FormulasOnly

I'm chasing an intermittent coughing/stalling problem on a 1989 Formula 350 TPI. A little history, I recreated this event 3 times as to eliminate pure coincidence. It had been running fine for a while, then if I ran the A/C for more that 20 minutes it would start cutting out... not completely stalling. Turn off the A/C and it would cut out for the next few minutes and then run fine.
So I just stopped using the A/C.... everything was fine for 2 weeks.... now it started cutting out again, sometimes stalling completely but then re starts...

Datalogging it, I don't see anything suspect.

Does the BLM adjust for the A/C and there's either a problem in the circuit or... Additional I do not know the history on the PROM, when I pulled it apart I found that the ECM had been replaced by a prior owner with a Standard brand ECM rebuild.

I had the ECM go bad on me about 5 months ago. got a new AC Delco ECM but used the same PROM

List of new parts ICM, ECM, Fuel pump, coil, Pulse coil pickup.

RBob

iTrader: (1)

A PROM can be bad. When it is the ECM may go into the SES flashing mode due to a bad checksum. If intermittently bad is can cause the ECM to reset, causing the engine to glitch each time this occurs.

If you can borrow another MEMCAL can try swapping it out.

It may also be that the ECM is bad. Can try this: drop the ECM down so it is on the floor, with the engine running at idle rap on the ECM case as if you ere knocking on a door.

If the engine stumbles or such good possibility the ECM is bad.

RBob.

FormulasOnly

Waiting for a new CHIP and ECM, should be here Monday. Been data logging it and I'm finally seeing some crazy readings..... My O2 sensor is ranging correct, then dumps to "4.4" but it shows in closed loop. The newest development is my speedometer is jumping all over the place, although the datalog shows constant and correct. I have no codes or flashing SES.

FormulasOnly

OK I know this is gonna get some flak... I bought the Hypertech Street Runner CA legal chip..... All of my symptoms are gone, it runs like a champ. Only did 25 miles but idle is better, everything is smoother. I didn't really do any hard acceleration stuff, but moderate throttle feels good....

Vanilla Ice

If you have an issue it may not manifest until fuel trims are fully relearned.

FormulasOnly

I'm going out for a longer drive today with the data logger running We''ll see...

IROCU2

FormulasOnly

Any results yet?

FormulasOnly

Yeah... it lasted another 25 miles then died ... No spark.... Just because I had one I changed the ICM. It started but ran poorly, dying intermittently. I managed to get it home.... Shut it off and its been dead ever since... No spark at all. Changed everything... still no spark. Old PROM Hypertech PROM Old ECU New ECU... I even swapped a coil and another ICM... nothing.

I've got a non CC HEI, a Edelbrock manifold and a Quadrajet just sitting here... I'm at wits end and just need something to drive.... I might just get a pressure regulator, do the swap and call it good.....

RBob

iTrader: (1)

Disconnect the 4-wire connector from the distributor. That will take the ECM completely out of the no-spark equation. Note that the injectors won't fire, but that can be a good thing to prevent the engine from flooding.

Can then troubleshoot the no-spark condition.

RBob.

881SA

RBob,
Since ECM chips are slowly becoming more expensive would know of or recommend any particular replacement prom?
I have the NN5 Ca compliant rpo so that's made it very expensive for an 88?

RBob

iTrader: (1)

Flash chips are still available. Flash one of those and use Moates G1 adapter.

RBob.

881SA

Thanks, I've read good things about Moates. Is it worth the cost of purchasing a programmer for a weekend show car?

RBob

iTrader: (1)

Hard to say, if anything it would be prudent to at least read the current PROM. This way you have the correct BIN for your car in the event the stock PROM goes belly up.

RBob.

Six_Shooter

iTrader: (2)

It sounds like there's an electrical issue, not necessarily a PROM or ECM issue.

I don't see any mention of testing for voltages and solid grounds, just throwing parts at the problem hoping it goes away.

Test what the voltages are using a DMM at the coil, ICM, etc to better diagnose the issue.

FormulasOnly

Voltages were all fine and then would cut to 0. I datalogued it to death. Moates and TunerPro. BINs were all correct. I found it was a power problem in the loom... Broken or corroded wire somewhere to the ECM. I'm not bothering to go any farther with it... I need something to go back and forth to work.. Its got a Q jet and a HEI on it now and its runs fine. I didn't hack any of the TPI stuff, its all taped/labeled and zip tied. If I, or a future owner ever decide to put it back it won't be that tough.