1994 SS 4L60E Help

[VZB]

I've got a 94 Impala SS with 6500 orig miles. My first trip in the car was a 500 mile journey home and I noticed what felt like a "miss" every once in awhile. Other than that it runs perfect. I drive the car very little but occasionally I stretch its legs. Lately I've notice the "miss" happening more often. One day while on the interstate I could "feel" a resonance like the RPM's were higher than they should so I turned down the radio and listened to the drivetrain as I was cruising along 70mph. It felt like I wasn't in overdrive but with a 3.08 gear sometimes its hard to tell......anyway I pulled the gearshifter down into D (3rd gear) and it didn't downshift. When I placed the gearshifter back in OD (4th gear) it upshifted normally, RPM's dropped and the resonance was gone. A few minutes later it started that "miss" again but this time I was more intuitive, what's happening is the tranny jumping in and out of OD which feels like an engine miss (clogged injector, etc). Sounds weird I know but thats the best I can explain it. The fluid is original (14 years old) but 6500 miles. I've not read where anyone else has experienced this. Any guidance would be appreciated.

[maxwedge]

A full scan with a trans functions scanner will reveal any issues with the trans loosing o/d or tcc, remember a misfire can cause a down shift as the pcm detects the additional load on the engine.

[j cAT]

Originally Posted by VZB

I've got a 94 Impala SS with 6500 orig miles. My first trip in the car was a 500 mile journey home and I noticed what felt like a "miss" every once in awhile. Other than that it runs perfect. I drive the car very little but occasionally I stretch its legs. Lately I've notice the "miss" happening more often. One day while on the interstate I could "feel" a resonance like the RPM's were higher than they should so I turned down the radio and listened to the drivetrain as I was cruising along 70mph. It felt like I wasn't in overdrive but with a 3.08 gear sometimes its hard to tell......anyway I pulled the gearshifter down into D (3rd gear) and it didn't downshift. When I placed the gearshifter back in OD (4th gear) it upshifted normally, RPM's dropped and the resonance was gone. A few minutes later it started that "miss" again but this time I was more intuitive, what's happening is the tranny jumping in and out of OD which feels like an engine miss (clogged injector, etc). Sounds weird I know but thats the best I can explain it. The fluid is original (14 years old) but 6500 miles. I've not read where anyone else has experienced this. Any guidance would be appreciated.

if it is miss firing and it has the original non vented opti distributor and having been sitting for a long time I would jump on the water pump leaking on the opti distributor causing misses that throw tranny out of OD..... do you have any pictures? was this original or modified impala ss you purchased.

[VZB]

Originally Posted by j cAT

if it is miss firing and it has the original non vented opti distributor and having been sitting for a long time I would jump on the water pump leaking on the opti distributor causing misses that throw tranny out of OD..... do you have any pictures? was this original or modified impala ss you purchased.

I've read where the 94 B-bodies have the vented opti and mine is a late production (6/94). Theres no coolant under the car so I presume the pump is tight. It's bone stock. It does "feel" like a miss but why didn't the tranny upshift back into OD (the engine was running smooth when I noticed it was staying in 3rd gear). Should there be codes on the ECM? It's confusing.

[j cAT]

Originally Posted by VZB

I've read where the 94 B-bodies have the vented opti and mine is a late production (6/94). Theres no coolant under the car so I presume the pump is tight. It's bone stock. It does "feel" like a miss but why didn't the tranny upshift back into OD (the engine was running smooth when I noticed it was staying in 3rd gear). Should there be codes on the ECM? It's confusing.

before you start vehicle on overnight shut down place index finger under water pump for red anti freeze at weep hole if its there its bad....



lets say you saw a puddle under the engine and this was because the water pump seal was leaking, do you think it would start ????? well if it did thats on hell of and opti distributor ....


what i'm saying is you know its leaking because the engine misses and you can't even feel the misses but the computer is counting them and it reacts......

[j cAT]

Originally Posted by VZB

I've read where the 94 B-bodies have the vented opti and mine is a late production (6/94). Theres no coolant under the car so I presume the pump is tight. It's bone stock. It does "feel" like a miss but why didn't the tranny upshift back into OD (the engine was running smooth when I noticed it was staying in 3rd gear). Should there be codes on the ECM? It's confusing.

on an unreleated issue with these vehicles the rear diff needs the oil replaced now and also the correct diff cover gasket that has holes in it for wheel bearing drain back to diff..if this is not done the rear wheel bearings will fail at 25-35,000mi..... if you do high speed driving it will fail at the lower mileage.....this needs to be monitored for graying of the oil and replace as needed... i found after 40,000mi and replacing this oil 3x it stabilized.....





obviously you will need to replace the dexcool as the coolant has a shelf life of about 8years.....to do this completely drain radiator then remove the knock sensors, after that use an air supply and blow out heater core....you will need 2.5 gallons of coolant as the system holds 4.25 gallons...use only distilled water and dexcool....i would also replace thermostat at this time since this will be good for 5years.....

[VZB]

I checked that weephole for moisture like you suggested, it's dry. I read they didn't start using Dexcool till 96 in the Imp, mines the "green" stuff but I will have it changed. Thanks for the reminder on the rear cover gasket. Wouldn't happen to know a P/N? The next time I drive it I'm going to leave it in D (3rd gear) and see if it acts up. If it does I'll know it the engine, if not I'm going to focus on having the trans checked. I'll also check that weephole periodically. Thanks.

[j cAT]

Originally Posted by VZB

I checked that weephole for moisture like you suggested, it's dry. I read they didn't start using Dexcool till 96 in the Imp, mines the "green" stuff but I will have it changed. Thanks for the reminder on the rear cover gasket. Wouldn't happen to know a P/N? The next time I drive it I'm going to leave it in D (3rd gear) and see if it acts up. If it does I'll know it the engine, if not I'm going to focus on having the trans checked. I'll also check that weephole periodically. Thanks.

another item that should be replaced is the exhaust manifold check valves these go to the electric air pump. if these check valves fail exhaust gases get into the electric air pump and cause failure this happened to me you will get check engine light and it also causes contaminates to coat the MAF which now that i think of it could also cause a miss.....the air pump runs on start up for 5min. this is supply the cat converter air to reduce pollutants.


the check valves last 5 years as the heat/age causes the rubber to crack.....mine failed at 30,000mi 7years old.........got 53,000mi now...