So the other day, I'm driving my Daytona (turbo IV), and at idle, it keeps dipping down to around 500 RPM, goes back to 1000, down to 500, back to 1000, and never stalls. I let it do it for 3 minutes, never stalled.
Come home, check engine light comes on, so I pull the codes. I got 12 (meaningless), 13 (MAP sensor vacuum problem), 15 (speed sensor), and 27 (control problem on number 3 and 4 injectors).
Today, I decided to check the MAP sensor. I read (in 'How to Tune and Modify Chrysler Fuel injection', which is a fantastic book) that if you put in a vacuum tee, and the MAP sensor is getting vacuum, then it should be replaced if you pull a code 13.
I check it, start it, car runs fine, and theres vacuum. But then, something funny (or horrible) happened when I put it back together. I started the car back up after taking out the tee, and now its running absolutely horrible.
It seems to me that the car is missing on 1, maybe 2 cylinders. The exhaust reeks, it idles rough, revs rough, and it smokes, which it has never done.
So my question is...could a bad MAP sensor cause a car to run like this? I just changed the plugs, wires, and distributor cap today, so those aren't the problem. If not, could it be one of my other codes? Even when the car runs like this, the check engine light doesn't come on, so I'm baffled.
I ordered a new MAP sensor, because I figure worst case...I'm replacing a 15 year old sensor.
Any information ya'll might have would be helpful. Thanks.

 

You say the exhaust reeks, maybe it's the catalytic converter. Does it reek like rotten eggs? This could also cause running problems like this.

 

Nope, just reeks like gas. I changed the MAP today, no change at all.

It seems electrical to me. I mean I know that electrical systems are sensitive (my '86 Turbo Z was running on 3 cylinders, so I took of the distributor cap, put it back on, and it ran fine), but I was working on the firewall...nowhere near the computer and everything.

Doesn't seem like its lost compression. I'm going to try advancing the timing. Then if that doesn't work, I'll try retarding it. After that...well, its got almost 230k miles on it, so maybe I'll take the engine apart.

And the funny thing is, it doesn't smell bad in the engine compartment, just the exhaust. And man, it smokes bad.

I have horrible luck with turbo Dodges...kinda makes me wonder why I love 'em so damn much. My Shadow blew a headgasket, my '86 Daytona Turbo Z died twice in 2 weeks, my '83 Rampage (T1 turbo) caught on fire in the school parking lot, my '88 Daytona Shelby Z had no brakes and pulled hard to the right under acceleration, and now...the '90 won't rev over 5k/won't boost when its warm, nearly stalls, and is now running as described. But man...its a damn pretty car, haha.

 

What do the plug's look like?

Have you replaced the cap, rotor and wires lately or do they have some age? The reason I asked is because it almost sound like you have a bad wire(s). You may also want to take a look at the Hall Effect Sensor (pick-up plate). Its located under the cap and rotor and has the 2 leads that connect to the main engine wiring harness. If you have a spare laying around, you might just want to switch it out to see if it makes any changes. While your in there also take a good look at the distributor shaft and make sure that it is solid and has no back-and-forth play. With that kind of mileage it may be time for a new distributor.

The only other thing I can think of is the fact that you pulled a code 27 and you said that you smell raw fuel through the exhaust. That could mean that injectors 3 & 4 may be stuck open which I think would throw that particular code. Even with 230k it would be no crime if the injector finally gave up the ghost.

Just some things that I thought you could take a look at.

Hope this helps
Troy

 

Since your car is what it is and has the mileage it does, you might as well treat it to some good new parts. Get an MSD Blaster ignition coil and get a set of all 4 fuel injectors, I think Accel makes some for it. Definately check or replace the hall effects as 87Indy500 said. With this high of mileage it also wouldn't hurt to replace all of your vacuum lines, they can also have a very significant effect on your car.

 

Yup!

I didn't even think about the vacuum lines. REPLACE THEM even if you find that they did not the cause of the problem. You will thank yourself later.

 

I did the plugs and wires after this happened. Didn't fix it, and when I pulled em, they were black.

Anyway, I did a compression check, and I only have 90psi in #2, so I'm pulling the head tonight. I'm thinking headgasket or a stuck valve...though I doubt I'd have 90 psi with a stuck valve. Maybe a poorly seated valve...cause I'd probably have under 90 with a headgasket, too.

I was actually kinda hoping I'd have a reason to pull it apart. I mean it runs well and everything, but with 230k, I'm kinda happy to be pulling it apart.

 

my 87 shelby z had alot of the same problems you have talk about. i had a bunch of little little prolbems thta cause alot of big prolbems. 1st i found a bad vacum line and bad vacum connections. 2nd the head gasket was bad in between cyclinders 2 and 3. 3rd the inner workings of the turbo where bad causing the compresser blades to move about and 1/8 in damaging the blades and total wreck all the interal seals causing the oil and coolant to mix in the turbo and suck through the intake.

hopefully for you it won't be so bad and you can fix it easly. i'd problaly start by checking all the vacum lines and then the turbo.

 

VNTShelby90,

I had the same problem in my 91 daytona es 2.5l 5sp. It idled too high or too low and shifted horribly. First I thought it was the plugs and cap, but i replaced them and they were black again like you said. So I finally gave up and went to the dealer. They did a diagnostics on my car and found out that it was the TPS (Throttle Positioning Sensor). They also replaced my vacuum lines and adjusted my timing belt. So if the new map sensor doesn't fix it, get a new TPS for your daytona. Total Part cost = $45.01 (but plus labor in my case )

Good luck