1998 P38 - Lack of acceleration at speed/uphill

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jjbusch

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I have a new-to-me 1998 P38 purchased for a song with the intent to either fix or part out. The one item that still needs to be identified and fixed is a power / acceleration issue. I have been told different things by a couple of different non-Rover mechanics and would like to see if anyone here might have seen this before.

Here is what I am seeing, based on observations over a 70 mile trip taken today up into the mountains outside Seattle, all of which appear to be pointing to the same problem:


  1. Going up a long grade of about 2 miles & starting the grade at 70MPH, the speed slowly reduces. I noticed that RPM was at 3500 (normally it is ~ 2500, so this was apparently due to a downshift). Stepping on the accelerator did not increase my speed, instead, the car actually slowed down a bit due to hesitation that occurred when stepping on the gas. At this point, about every 10 - 20 seconds there was a very small "surge", which could be felt and actually causes speed to reduce a little bit more. I ended the grade doing 45MPH.
  2. Going up a short grade, started grade at 70mph, the speed started to reduce. Stepping down harder on gas caused a bit of a hesitation and speed dropped more. RPM at < 2500 and finally about 55MPH, downshifts and RPM goes to 3,500, but no noticeable improvement in "umph", speed continues to drop.
  3. Going down grade at 70 MPH, let off accelerator and the RPM drops to 2,500, then about 2-3 seconds later, feel a bit of a "hesitation" and the rpm goes to ~2,750. Was able to repeat this at will coming down grade several miles. Tested doing the same thing on flat ground and I do not feel the hesitation or have an increase in RPMs.
  4. Driving on flat ground, step on gas. "Hesitation", no downshift, and speed begins to drop. Let off gas and slowly press accelerator, and car begins "responding" at consistent speed.
  5. Getting onto freeway, step on gas and car hesitates and acts sort of like it is flooded. Slowly step on accelerator, giving a little more gas every couple of seconds and car slowly gets up to speed.
  6. Cruising on flat ground at speed, no apparent issues. Also, car starts off the mark fine, gets to about 20 MPH and then I start seeing the hesitation.

Thoughts much appreciated!
 
I assumed petrol as they didn't sell diesel P38s over there - and he expected it to be able to go uphill without the throttle pedal welded to the floor! :)

I'd suspect airleak on the inlet side or MAF.
 
Today I cleaned the MAF using CRC cleaner. Cleaning the MAF definitely helped, but I would say it improved by at least 50%. When I looked at the MAF, the sensor cables were gray. After cleaning, I can now see the copper and yellow.

Flat ground acceleration, while not quite as good as I would expect, is now acceptable, and much improved from before I cleaned the MAF. I did not get a chance to test on the long freeway grades, but on a short 10% grade at 35 MPH, power went down and car would downshift briefly and then upshift. I dropped transmission into 2nd and rpm jumped to 3500 and car began gaining speed. So, with this experience on the short 10% grade, I do not believe all is fixed yet.

Are there other suggestions, or does this still sound like a MAF issue, and thus a replacement might be in order?

I am contacting an independent Land Rover repair shop this week to schedule a diagnostics apt to pull codes and reset anything that is needed.
 
jjbusch said:
Today I cleaned the MAF using CRC cleaner. Cleaning the MAF definitely helped, but I would say it improved by at least 50%. When I looked at the MAF, the sensor cables were gray. After cleaning, I can now see the copper and yellow.

Flat ground acceleration, while not quite as good as I would expect, is now acceptable, and much improved from before I cleaned the MAF. I did not get a chance to test on the long freeway grades, but on a short 10% grade at 35 MPH, power went down and car would downshift briefly and then upshift. I dropped transmission into 2nd and rpm jumped to 3500 and car began gaining speed. So, with this experience on the short 10% grade, I do not believe all is fixed yet.

Are there other suggestions, or does this still sound like a MAF issue, and thus a replacement might be in order?

I am contacting an independent Land Rover repair shop this week to schedule a diagnostics apt to pull codes and reset anything that is needed.
Click to expand...

Buy yourself an Nanocom and do your own diagnosis
 
Last edited:
Sorry for the delay in responding.

Plugs/wires were changed about 2k miles ago, per the person I purchased the truck from.

I had a chance today to take the same route as previously mentioned. this time, I was able to maintain 70 MPH uphill, but couldn't push it much past that, so there is still an issue.

I have an appointment for a diagnostics on Tuesday, but can cancel if it makes more sense for me to purchase my own diagnostics device. If I go that route, what one should I purchase? Is there a preferred vendor (i.e. cheaper)? Is there anything to look out for when purchasing so I don't waste money?

Thanks!
 
I had a '97 Gems and my wife had a '99 Thor. The difference between them was night and day as far as drivabily and acceleration was concerned. Diagnostics never helped explained the difference and I never managed to get to the cause. I doubt that the difference was just down to the different ignition systems.
 
jjbusch said:
Sorry for the delay in responding.

Plugs/wires were changed about 2k miles ago, per the person I purchased the truck from.

I had a chance today to take the same route as previously mentioned. this time, I was able to maintain 70 MPH uphill, but couldn't push it much past that, so there is still an issue.

I have an appointment for a diagnostics on Tuesday, but can cancel if it makes more sense for me to purchase my own diagnostics device. If I go that route, what one should I purchase? Is there a preferred vendor (i.e. cheaper)? Is there anything to look out for when purchasing so I don't waste money?

Thanks!
Click to expand...

Nanocom Evo i think maybe the best bet.
 
Maf sensor would be my bet. My previous P38 had exactly the same issues on long uphill stretches. Renewed the Maf and it was like a new engine was under the bonnet(hood). The fact you've cleaned it and found improvement would suggest it.

Ideal situation would be to swap for a known good unit to test, failing that a new one from Atlantic British is $227.

And from memory diagnostics doesn't show a Maf fault 100% it just gives you clues that point in that direction. Although it was several years ago that I changed mine so my memory might have dulled somewhat.
 
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