HELP! car starts on 4 cylinders (no slow down lights)

My '89 Mondial-t coupe had been running great. But recently after taking it out for a run (nothing dramatic) I stopped at a friend's house for a couple of hours. Upon starting the car it started on only one bank (no lights of any kind illuminated on the dash). About half way home the bank came on but then shut down again pulling into my driveway.

Ferrari of Denver looked it over and for a couple of days it ran fine for them and then on the third day it acted up. I have 2 new cat ECUs (black in color not green), one new ignition coil, new thermocouples, and redone cats. They did get the 1-4 slow down light to come and then it shut down that bank (cat was glowing red). They adjusted air-flow mixture (HC and CO levels were off) and everything else checked out just fine. They drove it for 35 miles and had no problems over 2 days.

Drove it home and it was fine. Did not drive it for a few days and today started it and it started on only one bank again...running on 4 cylinders (no lights at all on the dash). Drove it around the block and the bank did not come back on so drove it home (no red lights of any kind ever came on). FOD is picking it up today but everyone seems to be stumped. Any ideas anyone, PLEASE!!!!

Thanks,
Steve

 

Thanks for the heads up about the sensors Steve I will have that checked out. I'm going to call Helms tomorrow and see what he thinks. I have had very good service from FOD thus far...very good people. If 91TR doesn't respond to this thread I may PM him.

Steve

 

Yes all the correct lights illuminate when the key is turned to the on position and then all go off normally. Then when the car is started it starts on just one bank.
As to your and others advice I will check all grounds, sensors, MAFs, and fuel pressure regulator. When we figure it out I will let everyone know what we found.

Thanks,
Steve

 

Thanks ND that sounds like a good plan. I'll give a try.

 

Took a methodical approach and found a bad 1-4 crank sensor. The good thing about taking this approach (besides having your car run right) is that just about every electrical connection and sensor was checked and cleaned.

A big thank you to everyone who responded to this thread. Your advice and opinions were appreciated and heeded. I hope this helps someone else down the road.

Steve

 

Well we thought we had it but it was not to be. FOD went through all the wiring and sensors checking cleaning and stabilizing each one and found the 1-4 crank sensor to be faulty. It was replaced and the car was back on both bandks running great. The car was driven about 120 miles over 2-3 days and it ran perfectly.

I picked it up today and drove about 17 miles of the 20 mile drive home driving normally (65-80mph) in traffic. It's a hot day here today but I had the windows down and AC off so no extra load on the engine. When I exited the highway to the light the car was fine. When I took off from the light I was on 1 bank again. I drove slowly for about 5 blocks and one dash light flickered quickly and went off. I drove it another 5 blocks and the bank seemed to start up again running on 8 cylinders. I drove it slowly and the 1-4 slowdown light started flashing and I was back on 1 bank. Then the light went off and I drove a few more blocks the bank came back on and the 1-4 slowdown light came on and stayed on for about 20 to 30 seconds (but the car was running on 8 cylinders). After the light went off I drove the last half mile or so and it seemed to be OK but not perfect. I pulled into the garage and looked the the cats, which looked fine...not glowing red.

I let it cool for awhile and started it again and it idled OK for awhile but after a few minutes I revved it a bit and the tach came down below 500 rpm, ran roughly and just about died. I turned it off went into the house and called FOD. I will try again in the morning and see what happens but I will probably have to get it towed again and go from there. Very, very frustrating.

 

Thanks for the advice guys.

To ND: the problem with switching the cat ECUs is that the slowdown light does not always come on. Like this morning, I drove it and it started fine, let it idle for awhile and drove it till it warmed up...everything fine. Drove around some back roads and got on it pretty good, ran like a banshee. Started home and when I stopped at a light (about the fourth light on my way home) the car was fine. Took off and it was on 1 bank...no lights at all. Drove it about 50ft and the bank came back on. Drove home and as I pulled into the garage I could tell it was on 1 bank again (no lights came on). I let it idle for 1 minute or so and then revved it to 2000rpm (if everything is fine it comes right back down to 1000rpms and stays there) and then let my foot off of the accelerator and it dropped to 500rpm stuttered and died. I turned the key off and called FOD. So with this episode seems like it has something to do with running it and stopping and taking off, but no lights came on at all.

Also, the 1-4 bank was running CO levels low and HC levels high. It was adjusted properly and the car ran fine, but there's obviously something else going on, do you think?


To ferrarilou: I believe FOD did that but I will make sure.


To Birdman: I know what you mean but when the 1-4 slowdown light came on and stayed on yesterday for about 20-25 seconds I was going to stop but all 8 cylinders were firing. When I got home, which took about 2-3 minutes I immediately checked the cats and they were fine...not glowing red.

 

Well they are both new (green epoxy) ECUs but maybe you're right I just got a bad one. I'll see about getting that replaced and see what happens. Thanks.

Steve

 

I don't know Dr. but it's driving me crazy. If and when this gets corrected I'll post it so as to help prevent or fix others with similar problems.

 

Thanks all good information.

I'll see if I can put it to good use.
The ECUs have not been reset but that is a good idea if for nothing else just to see if it makes any difference at all. Interesting call on the difference between the 2.5 and the 2.7. I'll check it out.

I don't know why the CO and HC levels were off, the the O2 sensor was checked and is working perfectly.

Stay tuned we'll get this sorted out yet.

 

OK OK, it's at FOD right now but I will have that done.