Possible Trouble with my ECM

[JeffP]

1995 Tahoe LT 4wd/4dr  5.7L TBI

 

OBD-I  ( as confirmed by the sticker under the hood & by the connector style under the driver's dash ).

 

Been having a hesitation/stumble at light throttle from a stop or while cruising.  Also have some power loss, hard shifting feeling & "surging" while driving.

 

Replaced cap, rotor, plugs, wires, EGR, TPS, fuel filter, air filter.

 

Diagnosis at the shop came up empty!  No codes being thrown, fuel pressure ok, timing, etc. all checked out ( i.e. they told me they checked just about everything they could mechanically -said it all checks out ok ).

 

They did confirm that when the problem occurs, I'm getting a very lean fuel mix -CONFIRMED BY THEIR TESTING.

 

Happens only at operating temperature, will not do it 1st thing in the morning when cold.

 

They disconnected the battery during their diagnosing and the problem completely went away!  No stutter, good shifting, nice power!  1 week later ( today ) PROBLEM IS BACK!  Power loss, sluggish feeling, hard shifting, hesistation at low throttle.

 

I can only assume it might be the ECM.  The shop said that that was their next target to diagnose.

 

Anybody know anything about ECM's?  Can I relace it myself?  Should I just replace the whole ECM or have it re-programmed ( if possible )?  I got a price for one ( part no. 16197427 ) for $106.00.  Do I need a separate chip as well or would it all come as one unit?

 

Also, since I may replace the ECM, is it worth buying it from a company who can "power-tune" it for me?  I just don't know enough about these to go monkeying with them before I get some advice.

 

Any suggestions?  Anyone think definitely that is is the ECM, based on these symptoms, or should I take it back for a re-diagnosis (knowing that just to diagnose again it will cost me $85 ).

 

Thanks as always, everyone, for all your helpfulness.

 

Jeff

[95Yukon]

Sounds like the ecm to me, since it temporarily fixes it when you kill the power to it and let it reset. Probably once it settles in, its out of whack and starts the problems. I don't know if they come with the chip or not, but maybe the chip is all you need to change. You won't really know unless you swap one out and see. Its not a big deal.. pull the glove box and its right there. Theres 2 large connectors going into it and a few spring clamps holding it down on the left side, and then a couple of locator pins, and you just lift it out and plug in the new one. Maybe you can find a good one at a salvage yard just to try it and have some spare parts to mess with. That would be a lot cheaper than the dealer in any case.

[BMKAR]

Hi Jeff,

 

Just caught your post...

  Had a problem similar to yours with a mitsubishi gsx...when it was cold it was ok

but gradually worsened as it warmed up(transition from open loop to closed loop?).

 

On mine,the theory went  something like this...carbon deposit on back of valves and

on piston absorbed some of the "precisely measured"fuel (@closed loop) causing a lean

combustion condition, while the cold engine(open loop) was enriching the mixture so that symptoms were masked...

The fix for me was Sea Foam($4 can@Farm&Fleet),but there are various combustion

chamber cleaners on the shelf(some quite cheap). Follow directions on can,

It took me about 450 miles of driving (8 days of driving) with this stuff in the right solution

in my fuel tank to be completely free of stumble...the alternative of taking the car to "satan"

for diagnosis was a compelling fear.

 

Hope you catch this reply in time...

BK