on the water neck would set a code if there was a problem with regard to the cars inability to completely warm up.

If the C/E light is coming on ( or flashing ) while your driving the car, the car drives like crap while the lights on, and there is no code when you shut the car down and "JUMP" the connectors than my first guess is that the ECM is the problem.

If the motor swap was Very recent ......... everything changes. You could have problems anywhere, and in any of the cars systems. Did the problems arise Right After the swap, or has the car been driven 1000+ miles since the conversion ?

 

Is there a thermostat in the car at all? Stuck open perhaps?

 

I was kinda thinking the same as sonix, 100- 120 seems really low, mine runs at a steady 180 after the thermostat opens up, unless of course you live in alaska were it might be really cold outside air temp I would be looking at the thermostat too.

 

no car just had 10000 miles put on right before i bought it.ever thing was done by a professional shop and he said temps never went over 100-110 since he got it back.light started flashing two days after i got it and i was told every thing was swaped from a wrecked z-28.i have no idea whats up im good with tbi systems but ill check the thermostat could a gloged fuel filter mess with it.
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another quick ? should there be two map sensors on this car cause my tbi system only has one is this the right set up.

 

What about if you just do the paper clip thing?

I'm guessing the 100° thing is °C?

You don't have 2 MAP sensors. You have one MAP sensor and one baro sensor. "Vacuum" is the difference between the 2. Older cars used ONLY the MAP, and just sort of assumed a constant baro. Adding the baro sensor improves the accuracy and adaptability of the system somewhat. The one on the driver's side by the fender is the MAP and should have a vacuum line. The one on the windshield cowl above th eright valve cover is baro and doesn't get a vauum line.

Fix the water pump (duh) although I don't think it has anything to do with the Check Engine light flashing.

 

ok the baro sensor has a vacum line on it should i take it off.and the water pump is being fixed in process just wanting to figure all problems out at once.

 

Iunno... whaddya think?