Rough idle after installing mods

[Irish Pride]

This past weekend i changed the valve cover gaskets, and changed the plugs and wires on my 91. While i was at it i decided to go ahead and install my ported intake and BBBs. Now that i have it back together it runs fantastic and i can literally notice the difference, but it has a rough idle now too. It seems like it struggles to start now and when i just let it sit and idle it surges a little bit. In gear while driving it runs great. Just when sitting still the needle on the tach will start to wiggle. Its not much but it is noticable. Is this normal when installing a PP intake and BBBs?

 

[SuperHO]

have you reset the ECU and let it relearn the idle?

 

[Irish Pride]

have you reset the ECU and let it relearn the idle?

No i havent. Whats the process?

 

[CademiaX]

have you reset the ECU and let it relearn the idle?

+1 on the idle reset

1) Disconnect the negative battery terminal.
....Optionally, disconnect the keep alive memory (KAM) connector in the small
....wire also landed to the negative battery terminal.
2) Wait at least 30 seconds.
Idle Speed Program Reset Procedure
4) Reconnect the KAM connector or negative battery terminal.
5) Start engine normally (never press the gas pedal).
6) Allow the idle speed to settle for at least 30 seconds.
7) Within 70 seconds of starting the engine, concurrently apply all accessory loads.
....a) Climate control to MAX A/C.
....b) Headlight switch ON, brights ON.
....c) Turn steering wheel slowly ~1/4 turn side to side.
....d) Press brake pedal.
....e) ATX SHOs only: shifter to DRIVE.
8) Do not turn off engine for at least 5 minutes.

 

[SHOtime2511]

vac leak.

 

[rubydist]

or bad engine ground. my white 94 had a problem w/ jumpy tach needle due to a bad ground between the intake manifold and the firewall.

 

[Irish Pride]

or bad engine ground. my white 94 had a problem w/ jumpy tach needle due to a bad ground between the intake manifold and the firewall.

Well, heres what its doing now. The rough idle has turned into an intermittent miss. It still wants to start rough. Before this past weekend as soon as i turned the key it fired right up. Now i have to turn the key 2 - 4 times to get it to start. Once started it still has a rough idle, but now while i'm driving it will start to miss really bad. Its so bad that it loses all power. If i try to give it any gas the front end just starts to shake very violently. All i can do is hold the clutch in and coast and wait for it to clear up or turn the ignition off. If i turn it off and restart it it will usually run good for a bit but the miss will eventually come back. While it is missing the tach goes to zero. It doesnt read any rpm's while its missing. When the miss goes away the tach starts to work again.

I did the idle reset and it didnt do anything.

 

[SuperHO]

then brian may be right...check for vacuum leaks.

 

[Irish Pride]

I've been reading up in different threads about similar problems. Since it started after i pulled my intake i am thinking it might be a ground issue. There is a ground that connects onto the back left part of the intake. I remember removing it to pull the intake. I know i put it back on but maybe i didnt put it on in a good enough position. If that doesnt fix it then i will swap out the Camshaft position sensor tomorrow too. I also plan to change the fuel filter.

I would like to add that the back plug wells were full of oil when i pulled the plugs. I've read that oil leaking from the valve covers can cause the cam sensor to fail. Is this a likely senario?

 

[SHOmethewayhome]

usually oil leaking on electrical parts can cause issues.

double check your grounds, make sure all your plug wires are secure, and check for vacuum leaks. is your car EGR? when i had my intake off for the top 60K it ran like crap when i forgot to put the gasket in with the EGR to the intake.

if it ran fine before you did the work, then it should be pretty simple to track down what you screwed up to make it run like crap.

 

[Irish Pride]

Now that i think about it i do remember having some starting issues and misfiring issues before i pulled the intake. Those are what caused me to check the plug wells in the first place. I'm gonna go ahead and change the CID and see what happens.

 

[shobote]

Fix what needs fixing, as oil in the plug wells will create problems if it is not remedied, like damage to the plug wires, which you just replaced.
Check to make sure all the hose clamps on the couplers on the intake are tight, there are no cracks in any of the couplers or any of the small vacuum hoses, and make sure all the little vacuum hoses are connected. This sounds like a vacuum issue when the idle is surging around. If the couplers and hoses are the originals, they probably need to be replaced ayway, and SHO source has them in stock.

 

[SHOtime2511]

You don't have to make things more complicated than they are,listen to the advice everyone is giving you before you throw parts at your car.

A small amount of oil will not cause a cam sensor to fail.
seriously though,check that ground strap it is vital to a correctly running engine.
Where are you mounting it on the intake? The location is also important .
If it is correctly mounted,Id bet money you have a vac leak.

 

[frosho]

Well, heres what its doing now. The rough idle has turned into an intermittent miss. It still wants to start rough. Before this past weekend as soon as i turned the key it fired right up. Now i have to turn the key 2 - 4 times to get it to start. Once started it still has a rough idle, but now while i'm driving it will start to miss really bad. Its so bad that it loses all power. If i try to give it any gas the front end just starts to shake very violently. All i can do is hold the clutch in and coast and wait for it to clear up or turn the ignition off. If i turn it off and restart it it will usually run good for a bit but the miss will eventually come back. While it is missing the tach goes to zero. It doesnt read any rpm's while its missing. When the miss goes away the tach starts to work again.

I did the idle reset and it didnt do anything.

Tell-tale symptoms of a failing cam sensor right there. That's definitely the first thing I'd look at.

 

[Irish Pride]

Tell-tale symptoms of a failing cam sensor right there. That's definitely the first thing I'd look at.

Thats what i thought too. I unplugged the sensor and the car still started up. It still had a rough idle but the miss was gone. Drove it for 15 - 20 min and it didnt miss one time. Plugged the sensor back in and within 30 seconds it missed on me. I'm waiting on Autozone to get one from their hub and then its going on.

Couplers are all new. The vac hose to the fuel rail is good as is the one that goes to intake near the throttle body. What other vac lines am i looking for?

 

[SHOtime2511]

get a can of carb cleaner and spray around the couplers,gaskets,hoses,ext.
when the idle jumps,you have found a leak.

 

[Irish Pride]

Well, the CID did the trick. She's purring like a kitten now. I remember it gave me some trouble starting and missing the day i checked the plugs. Thats why i checked them in the first place. The back plugs were swimming in oil so i just figured that was what was causing the miss. If the CID didnt start to mess up i never would have checked the plugs. Funny how things always seem to work out.