Thread: Lack of power and poor throttle response

Hi, hoping that someone can give me some ideas on what next...

I have an 89 Rangie that I have recently swapped in a 3.9 V8 from a 97 Discovery. The engine has been rebuilt using standard parts and mechanically seems happy. I am using the wiring and ECU from the Discovery

I seem to be having some issues getting it tuned up right though. It will hunt at idle (not all of the time, but most of the time) and has really bad throttle response. it will rev freely in neutral, however in drive if you boot it nothing happens, you have to very slowly feed in the throttle for it to rev.
It also seems to be running fairly rich in neutral.

Over the weekend I have checked most things i can think of:

1. Reset TPS - 0.31V at no throttle, 4.96V at full throttle
2. Checked fuel pressure regulator - no fuel coming out the vacuum hose and applying and releasing vacuum changes the idle significantly (sorry no fuel pressure guage)
3. Checked and cleaned the crankcase breather "T" piece
4. Set base idle by blocking the stepper motor and adjusting with a good digital tacho to 525 RPM. Idle stepper motor and the whole manifold were cleaned up pretty well during the rebuild
5. Adjusted MAF CO value to 1.4V
6. Tried two different MAF sensors, the 5AM from the 97 Discovery, and the 3AM that was originally on the car. With the 5AM the idle was really bad and I couldn't get it to idle at all with the idle stepper motor blocked. With the 3AM I was able to set the idle speed and it did seem a bit better, but still not right.
7. Checked coolant temp sensor, had 280 ohms at 83 degrees, factory spec says 300-400 at 80 degrees, so maybe this is slightly out, but seemed fairly close.
8. Fuel temp sensor showed 9000 ish ohms at 50 or so degrees, seems reasonable, but I am fairly sure that this only affects start up anyway (atleast in the world of Nissan that I am more used to)
9. Checked neutral signal to engine ECU - continuous to ground in Park and Neutral and open line in all others
10. Set timing - 8 degrees BTDC, and checked that the bob weights were still attached by twisting the rotor button gently, it springs back to position nicely. Vac advance is also working properly.

My next idea is to get some MAF sensor cleaner and give both MAF sensors a good clean out, however I had driven both cars before the engines were removed and neither of them showed the symptoms I am having now. I can accept that one of the MAFs might have gone bad in the time of the swap, but both seems like a stretch.

I did notice as well that the timing seems to be jumping around a bit at idle, but I'm not totally sure. I think that i can see the mark occasionally drop to like 12 degrees AFTER TDC every now and then, but its in a ***** of a spot to see and i can't be sure. I had my dad (also a mechanic) double check it and he thinks it was OK...

FYI the original engine was removed due to having a miss (suspect worn cam) and the disco engine came up cheap. But then when I was doing some preventative stuff to the disco engine it was found to be a bit more worn out than I expected, so it got new rings, bearings, cam and lifters, oil pump etc. However the Disco drove and idled nicely before the engine came out. ALSO the Rangie is an Auto and the Disco was a Manual.

Any suggestions appreciated!

Did a mud wasp build a nest in the return fuel hose? Raised pressure may be your problem. Check it with a pressure gauge if needed.