[mjassows]

I have an intermittent problem with my Nissan Altima '96 GXE 2.4L A/T 153K miles:

After driving for a few minutes, I loose power with the engine above 2000 RPM (exactly). Below 2000 RPM, engine / transmission behaves normal, even at speeds of 40MPH (under light load/low RPM). Attempting to increase RPM to above 2000, causes engine speed to oscillate at 2000 RPM (Freq=~2/sec). This occurs at any vehicle speed including park.

I believe it is some kind of engine control issue, since when I turn off the car and let it sit for 15 seconds, the problem dissappears. I have replaced the fuel filter to rule this out as a cause, but did not believe that this was the culprit due to the precise way this failure occurs, and the ability to return the car to normal operation with a simple 15 second rest.

The first 6 times this happened, MIL light did not turn on, and no OBD-II codes were registered.
This morning, the problem did not occur, but the "check engine" light turned on, and 3 OBD-II codes were recorded:
P1900 "Manufacurer Contrl. Transmission" (SIC)
P0733 "Gear 3 Ratio Incorrect"
P1900 "Manufacurer Contrl. Transmission" (SIC)

Looking at sites with OBD-II codes for Nissan, P1900 appears as "Cooling Fan", so this is somewhat confusing.

Extensive searching on the web has turned up no pointers other than possibly TSB: 97-028 :
MIL ON - DTC P0731,P0732,P0733 (A/T Signals) No Symptoms. (although I'd have to admit, I do have a few symptoms -- although not when the MIL came on). I'm not able to locate the full text of the TSB.

Any assistance would be greatly appreciated!
Thanks,
--Michael

 

[mjassows]

Car overheated, now in shop

On the way home friday, the car overheated. Had the car towed to the nearest Altima dealer, and they diagnosed a cracked waterpump housing. After they completed the repairs, it still overheats, so they are looking into whether it may be related to the head gasket.
I'm thinking the RPM limit to 2000 was the controller's attempt to keep the engine from overheating further, although I am a bit confused as to why no PCM codes were reported for the first few times this happened, and temp gauge read normal.
Anyway, it sounds like this repair may be more than the car is worth...sigh -- it was a great car...
--Michael

 

[mjassows]

All,
Thanks for your help. Here's the current status:
The engine runs, but *very* rough. There is steam in the exhaust, and 180ppm of hydrocarbons in the coolant, indicating a head gasket failure, possibly worse. The exhaust manifold is cracked. Steam escapes from the engine near the exhaust manifold. On the (very slow) 6 mile drive home I had to stop half way to allow the car to cool enough to see through the steam, although the engine temp registered only a bit over where it normally registers.

The dealer recommended a re-man engine which runs about $4K including labor (approx $930) -- that is, if I were to do anything at all.

I'm guessing that at a minimum this will require a new head gasket and head resurface (along with a new manifold). I'm thinking about possibly attempting to rebuild this myself as a project (I knew there was a reason I cleaned out the garage .

So here are my questions:
1) Am I nuts?
2) I'm guessing that there won't be much material cost in tearing down the engine, and I'll decide whether or not to rebuild depending on the extent of the damage I find. What potential hidden problems should I be on the lookout for? It would be a bummer to repair the head, and get it all back together to find that there was some other problem lurking (like the shop did).
3) What diagnosics should I run while the engine still "works" to help me pin-point items which need replacing? (Compression values, anything else?)
4) What special tools should I have on hand for this project?

I'll definitely get the Haynes repair manual and give it a thorough review before starting.
--Michael