IDLE PROBLEMS --1990 5.7 AUTO

[BUDROW2]

HI GUYS , I REALLY NEED SOME HELP HERE ,I HAVE TRIED PLENTY OF NEW A EXPENSIVE PARTS AND STILL HAVE NOT SOLVED THE PROBLEM FIRST OFF TRIED A COMPLETE TUNE UP ,,NEW CAP ,WIRES .ROTOR ,PLUGS,NEW INJECTORS ,A NEW DISTRIBUTOR, IAC,HAVE CLEANED THE IAC THEN REPLACED IT ,REMOVED TB AND CLEANED ,CHECKED FOR WATER LEAK IN TB OR UNDER IT FROM THE WATER COOLING LINES ,HAVE DONE A SMOKE TEST ON ENGINE WHEN COLD AND WHEN HOT,HAVE REPLACED ECM AND ADDED A NEW PROM FOR PERFORMANCE (ITS A PIGGIE BACK PROM) IM AT WHITS END WITH THIS ONE ,I SURE COULD USE SOME MORE HELP AND THANK YOU IN ADVANCE
BUDROW2

 

[Key West Jack]

Do you have a FSM? Describe the problem with the idle, that will tell us a lot.

 

[BUDROW2]

Do you have a FSM? Describe the problem with the idle, that will tell us a lot.

HI JACK NOT SURE WHAT YOU MEAN WITH FSM BUT WIL TRY TO EXPLAIN PROBLEM , WHEN ENGINE IS WARMED UP AND YOU DRIVE IT SEEMS TO RUN FINE NO MISSING ,NO HESITATING ,BUT WHEN YOU STOP AT A LIGHT IT WILL IDLE FOR A FEW SECONDS AND THEN GET ROUGH AND QUIT ,STARTS RIGHT BACK UP AND STAY RUNNING AS LONG AS YOU ARE IN PARK OR NEUTERAL,PUT IT IN DRIVE AND IT SHUTS OFF . IT SHOWS NO CODES ? IT HAS GREAT FUEL PRESURE AT IDLE AND DRIVING I HOPE THIS HELPS THANKS

BUDROW2

 

[WhalePirot]

Vacuum reading? Should be steady and 18" or higher. Vacuum leak?

Static timing? Refer to the emissions sticker for the correct value, which is set the old way, but with the ECM not controlling the spark advance. On my HEI, the brown wire to the distributor gets unplugged.

 

[Key West Jack]

I would look at vaccum issues too. Specifically, look at things like PCV, hose etc. Last, check out your egr system. FSM = factory service manual

 

[BlackNBlue95]

I would almost suspect an EGR problem as key west jack said.. Does this problem happen only after to drive it and come to a stop? Does it happen if you let it idle and warm up without driving it? A vac. leak at idle can be a cause as well..
-=Rick

 

[BUDROW2]

thanks guys ill try all of the info you sent me but i tried the engine smoke test on the egr system and no leaks , but i wil try all over again

thanks again

 

[Key West Jack]

It real important to check the egr out in two ways. First, make sure that the actual valve works. In the event you have to replace it don't purchase an aftermarket, get a Delco. It is still carried by dealers. Second, check the operation of the egr solinoid. That is make sure it works and look at the vacuum lines to make sure they have no leaks. Regarding vacuum leaks, on my 90 I found a crack in the preformed pcv hose right at the inside of the 90* turn. It opened up when the engine warmed but leaked very little when the engine was cold. Good luck!

 

[gmboileau]

Hi
The problem you describe seems to indicate a lean mixture. Using a scanner and recording the engine data when the problem occurs and comparing it to the normal values can be can be very helpful in verifying the problem. The scan data should show that the Block learn and integrator values are high which would confirm that the ECM is trying to compensate for a lean mixture. The ECM can only do so much however and then the engine stalls. Things that can cause a lean mixture include stuck EGR, EGR commanded on at idle, coolant temp reading too high, shifted Map sensor, plus many others or just a leak in a vacuum hose. The scanner can really help narrow it down.

Cheers
Gary