'87 300TD weird engine / electrical, help!

[cantabridgian]

Hi All,

Hope this Holiday Season is treating you OK. Always a crazy time of year!

I finally bit the bullet and asked my Indy to deal with water issues in the passenger footwell...holes in the firewall (4, to be exact). He did a nice job with a grinder, metal plates, rivets and marine-grade epoxy. I'm happy, and dry.

Here's the problem: he had to take out all the stuff in the engine compartment on the passenger side to get to the firewall holes (from both sides). Battery, battery tray, and all the ECM, OVP and other stuff in there. After everything got put back, now the car starts rough, idles way high (about 1100, should be 750), and seems to be a little sluggish. Prior to this repair, it was running sweetly and idled about 750 like intended. It's a side note, but when I first got it back a day ago, the tach was dead. Came back to life through two trips to NH and hasn't died since. Car has a new OVP and the fuse is good, so I'm not worried about the OVP. Weirdly, the dome light won't go on when the driver's door is open. Works with other doors.

Help!! Thanks in advance,

Josh (freezing in MA, if you can believe that...going down to 8 degrees tonight)

[Aquaticedge]

The dead tach and other things makes me think it's a faulty OVP.. Sometimes new ones come bad, if you have a spare I'd start there. Also I'd unplug the ELR from the IP and see if that changes your idle

[Aquaticedge]

Other than that it's possible he accidently cut a wire or when welding burnt a wire.. I'd trace the computer wires and see where they a
L go and make sure there are no open circuits

[cantabridgian]

Thank you for that!! Very helpful. I replaced the OVP about a year ago; thus far no concerns, but you're right, I know they can easily fry. What is the ELR, please?

[zorecati]

Originally Posted by cantabridgian

Thank you for that!! Very helpful. I replaced the OVP about a year ago; thus far no concerns, but you're right, I know they can easily fry. What is the ELR, please?

Check the fuse on the ovp. Some times reconnecting the battery will pop the fuse.

[Aquaticedge]

Originally Posted by cantabridgian

Thank you for that!! Very helpful. I replaced the OVP about a year ago; thus far no concerns, but you're right, I know they can easily fry. What is the ELR, please?

ELR ( I hope i have it's name right) Is the electronic Idle controller, if you note on the left hand side near the fuse panel, there's a rotary dial with numbers on it, that is an idle controller. there's an electronics plug to the back of the IP, if you disconnect it, your RPM should drop to pretty low... if it does, then there's something up with your wiring and you should look in the area where they took things out. it could also be a crap ground in the area, there's quite a lot of grounds that come to that section of your vehicle

[cantabridgian]

I think you're right about a bad ground being a strong possibility. I'll check as soon as I can...after our snow-easter passes through and we dry out. I did get a chance to test the OVP yesterday before the snow hit, and it was good, fuse was good. thank you much!

[Aquaticedge]

there is IIRC 3 bundles of grounds, search the area for any missed connections there, brown/tan in the area I believe are the grounds, when it dries out here, I will take a picture of my grounds in the area in my 300TD

[cantabridgian]

that'd be hugely helpful, thank you!! The more I'm thinking it through, the more I think you are 100% correct. Nothing else was touched, changed or disturbed about the car other than this firewall area (well, "between the double firewalls") in front of the passenger side. Perhaps they even used some sealant of some sort where a ground should be.

I'll still pull the idle control knob next to the fuse box; if for no other reason than to lower idle temporarily. driving home through the snowstorm last night I found that the high idle caused the ABS to fire every time I approached a traffic light and the car wanted to go too fast, I wanted to slow it down.... wasn't exactly thrilling. I sincerely hope you're in a sunny area, perhaps one that just beat my football team.