Hey all, I just got signed on here and am looking for some information on what could be wrong with my car. I have tried doing the search on the boards and have gotten some information, but none of it is a problem with my car.

Here the skinny. My car is an 87 firebird with a 2.8. I have had no problems with the car until 4 days ago when while driving on the interstate is was surging to me while in cruise control. I took the cruise off and it was still doing it. It was surging from running normal to running rough. Brought it home and even at idle it was running rough, almost like it is either missing a cyclinder or being bogged down with too much pressure. By the time I had brought it home it was running rough the entire time (no surging). As I hit the throttle it hesitates a little before accelerating, very slowly I might add. All this is going on with no SES light.

Here is what I have done so far to diagnose. Engine while running: is not knocking or pinging in idle or driving. Checked compression: each cylinder is showing at 150. Checked spark plugs, wires, distributor cap, and rotor: all fine with normal wear. Even made sure current was going through them (aka timing light). Checked my coil pack, I have a spare new one and put it on (no change). I have pulled my upper intake off. Checked vacuum lines (fine). Fuel pressure (42 psi, which has been normal for this car for ever.) Checked the injectors all of them at cold are around 16.7 to 17.1 ohms. After a short running and recheck they all get up to 18.1ohm. Checked air filter (it is a CAI and is fine). Checked exhaust (pacesetter header exhaust) all was fine except a rusted pipe connector just after the catalytic converter. I have replaced that with no resolve. Pulled off catalytic converter and looked through (yeah, I can see light, so nothing broken inside).

I cannot think of anything else. I am stumped.

Anyone got any other ideas I can try?

This is very frustrating!

Thanks

 

Any codes?
Crappy gas?
Is this only when warmed up?

 

Check your vacuum lines for cracked or broken ones also check your throttle position sensor voltage with a voltmeter. It should read about .54 volts. Also your IAC valve might be dirty or faulty as well.

 

Hey all thanks for the ideas. But I had checked all them before. Although I did find out what it was. It appears that I did have a spark plug going bad. It was still working intermitatly. The first time I tested it it was working. I had tested it again tonight and it was not. So needless to say replaced all the plugs with new ones and running again on all cylinders.

So apparently even if the plug looks good still has some spark, doesn't mean it is good in my case.

Yay

 

well dropping a cylinder due to no spark going to it will certainly do it

 

Good job in diagnosing the problem. Wires can be funny like that too. I recommend using AC/Delco wires for stock cars. I have put other brans even with lifetime warranties and they dont seem to last.

Kevin

 

even though you found the problem this brings up something similar that happened to me. there was water in my tank and when running about 1/8 of a tank it does that. and seafoam takes care of alot of problems like that. just for everybody's future reference. most often it is the simple things.

 

I have found that both 2nd & 3rd Gen's eat Ign parts like candy and often need changed before you would think its time. And always a good place to start checking when ya have no codes.