Advice on getting it running (1989 MGM LS 5.0L EFI 46000)

[Ringting]

I purchased and drove the vehicle home from a retirement community, 10 miles away. Pictures in a photo album under Ringting

Odometer readings
2000 = 38,665, 2002 = 41,204, 2004 = 43,366
2006 = 44,698, 2008 = 45,560, 2010 = 46,192

It starts and runs rough if I feather the accelerator. The neighbor who runs a major auto manufacturer's race engine building shop thinks it might need a new exhaust system.

Installed new PVC/screen/grommet, flushed rad (no heat problem [still no heat]), cleaned plugs, new battery, recent oil change, new fuel filter, new thermostat.

Please suggest places (point me in a direction) on where to find the knowledge needed to get this beauty running. Otherwise she will be scrapped. MPG is not a major concern. If you think it is the exhaust system please offer up places to buy the parts (nothing fancy as I have a 330i for going just over 65).

I do not have a big budget (currently seeking new employment opportunities) yet will do what is right. It was purchased so I could drive the So Cal highways to and from work.

Any support is appreciated.
Thank you





While I really like this car, if someone wants it the price is $1700 as is, where is. I have the window sticker and most of the work orders as this sole owner kept great records.

[cld783]

first thing i would do is pull the codes.. what about dis cap and rotor? were those replaced as well?

scrap a car you just bought? yea that'll get you somewhere

[Ringting]

Pulling them today. Cleaned up cap & Rotor.

California will give me $1000 to scrap it due to age. Wife does not like it being around.

My preference is to get it going without creating a money pit. $700 on new cats is doable yet if it goes beyond that then the car goes.

[91waggin]

When doing tune-up, you should replace the spark plug wires.

Check timing
Check Throttle position sensor (TPS)
Check Engine coolant temp sensor (ECT)

If this car was sold in california, then it will have a mass air flow sensor (MAF), rather than a manifold absolute pressure sensor(MAP). If it has a MAF, clean it with carb cleaner.

How does it run when you get on it? Stumble? Pull strong? Does it idle well?

Also $700 for new cats seems REALLY steep. Upon looking up cats on Rockauto.com, I notice that none are legal for use in CA. Depending on how they check your emissions, this may or may not matter.

Simple test: Unbolt the exhaust from the exhaust manifolds...if this fixes your running problem, then clogged cats or another exhaust problem is the answer. I sincerely doubt however, that the exhaust is a problem, if this has been a California car all its life.

And the knowledge to get the beast running? You'll find it all here at GMN. We have a wealth of knowledge here.

[Ringting]

I will get on the four points you list.

Yes always in LA area. Initial Dealer: Urich Motor Company, Whittier, CA

One owner, (Drivers: husband I think for first while then woman for probably last 15 years).

It drove rough on way home, sputter/trying to stall. Will not idle.

The price for cats came from quick review on web. I can do that test today. THANKS!!

I really love this car and want to get it running. Boy down the street is enjoying learning about cars so it is for him as much as me.

Thank you to all. I shall contribute somehow as I gain knowledge.

[Freshmeat]

Check the firing order. If the tech wasn't paying attention during the tune-up he may have ran the HO (high output) firing order and not the SO (standard output) order.

[Freshmeat]

It should be 1-5-4-2-6-3-7-8
The #1 should be marked on the cap.
From #1 you must go counter-clockwise.

[Freshmeat]

From the front of the engine bay the cylinders are numbered like so:

4---8
3---7
2---6
1---5

#1 is the frontmost cylinder on the passenger side. The plug is hiding behind the A/C compressor.

[Ringting]

Excellent info. I will get on it and take pictures.

[PICKUP6772]

I noticed that nobody mention the idle air control (IAC) motor. This sits on the back of the throttle body, and is NOTORIOUS for clogging up with carbon, and causing all the running problems you have mentioned. While it is out, clean out the ports going into, and including the throttle body. In front of the throttlre body, is the EGR. This is also good for clogging up with carbon. Buy new gaskets for the EGR, IAC, and the throttle body, clean up everything. After this is done, then go for a test drive, and see how it is. It never ceases to amaze me how people LOVE to jump on the EXPENSIVE stuff first, without checking the simple things. As for the heat, I would check for a clogged heater core (did you flush the system out?), and if it has Automatic Temperature Control (ATC), make sure the temperature control valve isn't stuck shut. If it is, don't bother replacing it, just put a 5/8 hose connector in it's place, jump the two wires, or you'll have no floor heat, and block off the vacuum line at the switch.
MIKE

[pvillese]

I'm going to guess you don't have a temp gauge as my 85 didn't come with even a dumby temp gauge. The lack of heat could just be a bad thermostat. They are cheap and easy to replace.

[johnunit]

Check for vacuum leaks. That will cause a generally rough idle, among other things.

[packman]

+1 on what PICKUP6772 said. Even though your MGM has significantly less mileage than my '86 CV, I would check the IAC. It's the valve that sits adjacent to the EGR valve on the throttle body. My CV wouldn't idle for crap until I took the IAC off and cleaned it out with carb cleaner. It has run smoothly ever since.



Packman

[91waggin]

Some more exhaust things to consider:
Does your system have two or four cats?
Is the system particularly rusty?
---------------------------
If the exhaust system needs to be replaced:
If the system has four cats, will CA require that four new cats be installed (provided it needs new cats), or would you be able to get away with two modern ones?
Do the smog nazis require that you submit to a visual inspection, or just a sniffer test?

If you only have to pass a sniffer test, two things are likely:
1. You can get away with two cats instead of four
2. You can get away with buying cats not labeled for use in CA.
Remember: THESE ARE BOTH PROBABLE, BUT NOT GUARANTEED.

If you have to submit to a visual inspection, find out whether it has to have the same number of cats that it originally did, or whether it just has to have cats. Two cats are cheaper than four.

But none of the above matters if you only have two original cats. This could be the case, since you've got a later model car. Also, if the exhaust system looks like it's in good shape, it's probably not your problem.


Assuming the exhaust system is not the problem, have a look at these fairly common issues. These are listed with easier ones at the top.
1. Check for codes. These vehicles will set engine computer codes without the check engine light being on, for some reason. You can check codes with nothing more than a pad and paper, and a paperclip for a jump wire. Connect the paperclip like this, to the self-test connectors on the driver's side fender.

Then, get your pad and paper, get in the car, turn the key on, but don't start the engine. Some relays will click, the check engine light will flash rapidly a few times, and then you should start counting. Codes will flash like this:

Let us know what kind of codes you come back with.
Note: Since you've got an 89, you should have a yellow check engine light. That's the one I'm talking about, not the red "replace engine" light that comes on at low oil pressure or high coolant temp.

2. Remove the Exhaust Gas Recirculation valve and clean it with carburetor cleaner. Make sure it isn't stuck open. If it appears to operate normally, reattach it. Disconnect and plug the vacuum supply line for the EGR. If the engine runs properly, then something is the matter with the EGR. Let us know and we'll help you take it further.

3. Check throttle position sensor. Get out your voltmeter. Check the voltage between the black wire and each of the other two wires. With the key on and the engine off, you should have approximately 5v one one of the wires. With the throttle closed, the wire that doesn't have 5v should have between 0.2 and 1.4 volts. As you open the throttle, that wire should see a smooth increase in voltage right up to just under 5v at wide open throttle.

4. Check engine coolant temp sensor. It's in a radiator hose right by the distributor. Check the resistance across the two wires. Here are corresponding values:


5. Check your firing order like Freshmeat suggested.

6. Check your timing as outlined here:

http://grandmarq.net/vb/showthread.php?t=21502&highlight=timing

7. Do a full tune-up. This means new plugs, new wires, new cap, new rotor.
Most of us around here recommend caps and rotors with brass terminals, Motorcraft plugs, and Ford Racing wires.

Hopefully you get somewhere with one of these ideas. Most of these are pretty common problems that can really fuck with driveability.
Best of luck!
--Graham

[91waggin]

Check for vacuum leaks. That will cause a generally rough idle, among other things.

Wouldn't this cause a high idle, rather than a complete lack of idle?