Rough Idle and Stall

Every time I solve one issue another pops up. Had my Reatta out for it longest run so far and it involved crossing over two mountain passes at highway speed. The car has been running good but compared to other 3800's I have had was lacking power and a bit slow to accelerate. When I got back from this trip motor had blown off the PVC tube and had blown out some oil. I knew I had to have some exhaust work done but did not think the factory CAT was blocked. I order the Magnaflow direct fit Cat from Ronnie's store. Just got it installed and hooked up. Started up Fine, give it a test run and the performance is back. Now when I first started it my CRT screen was blank, been good for months so I can't see if its throwing any new codes. Sitting is the driveway after the test run, started idling rough then would stall, restarts fine then will go rough and will stall eventually. I know Cam Magnet can cause rough idle, what about the OX sensor or any other sensor the could have been affected by the back pressure from the clogged cat?

Suggestions Please, Since my CRT is blank I can't see any codes. ( I have cleaned all the ground lugs under the hood. )

Thanks in Advance!!!

If your cat was clogged I would also clean out the egr it is probable carboned up and replace oxy sensor. I do not know your milage but if the hose blows of either the hose is swollen or you are getting blowby from the rings, might want to check compression if the latter is the case.

EGR was new just before this run. Car has 100347 miles on it. Also in last 6 month or less then 300 miles. Injectors, Wires, Plugs , Delco Coil Pack. OX sensor is original. Many Vacuum lines have been changed. I did look at the cam magnet and it was still in place. Wish the CRT would light back up. I will try and OX sensor since its so old and that I am not sure if the CAT was bad when the original owner stopped driving it. I think the rings are good. The last drive over one of the mountains, I had to get up some speed and it downshifted into 2nd and revved up higher then it had in other test runs.

Seeing the all parts you have changed... I would be looking at the MAF sensor. Try tapping on it and see if the engine stumbles when you do. Also try disconnecting it and see if the engine will keep running without stalling.

Sitting is the driveway after the test run, started idling rough then would stall, restarts fine then will go rough and will stall eventually. I know Cam Magnet can cause rough idle, what about the OX sensor or any other sensor the could have been affected by the back pressure from the clogged cat?

I had an ISC cause mine to start up and die repeatedly, would run if throttle was held open slightly. I tapped on it, unplugged and reconnected, fixed it, hasn't done it again. I could see it also causing an abnormally low idle and die. Mine only did it that one day on startup, was running fine when parked last time.

You may want to consider connecting a vacuum guage and see if it is normal in range or possibly fluctuating which would indicate a leak at the intake manifold base gasket.

An inline spark test would indicate if it was spark related, an inductive pickup timing light works even better and quicker.

I drove my '88 for a yr or two without a cam magnet and light on but it never idled rough or affected fuel economy. I also question whether an O2 sensor could cause what you describe.

My most often problem is simple tune, either plugs and wires or an occassional coil failure. I tend to run my plugs too many miles and start picking up high load-low rpm miss, then I know it is time to look at the plugs and wires. In the many miles I have put on 3800 engines, I have never had fuel injection problems, Knock on wood.

Ronnie

After the test run and first stall, I restarted it when it was idling rough (up and down rpm) I un-plugder the maf it stayed running, when I plugged it back in it stalled. I did clean the MAF when I worked on the fuel injection and did the plugs. Its funny that the car ran almost perfectly smooth with the clogged cat.

I did order an OX sensor from the Reatta Store. I will look closer at the MAF. Thanks for the tips everyone.

Ronnie

After the test run and first stall, I restarted it when it was idling rough (up and down rpm) I un-plugder the maf it stayed running, when I plugged it back in it stalled. I did clean the MAF when I worked on the fuel injection and did the plugs. Its funny that the car ran almost perfectly smooth with the clogged cat.

I did order an OX sensor from the Reatta Store. I will look closer at the MAF. Thanks for the tips everyone.

I can't explain why the engine ran smooth with the old cat and not with the new one. However, if the engine is stalling when the engine is cold I don't think a new O2 sensor will fix it although I hope I'm wrong and it does. My reasoning: The ECM does not use the O2 sensor as an input when adjusting the fuel mixture until the engine is fully warmed up to over 160 degrees.

If the engine didn't stall when you unplugged the MAF I think you have found your problem. Did you try tapping on it (I use the plastic handle of a larger screwdriver) to see if the engine stumbles? That will also give an indication that the MAF is failing. Be aware that cleaning sometimes helps the engine idle smoother but it won't fix a bad MAF. The only way to know for sure the MAF is causing the problem is to swap it out with one that you know for certain is good. You can pick up a used one at the local salvage yard cheap if you don't have a good one on hand. I recommend picking up a couple of them in case one is bad. And it's all ways good to have a spare on hand. You only need to get the sensor itself that is held on with two screws. No need to get the housing it bolts to. Be sure you get the right one for your car.

Ronnie

I let the car warm up after the new CAT install idling in driveway. My CTR was working before the install but blank when I started after the install. I took it for about a 2 mile run and had it up to 60mph for part of it. It did not act up till I returned. Since I have no gauges I will assume it was warmed up and in Closed loop. I unhooked the battery and let it sit unhooked for about 5 minutes. I then started it and drove it into the garage. I cleaned the MAF again this morning. Car has 100k on it so OX sensor wont hurt.

Ronnie, Reatta Store, The prices there are very good and I appreciate what you do to keep the store so we can get good parts at reasonable prices.

Just some of the parts I have ordered recently. EGR, Dash Mat, Cat, OX sensor.

It's odd that your problem with the CRT and the problems with the engine started after you changed the cat. Did installing the cat require any welding that might have caused electrical problems?

I'm happy to hear that you find the Reatta Store useful when you need parts. Thanks again for using it. It helps with the cost of maintaining Reatta Owners Journal.

No welding, Had problems getting it to unbolt on one side. So I cut off the old CAT as close as I could for more working room. I had one side unbolt at the nut. The other side unbolted the whole stud. Just happy I did not break any off. Used alot of BP Blaster on those studs and bolts. Use some Lock-tite Freeze spray also. Letting it warn up some out side then I will see what it does. I should have the new OX sensor tomorrow. I may take some voltage reading on this one using a Digital Meter just to see what its doing.

If you haven't checked the grounds near the battery you should do so. I don't think it will help the stalling issue but making sure the grounds are clean and tight might get the CRT working again. Good luck with the O2 sensor. I hope if fixes your problem.

i agree with Ronnie about the MAF , but hope the O2 sensor does the trick. however, i'd check your fuel pressure: http://reattaowner.com/roj/component/content/article/67-engine-a-drivetrain/fuel-system/288-fuel-pressure-testing

and check the crankshaft (harmonic balancer) for cracks/missing rubber - front and back. possibly could cause or be a bad crank sensor. that won't throw a code (if your CRT comes back on).

i'm just going from what i've had to replace - fuel pump/filter, crank balancer/sensor and O2 sensor. the MAF - i just had to clean it with sensor cleaner a few times.

the CRT is probably a separate issue, but i "almost" always disconnect the negative battery cable on "electronic cars" just to make sure a static discharge doesn't occur.

good luck!!!

I did a test run of the car, let it warm up, idled fine in open loop. When it whent into close loop, idle stared fluctuating like before and close to stall. I could not easily probe the OX wire while connected so I disconnected it and tested just the sensor. Best voltage reading I got on from it using digital meter set to 2 volt scale. .02 to.09. this is way below spec. So will se what it does after new OX sensor.

Ronnie, I have cleaned the Ground terminals around the battery last fall and re-checked them today, all good, CRT still blank

Corvanti: Thank You for the suggestions, to get this car running from sitting for 10 years everything in the fuel system has been replaced. Crank Sensor is new, Balancer was visually checked when I did it. I have a laundry list of things I have had to do to get this car on the road. I did get the car for free, But its cost a good penny so far to get it back on the road. I will have do a write up on this car for people who may be considering a car in the salt areas and from sitting long term what problem they may face getting it road ready.

My 89 when I bought it had some issues with a rough idle, I went through everything just like you are doing. I'm not saying this is your problem, but there are some fusible links hidden by the antifreeze tank up against the fender. Mine were all frayed and some of the wires were in contact with the metal, I'm sure that did not help the idle. I replaced all mine, you might check them out. Section 42 8 A 10 shows them in the data base.

A few years ago, my Reatta had similar symptoms when going into closed loop. Wouldn't idle right, and even stalled. Turned out the Fuel Pressure Regulator was bad and letting unmetered fuel into the intake via the little vacuum hose. Try pulling the vacuum hose and check for any sign of gas in it. If gas is present, the FPR is bad.

Installed new OX sensor and problem is solved. Now to have the CRT fixed and just found wipers not working properly.

After getting the CRT back and wipers fixed I began to drive the car again to see what else it may need. It did start the rough idle again not as bad as before the OX, and it also started having hesitation when starting off and random shudder at highway speeds. I did some more research and replaced the IAC (Purchased from the Reatta Store ). Idle problem solved. I then check my coils since they were from the junkyard and they were in spec. All Plugs and wires were new. When I first stated working on the car I had fuel injection issues and replaced the injectors with fuel rail from junk yard. Clean all injectors before install. Used the fuel regulator that was on the rail. Found fuel in the vacuum line so I replaced it with the old one. Hesitation now gone and runs best it has so far.

The OX sensor and IAC is what fixed the rough idle and stall.

You're making progress! You're getting to the point where you can get out and do some driving. That's what it's all about. I drove mine for about 125 miles on the back roads through the foothills of the Smoky Mountains. It was a beautiful day and we had a ball!

I can add a little to this topic now....oddly enough. Car has run terrific since I bought it but could hear a vacuum leak. Found that the 3 way vacuum connector at the fire wall was split in half. Replaced it and now I have the rough and diving idle. Power and driving is as smooth as ever but car could stall without warning at any stop sign. One of the vacuum lines was in poor condition and I replaced it. This improved things slightly but I believe I have it down to yet another 3 way connector. Will see where it leads. Funny that it idled fine when there was a fairly big leak and now its loopy when warm.

P.S. No codes generated either.

Robert,

I had an issue with a machine at work years ago. At the change of shifts, I told the day shift guy that the problem had something to do with the air flow to an actuator. The next day I came in and the problem was even worse. I asked him what all he did. He said he installed new air lines, new fittings, new valve assembly etc. So... I fought a jamming machine for half a shift before deciding to go through everything he replaced. I found a brand spanking new brass "T" fitting that wasn't drilled completely through on one leg. Replaced it with another new one that I checked had been made properly and the machine ran flawlessly after that.

New parts don't necessarily mean good parts.

My suggestion is to check the "T". If good, then check all of the other Vac. lines and the points where they connect. Once you are certain there are no leaks, then play the game I call "What else could it be?".

John F.

Little late but if the CRT is not working, all you need is a GM P4 ("OBD I") scan tool. I have an OTC 2000 with the '93 "All in One" that takes care of me. Used to be common/cheap on eBay but not as many now.

[quote=Dashmaster;

The OX sensor and IAC is what fixed the rough idle and stall.

First , Would this work you did be similar to 1990 Park Ave.3800 with same problem? If so, Can I clean and/or replace the IAC without removing the entire intake housing? Manual shows that repair done on a bench.

Yes

First , Would this work you did be similar to 1990 Park Ave.3800 with same problem? If so, Can I clean and/or replace the IAC without removing the entire intake housing? Manual shows that repair done on a bench.

Thanks to Padgett for supplying the instructions.

That' just great. I am trying to get my Dad's old Buick running right (it's my emergency back-up to a Tundra). I also have a 1984 Buick Park Ave that runs good except the carb and a tree that crushed the trunk. I use it like a tractor around the property. Another one of my Dad's "bought new" cars. He loved those Buicks... My favorite car is the MAzda RX7. Still have one from 1984 with Fuel injection. Looks a lot like the Reatta in your picture. Thanks I'm going to start searching Reatta sites for fix-up info needed.

Thanks I'm going to start searching Reatta sites for fix-up info needed.

Kurtk,

You can find no better than HERE.

John F.

I decided just to replace the IAC instead of cleaning. My car sat for a long time and had a clogged cat. So since I have had to fix other stuff related to the clogged cat i figured I would just replace it. I did clean the car side ports before installing the new IAC.