1999 Grand Am 2.4l Twin Cam engine issues.. Updated

[TilliamWe]

It has idled EXTREMELY rough since I got it in December. (Harleys idle smooth compared to this thing!) It has 183,000 miles on it! The guy I bought it from is a quasi-mechanic. He says he changed spark plugs to correct the rough idle condition. it didn't work. I also found a GM MAP sensor in the glove compartment, so someone has changed it. CEL code is P0300, random cylinder misfire. Causes: vacuum leak, iginition, injection fault, high or low fuel pressure.

Here's what I've done:

- Check compression, not good news. 215 on #s 1-3, but only 190 on #4. (It's spark plug was also in much tighter than the others) Squirted fogging oil in #4 (didn't have any 5-30 handy) and it went to 240psi!
-Found one spark plug boot sping int he valley when i removed the ignition cover. Not sure it it was installed that way, or fell out as I lifted.
- Changed spark plugs. One had a weird mark on its electrode, but all appeared to be firing. All pistons had some carbon on their tops, as viewed thru the spark plug holes.
- Cleaned throttle body and plate of some carbon looking stuff.

Put it all back together, and it idled better, like only the low cylinder was what I could feel. Didn't have the "hard/dead" miss. That lasted about 12 miles, when the CEl came on flashing under acceleration, and it hesitates and bogs while accelerating now. It also has a little more roughness at idle too. The CEl code for it is P0105 Which is MAP sensor. Causes: Vacuum hose off, plugged, cracked. Throttle body intake off or loose. MAP defective, engine mechanical timing off.

So I:
-Removed intake, all hoses tight, vacuum hose to it is open and not cracked.
- Removed vacuum hose from MAP while running, it made it run a little worse.
- Checked other vacuum hoses to throttle body, they are on and don't appear broken or cracked.
- Unplugged MAP sensor, it ran worse.
- Unplugged TPS and it wouldn't stay running

So what do I do now? Could the low cylinder been messing with the vacuum enough to screw up all this other stuff? Or is there some common issue with these motors that I am missing?

Thanks in advance.

 

[dolluper]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

#3 fuel injector bad or O-rings.....failing crank sensor...coil....low fuel pressure......or out of the blue rear trannie mount

 

[TilliamWe]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Was the #3 injector more prone to failure than the others?

 

[wifisher]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Well, you have a code for the map that you have not resolved. Look at the scan tool while it is running, and see what the MAP is reading. Then put a vaccum gage on it and verify that the MAP is accurate. Once the MAP issue is resolved, you can continue looking for other causes.

 

[scrambler45]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

With low vacuum, it is very common for the camshaft timing to be off on these engines.

 

[wifisher]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

With low vacuum, it is very common for the camshaft timing to be off on these engines.

Yeah, the timing chains are a real PITA on them too.

But until there is a vacuum gauge on it to verify the vacuum is actually low, I would not want to condemn the motor.

 

[TilliamWe]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Well, you have a code for the map that you have not resolved. Look at the scan tool while it is running, and see what the MAP is reading. Then put a vaccum gage on it and verify that the MAP is accurate. Once the MAP issue is resolved, you can continue looking for other causes.

The guage was the one at Autozone, of course, so I can not look at it while it's on. But I can get a guage and test the vacuum. Does the fact that I took the vacuum line off the MAP and it only ran a little worse mean anything? Or does that mean if I had even more vacuum, (i.e no low cylinder #4) it would run better?
The cam timing has me worried, as the motor improved after the plug change, then all of a sudden it got worse (10 miles later). But I don't understand how the vacuum affect the camshaft timing. Can you explain that in small words? And is it even possible for these engines to run if the cams are out of time?

 

[dolluper]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

So all you have now is the map code no others....check and see if you have power from PCM wire to map about 4-5 volts if good if not check for break or bad ground ...start and check voltage at map at idle about 1 volt or less and then raise speed of engine check voltage again there will be a change if good about 4-5 volts you will notice a change as speed increases.....without running check TPS with key key on and WOT should read 4-5 volts
ohem test the injectors good ones are around 11.8 ohem"s

 

[wifisher]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

The guage was the one at Autozone, of course, so I can not look at it while it's on. But I can get a guage and test the vacuum. Does the fact that I took the vacuum line off the MAP and it only ran a little worse mean anything? Or does that mean if I had even more vacuum, (i.e no low cylinder #4) it would run better?
The cam timing has me worried, as the motor improved after the plug change, then all of a sudden it got worse (10 miles later). But I don't understand how the vacuum affect the camshaft timing. Can you explain that in small words? And is it even possible for these engines to run if the cams are out of time?

The vacuum does not effect the cam timing. The cam timing effects the vacuum. The timing chain on your motor is very long. It is common for them to stretch a little, and the timing suffers as a result. Because the valves are not opening and closing at the proper times, the vacuum is low. The timing is not out far enough to prevent it from running, but they don't run well.

This is all irrelevant until you get a known good vacuum gauge hooked up, and see what the vacuum actually is.

Timing problems are common on this engine, but that does not mean it is the problem that you have.

Unplugging the MAP does not really mean anything. If a sensor goes bad (unplugged) the ECM will see that there is no signal from it, set a code, and make its best guess as to how it should run.

 

[TilliamWe]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

fisher, when i read you first response, I read it in an order that sounded like you were saying vacuum affected valve timing. I see that you werre referring to the valve timing affecting the vacuum, which I understand. Thanks for the clarification.

What should the PSI of compression be on this engine? Is the 215 I got on #s 1-3 pretty good, or are they low too, and #4 is just REAL bad?

I'll get me a digital multi-meter and a vacuum guage and see what they reveal.

I'll post an update, if/when I get the time ti diagnose it. (Working 48hrs/week this week, and 2nd shift next week, I get very little time for these things. Oh and considering it won't stop raining for more than about 6 hous at a time, and I am always working those 6 hours!)

 

[TilliamWe]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Okay, I ran some tests on it

Vacuum at idle (600 rpm) is 6in Hg. My cheapo gauge says that's real bad, and that valve timing is the usual culprit. (Darn timing chain?) Could the low compression of one cylinder cause that, though?

I was able to get some readings on the MAP (forgot to do/didn't have time to do the TPS). Took the wire off, and with the key on, I got 5.02 volts at the plug. Plugged it in, and at idle, I got 1.65-2.12 volts, flucuating. Increased throttle, (not sure how much, though, my 5 year old was the one trying to push the gas pedal for me!) and got between 3.00 and 4.5. If this is critical, i could get my wife to hold the throttle at certain rpms for additional readings. Incidently, I tested the "old" MAP that was in the glove compartment and I got the same idle readings as the one installed on the car.

Okay, so what's next? Is the TPS test critical, or do you all have enough info to tell me it's timing chain replacement time? Or is it a dead cylinder?

Thanks.

 

[rbh]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Well a timing chain could explain the low compression due to it being out of time with the piston coming to TDC?????


I mean really your only down 25 pounds, so your still making fairly good compression.

 

[Sixmark]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

rbh is right in lin with my thinking here.

When was the last time the timing chain was done on this engine? On the Quad 4 you consider yourself extremely lucky if you get 80,000 miles on one, being that this motor has 183,000 on it I would have replaced it 3 times already.

 

[TilliamWe]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

I bought the car with 182,000 on it. No idea when the timing chain was done. It's getting worse, though. On the way home tonight, I had NO power, and it was smoking when I shut it off. Too dark to tell exactly where the smoke was coming from, though.

rbh, so you are saying that the 215ish on 1-3 is pretty normal compression?

 

[rbh]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

I bought the car with 182,000 on it. No idea when the timing chain was done. It's getting worse, though. On the way home tonight, I had NO power, and it was smoking when I shut it off. Too dark to tell exactly where the smoke was coming from, though.

rbh, so you are saying that the 215ish on 1-3 is pretty normal compression?

Honestly, dont know, I do not know the spects for your engine

But any cylinder that is down 25 PSI and your having compression issues with a streached timing chain is well worth checking out.

 

[dolluper]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Humm at this point I would disconnect the exhaust in front of the cat and see if the vac increases....make sure the pcv is not plugged and injectors ohem tested at least...check tps also before assuming the chain

 

[Sixmark]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

You don't need to assume anything, simple testing of most of the issues discussed can be done, check the timing it's not that hard to do. You can also get the spec sheets for the different sensors and test most of them using a simple multimeter to see if they fall within spec.

You won't be able to test all of them in circuit without an analyzer but if they are out of spc to begin with then you know where to start.

The 2 most common issues with the quad 4 2.4L were timing chains and head gaskets.

Regardless if you continue to use the car in it's current state you are going to continue to damage the engine.

 

[TilliamWe]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Humm at this point I would disconnect the exhaust in front of the cat and see if the vac increases....make sure the pcv is not plugged and injectors ohem tested at least...check tps also before assuming the chain

No PCV system on that motor.

Six, I am trying to test what I can, when I can. My problem is I work 45 hours a week, and have two children and a wife. No garage, so my time is very limited.
Today I pulled plugs, and #1 and #4 both smelled of gas. Tried to test spark, but my in-line tester broke on the last cylinder. #4 and #1 seemd to have weak spark, though. Eye Yi Yi!!!

 

[Sixmark]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Hey there's no pressure here friend, your not on a pit crew so don't rush anything.

 

[wifisher]

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Re: 1999 Grand Am 2.4l Twin Cam engine issues

Okay, I ran some tests on it

Vacuum at idle (600 rpm) is 6in Hg. My cheapo gauge says that's real bad, and that valve timing is the usual culprit. (Darn timing chain?) Could the low compression of one cylinder cause that, though?

I was able to get some readings on the MAP (forgot to do/didn't have time to do the TPS). Took the wire off, and with the key on, I got 5.02 volts at the plug. Plugged it in, and at idle, I got 1.65-2.12 volts, flucuating. Increased throttle, (not sure how much, though, my 5 year old was the one trying to push the gas pedal for me!) and got between 3.00 and 4.5. If this is critical, i could get my wife to hold the throttle at certain rpms for additional readings. Incidently, I tested the "old" MAP that was in the glove compartment and I got the same idle readings as the one installed on the car.

Okay, so what's next? Is the TPS test critical, or do you all have enough info to tell me it's timing chain replacement time? Or is it a dead cylinder?

Thanks.

6" vacuum is your problem. Checking the TPS will tell you nothing. Check to be sure that there are no major vacuum leaks anywhere, and that the exhaust is not restricted. If these check OK, I would say that it is probably the timing chain. A dead cylinder will usually not effect the vacuum reading if it has compression. (that is how it gets the compression) Your compression is high enough that it is not causing the problem.

I do not know if you would try to do the timing chain yourself, or take it somewhere, but be warned that it is a fairly large job. (this may be why the quasi-mechanic sold it)