T1 87 SC suddenly has ERRATIC IDLE - need help!

1987 T1 Shelby Charger. Car has been running fine for two weeks. Went to DMV, and right in the middle of the emissions test, the Idle starts jumping from 1000 to 3000 and a few points in between. Symptoms:

1) When car hit about 3000, Power Loss triggers and Idle drops to 500-1000, then back up. It cycles like this, sometimes gets stuck at 3000 for 3 or 4 seconds, then Power Loss and drop.
2) My boost gauge shows 20 on vacuum, but doesn't seem to get past 0 now when I hit throttle. Not sure how normal behavior is.
3) When I turn off car, Tach is showing needle stuck at 2000 sometimes.
4) Removed two wires on AIS, the Idle Control motor on the TB. No change in behavior.
5) Checked all the vacuum lines I can think of, all look good.
6) No Codes. Just 55 on the dash when I do the key on-off thing.

So I figure some sensor went bad? The car was idling for a while in line and in the test area. Maybe heat destroyed a sensor?

Any ideas?? I need to this through inspection, I obviously have a nice big red REJECTED sticker and I had to get towed home...

Thanks! I am home now to try anything out!

Derek

Also, no amount of playing with the throttle will help, it just goes nuts. I can barely drive the car around the parking lot where I was stranded. It doesn't smooth out with any amount of throttle application, it will still cycle, just at higher RPMs.

I'd ask the testers what the h#!! they broke!

Well Im not too keen on suck through setups, but make sure your map sensor tube is okay, itll run like sh$$ if it isnt. Maybe try another one. Also make sure you dont have any leaks on the system, the suck through dont do well with leaks. You might want to pull kick panel and ensure you dont have coroded LM wires. Firstly make sure they didnt unhook something accidentally.

I unplug the map sensor, and the idle drops, but it does run like crap and backfires a bit. Plugged it back in...

Can a bad MAP sensor cause it to be erratic? Also, could my LM go bad and make it behave this way?

---------- Post added at 05:52 PM ---------- Previous post was at 05:52 PM ----------

Here is a video of the situation:

http://s1141.photobucket.com/albums/n599/ohlarikd/

---------- Post added at 05:55 PM ---------- Previous post was at 05:52 PM ----------

Quote:

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Originally Posted by trannybuster

Well Im not too keen on suck through setups, but make sure your map sensor tube is okay, itll run like sh$$ if it isnt. Maybe try another one. Also make sure you dont have any leaks on the system, the suck through dont do well with leaks. You might want to pull kick panel and ensure you dont have coroded LM wires. Firstly make sure they didnt unhook something accidentally.

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I did pull the LM out and it seems fine. I want to replace the MAP sensor, but its $75 and an order, so I am not sure about that yet...

Thats some sort of igniton cut out. I wonder if its the HEP.

EDIT: or the coil

Quote:

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Originally Posted by Orangetona

Thats some sort of igniton cut out. I wonder if its the HEP.

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What is this mysterious HEP I keep hearing about?

The HEP is the hall effect pickup that sits under the distributor cap. They are fairly expensive from the dealer but really cheap from the junkyard. :)

Whenever a TD acts funny change the HEP and see if it helps... The HEP will often allow the car to run great until it gets hot and then it just dies. I always have 2-3 junkyard HEPs sitting around even the new ones fail sporadically so it is better to just get a really cheap one at the yard and keep a spare in the car. Once you get a good one it will last for years.

-Rich

The HEP is the distributor pick up under the distributor cap. The thing with 2 sets of wires coming out of it.

Quote:

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Originally Posted by Orangetona

The HEP is the distributor pick up under the distributor cap. The thing with 2 sets of wires coming out of it.

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I agree that it looks like a HEP...

A completely pinched MAP line usually makes for a ton of black smoke.
A bad MAP usually has a 4k RPM cutout.

-Rich

This thing?Attachment 31119

indeed

Quote:

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Originally Posted by ohlarikd

This thing?Attachment 31119

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Yea try replacing it.

Note that they are different between turbo and non turbo cars. and the 85 and older ones were also different.

-Rich

Ok, I did have a spare one... going out now. Hoping for the best...

Good luck!

Ok I am back already. I removed the dist dust cover, and lo and behold, the cable for Cylinder 4 had been pulled out! DMV must have tugged at the wires for some unknown reason. I did see them open the hood and they were fishing around in there, I have no idea why.

I plugged it back in and it idles perfectly and runs great! Can you believe that??? Well, until I get a PASS for inspection, I won't say anything to those guys.

THANKS!!!!!

Derek

---------- Post added at 06:40 PM ---------- Previous post was at 06:35 PM ----------

Ok, I am not going to totally blame DMV. I noticed that the car is actually running much smoother now than before. I think it may have been very loose and misfiring a bit on cylinder 4. At DMV it must have just completely pulled out and killed number 4. It did seem a bit down on power, but I wasn't sure. Going out for a test run!

Derek

Id take that right down there and say you want a free inspection. Thats their fault.(Oh ok nvm)

Thats pretty crazy that caused that much rpm havoc lol. I knew it was ignition cutout, but I wouldnt have guessed that.

Yeah you need to pay close attention to them because they are tough to get in there right sometimes.

This car runs like a total ANIMAL now. I suppose cylinder 4 was getting a weak spark or erratic spark before. Now this car is completely out of control, love it!

Thanks again Reeves for pointing me to the distributor area, I never was going to look there.

Derek

Hey good for you!! Ive never had one fail like that, mine just plain old fashioned quit working leaving me stuck on side of the road while I put the backup on. Yes I carry a backup as should any TD'er!

Quote:

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Originally Posted by trannybuster

Hey good for you!! Ive never had one fail like that, mine just plain old fashioned quit working leaving me stuck on side of the road while I put the backup on. Yes I carry a backup as should any TD'er!

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Well, the HEP was never replaced - it was just the pulled out #4 plug on the distributor. But I did have the spare HEP in my glove box, the previous owner (4 l-bodies) advised I should always have one around.

Thanks!
Derek