'89 RRC rough idle

R

RKORES

Well-known member
Apr 21, 2004
155
0
Lowgap, NC
Ok, so here's the deal:

- In neutral with my foot on the brake the vehicle idles at a perfect 500RPM.
- In drive with my foot on the brake the vehicle searches for idle between 150RPM and 400RPM.
- At a stop light, it feels almost like it is going to stall out.
- Why would it be doing this in Drive but not in Neutral?
- Also if I am driving at say 1500RPM's and I let of the gas completely, the RPM's will quickly drop down to 500, and then up to around 1000...after that they will then come down like normal.
- Any clue as to what may be causing this?

- This summer I replaced the plugs, wires, cap, stepper motor (IAC), PCV hoses and T-piece.
- I have not replaced the flame trap.
- The belt to the alternator seems to be at the right tension.

Thanks!

Will Bobbitt
 
B

barefoot

Guest
i had a similar prob on a d1...strangely it turned out to be a broken gas cap!!!!! just throwing that one out atcha...
 
R

RKORES

Well-known member
Apr 21, 2004
155
0
Lowgap, NC
Chris,

Where would you recomend looking? I replaced the small hose that comes off of the plenum this summer.

Thanks,
Will
 
Chris-St Louis

Chris-St Louis

1
Oct 27, 2004
3,000
4
Tough to say, there are so many places. THe intake loostens up. Lines go back... Regualtors leak internally.

How is your intake? Is it leaking coolant yet? if it is, why not replace it. It gives you a chance to check everything, and it needs it anyways.

Bottom line. if it runs ok, but can't idle........ The engine is getting air the computer cannot compensate for.
 
R

RKORES

Well-known member
Apr 21, 2004
155
0
Lowgap, NC
I am gonna go over all this stuff tomorrow...To bad I gotta study for a calculus exam :( Thanks for your help guys! I will post back up once I can hopefully figure stuff out.

Thanks,
Will
 
R

RKORES

Well-known member
Apr 21, 2004
155
0
Lowgap, NC
Ok, I have done a few things but plan on doing some more work tomorrow. Just out of curiosity though, what is the deal with a vacuum delay valve? I was looking at some drawings and noticed it, but mine does not have it. On mine there is just the the vacuum hose between the plenum and the vacuum advance on the distributor. Could this be the source of my issues? Also, if I undo the plenum side of the hose, and take the cap off, shoud I be able to see the vacuum advance move if I suck on it? Also, what is the best way to clean the mass airflow sensor?

Thanks guys!

Will Bobbitt
 
R

RKORES

Well-known member
Apr 21, 2004
155
0
Lowgap, NC
Will,

I have done some searching around, and I cannot find a VSS listed in any of the parts suppliers catalogs. Any other name it goes by? How hard is it to replace?

Thanks,
Will
 
nosivad_bor

nosivad_bor

Well-known member
Mar 27, 2004
6,061
64
Pittsburgh, PA
shit i must have missed that.

um look for them thier vaccume lines again and i doubt its the VSS

Fuckit , i still say its the IAC change that bitch out again!
 
R

rrrandall

Guest
VSS/vehicle speed sensor/transducer. I think the part# is AMR3386 up to VIN# LA647644, AMR1253 up to the end of RRC. Verify before you buy according to year/model.

The VSS is the only original EFI part still on my 160K 92RRC(everthing else is new). It is not required to operate CU/CUX systems. I think that manual transmission Land Rovers of this era do not have a VSS. You can install a 500ohm resistor where the park/neutral switch is, and the ECU will no longer look for input from the VSS.

If you have an automatic trans truck, the idle can get all screwed up if the VVS is not telling the ECU whether the truck is moving or not. You can test VSS operation by rolling the truck a few feet while probing the wiring harness conector in the right places.

Randall
 
R

RKORES

Well-known member
Apr 21, 2004
155
0
Lowgap, NC
Ok,

After reading through the shop manual, it seems as if the VSS is part of the cruise control system, so I was finally able to find it. In saying that, my cruise control (knock on wood), seems to work perfectly, so would that cancel out the VSS? I will check it out on the ECU while I am checking the IAC just to make sure.



Thanks for all the help!

Will
 
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R

RKORES

Well-known member
Apr 21, 2004
155
0
Lowgap, NC
Ok,

So the shop manual says to test the VSS to "Raise and rotate the LEFT hand teat road wheel slowly." I am also using the updated version of the shop manual for 1989. Well I don't know what the "teat" is supposed to mean. Also, if I raise the left hand rear wheel, it doesn't rotate much, but the test calls for it to rotate atleast one full turn. I have tried different combonations of having the T case in neutral or engaged, along with the T R A N N Y in neutral or park. I know that if I jack up both sides then they will spin, but it won't turn the drive shaft, so that would be useless. So far the IAC seems to check out ok.

Thanks,
Will
 
R

RKORES

Well-known member
Apr 21, 2004
155
0
Lowgap, NC
Ok, I have been doing some research on the VSS part and whatnot...But out of curiosity...Could I be having a problems since I have unplugged the speedo cable from the right angle drive? I wouldn't think it would be an issue, but....

Randall...if you have any free time this week or the next, I might get you to help me put in the 500ohm resistor if it is a pain and if you have any free time. I will buy you a six pack in two months (21st bday!) When I get back to the room I am gonna hit up the shop manual and see what I can figure out.

Thanks,
Will
 
R

rrrandall

Guest
Will

Can't meet you right now because I am rebuilding a car and may be driving a van load of teenagers to Blowing Rock this weekend too. For a keg I may change my mind though.

You should try reconnecting the speedo cable first. Was that stepper motor you put in a "one size fits all", or the correct Lucas motor?? I suspect the problem here is lots of small things adding up to a poor idle. The load from engaging the transmission is enough to overwhelm your idle control system.

The base idle, timing and the gap in the distributor needs to be set correctly. If not, then it's harder to diagnose.

There are only about 5 wires that are needed to connect the EFI system to the vehicle. They are all on a connector which sprouts from the harness at the firewall under the dash. Wire#34(black with orange trace) tells the ECU if you have an manual or automatic, and if you are in drive or neutral with the auto trans. In regards to idle speed, this wire tells the ECU which idle speed to maintain. The VSS(if installed) tells the ECU if the vehicle is moving or not(turns on the idle control when you are not moving). You also have other idle speed settings with the A/C input wire.

To test the function of wire# 34: Remove the harness connector from the ECU and attach an ohm meter probe to it. Attach the other probe to the chassis or neg terminal of the battery. The reading should be ~500ohms if you have a manual trans. If you have auto trans check for continuity(buzzer). There should be no continuity when the gear selector is in park or nuetral. There should be continuity in any drive position. If not then that may be a big part of your problem, and you need to fix the park/neutral switch, the wire or it's chassis connection(ground). All easy to do if you have a plan, which is what I just gave you.

You can intercept wire#34 and put a ~500ohm resistor between it and ground. This may be best done by removing the wire from the park/neutral switch and adding it there. I would not recommend doing this unless you actually have a manual trans, or are doing a retrofit to an non-VSS vehicle. The fueling is different between a manual and an auto.

Randall
 
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