Help! 88 Starts, rough idle then dies!

[101]

my 88 doesn't seem to want to run. I recently changed cap and rotor, wires and plugs. seemed to fix it for a week, then one wire ended up getting burnt, so i replaced them all again. Now it will start, then die, try it a few more times will idle at 800RPM for sec then kick down to 300RPM. Then if i start it and give it gas from the start it will stay running but when i let off the gas it dies, have tried turning on the a/c to keep it going but did nothing, and if i give it a little gas around 500RPM it will hesitate then die. Any help would be great! Thanks!

 

[Schrade]

Welcome onto the boards there!

What do you mean by 'seemed' to run better? Maybe like 'hoped'?

Start basic - air, fuel, fire. Forget the guessing game repairs. They cost money, and fix nothing - EVER.

Air - filter clear?
Fuel - get pressure readings. Static and dynamic (search my posts for SPECIFIC procedure for pressure tests, and see youtube for reference FP test vids (not exact procedure tho').
Fire - plugs, wires, timing (don't replace stuff without testing). Do you know how to do static timing?

You might well have a vacuum leak also. Search my posts for vac leak tests, and do EXACT procedure.

 

[garyg]

starts then dies

I had an experience similar after doing some relay changes. My 88 would start , run smooth then die. I found out I needed to disconnect the battery and reconnect it to reset the ECM. It worked perfectly, car runs smooth and idles well. Try disconnecting the battery and reconnecting it, easy to do and it's FREE.

 

[101]

lol, not just hoped, it ran perfect, I do not know much about timing and wouldnt even know where to begin, i have noticed a pop every know and then when i am trying to get it to start, i have heard that that could be the EGR. i will disconnect the battery when i get off work, thanks for all of your help, if that doesnt do the trick i guess i will look up your previous posts about timing. THANKS!

 

[vetteoz]

have tried turning on the a/c to keep it going but did nothing,

Why would the A/c keep it going?

 

[Schrade]

... i have heard that that could be the EGR. ...!

People love to make noise (be heard). 99 times of 100 means nothing. 100 times of 100 is CO2 emission - greenhouse gas.

Do these tests exactly, and you'll find the problem. GAURANTEED.

Air, fuel, fire.

Air filter ok?

Fuel - pressure good? You HAVE TO know this. Get static fuel pressure. Plug in the gauge onto the schrader valve, turn the key to 'ON' (don't start it), note the pressure, and note it quickly after turning the key on. Note the time the pressure goes down to '0' psi.

You tube has pressure test vids for reference. Don't do dynamic pressure (motor running) - you don't need that yet; just do as I describe. Just like testing air pressure in a tire.

Fire - when it is running, is it running VERY smoothly at idle? If not, then exactly how does it idle?

Jump timing is the first thing I'm thinkin' too. Was it running VERY near perfect (or better) before???

Do a static timing check. Disconnect the battery, get a breaker bar socket on the crank, spin it to 0 degrees on the damper marks. Then pull the distributor cap, and see if the rotor is just past the #1 contact in the cap, on its way toward #8. If its NOT just past #1, it should be just past #6, headed toward #5.

One or the other, then post back.

You HAVE TO do these tests to figure out what's up. They're not hard, no special tools. Need a tip, ask...

Why would the A/c keep it going?

Someone told him that the motor runs better with it on (which it might seem to do, but only 'cause the computer increases revs for extra load).

Not a good diagnostic 101... EVERYTHING SEEMS to run better when revs are up. Idle quality is the tell-all uh huh.

 

[101]

Was running very well at idle before,when i attempt to start there is a pop every few times i try and get it started it will get to about 8rpm then slowly die, struggle at about 5rpm then will drop to 3rpm and will try to stay going then will shake and die. i did not know that about the a/c so i guess thats good i know that know, Air filter is good (K&N just purchased). Did try and disconnect the battery to reset everything, did not work. tried again tonight it would fire up and do as described, but did notice when revs were up (foot on gas) the quality was not smooth. I will try all of the tests you have recommended tommorow after the daily grind, thanks for all the help , ill tell you how it goes

 

[Schrade]

New K&N, huh?

Put too much oil on the filter? How long did it run with the K&N in? Too much oil will foul the air mass sensor, and the car will not run.

Pull the sensor from the snorkel, and spray it with element cleaner. If there's a suitable substitute for element cleaner, I don't know about it. If no one posts up on that, get to the store, and buy some.

Be careful doing it. It's a fragile gig.

Then we'll get FP testing...

 

[101]

Had it for 2 months in there, i have an oil kit, and i replaced the MAF about a month ago as it was bad, so i don't think that is the problem, i have cleaned out the MAF and did that first thinking that was the problem, but that didnt work

 

[101]

Update: So fuel pressure was fine and so was timing, did go out and buy a GM code reader, reading code:33 MAF or MAP, changed the MAF because from my understanding there is no MAP on an 88, (only 3 ports on the throttle body thats run out to vaccum lines) Sprayed some started fluid on the lines but when started no change in vehicle revs. Let is run for about 10 mins with my foot on gas. let off and it idles right between 5 to 6 but no higher, then took it out on the road for about ten minutes when pullin in the driveway, was then idling at 8 but still sounded crappy. any ideas on this so i can finally fix this problem??

 

[Schrade]

What were your FP readings? Did you do static reading and dynamic too? What were pressure bleed down times? All of these measurements are critical - just gettin' gas to the fire is for lawnmowers anymore. It's NOT hard to do these tests either, and they HAVE to be done. No fuel injected car will run well without proper pressure, without proper vacuum to the FP regulator, and with vacuum leaks...

Is it loping idle at all when warm?

 

[101]

ok , so problem solved. ended up being the wires that plug into my MAF, for some reason they were shorting in and out, had to do test them about 4 times, because sometimes they would work.finally figured it out. thanks for all of your help guys!