Last resort for my p38

[JayNadell]

I own a 98 4.0 p38. It is currently sitting at the dealership. I took it in due to rough running , excessive gas mileage , foul smelling exhaust as the main symptoms. Check engine light is on and has been for quite some time. After nearly 2 weeks of diagnosis, the stealer-ship is now telling me the o2 sensors look fine and they have narrowed it down to a faulty ECM causing the poor performance . Quote for part alone is 3300 dollars! Wtf! I am really at a loss for words at this point....I am really trying to decide if I should attempt to fix this or just send it down the river. Love my rover but it has many other minor common issues too. If I can get the engine back is shape I will keep it but what is everybody else's opinions ? Thanks for any and all help. Thanks J in Sarasota .

[RRToadHall]

Sadly that is expected when you send an older rig to the dealership for diagnostics and "repair". If you are not up for learning about your rig and getting dirty it sounds like it is time to find something else. If you take the time to do some research and make many repairs yourself there is hope for the old girl. For instance installing a used ECU and syncing the ECU to the BeCM can be done for a couple hundred bucks.

[wreckrunner]

Beg, borrow or steal one of those laser temperature guns.... get underneath with the engine nice and warm after your drive home from the dealer/stealer.... and aim the temp gun in front of the catalytic convertor, write down the temp then aim it at the rear of the same cat, if the temps are similar the cats are bad, it should be hotter at the rear or outlet of the cat! Look at the stickies at the top of this forum and see if there is an independant repair shop in your area with a good reputation. With all of the vendors on here and the availability of good aftermarket parts and discounted original parts (Worldpac) there is little if any need to go to the dealer!

[SpiggyTopes]

Bosch ECU is 500 USD -- not sure about the earlier type.

Don't trust the dealer!!!

[carcharodon]

How many miles? Whats the rest of the motor look like? There are many more variables for a fault here. First is you're trusting the dealer. Did my timing chain at 210k miles, took care of the lights and foul exhaust, more pep idled better (see where I'm going with this?) then the liner slipped . If you haven't the funds to keep after a Range Rover, the where withall to diagnose on your own or have a really good independent Rover tech to keep after your truck you are better off selling it or parting it out and getting something less temperamental. To be honest, I would NEVER suggest anybody buy a Range Rover unless they were mechanically inclined, I am a mechanic I'm on my second RR and I am looking at a 3rd.

[Rowant]

I agree with carcharodon on this one but I also question the build quality of some of the systems. Great ideas but not thought through properly.

Anyway I have done a little investigation and suggest the following:
Firstly get it away from the dealer! - you want service not ´servicing´.
More than the odd problem like you describe has be traced back to faulty ignition leads (1 or more). I am not saying this WILL be the answer but it appears to be a good place to start. Bad leads or connections causing lack of spark hence rough running and bad mixture burning - O2 sensors messed up and so it runs and smells like a bucket of manure.
If you don´t mind getting your hands a little dirty then try checking all the connections starting where the leads plug into the coils. One of mine was burnt with arcing and so a replacement coil cured that. Then, with the engine running, pull each lead off it´s plug to see if the revs drop. Try idling it at night with the lights off so you can easily see if there is any tracking or arcing of voltage around the leads etc. Maybe remove all the leads so that an electrician can measure them to see if they are broken (or breaking up) inside.

I am not saying this IS the answer but it will save your sanity and might just give a warm fuzzy feeling if it works.

[carcharodon]

Not to assume anything here... were the plugs changed, just asking. MAF?

[getlost4x4]

are the catalytic converters dead and plugged?

That is usually a reason for rotten egg smell. and the engine may be running to rich because it can't get the exhaust gas out.

How is the engine temp? is it above half way a lot of the time?

I wouldn't trust the dealer. ITs an OBDII vehicle. you can hook a scan tool to it yourself and pull the codes. Don't waste your time with this stealer.

[spikemd]

Get it back from the dealer. That is a ridiculous diagnosis. It is probably something relatively simple and paying $3000 for one part on a P38 is unbelievable and I will bet a lot of money, won't fix your problem.

Do some diagnostics yourself and then take it to a reputable independent shop if you can't fix it yourself. You will pour much more money into the truck than it is worth if you can't fix it yourself. Go to a local auto parts shop and borrow their OBDII reader or buy one for $30. Check everything posted above.

How many miles? What year is the truck? What recent maintenance has been done?

[JayNadell]

So I picked up the rover from the dealer with little more than tHe diagnosis being that the ecu is faulty. I immediately went to a independent guy who hooked it up and came to the same conclusion. While the car is running and drivable, all the reading while on the scanner indicate no switching of o2 sensors and maf is not operating in the correct range. He said it is more than likley the problem as well. (took him 10 min and no charge btw. Stealership got me for 300). So, now what? The indepentant guy said I didn't have to many options due to the interaction of the other computer systems in the rover. I am on the fence with this one. Any links to ecu becm repair or replacement would be appreciated. Thanks again J

[RRToadHall]

As outlines above, buy a used ECU and your indie install it and sync the ECU/BeCM code. Should take all of 15 mintues. It really is not that big of a deal and not nearly as dramatic as it sounds. You can also buy a SyncMate or similar plug in device and install an ECU yourself then sync it.

[glenhendry]

Agree with above, get a new ECU. Here is one. Then buy or borrow a syncmate or faultmate and get the new ECU talking to the BeCM. (The immobilisation codes have to match). Then drive off happy. I have never heard of all the sensors being fine and the ECU messing up their signals though. Id be pulling the ECU and BeCM and carefully checking and cleaning and tightening all connectors and terminals. More likely an errant earth is messing the data somewhere?

[LarryS]

the ECM is imo a very rare failure, i would before all else check those sensors/wiring, it is starting and running after all, whats actually failed? what does the live data show? it seems alot more could be done and checked before such a drastic resort is called for.

[Trionic]

on the scanner indicate no switching of o2 sensors and maf is not operating in the correct range.

If your MAF is bad, reading an artificially high mass value, then the ECU will call for fueling to match air that isn't there. If you have too much fueling, then you're going to be running rich, and if you're running rich then you won't see any O2 sensor switching and the symptoms that you're describing. What data says your MAF is good vs. the controller being bad?

Nothing you've written indicates a bad control unit exactly. It might be that, but there's a bunch of other stuff that could cause the same symptoms it just seems like there's some information missing. Like, what codes are you seeing over the OBDII connection, exactly?

For instance, like GetLost wrote, if your thermostat is stuck open and running too cool, then your truck will run in warm up enrichment mode indefinitely which can cause everything that you're describing. What does your coolant temperature look like?

Or if your plugs or wires are bad, then you'll be seeing misfires and dumping raw air with unignited fuel, which will cause running that's too rich, because the O2 sensors are seeing all that raw unburnt O2, indicating a false lean condition to which the controller responds by injecting more fuel...also causing all the symptoms you're describing.

[wreckrunner]

Lets not rule out rodent damage too! X2 on what Glen suggested about the grounds!