| Author | Message | ||
     John Wester (Johnw94) New Member Username: Johnw94 Post Number: 1 Registered: 10-2003 |
Hi all, I thought the collective intelligence here could give me some insight into a nagging Disco I problem. My 1994 Discovery with 5 speed and 197,000 miles on the clock, has a serious hesitation/sputtering problem between 2000 and 3000 rpm under load. Idles fine & revs fine at a stop. Under load over 3000 rpm, the sputtering stops & I can run it to the red line(something near 100mph in 4th). I figured some basics needed to be changed after so many miles, so I replaced the distributor cap, plug wires, plugs, ignition coil, ignition amplifier, and fuel filter, in sequence, but did not see a remedy yet. I checked the ignition pick up in the distributor, but it's fine at 3.5K Ohms. Checked for intermittent grounding issues in the ignition wiring loom but came up blank. I'm sort of leaning to a fuel delivery problem either in the pressure regulator or fuel pump. What do you all think? | ||
| carl seashore (Drcarl) New Member Username: Drcarl Post Number: 37 Registered: 07-2003 |
john, another place to look is your O2 sensors. they can adversly effect fuel delivery if they are out of whack. any p-codes (is check engine coming on)? cheers, carl | ||
| Randall Smith (Mr_smith) Member Username: Mr_smith Post Number: 103 Registered: 04-2003 |
If the problem occurs at specific rpm, not specific speed, then it is most likely the alternator. | ||
| Bill Howell (Billh13) Member Username: Billh13 Post Number: 238 Registered: 03-2003 |
Please exsplain the alternator being the problem. | ||
| Randall Smith (Mr_smith) Member Username: Mr_smith Post Number: 105 Registered: 04-2003 |
I can't explain it because I am not an electrical engineer. However looking at the overall EFI system; you have inputs, a computer and outputs. Every piece of the system is voltage sensitive. The alternator is the only device in the EFI system which can fail at a specific rpm. If the voltage from the alternator falls outside of specs(which is monitored by the ECU), then chaos will occur in the EFI system. You will have to devise an experiment to show that the problem is rpm related, and that it can be repeated to prove it is rpm related. If the problem is simply hesitation under light accelleration, then it might be a problem with the charcaol canister system, or TPS. Randall | ||
| John Wester (Johnw94) New Member Username: Johnw94 Post Number: 2 Registered: 10-2003 |
Thanks for the all the replies. I replaced the alternator about six months ago. I did a quick check but it seems to be maintain appropriate voltage throughout the rpm range, it was pretty steady. I'll keep you all posted on what I do next, probably the fuel pressure regulator. | ||
| John Wester (Johnw94) New Member Username: Johnw94 Post Number: 3 Registered: 10-2003 |
Finally got to change the fuel pressure regulator with a new one but no luck yet on my problem. I did notice an exhaust leak I didn't have before this problem started...hmmm might be O2 sensor related after all. | ||
| David D Banicz (Dave_banicz) New Member Username: Dave_banicz Post Number: 15 Registered: 11-2003 |
Have you considered the speed sensor? | ||
| David Ohlberg (David_o) New Member Username: David_o Post Number: 6 Registered: 08-2003 |
Replace your vacuum advance unit NOW. I had same symptoms with 98 V8 manual at 176k. Try removing the small black vacuum hose from the intake manifold end, with motor off, & suck on it to see if it will hold a vacuum. Mine pulls like an Aussie built V8 supercar now, even while it's running on turpentine, or whatever it is they sell at the pumps here. Hope it helps. | ||
| John Wester (Johnw94) New Member Username: Johnw94 Post Number: 4 Registered: 10-2003 |
Haven't thought about the speed sensor. I have noticed a small flickering of the speedometer when I'm going about 75-80 mph, although I had that since new. I checked the fuel pressure at idle and it holds a steady 36-38 psi, reving at idle to 2000 rpm causes the pressure to drop to 28 psi or so. It held 38 psi of pressure in the line for at least 20 minutes after shutoff. I'll checked the vacuum advance(retard) unit next. | ||
| John Wester (Johnw94) New Member Username: Johnw94 Post Number: 5 Registered: 10-2003 |
Well I checked the distributor vacuum unit and it was in good shape. Decided to remove the upper manifold housing and examine more closely. I did find a boogered up IAC valve which I replaced. Cleaned up the rest of the ports with carb cleaner, cleaned the emissions control t-restrictor and reassembled. Took it out for a test and it was fine until it warmed up then it went back to sputtering between 1900 and 2200 rpm. Guess I'll try changing the O2 sensors next. I haven't a clue what to do after that. |
