1992 caprice runs rough

4evrbad · #1 02-09-2009, 05:08 PM

Hello to all, I have a 1992 caprice tbi with the 350 engine. The car runs rough at times, it is not consistent but almost seems to be getting progressively worse. It takes longer then normal to start it when the engine is cold, when warm it starts easily. While the car is parked or in drive when it is running badly the tach will bounce a bit but the engine usually doesnt die. While accelerating the car is a bit jerky, and lacks power, as if its running on 3 cylinders, while running poorly i can throw it in nuetral rev it up and acts as if its running well, put it back in drive and runs rough. I have replaced many, many parts and am still cluless. The service engine soon light comes on and I get code 44 which to my knowledge is lean exhaust. I have been thinking about replacing the fuel pump and fuel filter but I'm guessing at this point. It has new oxygen sensor, egr valve, egr solenoid, idle air control motor, cap, rotor, plugs, wire set, distributor, ignition coil, and a few others im forgetting. The fuel filter was replaced about 2 yrs back put 6k miles on it since. Anyone have an idea?

4evrbad · #2 02-09-2009, 05:10 PM

Forgot to add that while it runs like crap one day the next day I'll start it up and will run fine

soulmonger · #3 02-10-2009, 05:58 PM

Not positive that this is the problem but that sounds exactly like how mine was acting before I replaced the fuel pump. There is a good chance that yours is on the way out. I noticed that the fuel pump on my 1990 is about half the size of the one in my 89 prelude with a 4 cylinder so I think the slightest weakening in the pump may be pretty noticable performance wise.

4evrbad · #4 02-17-2009, 05:21 PM

Could be the fuel pump, it was tested at one point and had good pressure. When it runs poorly while accelerating why does it run great when i pop it in neutral and rev it, it seems to have all the fuel it wants? How could it be the fuel pump?

j cAT · #5 02-18-2009, 10:11 AM

Quote:

Originally Posted by 4evrbad

Could be the fuel pump, it was tested at one point and had good pressure. When it runs poorly while accelerating why does it run great when i pop it in neutral and rev it, it seems to have all the fuel it wants? How could it be the fuel pump?

when in gear you need the max fuel to engine your moving 4,ooolbs..in neutral no load min fuel..

you must drive around with the fuel gauge hooked up....what is the pressure.....? fuel pump grounds/relay etc...could cause erratic pressures

the other problem is the tach jumping this is usually a bad cps/connector/wiring...I have seen this before...

RageCage · #6 02-18-2009, 12:31 PM

my 2 cents. I had a similar problem. Jerky starts, intermittent. Once it was a vacuum hose with a tear in it. Fixing the vac hose fixed the prob. Another time it was a spark plug wire that had burned itself against the exhaust and was intermittently shorting out onto the exhaust and causing a miss.

4evrbad · #7 02-20-2009, 12:09 PM

fuel pressure was tested a few months back by my mechanic and was at 13 psi at this point he could not figure it out. Vacumn lines were checked no cracks or debri. Plug wires are new, no tears holes or melted spots.

Blt2Lst · #8 02-20-2009, 12:19 PM

Maybe you have an intermittent problem with the EGR valve.
Take it off and see if there is any carbon build up which could be causing the valve to stick open at times.

Just a thought

RageCage · #9 02-21-2009, 05:07 PM

Does that have OptiSpark computer? Is the waterpump leaking down onto the OptiSpark ?

Speaking of computers, my 1988 Trans Am ran real rough when driving, but idled sort of OK, and it was the computer that was causing the prob.

Let us know what happens.

Rage

4evrbad · #10 02-23-2009, 09:03 PM

No carbon build up by egr. All vacumn lines have been inspected. Also it does not have opti spark, wasnt on the caprice till 94 to my knowledge. car does have new distributor, cap, rotor, plugs & wires. The car Idles fine, just lacks acceleration while in drive. While accelerating the engine falls flat, like I said before I can pop it in neutral at any time and revs up perfectly.

j cAT · #11 02-24-2009, 09:27 AM

Quote:

Originally Posted by 4evrbad

No carbon build up by egr. All vacumn lines have been inspected. Also it does not have opti spark, wasnt on the caprice till 94 to my knowledge. car does have new distributor, cap, rotor, plugs & wires. The car Idles fine, just lacks acceleration while in drive. While accelerating the engine falls flat, like I said before I can pop it in neutral at any time and revs up perfectly.

block off the EGR valve...then see if the problem stops..if so it could be the EGR spring has weakened and is opening to much...

JohnTheEclectic · #12 02-28-2009, 04:11 PM

My 86 305 has the same problems, ie, runs fine one day, bad next, finally not starting at all. In fact, I'm having that problem now (won't start), which is why I'm on here. I have replaced the ignition module twice and it fixed the problem right away but then after time the same problem came back. Also was having the 'running 3 cylinders' problem and burning black smoke on those days. Next day everything would work fine. Still haven't fixed it but in short, try the ignition module in the distributor and if anyone else can help me, please do!
It's getting plenty of fuel. You can smell it after trying to start.

j cAT · #13 03-01-2009, 09:48 AM

Quote:

Originally Posted by JohnTheEclectic

My 86 305 has the same problems, ie, runs fine one day, bad next, finally not starting at all. In fact, I'm having that problem now (won't start), which is why I'm on here. I have replaced the ignition module twice and it fixed the problem right away but then after time the same problem came back. Also was having the 'running 3 cylinders' problem and burning black smoke on those days. Next day everything would work fine. Still haven't fixed it but in short, try the ignition module in the distributor and if anyone else can help me, please do!
It's getting plenty of fuel. You can smell it after trying to start.

repeated ignition module failures are high voltage arcing problems..

plug wires need be routed with protecting loom/resistance measured......also cap rotor cleaned with electronic cleaner NO CARBON,,,,this also needs the coil cleaned and connections secured ...

the the application of a dielectric grease should keep this from repeating..

JohnTheEclectic · #14 03-01-2009, 10:09 AM

Quote:

Originally Posted by j cAT

repeated ignition module failures are high voltage arcing problems..

plug wires need be routed with protecting loom/resistance measured......also cap rotor cleaned with electronic cleaner NO CARBON,,,,this also needs the coil cleaned and connections secured ...

the the application of a dielectric grease should keep this from repeating..

Thanks. Also all new rotor, distributor cap, coil, and lots of grease under module was done when replacing module. Reroute plug wires? Why would it run fine for 20 years and suddenly have a plug wire routing problem?

j cAT · #15 03-01-2009, 02:01 PM

Quote:

Originally Posted by JohnTheEclectic

Thanks. Also all new rotor, distributor cap, coil, and lots of grease under module was done when replacing module. Reroute plug wires? Why would it run fine for 20 years and suddenly have a plug wire routing problem?

I stated to use LOOM to protect the plug wires,when routing......the original wires had LOOM in areas of concern....routing should not change ...the original loom fell off 10years ago...

new wires don't mean sh*t.....I can't tell you how many times new went back to the store..all wires need resistance checks and should be close to the required spec....if you had this vehicle 20years then you should know exactly what the resistance should be ...when the resistance increases as age takes over this is the result..

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