Gold85Vette

I have an 85 Vette that I have began restoration on. Here's what I have done so far.

New fuel pump, TPS, IAC, MAF, Distributor Cap and Wires, Plugs, and Fuel Pump Relay. I followed carefully the procedure for resetting the timing right at "6" from TEC. Had a high idle issue which turned out to be the TPS. After replacing it and setting it at .54V, and replacing the MAF (also faulty), I now have a rough or purging idle issue and it struggles to accelerate beyond just easing on the throttle. Have not yet checked the injectors not the fuel pressure at the rails. Where should I begin? Please, any help would be greatly appreciated. Again, she ran fine other than the high idle until the MAF was replaced. Now fouling plug #1.

ghoastrider1

their are 3 kinds/colors of smoke, all meaning a different thing. Blue is oil .. usually see on cold start up with worn valve seals. White is coolant, sometimes seen with cracked head or bad gasket. Black is fuel.. sounds like your running way to rich..many causes for each color smoke but will lead in a certain direction. Injectors leaking ? air filter blocked? Fuel pressure reg gone bad? just check your fuel system first. weak spark? fuel not getting burnt completely? Others will chime in that know more than me. best of luck and let us know what you find.

Gold85Vette

I did get it to read once that the O2 sensor was reading rich. Replaced the sensor to ensure it wasn't faulty. Still running rich and loading up. My first guess was fuel pressure regulator but it's never been off and I hate to take the intake apart to replace it. Any ideas on a fairly simple way of checking injectors for leaks first?

chevyman_ky

put on fuel pressure gauge, key on to build pressure then turn key off pressure should stay up if goes down quick probably inj leaking

xrav22

An easy way to check the fuel pressure regulator is pull the vacume line and it should be dry. I just checked mine today (85). After I reset my timing I had loping idle but turned it off and restarted it and it was gone. try unhooking the battery to clear the computer. Make sure vacume lines are tight, I would guess from what you are saying you have a bad injector on your fouled plug. Try some fuel injector cleaner also. Good luck
Edit Use the $5 dollar fuel injector cleaner not the strong one or it may clean too much.

Gold85Vette

Uses a fuel pressure gauge on it today and it dropped from 38 psi to 20 psi in less than 10 minutes. Pretty sure the injectors are going to need to be replaced.

Tod Stiles

I would cover the basics first. So the timing was set with the set timing (also called EST) connector disconnected, and set to 6 degrees BTDC, right? You could also check the fuel pressure while running, but be careful make sure there are no leaks etc.

Puzzled over why you don't have a more constant SES light. You said you once had a rich O2 sensor so it seems the wiring is good. I'd check that anyway just to make sure. If you have a big vacuum leak the sensor will show lean and richen up the mixture. I'd stay away from any more additives they can cause trouble.

Good luck!

Edit: Just wanted to add-make sure you don't have crossed wires, you said you did the plugs...

Paul Workman

I sold my 95 LT1 car back in 07. I'm running on memory... But, it sounds like your issue is very similar to the one my car had. So, take this with a grain of salt!

Dropping 18# in 10 minutes could be an injector, yes. Or, it could just be the check valve in the fuel pump, or the diaphragm in the pressure regulator is seeping. But, that leak (over 20 minutes) is too small to cause black smoke and acceleration issues. Tho it does indicate some other (relatively minor) issues, that isn't (in and by itself) bad enough (by far) to be causing the smoking.

You'll need to scan it while running, and check the O2 sensor(s) average voltage and also see how the "cross points" compare.

An average reading around .05 volts (scanner) ± 0.1 is normal. 0.9 is at the rich end of the scale, and 0.0 is at the lean end. If one side is reading at or near zero volts, it indicates a "lean" condition and the computer will fatten up the injector pulse-width (adding fuel) to try to deal with a lean condition.

Note: You may or may not get an SES light, depending on the nature of the failure. (Ask me how I know...).

The key is "parity", far as O2 sensor operation goes. If one is reading 0.2+ different from the other (toward 0.9 or 0.0) swap positions and retest. If the issue follows the sensor, then replace it. If not, then the sensor is telling the truth and something else is out of spec.

I gotta tell ya, buying a scanner capable of reading the static data as well as monitor the sensors when it is running, was by far the best money I ever spent on tools!!


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Gold85Vette

I put new O2 sensors in when it first started idling rough. Changed the fuel filter as well. There are no fuel leaks (from outside the intake) that we can find. I will pull the fuel pump today and ensure nothing is going on around the screen.

in the first couple of minutes the psi dropped 10 lbs and you could literally watch the needle drop. The 1, 3, and 5 plugs were all wet with fuel and fouled. I, by the way, always replace plugs one by one so that I don't rush crossing the plug wires. It has become very hard to start as of late, taking 4 ton5 cranks to get it started, and only appears to have started smoking after the plugs fouled. About a month ago I ran Seafoam in it because of similar symptoms minus the black smoke. It ran great for a few days and after running near empty a tank that had 2+ year old gas in it. Filled with Premium pure gasoline and Seafoam.

It was only after changing a faulty MAD that it began idling rough. However, unplugging it changed nothing so I have all but chalked that up to coincidence.

Gold85Vette

I set the timing following a very useful YouTube video by unplugging the fuseable link for the IS at 6 degrees BTDC. Then, disconnected the negative terminal, connected the IAC, and hooked the ground back up after about 2 minutes.

Silver85

You have gotten good advice here. One thing that really sticks out to me is "she ran fine until the MAF was replaced". Ever think of throwing the old one back on to see what happens?

Gold85Vette

Sorry I should have said I had a faulty MAF sensor that I replaced with a new one. Shortly after it began running rough. I tried putting the old one back on and no change in the roughness.

xrav22

To set the timing all you need to do is disconnect the tan/ connector. I only say this because once mine ran very rough so I reset the timing and it was fine. Make sure a plug wire is not loose.

Gold85Vette

Ok here's an update.

The car now won't start.
I've replaced the injectors, O2 sensor, MAF sensor, TPS, IAC, points, ICM, ECM, and Fuel Filter. The Fuel Pump and Fuel Pump Relay are fairly new with less than 400 miles on each. Full tank of Premium Unleaded with NO Ethanol was used last fuel up.

What should be my next step???

ToniJ1960

this should be fun to watch

Gold85Vette

Ok now I have replaced those stupid Bosch Platinum plugs with good old fashioned AC Delco plugs and starts fine. Idle is purging on me from first startup to even when it is warm (open and closed loop). Drives pretty good now but will purge when stopped and often dies. New coil and ICM so doubting heavily anything wrong with firing. Seems to me i could have gotten a bad IAC? No fuel in the vacuum line coming off the fuel pressure regulator so i assume it's good to go.

On a side note, I keep finding a bit of oil on top of my intake after sitting overnight. I clean it off each day and find more there the next day. Any clues as to where this could be coming from?

Silver85

You beat me to it....

xrav22

You should reset the timing to 6 btdc and do a ilde adjustment setting. I had loping one time after resetting the timing but I restarted it and it hasn't done it since. Also check your wiring and clean all connectors

Gold85Vette

So not 6 btdc? I have set it to 6 due to a few instructional videos and other posts. However, I am willing to try about anything now. When I plug in the MAF, it will barely stay running and runs extremely rich (heavy black smoke).

xrav22

Yes 6 my typo